Next Article in Journal
Effect of Chemical Surface Texturing on the Superhydrophobic Behavior of Micro–Nano-Roughened AA6082 Surfaces
Next Article in Special Issue
Investigation of the TeO2/GeO2 Ratio on the Spectroscopic Properties of Eu3+-Doped Oxide Glasses for Optical Fiber Application
Previous Article in Journal
Precipitation Hardening at Elevated Temperatures above 400 °C and Subsequent Natural Age Hardening of Commercial Al–Si–Cu Alloy
Previous Article in Special Issue
Structural and Photoluminescence Investigations of Tb3+/Eu3+ Co-Doped Silicate Sol-Gel Glass-Ceramics Containing CaF2 Nanocrystals
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Materials
Volume 14
Issue 23
10.3390/ma14237156
materials-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Transition Metals (Cr3+) and Lanthanides (Eu3+) in Inorganic Glasses with Extremely Different Glass-Formers B2O3 and GeO2

by
Karolina Kowalska
*,
Marta Kuwik
*,
Justyna Polak
,
Joanna Pisarska
and
Wojciech A. Pisarski
Institute of Chemistry, University of Silesia, Szkolna 9 Street, 40-007 Katowice, Poland
*
Authors to whom correspondence should be addressed.
Materials 2021, 14(23), 7156; https://doi.org/10.3390/ma14237156
Submission received: 9 September 2021 / Revised: 8 November 2021 / Accepted: 19 November 2021 / Published: 24 November 2021
(This article belongs to the Special Issue Rare Earth Doped Glasses/Ceramics: Synthesis, Structure, Properties, and Optical Applications)
Browse Figures
Versions Notes

Abstract

:
Glasses containing two different network-forming components and doped with optically active ions exhibit interesting properties. In this work, glass systems based on germanium dioxide and boron trioxide singly doped with lanthanides (Eu3+) and transition metals (Cr3+) ions are research subjects. Optical spectroscopy was the major research tool used to record excitation and emission spectra in a wide spectral range for studied systems. The emitted radiation of glasses doped with Cr3+ ions is dominated by broadband luminescence centered at 770 nm and 1050 nm (4T2 → 4A2). Interestingly, the increase of concentration of one of the oxides contributed to the detectable changes of the R-line (2E → 4A2) of Cr3+ ions. Moreover, EPR spectroscopy confirmed the paramagnetic properties of the obtained glasses. The influence of molar ratio GeO2:B2O3 on spectroscopic properties for Eu3+ ions is discussed. The intensity of luminescence bands due to transitions of trivalent europium ions as well as the ratio R/O decrease with the increase of B2O3. On the other hand, the increase in concentration B2O3 influences the increasing tendency of luminescence lifetimes for the 5D0 state of Eu3+ ions. The results will contribute to a better understanding of the role of the glass host and thus the prospects for new optical materials.

Graphical Abstract

1. Introduction

In recent years, the field of engineering materials (including glasses) has evolved, introducing new information about the interesting properties of systems [1,2,3]. Glass is a material characterized by a lack of long-range order with no defined glass transition temperature [4]. In an excellent communication [5], Zanotto and Mauro declared that a comprehensive definition of glass, combining the aspect of knowledge improvement and modernity, is still being explored. Interestingly, to this day, the technology to prepare glass is based on substances such as SiO2, B2O3, GeO2, P2O5, which are the only ones that meet Zachariasen’s rules for glass formation [6]. A variety of modifications in the chemical composition of glasses enables the introduction of different optically active ions such as transition metal and rare-earth ions. This allows obtaining unique luminescent properties and developing new optical materials operating in a wide spectral range. The glass systems are applied in light-emitting diodes, lasers, phosphors, or optical amplifiers [7,8,9]. In defining the spectroscopic properties of amorphous materials, a significant contribution is the composition of the glass matrices. In particular, the type and concentration of the network-former and/or network-modifier influence structural [10,11], thermal [12], and optical properties [13,14,15]. Recently, Jiao et al. [16] presented that increasing the boron oxide ratio visibly improves the luminescence characterizations of Sm3+, Dy3+, and Tb3+ ions in glass systems. However, the wide range of compositional modifications presented for silicate glasses containing different network modifier oxides [17] indicated significant differences in the local surroundings of Eu3+ ions. Very satisfactory results of analysis of luminescence decay kinetics were also obtained for phosphate glasses. The value of measured lifetime for 4F3/2 level of Nd3+ ions increased to 2.49 ms with changing the glass composition [18].
The number of publications indicates that among various inorganic systems, borate glasses are preferred for the luminescent centers due to their spectroscopic properties [19]. Divina et al. [20] carried out spectroscopic studies of alkali lead-bismuth borate glasses doped with Dy3+ ions. It was reported that these systems exhibit yellowish-white luminescence and suggested the utility for w-LED applications. Borate glasses can also be useful for infrared emitting device applications due to intense near-infrared emission at 1056 nm corresponding to the 4F3/2 → 4I11/2 transition of Nd3+ ions [21]. However, these glasses are characterized by high phonon energy (1300–1500 cm−1), and it could have a negative effect on the photoluminescence properties of systems doped with rare-earth ions [22]. On the other hand, it limits their application potential in photonic applications. Therefore, it is preferable to introduce other oxides to the host matrix to reduce the probability of non-radiative transitions. Germanate glasses have been of great interest for many years because of the specificity of their physical properties, such as glass transition temperature, particularly [23]. Moreover, germanate glass systems exhibit the ability to absorb X-rays and high transparency in the near-infrared spectral region [24]. These systems have unique properties such as low phonon energy (~800 cm−1), good thermal stability, and good lanthanide ions solubility [25]. The results obtained in our previous works [26] proved that the developed glasses containing germanate (IV) oxide and titanate (IV) oxide determine the differences in the profile of the registered luminescence bands of d-transition metal and rare-earth ions. The present paper presents the correlation between the content of two different glass-network formers (GeO2 and B2O3) and the spectroscopic properties of inorganic glasses singly doped with transition metal ions (Cr3+) and lanthanide ions (Eu3+).
The spectroscopic properties of rare-earth and transition metal ions in materials are subject to rigorous interpretation that provides important contributions to contemporary scientific investigations. The luminescence spectra of Eu3+ ions are characterized by f–f transitions [27,28], respectively. The first observation of these transitions dates from 1901 by Demarcay, considered the discoverer of the europium ion [29]. According to the work of Binnemans [30], the relative intensities of transitions in emission spectra can be used to probe the local environment around Eu3+ ions. Analysis of the properties of glass systems can also be spectroscopically monitored by trivalent chromium ions [31]. Modification of the quantitative relationship of glass-former and glass-modifier oxides causes them to occupy different sites with different crystal field strengths [32,33]. Moreover, the laser transition 4T2 → 4A2 of Cr3+ ions is very sensitive to its chemical environment.
Based on these criteria, a series of glasses with the following chemical formula GeO2-B2O3-BaO-Ga2O3-Cr2O3 and GeO2-B2O3-BaO-Ga2O3-Eu2O3 were synthesized. The glass systems were obtained using the conventional high-temperature melt-quenching technique of high-purity metal oxides as starting materials. The selected optically active ions have a special role in the research because they are useful spectroscopic probes. For this reason, the structural properties of glasses doped with Cr3+ ions were investigated using electron paramagnetic resonance spectroscopy. The luminescence characterization of this study was aimed at determining which of the glass-network oxides favorably influence the optical properties of the obtained glasses. Excitation and emission spectra in the visible and near-infrared ranges were recorded. In particular, spectroscopic features such as R-line luminescence, superimposed on the broad emission band 4T2 → 4A2 transition of chromium ions, were analyzed. On the other hand, a fluorescence intensity ratio (R/O) parameter as a function of GeO2:B2O3 concentration was estimated of 5D0 → 7FJ (J = 1–2) transitions of europium ions. Moreover, luminescence lifetimes for the upper 5D0 excited level of Eu3+ ions are evaluated and discussed.

2. Materials and Methods

2.1. Glass Synthesis

In the present work, a series of inorganic glasses were synthesized using a high-temperature melt quenching-technique. The appropriate amounts of anhydrous metal oxides: germanium (IV) oxide (Sigma-Aldrich Chemical Co., St. Louis, MO, USA, ≥99.99%), boron trioxide (Sigma-Aldrich Chemical Co., St. Louis, MO, USA, 99.98%), barium oxide (Sigma-Aldrich Chemical Co., St. Louis, MO, USA, 99.99%), gallium (III) oxide (Sigma-Aldrich Chemical Co., St. Louis, MO, USA, >99.99), chromium (III) oxide (Sigma-Aldrich Chemical Co., St. Louis, MO, USA, 99.9%), europium (III) oxide (Sigma-Aldrich Chemical Co., St. Louis, MO, USA, 99.99%), were carefully homogenized in an agate mortar. Melting of the desired mixtures in corundum crucibles was carried out in an electric furnace in an air atmosphere at the temperature of 1250 °C. The glass samples were kept at this temperature for 1 h before slowly cooled down to room temperature. Then the samples were subjected to grinding and polishing treatment. Based on X-ray diffraction measurements it has been confirmed that all samples are fully amorphous. As a result of the above synthesis procedure, two series of glass samples doped with transition metal (Cr3+) and lanthanide (Eu3+) ions were obtained (Table 1 and Table 2).

2.2. Characterization Techniques

We used the following research tools to characterize the sample properties: electron paramagnetic resonance (EPR) spectroscopy and optical spectroscopy. EPR spectroscopy was used to describe the composition of glasses doped with transition metal ions (Cr3+). Each glass sample in powdered form was placed inside a special quartz tube. EPR spectra were recorded using Bruker EMX EPR spectrometer (Bruker-Biospin, Karlsruhe, Germany) operating at X-band frequency (9.8 GHz) with a modulation amplitude of 2.0 G. The magnetic field was scanned from 1000 G to 5000 G. The EPR instrument parameters are as follows: central field 3480 G, time constant 40.96, gain 1 × 104 G, microwave power 20.12 mW.
The optical properties of glasses were analyzed using luminescence spectroscopy with the system PTI QuantaMaster QM 40 UV/VIS Steady State Spectrofluometer (Photon Technology International, Birmingham, NJ, USA). The laser equipment was coupled with a tunable pulsed optical parametric oscillator (OPO), pumped by the third harmonic of a Nd:YAG laser (Opotek Opolette 355 LD, Carlsbad, CA, USA). The system consisted of a double 200 mm monochromators, a xenon lamp as a light source, a multimode UV-VIS PMT (R928) (PTI Model 914), and Hamamatsu H10330B-75 (Hamamatsu, Bridgewater, NJ, USA) detectors, PTI, and ASOC-10 USB-2500 oscilloscope. Resolution for spectral measurements (excitation and emission spectra) was ±0.25 nm (Cr3+-doped glass samples) and ±0.5 nm (Eu3+-doped glass samples), whereas decay curves with accuracy 0.5 µs were acquired. All measurements were performed at room temperature.

3. Results and Discussion

3.1. Transition Metals—Cr3+

Electron paramagnetic resonance (EPR) is a significant experimental technique for determining the environment of transition metal (Cr3+) ions in glasses. Analysis of EPR spectra gives information about the glass network and symmetry around transition metal ions. Figure 1 presents electron paramagnetic resonance spectra of glassy systems containing two types of glass-formers and doped with Cr3+ ions. Independently on the molar ratio GeO2:B2O3, the similar registered EPR spectra show one signal at a low magnetic field and one resonance line at a high magnetic field.
The broad asymmetric signal with g value ~4.8 corresponds to isolated Cr3+ centers in strongly distorted octahedral sites [34]. On the other hand, the narrow resonance line with g close to 1.97 is assigned to exchange-coupled Cr3+-Cr3+ pairs [35], or this signal can be attributed to the trivalent chromium ions in cubic sites of the glass network [36]. The similar measured effective g values obtained for studied glasses were also noticed for Cr3+ ions in CdO-SrO-B2O3-SiO2 [37], ZnO-As2O3-Sb2O3 [38], and Li2CO3-B2O3-P2O5 systems [39].
The intensity of the signals is higher for glasses with a dominant concentration of glass-former GeO2 (samples from Cr59:1 to Cr2:1). However, the intensity of resonance lines is lower for samples with increasing content of glass-former B2O3. Apart from the variation in signal intensity, no important modifications were observed when the glass-formers concentrations in glass composition changed. The influence of glass-formers on the spectral properties of systems doped with Cr3+ ions was studied. To this goal, the excitation spectra were monitored at λem = 780 nm (Figure 2), and two broad bands were observed due to transitions from the 4A2 ground level of trivalent chromium ions. From the literature, it is well known that Cr3+ ions have strong visible absorption due to the spin-allowed but parity-forbidden transitions [32].
The first excitation band around at 480 nm corresponds to the transition 4A2 → 4T1 of Cr3+ ions. In contrast, the second band consists of three overlapped peaks located at 600 nm, 625 nm, 690 nm and related to transitions originating from ground level to the 4T2, 2T1, and 2E excited levels of Cr3+ ions, respectively. It is worth noting that the intensity of band maxima of the 4A2 → 4T2 and 4A2 → 2T1 transitions change with the molar ratio of glass-formers (GeO2:B2O3). The intensity of the band corresponding to the transition 4A2 → 4T2 of Cr3+ ions increases when the content of germanium dioxide decreases. On the other hand, the intensity of band attributed to excitation level 2T1 is the highest for system Cr59:1 and the lowest for glass sample Cr1:5. The effect of changing the glass composition on the intensity of excitation bands was also observed for borate glass-ceramics with a constant concentration of trivalent chromium ions [40]. Moreover, the analysis of excitation spectra indicates that the forbidden electron transition 4A2 → 2E of Cr3+ ions is more clearly separated for glasses with a higher concentration of boron trioxide as glass-former (Cr1:1, Cr1:2, Cr1:5). To study the luminescence properties of systems with both glass-formers (GeO2 and B2O3), the wavelength λ = 600 nm was chosen for registration emission spectra.
Figure 3 and Figure 4 show luminescence spectra registered in the red and near-infrared spectral region. The band located in the range 650–850 nm with a maximum at about 780 nm indicates that all samples exhibit red luminescence irrespective of the molar ratio of glass-formers. The presence of this broad emission band confirms results from analysis of EPR spectra and proves that trivalent chromium ions are in octahedral sites [41]. It is interesting to see that the band is a result of overlapping two transitions of Cr3+ ions: allowed 4T2 → 4A2 and forbidden 2E → 4A2. The broad band corresponds to allowed transition, and it is attributed to the Cr3+ centers in low-field sites [42]. However, the narrow emission band corresponding 2E → 4A2 transition called R-line suggests that chromium ions are subjected to high-field sites [43]. The appearance of the two luminescence bands proves the existence of both octahedral sites. Therefore, some of the Cr3+ ions emit from the 4T2 level and some from the 2E level [44].
The shape of emission resulting from trivalent chromium ions occupying different sites was changed with molar ratio GeO2:B2O3. The intensity of R-line increases with decreasing concentration of glass-former GeO2 in studied systems. It was clearly observed for sample Cr5:1 with weak R-line and sample Cr1:5 with intense narrow emission band (Figure 4). The region 680–700 nm, where the R-line is situated, shows that the spectral lines are slightly shifted toward lower wavelengths with increasing B2O3 concentration. Simultaneously, the intensity of the broad band related to transition originating from excited level 4T2 to the ground level 4A2 of Cr3+ ions decreases with changing of glass-formers concentration. However, it is still the dominant emission for Cr3+ ions in studied systems. The blue shift of the maximum of this emission band was also stated (λmax = 773 nm and λmax = 753 nm for Cr59:1 and Cr1:5 sample, respectively). According to Narendrudu et al. [45] changing the intensity of transitions 4T2 → 4A2 and 2E → 4A2 of trivalent chromium ions can be related to the energy transfer between isolated Cr3+ centers and coupled Cr3+-Cr3+ pairs. Furthermore, Yang et al. [46] reported that the substitution of BaF2 in germanate glasses causes enhance broad emission attributed to the 4T2 → 4A2 transition of trivalent chromium ions. Our results indicate that luminescence emitted by Cr3+ ions in studied systems depends on glass composition. Especially, different glass-formers influence the shape and intensity of emission corresponding to transitions of Cr3+ ions. It can be concluded that low-field sites are occupied by the greater part of trivalent chromium ions in samples Cr59:1, Cr11:1, Cr5:1, and Cr2:1 than in glasses with higher B2O3 concentration. On the contrary, more Cr3+ ions are located in high-field sites in glass systems Cr1:2 and Cr1:5 than in samples with dominant content of GeO2 as glass-former.
Near-infrared spectra for glass samples with two glass-formers present one luminescence band in the 1000–1400 nm spectral region. Similar emission was observed for lithium, and lithium potassium borate systems and the broad registered band was assigned to transition from the 4T2 level to the 4A2 ground level of trivalent chromium ions [47]. Previously published results by Li et al. [48] indicate the luminescence centered at about 1030 nm corresponds to the 4T2 → 4A2 transition in tetrahedral sites of Cr3+ ions. For that reason, we can conclude that both emission bands with maxima at about 780 nm and 1070 nm are related to the same transition of trivalent chromium ions. However, red luminescence is attributed to Cr3+ ions in octahedral sites, and near-infrared emission corresponds to trivalent chromium ions in tetrahedral sites. The molar ratio GeO2:B2O3 influences the intensity of emission but significant differences in the shape of spectra were not observed.

3.2. Lanthanides—Eu3+

Next, we undertook the characterization of the optical properties for the obtained glass samples doped with europium ions by recording the excitation spectra shown in Figure 5. The excitation spectra were registered in the spectral range from 350 to 500 nm and monitored at 611 nm, the wavelength corresponding to the red emission of the 5D0 → 7F2 transition of Eu3+ ions.
The spectra show the occurrence of bands associated with typical 4f6–4f6 intra-configuration electronic transitions of trivalent europium ions, which can be attributed to individual transitions from the ground state 7F0 to higher excited states of Eu3+ ions [49]. In the analyzed spectral range, bands centered at 363 nm (7F0 → 5D4), 383 nm (7F0 → 5L7), 396 nm (7F0 → 5L6), 415 nm (7F0 → 5D3), and 466 nm (7F0 → 5D2), were recorded. Preliminary observations of the excitation spectra clearly demonstrated that the intensity of individual bands depends on the molar ratio GeO2:B2O3. By considering the three glass samples Eu1:5, Eu5:1, and Eu59:1, it was concluded that increasing the germanium dioxide content contributes to a gradual increase of the intensity. However, among registered excitation bands, the most intense correspond to 7F0 → 5L6 (396 nm) and 7F0 → 5D2 (466 nm) transitions of trivalent europium ions, regardless of the molar ratio GeO2:B2O3. According to the results obtained for glasses based on germanium dioxide, the intensity ratio of these excitation bands significantly depends on the glass composition. Ramesh et al. [50] showed that in germanate glasses with PbO the bands related to 7F0 → 5L6 and 7F0 → 5D2 transitions of Eu3+ ions are equally intense. On the other hand, for the same glass systems where PbO was replaced by Bi2O3, the intensity of the band located at 464 nm (7F0 → 5D2) is two times stronger than that centered at 393 nm (7F0 → 5L6). Obtained results indicate that the intensity of the excitation bands attributed to 7F0 → 5L6 and 7F0 → 5D2 transitions of Eu3+ ions is similar for system Eu59:1. In contrast, the increase of concentration of boron trioxide causes the decreasing intensity of the band corresponding to the 7F0 → 5D2 transition. Additionally, as a function of the concentration of the glass-formers, any spectral shifts were not observed. It is well known that the sharp excitation wavelength gives the intense emission. Hence, bands related to the 7F0 → 5L6 and 7F0 → 5D2 transitions suggest a potential for effective optical excitation of amorphous materials containing Eu3+ ions. For this reason, we chose a wavelength λexc = 396 nm in the luminescence investigations, to demonstrate the suitability of the obtained glasses for lighting applications.
The main role analysis of emission and functional properties of the glasses doped with lanthanides ions is the characterization of the emitted radiation, which results from the electron transitions of Ln3+ ions [51]. Noticeably, the most significant point of the studies of systems containing trivalent europium ions is to obtain efficient red emission. It is known that the excitation energy of the Eu3+ ions is transferred non-radiatively from excited levels 5L6, 5D3, 5D2, and 5D1 to the energy level 5D0. Then the energy transfers back to the ground state causing characteristic visible emissions corresponding to the 5D0 → 7FJ transitions (where J = 0–6) of Eu3+ ions [52,53,54]. The emission spectra in the visible range under xenon lamp excitation for the obtained glasses were recorded and five well-separated bands were observed. According to the energy level scheme of Eu3+ ions, the registered emission bands presented in Figure 6 correspond to the transitions from the excited level 5D0 to the lower-lying levels 7F0, 7F1, 7F2, 7F3, and 7F4 were assigned using the references [55,56]. The presented spectra demonstrate that the intensity of the luminescence band at 611 nm attributed to the red emission of europium ions increases two times when the molar ratio GeO2:B2O3 increases in the direction from 1:5 to 5:1.
As is generally known, the presence of all emission bands depends on the local centrosymmetry of Eu3+ ions in the studied glasses [57]. If trivalent europium ions in glass hosts are in a higher asymmetrical environment, the band related to transition 5D0 → 7F0 could be recorded [58]. Moreover, the emission transitions 5D0 → 7F1 and 5D0 → 7F2, 5D0 → 7F4 are allowed by magnetic and electric dipole interactions, respectively. It should be emphasized here that Eu3+ ions in the literature represent an attractive active dopant because, in addition to very efficient emission, they play an important role as a sensitive spectroscopic probe [59,60]. Two spectral ranges are relevant from this point of view.
The first range (580–600 nm) includes the band corresponding to the 5D0 → 7F1 transition, and this transition follows the selection rule ∆J = 1. However, the second range (602–636 nm) contains a band associated with the 5D0 → 7F2 transition defined as a “hypersensitive” transition because the local environment strongly influences it and this transition of Eu3+ ions follows the selection rule ∆J = 2. Similar to the excitation spectra, the concentration of germanium dioxide is a critical factor determining the intensity of the narrow emission band associated with the 5D0 → 7F2 transition. This indicates that its intensity depends on the distortion (asymmetry) of the Eu3+ coordination polyhedron. The intensity of the band corresponding to the 5D0 → 7F1 transition is usually independent of the environment of the Eu3+ centers, which is also confirmed by the recorded emission spectra. For this reason, these transitions are fundamental in the analysis of the asymmetric ratio R/O = I(5D0 → 7F2)/I(5D0 → 7F1). Considering the spectral range of these two transitions, the parameter R/O is also called the red-to-orange fluorescence intensity ratio of Eu3+ ions. In agreement with the literature, an appropriate selection of the oxides in glass compositions can influence the value of red-to-orange fluorescence intensity ratio of Eu3+ ions (Table 3). The reported results inform us about the local structure around the trivalent europium ions and the covalence degree of the Eu3+-O2− bond. The low value of the R/O ratio is usually attributed to the higher symmetry of the local environment around the Eu3+ ions. In contrast, an increase of the R/O value is due to an increase in the asymmetry of the local environment around the dopant ions [61,62]. The results of the conducted experiment showed an interesting correlation, which is shown in Figure 7a and Table 4.
The R/O ratio of the prepared systems with two glass-formers was found to have a minimum of 3.08 for the glass sample containing the predominant concentration of B2O3 (Eu1:5). Interestingly, as a function of increasing germanium dioxide concentration, the value of R/O parameter is a maximum of 3.63. Therefore, the local symmetry around the Eu3+ ions and ionic character of Eu3+-O2− bond increases with the change in the molar ratio GeO2:B2O3 (from Eu59:1 to Eu1:5). The observed differences in the local environment around trivalent europium ions are due to the quantitative relationship of the two different glass-former oxides, which act as a more network-former or network-modifier component depending on the concentration.
Based on luminescence decay curves of the 5D0 level of Eu3+ ions in glass systems with two glass-formers GeO2 and B2O3, the luminescence lifetimes were determined. Another notable observation of the consequence of the change in the molar ratio (GeO2:B2O3) is schematized in Figure 7b and Table 4. In the studied glasses, the luminescence lifetime from upper excitation state 5D0 of trivalent europium increased in the direction from 1.25 ms to 1.68 ms for samples Eu59:1 and Eu1:5, respectively.
Analyzing the composition of obtained glass systems doped with Eu3+ ions, it can be stated that due to a higher concentration of boron trioxide, the lifetime for the 5D0 level is getting longer. Venkatramu et al. [71] reported that the decrease in the luminescence lifetime of the 5D0 in borate glasses is attributed to the electronegativities of the modifying oxide metals. Simultaneously, in the case of our study, the value of electronegativity Ge and B are comparable, therefore this factor does not significantly affect the luminescence lifetime. It was found that the observed decreasing tendency of a lifetime of the 5D0 level of Eu3+ ions is the effect of the phonon energy of the glassy matrix. From the literature data it is experimentally proved that when the phonon energy of the matrix is higher, there is a higher probability of non-radiative relaxation multiphonon processes, which may result in a reduction of luminescence lifetime for lanthanide ions [72]. A completely opposite relationship was observed, although systems with B2O3 as glass-former have higher phonon energy than glasses with GeO2. In this case, radiative relaxation from the excited levels of trivalent europium ions is dominant due to the very large energy gap between the 5D0 and 7F6 energy states of Eu3+ ions (ΔE = 12,500 cm−1). Consequently, more phonons are required for non-radiative relaxation multiphonon processes in studied systems with glass-former GeO2 than samples with B2O3. Previous experimental results proved this phenomenon because low-phonon germanate glasses doped with Eu3+ ions indicated relatively low luminescence lifetime values, 1.43 ms [73], 1.22 ms [74]. It is worth noting that the same parameter determined for high-phonon borate glasses was evaluated at 2.57 ms [75], 2.25 ms [76]. Moreover, the variations in the spectroscopic parameters—the decrease in the R/O ratio and the increase in the lifetimes with increasing B2O3 and GeO2—correlate with the changes in the intensity of the emission bands. The obtained results confirmed the research question of the authors’ investigations and indicated the critical role of glass-former in spectroscopic properties of systems that may find potential use as optical materials.

4. Conclusions

In the present work, GeO2-B2O3-BaO-Ga2O3 glass systems singly doped with transition metals (Cr3+) and lanthanides (Eu3+) were prepared by high-temperature melt-quenching method. The proposed modification of the concentration of the two main glass-formers components provided the following conclusions:
  • Analysis of EPR spectra indicates that the trivalent chromium ions at octahedral sites are present in the glass network. Independently of the molar ratio of different glass-formers, red luminescence was observed for systems doped with Cr3+ ions in octahedral sites. The influence of changing concentration glass-formers on the intensity of R-line attributed to Cr3+ ions in high-field sites was proved. It was stated that the emission bands with maxima at about 780 nm and 1070 nm are related to the same transition (4T2 → 4A2) of trivalent chromium ions in octahedral and tetrahedral sites, respectively.
  • Confirmation that the type of glass-formers has a significant contribution to the properties of amorphous materials is presented by the results of spectroscopic studies conducted for glass samples doped which Eu3+ ions. Detailed spectroscopic analysis of the emission spectra showed a gradual quenching of the luminescence as a function of boron oxide concentration. The obtained values of the ratio R indicate a more covalent nature of the bond between the lanthanide ions and the surrounding ligands for samples with a higher concentration of germanium dioxide. On the other hand, the increase in boron oxide concentration results in an increase in the values of luminescence lifetimes of 5D0 level of Eu3+ ions.
In summary, the results presented in this manuscript demonstrate that spectroscopic properties of systems doped with transition metal and lanthanides ions should be controlled by the choice of glass-formers. The developed oxide glasses emit efficient radiation in the visible and near-infrared range. From the application point of view, the prepared glasses can be classified as interesting and useful optical materials for potential application in the field of photonics.

Author Contributions

Conceptualization, W.A.P.; methodology, J.P. (Joanna Pisarska) and W.A.P.; formal analysis, K.K., M.K. and W.A.P.; investigation, K.K., M.K. and J.P. (Justyna Polak); writing—original draft preparation, K.K. and M.K.; writing—review and editing, W.A.P.; visualization, K.K. and M.K. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

Publication co-financed by the funds granted under the Research Excellence Initiative of the University of Silesia in Katowice.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Pascuta, P.; Stefan, R.; Olar, L.E.; Bolundut, L.C.; Culea, E. Effects of Copper Metallic Nanoparticles on Structural and Optical Properties of Antimony Phosphate Glasses Co-Doped with Samarium Ions. Materials 2020, 13, 5040. [Google Scholar] [CrossRef]
  2. Hongisto, M.; Veber, A.; Petit, Y.; Cardinal, T.; Danto, S.; Jubera, V.; Petit, L. Radiation-Induced Defects and Effects in Germanate and Tellurite Glasses. Materials 2020, 13, 3846. [Google Scholar] [CrossRef]
  3. Østergaard, M.B.; Bødker, M.S.; Smedskjaer, M.M. Structure Dependence of Poisson’s Ratio in Cesium Silicate and Borate Glasses. Materials 2020, 13, 2837. [Google Scholar] [CrossRef]
  4. Wang, X.; Sakakura, M.; Liu, Y.; Qiu, J.; Shimotsuma, Y.; Hirao, K.; Miura, K. Modification of long range order in germanate glass by ultra fast laser. Chem. Phys. Lett. 2011, 511, 266–269. [Google Scholar] [CrossRef] [Green Version]
  5. Zanotto, E.D.; Mauro, J.C. The glassy state of matter: Its definition and ultimate fate. J. Non-Cryst. Solids 2017, 471, 490–495. [Google Scholar] [CrossRef]
  6. Zachariasen, W.H. The atomic arrangement in glass. J. Am. Chem. Soc. 1932, 54, 3841–3851. [Google Scholar] [CrossRef]
  7. Laksminarayana, G.; Meza-Rocha, A.N.; Soriano-Romeo, O.; Huerta, E.F.; Caldino, U.; Lira, A.; Lee, D.-E.; Yoon, J.; Park, T. Analysis of fluorescence characteristics of Sm3+-doped B2O3-rich glasses for Orange-light-emitting diodes. J. Alloys Compd. 2021, 884, 161076. [Google Scholar] [CrossRef]
  8. Fan, X.; Zhang, W.; Lu, F.; Sui, Y.; Wang, J.; Xu, Z. Research of Fluorescent Properties of a New Type of Phosphor with Mn2+-Doped Ca2SiO4. Sensors 2021, 21, 2788. [Google Scholar] [CrossRef]
  9. Tanabe, S. Rare-earth-doped glasses for fiber amplifiers in broadband telecommunication. Comptes Rendus Chim. 2002, 5, 815–824. [Google Scholar] [CrossRef]
  10. Zaini, N.A.; Mohamed, S.N.; Mohamed, Z. Effects of Vanadium on the Structural and Optical Properties of Borate Glasses Containing Er3+ and Silver Nanoparticles. Materials 2021, 14, 3710. [Google Scholar] [CrossRef]
  11. Veselský, K.; Lahti, V.; Petit, L.; Prajzler, V.; Šulc, J.; Jelínková, H. Influence of Y2O3 Content on Structural, Optical, Spectroscopic, and Laser Properties of Er3+, Yb3+ Co-Doped Phosphate Glasses. Materials 2021, 14, 4041. [Google Scholar] [CrossRef] [PubMed]
  12. Santos Barbosa, J.; Batista, G.; Danto, S.; Fargin, E.; Cardinal, T.; Poirier, G.; Castro Cassanjes, F. Transparent Glasses and Glass-Ceramics in the Ternary System TeO2-Nb2O5-PbF2. Materials 2021, 14, 317. [Google Scholar] [CrossRef] [PubMed]
  13. Yue, Y.; Shao, C.; Kang, S.; Wang, F.; Wang, X.; Ren, J.; He, D.; Chen, W.; Hu, L. Investigation of luminescence mechanism of Nd3+-doped calcium aluminate glasses: Effect of glass-formers. J. Non-Cryst. Solids 2019, 505, 333–339. [Google Scholar] [CrossRef]
  14. Kuusela, L.; Veber, A.; Boetti, N.G.; Petit, L. Impact of ZnO Addition on Er3+ Near-Infrared Emission, the Formation of Ag Nanoparticles, and the Crystallization of Sodium Fluorophosphate Glass. Materials 2020, 13, 527. [Google Scholar] [CrossRef] [Green Version]
  15. Liu, R.; Chen, M.; Zhu, X.; Zhu, Y.; Zeng, F.; Su, Z. Luminescent properties and structure of Dy3+ doped germanosilicate glass. J. Lumin. 2020, 226, 117378. [Google Scholar] [CrossRef]
  16. Jiao, Q.; Li, G.; Zhou, D.; Qiu, J. Effect of the Glass Structure on Emission of Rare-Earth-Doped Borate Glass. J. Am. Ceram. Soc. 2015, 98, 4102–4106. [Google Scholar] [CrossRef]
  17. Herrmann, A.; Kuhn, S.; Tiegel, M.; Russel, C. Fluorescence properties of Eu3+-doped alumino silicate glasses. Opt. Mater. 2014, 37, 293–297. [Google Scholar] [CrossRef]
  18. Linganna, K.; Narro-Garcia, R.; Desirens, H.; De la Rosa, E.; Basavapoornima, C.; Venkatramu, V.; Jayasankar, C.K. Effect of P2O5 addition on structural and luminescence properties of Nd3+-doped tellurite glasses. J. Alloys Compd. 2016, 684, 322–327. [Google Scholar] [CrossRef]
  19. Marzouk, M.A. Optical characterization of some rare earth ions doped bismuth borate glasses and effect of gamma irradiation. J. Mol. Struct. 2012, 1019, 80–90. [Google Scholar] [CrossRef]
  20. Divina, R.; Evangelin Teresa, P.; Marimuthu, K. Dy3+ ion as optical probe to study the luminescence behavior of Alkali lead bismuth borate glasses for w-LED application. J. Alloys Compd. 2021, 883, 160845. [Google Scholar] [CrossRef]
  21. Djamal, M.; Yuliantini, L.; Hidayat, R.; Rauf, N.; Horprathum, M.; Rajaramakrishna, R.; Boonin, K.; Yasaka, P.; Kaewkhao, J.; Venkatramu, V.; et al. Spectroscopic study of Nd3+ ion-doped Zn-Al-Ba borate glasses for NIR emitting device applications. Opt. Mater. 2020, 107, 110018. [Google Scholar] [CrossRef]
  22. Pisarska, J.; Pisarski, W.A.; Lisiecki, R.; Ryba-Romanowski, W. Phonon Sideband Analysis and Near-Infrared Emission in Heavy Metal Oxide Glasses. Materials 2021, 14, 121. [Google Scholar] [CrossRef] [PubMed]
  23. Pipes, R.S.; Shelby, J.E. Formation and properties of soda lime germanate glasses. J. Non-Cryst. Solids 2021, 553, 120506. [Google Scholar] [CrossRef]
  24. Koroleva, O.N.; Shtenberg, M.V.; Ivanova, T.N. The structure of potassium germanate glasses as revealed by Raman and IR spectroscopy. J. Non-Cryst. Solids 2010, 510, 143–150. [Google Scholar] [CrossRef]
  25. Żmojda, J.; Kochanowicz, M.; Miluski, P.; Golonko, P.; Baranowska, A.; Ragiń, T.; Dorosz, J.; Kuwik, M.; Pisarski, W.; Pisarska, J.; et al. Luminescent Studies on Germanate Glasses Doped with Europium Ions for Photonics Applications. Materials 2020, 13, 2817. [Google Scholar] [CrossRef]
  26. Pisarski, W.A.; Kowalska, K.; Kuwik, M.; Polak, J.; Pietrasik, E.; Goryczka, T.; Pisarska, J. Novel Multicomponent Titanate-Germanate Glasses: Synthesis, Structure, Properties, Transition Metal, and Rare Earth Doping. Materials 2020, 13, 4422. [Google Scholar] [CrossRef]
  27. Tanaka, M.; Kushida, T. Studies of the vibronic interaction between Eu3+ ions and glass-forming units in oxide glasses. Chem. Phys. Lett. 1999, 315, 428–432. [Google Scholar] [CrossRef]
  28. Rolli, R.; Camagni, P.; Samoggia, G.; Speghini, A.; Wachtler, M.; Bettinelli, M. Fluorescence line narrowing spectroscopy of a lead germanate glass doped with Eu3+. Spectrochim. Acta Part A 1998, 54, 2157–2162. [Google Scholar] [CrossRef]
  29. Hanyes, W.M. CRC Handbook of Chemistry and Physics, 93rd ed.; CRC Press: Boca Raton, FL, USA, 2004; pp. 4–13. [Google Scholar]
  30. Binnemans, K. Interpretation of europium (III) spectra. Coord. Chem. Rev. 2015, 295, 1–45. [Google Scholar] [CrossRef] [Green Version]
  31. Fujihara, S.; Shibata, Y. Luminescence of Cr3+ ions associated with surpassing the green-emissive defect centers in B-Ga2O3. J. Lumin. 2006, 121, 470–474. [Google Scholar] [CrossRef]
  32. Rasheed, F.; O’Donnell, K.P.; Henderson, B.; Hollis, D.B. Disorder and the optical spectroscopy of Cr3+-doped glasses: I. Silicate glasses. J. Phys. Condens. Matter 1991, 3, 1915–1930. [Google Scholar] [CrossRef]
  33. Rossi, F.; Montagna, M.; Ferrari, M.; Capobianco, J.A.; Bettinelli, M. Line width measurements of Cr3+ in a zinc borate glass. J. Non-Cryst. Solids 1998, 240, 232–236. [Google Scholar] [CrossRef]
  34. Samdani, M.; Ramadevudu, G.; Narasimha Chary, M.; Shareefuddin, M. EPR, optical and physical studies on Cr3+ doped MgO-BaO-B2O3-TeO2 glasses. St. Petersburg Polytech. Univ. J. Phys. Math. 2017, 3, 299–307. [Google Scholar]
  35. Costa, V.C.; Lameiras, F.S.; Pinheiro, M.V.B.; Sousa, D.F.; Nunes, L.A.O.; Shen, Y.R.; Bray, K.L. Laser spectroscopy and electron paramagnetic resonance of Cr3+ doped silicate glasses. J. Non-Cryst. Solids 2000, 273, 209–214. [Google Scholar] [CrossRef]
  36. Samdani; Ramadevudu, G.; Narasimha Chary, M.; Shareefuddin, M. Physical and spectroscopic studies of Cr3+ doped mixed alkaline earth oxide borate glasses. Mater. Chem. Phys. 2017, 186, 382–389. [Google Scholar] [CrossRef]
  37. Santhan Kumar, J.; Lakshmi Kumari, J.; Subba Rao, M.; Cole, S. EPR, optical and physical properties of chromium ions in CdO-SrO-B2O3-SiO2 (CdSBSi) glasses. Opt. Mater. 2013, 35, 1320–1326. [Google Scholar] [CrossRef]
  38. Bala Murali Krishna, S.; Vinaya Teja, P.M.; Krishna Rao, D. Role of chromium ion valence states in ZnO-As2O3-Sb2O3 glass system by means of spectroscopic and dielectric studies. Mater. Res. Bull. 2010, 45, 1783–1791. [Google Scholar] [CrossRef]
  39. Kesavulu, C.R.; Chakradhar, R.P.S.; Muralidhara, R.S.; Rao, J.L.; Anavekar, R.V. EPR, optical absorption and photoluminescence properties of Cr3+ ions in lithium borophosphate glasses. J. Alloys Compd. 2010, 496, 75–80. [Google Scholar] [CrossRef]
  40. Babkina, A.; Valiev, D.; Zyryanova, K.; Nuryev, R.; Ignatiev, A.; Kulpina, E.; Kuzmenko, N.; Osipova, A.; Koroleva, A.; Platonova, N. Spectroscopic properties of chromium/antimony co-doped alkali-alumina-borate glass-ceramics. Opt. Mater. 2020, 106, 109983. [Google Scholar] [CrossRef]
  41. Kiran, N.; Kesavulu, C.R.; Suresh Kumar, A.; Rao, J.L. Spectral studies on Cr3+ ions doped in sodium-lead borophosphate glasses. Phys. B 2011, 406, 1897–1901. [Google Scholar] [CrossRef]
  42. Wen, H.; Xie, S.; Cui, J.; Mao, S.; Luo, L.; Brik, M.G. Optical properties of 3d transition metal ion-doped aluminophosphate glasses. J. Lumin. 2019, 213, 263–272. [Google Scholar] [CrossRef]
  43. Saad, N.; Haouari, M.; Bulou, A.; HadiKassiba, A.; Ben Ouada, H. Structural and optical properties of Cr3+ embedded in a P2O5-B2O3-ZnO-BaF2-AlF3 fluoroborophosphate glasses. Mater. Chem. Phys. 2018, 212, 461–470. [Google Scholar] [CrossRef]
  44. Rodríguez-Mendoza, U.R.; Speghini, A.; Jaque, D.; Zambelli, M.; Bettinelli, M. Optical properties of single doped Cr3+ and co-doped Cr3+-Nd3+ aluminum tantalum tellurite glasses. J. Alloys Compd. 2004, 380, 163–166. [Google Scholar] [CrossRef]
  45. Narendrudu, T.; Suresh, S.; Chinna Ram, G.; Veeraiah, N.; Krishna Rao, D. Spectroscopic and structural properties of Cr3+ ions in lead niobium germanosilicate glasses. J. Lumin. 2017, 183, 17–25. [Google Scholar] [CrossRef]
  46. Yang, X.I.; Wang, W.C.; Zhang, Q.Y. BaF2 modified Cr3+/Ho3+ co-doped germanate glass for efficient 2.0 μm fiber lasers. J. Non-Cryst. Solids 2018, 482, 147–153. [Google Scholar] [CrossRef]
  47. Mikulski, J.; Koepke, C.; Wiśniewski, K.; Padlyak, B.V.; Adamiv, V.T.; Burak, Y.V. Excited state characteristics of the Li2B4O7 and KLiB4O7 glasses active by Cr3+ ions. Opt. Mater. 2014, 38, 24–27. [Google Scholar] [CrossRef]
  48. Li, Y.; Ye, S.; Zhang, Q. Ultra-broadband near-infrared luminescence of ordered-disordered multi-sited Cr3+ in La3Ga5.5Nb0.5O14:Cr3+. J. Mater. Chem. C 2014, 2, 4636–4641. [Google Scholar] [CrossRef]
  49. Babu, P.; Jayasankar, C.K. Optical spectroscopy of Eu3+ ions in lithium borate and lithium fluoroborate glasses. Phys. B 2000, 279, 262–281. [Google Scholar] [CrossRef]
  50. Ramesh, P.; Hegde, V.; Pramod, A.G.; Eraiah, B.; Agarkov, D.A.; Eliseeva, G.M.; Pandey, M.K.; Annapurna, K.; Jagannath, G.; Kokila, M.K. Compositional dependence of red photoluminescence of Eu3+ ions in lead and bismuth containing borate glasses. Solid State Sci. 2020, 107, 106360. [Google Scholar] [CrossRef]
  51. Fabian, M.; Pinakidou, F.; Tolnai, I.; Czompoly, O.; Osan, J. Lanthanide (Ce, Nd, Eu) environments and leaching behavior in borosilicate glasses. Sci. Rep. 2021, 11, 13272. [Google Scholar] [CrossRef]
  52. Wang, B.; Li, D.S.; Shen, L.F.; Pun, E.Y.B.; Lin, H. Eu3+ doped high-brightness fluorophosphate laser-driven glass phosphors. Opt. Mater. Exp. 2019, 9, 1749–1762. [Google Scholar] [CrossRef]
  53. Mahato, K.K.; Rai, S.B.; Rai, A. Optical studies of Eu3+ doped oxyfluoroborate glass. Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 2004, 60, 979–985. [Google Scholar] [CrossRef]
  54. Rodriguez, V.D.; Lavin, V.; Rodriquez-Mendoza, U.R.; Martin, I.R. Spectroscopy of rare earth ions in fluoride glasses for laser applications. Opt. Mater. 1999, 13, 1–7. [Google Scholar] [CrossRef]
  55. Han, L.; Zhang, Q.; Song, J.; Xiao, Z.; Qiang, Y.; Ye, X.; You, W.; Lu, A. A novel Eu3+-doped phosphate glass for reddish orange emission: Preparation, structure and fluorescence properties. J. Lumin. 2020, 221, 117041. [Google Scholar] [CrossRef]
  56. Aryal, P.; Kim, H.J.; Khan, A.; Saha, S.; Kang, S.J.; Kothan, S.; Yamsuk, Y.; Kaewkhao, J. Development of Eu3+-doped phosphate glass. For luminescent solid-state optical devices. J. Lumin. 2020, 227, 117564. [Google Scholar] [CrossRef]
  57. Chen, M.; Liu, R.; Wang, D.; Zhou, Y.; Zeng, F.; Su, Z. Luminescent properties of Eu3+ doped germanosilicate red glass. J. Non-Cryst. Solids 2021, 566, 120895. [Google Scholar] [CrossRef]
  58. Balda, R.; Fernandez, J.; Duhamel, N.; Adam, J.L.; Imbusch, G.F. Site-selection spectroscopy and energy transfer studies of Eu3+ ions in a new fluorophosphate glass. J. Lumin. 1995, 66–67, 290–293. [Google Scholar] [CrossRef]
  59. Cascales, C.; Balda, R.; Gercia-Revilla, S.; Lezama, L.; Barredo-Zuriarrain, M.; Fernandez, J. Site symmetry and host-sensitization-dependence of Eu3+ real time luminescence in tin dioxide nanoparticles. Opt. Exp. 2018, 26, 16155–16170. [Google Scholar] [CrossRef] [Green Version]
  60. Wen, H.; Jia, G.; Duan, C.K.; Tanner, P.A. Understanding Eu3+ emission spectra in glass. Phys. Chem. Chem. Phys. 2010, 12, 9933–9937. [Google Scholar] [CrossRef]
  61. De, M.; Jana, S. Optical characterization of Eu3+ doped titanium barium lead phosphate glass. Optik 2020, 215, 164718. [Google Scholar] [CrossRef]
  62. Mariselvam, K.; Arun Kumar, R.; Karthik, S. Optical and luminescence characteristics of europium doped barium lithium fluoroborate glasses. Chem. Phys. 2019, 525, 110379. [Google Scholar] [CrossRef]
  63. Oomen, E.W.J.L.; van Dongen, A.M.A. Europium (III) in oxide glasses: Dependence of the emission spectrum upon glass composition. J. Non-Cryst. Solids 1989, 111, 205–213. [Google Scholar] [CrossRef]
  64. Reisfeld, R.; Boehm, L.; Ish-Shalom, M.; Fischer, R. 4f yields 4f transitions and charge transfer spectra of Eu3+, 4f yields 5d spectra of Tb3+, and 1S0 yields 3P1 spectra of Pb2+ in alkaline earth metaphosphate glasses. Phys. Chem. Glasses 1974, 15, 76. [Google Scholar]
  65. Gokce, M.; Senturk, U.; Uslu, D.K.; Burgaz, G.; Sahin, Y.; Gokce, A.G. Investigation of europium concentration dependence on the luminescent dependence on the luminescent properties of borogermanate glasses. J. Lumin. 2017, 192, 263–268. [Google Scholar] [CrossRef]
  66. Zmoja, J.; Kochanowicz, M.; Miluski, P.; Baranowska, A.; Pisarski, W.A.; Pisarska, J.; Jadach, R.; Sitarz, M.; Dorosz, D. Structural and optical properties of antimony-germanate-borate glass and glass fiber co-doped Eu3+ and Ag nanoparticles. Spectrochim. Acta A Mol. Biomol. Spectrosc. 2018, 201, 1–7. [Google Scholar] [CrossRef]
  67. Sołtys, M.; Janek, J.; Zur, L.; Pisarska, J.; Pisarski, W.A. Compositional-dependent europium-doped lead phosphate glasses and their spectroscopic properties. Opt. Mater. 2015, 40, 91–96. [Google Scholar] [CrossRef]
  68. Kesavulu, C.R.; Kumar, K.K.; Vijaya, N.; Lim, K.S.; Jayasankar, C.K. Thermal vibration and optical properties of Eu3+-doped lead fluorophosphate glasses for red laser applications. Mater. Chem. Phys. 2013, 141, 903–911. [Google Scholar] [CrossRef]
  69. Deopa, N.; Kaur, S.; Prasad, A.; Joshi, B.; Rao, A.S. Spectral studies of Eu3+ doped lithium lead alumino borate glasses for visible photonic applications. Opt. Laser Technol. 2018, 108, 434–440. [Google Scholar] [CrossRef]
  70. Szal, R.; Zmoja, J.; Kochanowicz, M.; Miluski, P.; Dorosz, J.; Lesniak, M.; Jeleń, P.; Starzyk, B.; Sitarz, M.; Kuwik, M.; et al. Spectroscopic properties of antimony modified germanate glass doped with Eu3+ ions. Ceram. Int. 2019, 45, 24811–24817. [Google Scholar] [CrossRef]
  71. Venkatramu, V.; Babu, P.; Jayasankar, C.K. Fluorescence properties of Eu3+ ions doped borate and fluoroborate glasses containing lithium, zinc and lead. Spectrochim. Acta A Mol. Biomol. Spectrosc. 2006, 63, 276–281. [Google Scholar] [CrossRef]
  72. Shojiya, M.; Kawamoto, Y. Judd-Ofelt parameters and multiphonon relaxation of Ho3+ ions in ZnCl2-based glass. J. Appl. Phys. 2001, 89, 4944–4950. [Google Scholar] [CrossRef]
  73. Wang, X.; Huang, L.; Zhao, S.; Xu, S. Eu3+ doped heavy germanate scintillating glasses. J. Lumin. 2018, 196, 256–258. [Google Scholar] [CrossRef]
  74. Zur, L.; Janek, J.; Pietrasik, E.; Sołtys, M.; Pisarska, J.; Pisarski, W.A. Influence of Mo/MF2 modifiers (M = Ca, Sr, Ba) on spectroscopic properties of Eu3+ ions in germanate and borate glasses. Opt. Mater. 2016, 61, 59–63. [Google Scholar] [CrossRef]
  75. Vijayalakshmi, L.; Kumar, K.N.; Hwang, P. Dazzling red luminescence dynamics of Eu3+ doped lithium borate glasses for photonic applications. Optic 2019, 193, 163019. [Google Scholar] [CrossRef]
  76. Yao, L.; Chen, G.; Cui, S.; Zhong, H.; Wen, C. Fluorescence and optical properties of Eu3+-doped borate glasses. J. Non-Cryst. Solids 2016, 444, 38–42. [Google Scholar] [CrossRef]
Materials 14 07156 g001 550
Figure 1. Electron paramagnetic resonance spectra of Cr3+ ions doped glass samples with different concentrations of glass-former components (GeO2 and B2O3).
Figure 1. Electron paramagnetic resonance spectra of Cr3+ ions doped glass samples with different concentrations of glass-former components (GeO2 and B2O3).
Materials 14 07156 g001
Materials 14 07156 g002 550
Figure 2. Excitation spectra of Cr3+ ions doped glass samples with different concentrations of glass-former components (GeO2 and B2O3) monitored at 780 nm.
Figure 2. Excitation spectra of Cr3+ ions doped glass samples with different concentrations of glass-former components (GeO2 and B2O3) monitored at 780 nm.
Materials 14 07156 g002
Materials 14 07156 g003 550
Figure 3. Emission spectra of Cr3+ ions doped glass samples (Cr59:1, Cr11:1, Cr5:1) with different concentrations of glass-former components (GeO2 and B2O3). Insets show an enlargement of the emission spectrum corresponding to the R-line and a photographic image of a glass sample doped with Cr3+ ions.
Figure 3. Emission spectra of Cr3+ ions doped glass samples (Cr59:1, Cr11:1, Cr5:1) with different concentrations of glass-former components (GeO2 and B2O3). Insets show an enlargement of the emission spectrum corresponding to the R-line and a photographic image of a glass sample doped with Cr3+ ions.
Materials 14 07156 g003
Materials 14 07156 g004 550
Figure 4. Emission spectra of Cr3+ ions doped glass samples (Cr5:1, Cr2:1, Cr1:1, Cr1:2, Cr1:5) with different concentrations of glass-former components (GeO2 and B2O3). The inset is an enlargement of the emission spectrum corresponding to the R-line of Cr3+ ions.
Figure 4. Emission spectra of Cr3+ ions doped glass samples (Cr5:1, Cr2:1, Cr1:1, Cr1:2, Cr1:5) with different concentrations of glass-former components (GeO2 and B2O3). The inset is an enlargement of the emission spectrum corresponding to the R-line of Cr3+ ions.
Materials 14 07156 g004
Materials 14 07156 g005 550
Figure 5. Excitation spectra of Eu3+ ions doped glass samples with different concentrations of glass-former components (GeO2 and B2O3) monitored at 611 nm. Insets show the energy level diagram of trivalent europium ions and a photographic image of a glass sample doped with Eu3+ ions.
Figure 5. Excitation spectra of Eu3+ ions doped glass samples with different concentrations of glass-former components (GeO2 and B2O3) monitored at 611 nm. Insets show the energy level diagram of trivalent europium ions and a photographic image of a glass sample doped with Eu3+ ions.
Materials 14 07156 g005
Materials 14 07156 g006 550
Figure 6. Emission spectra of Eu3+ ions doped glass samples with different concentrations of glass-former components (GeO2 and B2O3). Insets present the emission transitions from the excited 5D0 level of lanthanide ions (Eu3+) and photographic image of glass sample under excitation of 396 nm.
Figure 6. Emission spectra of Eu3+ ions doped glass samples with different concentrations of glass-former components (GeO2 and B2O3). Insets present the emission transitions from the excited 5D0 level of lanthanide ions (Eu3+) and photographic image of glass sample under excitation of 396 nm.
Materials 14 07156 g006
Materials 14 07156 g007 550
Figure 7. (a) Asymmetric ratio and (b) luminescence lifetime of obtained glass samples doped with trivalent europium ions containing extremely different glass-formers concentrations.
Figure 7. (a) Asymmetric ratio and (b) luminescence lifetime of obtained glass samples doped with trivalent europium ions containing extremely different glass-formers concentrations.
Materials 14 07156 g007
Table
Table 1. Chemical compositions (mol%) of glass samples doped with transition metal (Cr3+) ions.
Table 1. Chemical compositions (mol%) of glass samples doped with transition metal (Cr3+) ions.
Sample
Code		GeO2B2O3BaOGa2O3Cr2O3
Cr59:1591309.750.25
Cr11:1555309.750.25
Cr5:15010309.750.25
Cr2:14020309.750.25
Cr1:13030309.750.25
Cr1:22040309.750.25
Cr1:51050309.750.25
Table
Table 2. Chemical compositions (mol%) of glass samples doped with lanthanides (Eu3+) ions.
Table 2. Chemical compositions (mol%) of glass samples doped with lanthanides (Eu3+) ions.
Sample
Code		GeO2B2O3BaOGa2O3Eu2O3
Eu59:1591309.750.25
Eu11:1555309.750.25
Eu5:15010309.750.25
Eu2:14020309.750.25
Eu1:13030309.750.25
Eu1:22040309.750.25
Eu1:51050309.750.25
Table
Table 3. R/O-ratio values in various glass matrices.
Table 3. R/O-ratio values in various glass matrices.
Glass Composition [mol%]R/OReferences
10GeO2-50B2O3-30BaO-9.75Ga2O3-0.25Eu2O33.08Present work
59GeO2-1B2O3-30BaO-9.75Ga2O3-0.25Eu2O33.63Present work
89.5B2O3-10Li2O-0.5Eu2O32.41[63]
0.5GeO2-63.5SiO2-16K2O-16BaO-4Eu2O33.46[63]
84.5GeO2-12.5K2O-3Eu2O34.60[63]
49.5BaO-49.5P2O5-1Eu2O35.28[64]
30B2O3-40GeO2-29Gd2O3-1Eu2O33.54[65]
25Sb2O3-25GeO2-29.2B2O3-5Al2O3-10Na2O-0.6AgNO3-0.2Eu2O32.75[66]
45P2O5-45PbO-9Ga2O3-1Eu2O31.70[67]
44P2O5-17K2O-9Al2O3-23PbF2-6Na2O-1Eu2O32.36[68]
10Li2O-10PbO-7Al2O3-70B2O3-3Eu2O32.02[69]
59.8GeO2-15Ga2O3-25BaO-0.2Eu2O33.72[70]
Table
Table 4. R/O parameter and lifetimes calculated for glass samples doped with Eu3+ ions.
Table 4. R/O parameter and lifetimes calculated for glass samples doped with Eu3+ ions.
Sample
Code		GeO2:B2O3
[mol%]		R/O (Eu3+)τm [ms]
Eu59:159:13.631.25
Eu11:155:53.431.30
Eu5:150:103.381.36
Eu2:140:203.301.43
Eu1:130:303.261.50
Eu1:220:403.171.60
Eu1:510:503.081.68
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Kowalska, K.; Kuwik, M.; Polak, J.; Pisarska, J.; Pisarski, W.A. Transition Metals (Cr3+) and Lanthanides (Eu3+) in Inorganic Glasses with Extremely Different Glass-Formers B2O3 and GeO2. Materials 2021, 14, 7156. https://doi.org/10.3390/ma14237156

AMA Style

Kowalska K, Kuwik M, Polak J, Pisarska J, Pisarski WA. Transition Metals (Cr3+) and Lanthanides (Eu3+) in Inorganic Glasses with Extremely Different Glass-Formers B2O3 and GeO2. Materials. 2021; 14(23):7156. https://doi.org/10.3390/ma14237156

Chicago/Turabian Style

Kowalska, Karolina, Marta Kuwik, Justyna Polak, Joanna Pisarska, and Wojciech A. Pisarski. 2021. "Transition Metals (Cr3+) and Lanthanides (Eu3+) in Inorganic Glasses with Extremely Different Glass-Formers B2O3 and GeO2" Materials 14, no. 23: 7156. https://doi.org/10.3390/ma14237156

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop