Search Results (22)

The interest in synthesizing new dielectric materials is caused by their potential application in various electronic and sensor devices as well as in a large variety of electronic components. The present work reports the synthesis of glasses in the Na₂O/Al₂O₃/BaO/ZrO₂/TiO₂/B₂O₃/SiO₂ system prepared by melt-quenching. These glasses were then crystallized to glass–ceramics by a controlled thermal treatment. X-ray diffraction experiments reveal the precipitation of Ba₂TiSi₂O₈ (fresnoite) and BaTiO₃, which probably forms a BaZr_xTi_1−xO₃ solid solution. The microstructure is studied by scanning electron microscopy and shows the presence of mulberry-shaped, crystallized structures with a densely-branching morphology. Microcomputed X-ray tomography is used to gather information on the volume fraction and average size of the crystallized volume as an effect of the applied temperature–time schedule. Longer annealing times lead to a higher volume fraction and increasing average size of the crystallization structures obtained. The dielectric properties analyzed by impedance spectroscopy are insulating and show relatively high dielectric constants ≥ 100 and moderate loss tangent values at 10 kHz. Full article

This study employs advanced structural characterization techniques, including anomalous small-angle X-ray scattering (ASAXS), small-angle X-ray scattering (SAXS), and X-ray photoelectron spectroscopy (XPS), to investigate erbium (Er³⁺)-doped silica-based glass-ceramic thin films synthesized via the sol–gel method. This research examines the SiO₂-TiO₂ and SiO₂-TiO₂-PO_2.5 systems, focusing on the formation, dispersion, and structural integration of Er³⁺-containing nanocrystals within the amorphous matrix under different thermal treatments. Synchrotron radiation tuned to the L_III absorption edge of erbium enabled ASAXS measurements, providing element-specific details about the localization of Er³⁺ ions. The findings confirm their migration into crystalline phases, such as erbium phosphate (EPO) and erbium titanate (ETO). SAXS and Guinier analysis quantified nanocrystal sizes, revealing trends influenced by their composition and heat treatment. Complementary XPS analysis of the Er 5p core-level states provided detailed information on the chemical and electronic environment of the Er³⁺ ions, confirming their stabilization within the crystalline structure. Transmission electron microscopy (TEM) highlighted the nanoscale morphology, verifying the aggregation of Er³⁺ ions into well-defined nanocrystals. The results offer a deeper understanding of their size, distribution, and interaction with the surrounding matrix. Full article

xTiO₂-(1-x)SiO₂ (x = 2.9~8.2 mol%) glass specimens were synthesized using the flame hydrolysis technique. This study aimed to elucidate the influence of TiO₂ incorporation on the optical characteristics, defect behavior, and microwave dielectric performance of these materials. UV–vis and near-infrared spectroscopic analyses were employed to investigate the hydroxyl and optical bandgap properties. Electron paramagnetic resonance (EPR) and AC impedance spectroscopy were utilized to examine oxygen vacancies, Ti³⁺ defects, and their respective behaviors. The findings revealed that, with increasing TiO₂ content, the generation and migration of defects became more favorable, consequently leading to higher dielectric losses. The imaginary component of the electric modulus experimental data was fitted using the modified Kohlrausch–Williams–Watts (KWW) function, while the frequency-dependent AC conductivity was analyzed using the Jonscher power law. The calculated activation energy exhibited a decreasing trend with increasing TiO₂ content, consistent with the characteristics of doubly ionized oxygen vacancies, suggesting the involvement of identical charge carriers in the relaxation and conduction mechanisms. Notably, the 8.2TiO₂–91.8SiO₂ glass specimen demonstrated exceptional microwave dielectric performance, exhibiting ε_r = 4.13, Q × f = 57,116 GHz, and τ_f = −4.32 ppm/°C, rendering it a promising candidate for microwave substrate applications. Full article

In the framework of luminescent rare-earth-doped glasses for near-infrared applications, TiO₂-containing inorganic glasses have been recently demonstrated to be a promising alternative to commercially used high-phonon SiO₂-based glasses. This study investigates the effect of TiO₂ concentration on the near-infrared spectroscopic properties of Yb³⁺ ions in multicomponent titanate–germanate glasses. A series of glass samples in the xTiO₂-(60−x)GeO₂-BaO-Ga₂O₃-Yb₂O₃ system (x ranging from 0 to 50 mol%) were synthesized using the melt-quenching technique. X-ray diffraction analysis confirmed the fully amorphous nature of the fabricated titanate–germanate samples. Fundamental spectroscopic properties of Yb³⁺-doped titanate–germanate system consisting of absorption spectra, near-IR emission spectra, and luminescence decay curves have been determined based on measurement using optical spectroscopy. The intensity of the emission band at 1 µm due to the ²F_5/2 → ²F_7/2 laser transition of Yb³⁺ ions increases by over 2.3-fold (TiO₂ as the network former) compared to a barium gallo-germanate sample without TiO₂. Our previous studies indicate that Yb³⁺-doped titanate–germanate glass is a promising optical material and could be successfully applied to laser technology. Full article

We performed an electrochromic investigation to optimize the composition of reactive magnetron-sputtered mixed layers of zinc oxide and tin oxide (ZnO-SnO₂). Deposition experiments were conducted as a combinatorial material synthesis approach. The binary system for the samples of SnO₂-ZnO represented the full composition range. The coloration efficiency (CE) was determined for the mixed oxide films with the simultaneous measurement of layer transmittance, in a conventional three-electrode configuration, and an electric current was applied by using organic propylene carbonate electrolyte cells. The optical parameters and composition were measured and mapped by using spectroscopic ellipsometry (SE). Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) measurements were carried out to check the SE results, for (TiO₂-SnO₂). Pure metal targets were placed separately from each other, and the indium–tin-oxide (ITO)-covered glass samples and Si-probes on a glass holder were moved under the two separated targets (Zn and Sn) in a reactive argon–oxygen (Ar-O₂) gas mixture. This combinatorial process ensured that all the compositions (from 0 to 100%) were achieved in the same sputtering chamber after one sputtering preparation cycle. The CE data evaluated from the electro-optical measurements plotted against the composition displayed a characteristic maximum at around 29% ZnO. The accuracy of our combinatorial approach was 5%. Full article

Multilayered TiO₂ films doped either with Niobium or Vanadium (1.2 at. %) were deposited by the sol-gel dip coating method on c-Si and glass substrates. The films on glass substrates were tested for CO sensing and photocatalytic degradation of methylene blue. X-ray diffraction data analysis showed that all the TiO₂:Nb(V) films were nanocrystalline in the anatase phase, with a uniform and compact microstructure and a homogeneous superficial structure of small grains with diameters in the range of 13–19 nm. For the electrical characterization, the TiO₂:Nb(V) films were incorporated in Metal-Insulator-Semiconductor (MIS) structures. The specific resistivity is of the order of 10⁴ Ωcm and its value decreases with increasing the electrical field, which testifies to the injection of electrons into these layers. From the analysis of the current–voltage curves taken at different temperature- and frequency—dependent capacitance–voltage and conductance–voltage characteristics, the density and parameters of deep levels in these TiO₂ films are evaluated and the electron charge transport mechanism is established. It was shown that the current in these TiO₂:Nb(V)-Si MIS structures is mainly carried out by inter-trap tunneling via deep levels energetically distributed in the TiO₂ bandgap. Testing these sol-gel TiO₂:Nb(V) layers for gas sensing and photocatalytic capabilities proved that they could serve such purposes. In particular, the results of the V-doped sol-gel TiO₂ film confirm its CO detection capability, which is rarely reported in the literature. For the photodegradation of methylene blue, the Nb-doped TiO₂ samples were superior, with nearly double the photocatalytic efficiency of undoped TiO₂. Full article

Lead-free ceramics with excellent energy storage performance are important for high-power energy storage devices. In this study, 0.9BaTiO₃-0.1Bi(Mg_2/3Nb_1/3)O₃ (BT-BMN) ceramics with x wt% ZnO-Bi₂O₃-SiO₂ (ZBS) (x = 2, 4, 6, 8, 10) glass additives were fabricated using the solid-state reaction method. X-ray diffraction (XRD) analysis revealed that the ZBS glass-added ceramics exhibited a perovskite structure, with the maximum relative density achieved at x = 6. The average grain size reduced obviously as the glass additive wt% increased. Also, the dielectric constant decreased and the breakdown strength increased with increases in the glass additives. The optimal energy storage density of 1.39 J/cm³ with an energy storage efficiency of 78.3% was obtained at x = 6 due to high maximum polarization and enhanced breakdown strength. The results demonstrate that this material is a potential candidate for high-pulse-power energy storage devices. Full article

The current policy of managing high-level waste (HLW) derived in the closed nuclear fuel cycle consists in their vitrification into B-Si or Al-P vitreous forms. These compounds have rather limited capacity with respect to the HLW (5–20 wt%), and their properties change over time due to devitrification of the glasses. Cardinal improvement in the management of HLW can be achieved by their separation onto groups of elements with similar properties, followed by their immobilization in robust waste forms (matrices) and emplacement in deep disposal facilities. One of the possible fractions contains trivalent rare-earth elements (REEs) and minor actinides (MAs = Am and Cm). REEs are the fission products of actinides, which are mainly represented by stable isotopes of elements from La to Gd as well as Y. This group also contains small amounts of short-lived radionuclides with half-lives (T_1/2) from 284 days (¹⁴⁴Ce) to 90 years (¹⁵¹Sm), including ¹⁴⁷Pm (T_1/2 = 2.6 years), ¹⁵⁴Eu (T_1/2 = 8.8 years), and ¹⁵⁵Eu (T_1/2 = 5 years). However, the main long-term environmental hazard of the REE–MA fraction is associated with Am and Cm, with half-lives from 18 years (²⁴⁴Cm) to 8500 years (²⁴⁵Cm), and their daughter products: ²³⁷Np (T_1/2 = 2.14 × 10⁶ years), ²³⁹Pu (T_1/2 = 2.41 × 10⁴ years), ²⁴⁰Pu (T_1/2 = 6537 years), and ²⁴²Pu (T_1/2 = 3.76 × 10⁵ years), which should be immobilized into a durable waste form that prevents their release into the environment. Due to the heat generated by decaying radionuclides, the temperature of matrices with an REE–MA fraction will be increased by hundreds of centigrade above ambient. This process can be utilized by selecting a vitreous waste form that will crystallize to form durable crystalline phases with long-lived radionuclides. We estimated the thermal effects in a potential REE–MA glass composite material based on the size of the block, the content of waste, the time of storage before immobilization and after disposal, and showed that it is possible to select the waste loading, size of blocks, and storage time so that the temperature of the matrix during the first decades will reach 500–700 °C, which corresponds to the optimal range of glass crystallization. As a result, a glass–ceramic composite will be produced that contains monazite ((REE,MA)PO₄) in phosphate glasses; britholite (Ca_x(REE,MA)_10-x(SiO₄)₆O₂) or zirconolite ((Ca,REE,MA)(Zr,REE,MA)(Ti,Al,Fe)₂O₇), in silicate systems. This possibility is confirmed by experimental data on the crystallization of glasses with REEs and actinides (Pu, Am). The prospect for the disposal of glasses with the REE–MA fraction in deep boreholes is briefly considered. Full article

In this work, we investigated the MOCVD conditions to synthesize thin films with the hexagonal P6₃cm h-LuMnO₃ phase as a potential low-band gap ferroelectric material. The main parameters investigated were the ratio of organometallic starting materials, substrate temperature, and annealing effect. Two different substrates were used in the study: fused silica (SiO₂) glass and platinized silicon (Pt\Ti\SiO₂\Si(100)). In order to investigate the thermodynamic stability and quality of the developed phases, a detailed analysis of the crystal structure, microstructure, morphology, and roughness of the films was performed by X-ray diffractometer, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), Raman spectroscopy, and piezoelectric force microscopy (PFM). Molar compositions in the film within 0.93 < |Lu|/|Mn| < 1.33 were found to be suitable for obtaining a single-phase h-LuMnO₃. The best films were obtained by depositions at 700 °C, followed by thermal treatments at 800 °C for long periods of up to 12 h. These films exhibited a highly crystalline hexagonal single phase with a relatively narrow direct band gap, around 1.5 eV, which is within the expected values for the h-LuMnO₃ system. Full article

We determined the optimal composition of reactive magnetron-sputtered mixed layers of Titanium oxide and Tin oxide (TiO₂-SnO₂) for electrochromic purposes. We determined and mapped the composition and optical parameters using Spectroscopic Ellipsometry (SE). Ti and Sn targets were put separately from each other, and the Si-wafers on a glass substrate (30 cm × 30 cm) were moved under the two separated targets (Ti and Sn) in a reactive Argon-Oxygen (Ar-O₂) gas mixture. Different optical models, such as the Bruggeman Effective Medium Approximation (BEMA) or the 2-Tauc–Lorentz multiple oscillator model (2T–L), were used to obtain the thickness and composition maps of the sample. Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS) has been used to check the SE results. The performance of diverse optical models has been compared. We show that in the case of molecular-level mixed layers, 2T–L is better than EMA. The electrochromic effectiveness (the change of light absorption for the same electric charge) of mixed metal oxides (TiO₂-SnO₂) that are deposited by reactive sputtering has been mapped too. Full article

TiO₂-SiO₂ thin films were created on Corning glass substrates using a simple method. Nine layers of SiO₂ were deposited; later, several layers of TiO₂ were deposited, and their influence was studied. Raman spectroscopy, high resolution transmission electron spectroscopy (HRTEM), an X-ray diffractometer (XRD), ultraviolet-visible spectroscopy (UV-Vis), a scanning electron microscope (SEM), and atomic force microscopy (AFM) were used to describe the sample’s shape, size, composition, and optical characteristics. Photocatalysis was realized through an experiment involving the deterioration of methylene blue (MB) solution exposed to UV-Vis radiation. With the increase of TiO₂ layers, the photocatalytic activity (PA) of the thin films showed an increasing trend, and the maximum degradation efficiency of MB by TiO₂-SiO₂ was 98%, which was significantly higher than that obtained by SiO₂ thin films. It was found that an anatase structure was formed at a calcination temperature of 550 °C; phases of brookite or rutile were not observed. Each nanoparticle’s size was 13–18 nm. Due to photo-excitation occurring in both the SiO₂ and the TiO₂, deep UV light (λ = 232 nm) had to be used as a light source to increase photocatalytic activity. Full article

The glass crystallization regime plays a crucial role in the fabrication of glass ceramics: it affects both phase composition and microstructure, and thus the properties of the final product. In the search for new glass-ceramic materials, the development of a proper heat-treatment schedule involves the utilization of numerous glass samples that need to be thermally treated and then investigated to determine the values of the target characteristics. In this study, we evaluated the effect of crystallization temperature on the glass structure, phase composition, and hardness of glass ceramics in the ZnO-MgO-Al₂O₃-SiO₂ system containing TiO₂ and ZrO₂ as nucleators. To maximize the number of heat treatments, we performed polythermal crystallization of the glass in a wide temperature range with the help of a gradient furnace. Using X-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we showed the precipitation of gahnite nanocrystals as the main phase in the bulk of a single glass sample and observed a gradual change in its microstructure, transparency, and hardness. The dependence of Vickers hardness values on heat treatment temperature was found to follow a non-linear trend, revealing the optimal thermal range for glass crystallization. Full article

Glass-ceramics containing pyroelectric Sr₂TiSi₂O₈ (STS) crystals are produced from parent glasses of compositions STS + 0.8 SiO₂ + (0.2 − x) Na₂O + x CaO, with x = 0; 0.05; 0.10; and 0.15. The aim of this work is to investigate the effect of the additions to the stoichiometric STS composition on the crystallization mechanisms and on the piezoelectric properties of the glass-ceramic. The DSC analyses evidence that the glass transition temperatures T_g, the onset temperature of the crystallization peak T_o and the temperature T_c of the maximum of this peak increase with the CaO/Na₂O ratio. On the basis of the DSC data, the crystallization of the parent glass samples was operated by thermal treatment. The observation of the cross-sections of the heat-treated samples highlights that the competition between the surface and volume crystallization mechanisms is influenced by the CaO/Na₂O ratio and the temperature. For all the samples, the XRD analyses performed on the surfaces as obtained after the crystallization treatment evidenced a preferential orientation of the STS crystals with the plans (00l) parallel to the surface. The XRD analyses performed after grinding the surface show that only the surface crystallized layers are preferentially oriented. Moreover, changes in preferential orientation to plans (202) or (201) are observed over the depth, depending on the composition and the temperature of the thermal treatment. These changes influence the polarization of the surface crystallized layer and, consequently, its piezoelectric charge coefficient d₃₃. The highest values of d₃₃ were measured on the glass-ceramic samples exhibiting mainly a (202) preferential orientation over their thickness. Full article

Peri-implantitis is defined as a bacterial infection-induced inflammation and suppuration of soft and hard tissues surrounding a dental implant. If bacteria further invade the alveolar bone, they can easily cause bone loss and even lead to the early failure of a dental implant surgery. In the present study, an 80SiO₂–15CaO–5P₂O₅ mesoporous bioactive glass film system containing 1, 5, and 10 mol% of silver was prepared on titanium implant discs (MBG–Ag–coated Ti) using sol-gel and spin coating methods. The wettability and adhesion strength of the films were evaluated using contact angle measurements and adhesion strength tests, respectively. The phase composition, chemical bonding, morphology, and oxidation states of the films were analyzed via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). In vitro bioactivity analysis of the films was performed by immersion in a simulated body fluid (SBF) for 24 h. Disk diffusion tests were performed on the early colonizing bacteria Aggregatibacter actinomycetemcomitans and Streptococcus mutans to evaluate the antibacterial ability of the films. A silver-containing mesoporous bioactive glass film with excellent biocompatibility and antibacterial properties was successfully prepared. Full article

Gold nanoparticles precipitated in transparent glass-ceramics could pave the way for the development of multifunctional materials that are in demand in modern photonics and optics. In this work, we explored the effect of gold nanoparticles on the crystallization, microstructure, and optical properties of ZnO-MgO-Al₂O₃-SiO₂ glass containing TiO₂ and ZrO₂ as nucleating agents. X-ray diffraction, transmission electron microscopy, Raman, and optical spectroscopy were used for the study. We showed that gold nanoparticles have no effect on the formation of gahnite nanocrystals during the glass heat treatments, while optical properties of the glass-ceramics are strongly dependent on the gold addition. A computational model was developed to predict optical properties of glass during the crystallization, and the possibility for adjusting the localized surface plasmon resonance band position with the heat treatment temperature was shown. Full article