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13 pages, 3640 KiB

Open AccessArticle

Ferroelectric, Magnetic and Dielectric Properties of SrCo_0.2Zn_0.2Fe_11.6O_18.8 Hexaferrite Obtained by “One-Pot” Green Sol-Gel Synthesis Utilizing Citrus reticulata Peel Extract

by Maria Vesna Nikolic, Souad Ammar-Merah, Nikola Ilić, Charanjeet Singh, Milena P. Dojcinovic and Rajshree B. Jotania

Crystals 2023, 13(10), 1452; https://doi.org/10.3390/cryst13101452 - 29 Sep 2023

Viewed by 719

Abstract

SrCo_0.2Zn_0.2Fe_11.6O_18.8 hexaferrite was obtained by a “one-pot” green sol-gel synthesis method utilizing aqueous mandarin orange (Citrus reticulata) peel extract as an eco-friendly reactant. The research objective was to analyze the influence of cobalt and [...] Read more.

SrCo_0.2Zn_0.2Fe_11.6O_18.8 hexaferrite was obtained by a “one-pot” green sol-gel synthesis method utilizing aqueous mandarin orange (Citrus reticulata) peel extract as an eco-friendly reactant. The research objective was to analyze the influence of cobalt and zinc co-doping and the synthesis process on the structure, morphology, magnetic, dielectric and ferroelectric properties of strontium hexaferrite in view of future applications. Structural and morphological characterization using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled to energy dispersive X-ray spectrometry (SEM-EDX) confirmed the formation of a Co and Zn ion incorporated M-type magnetoplumbite with c/a lattice parameter ratio of 3.919 as crystallite nanoplatelets of 32 and 53 nm in thickness and width, respectively. The magnetic hysteresis loop of the synthesized powder recorded by a vibrating sample magnetometer (VSM) at room temperature confirmed its ferromagnetic nature with a coercive field (H_c) of 2539 Oe and a saturation magnetization (M_s) and remanent magnetization (M_r) of 44.6 emu/g and 21.4 emu/g, respectively. Room temperature ferroelectric loops measured at 100 Hz showed a maximal (P_max) and a remanent (P_r) polarization of 195.4 and 31.0 nC/cm², respectively. Both increased when the magnitude of the applied electrical field increased in the 1–24 kV/cm range. The dielectric constant decreased with the frequency increase, in accordance with the Maxwell–Wagner model, while the conductivity changed according to the Jonscher power law. The complex impedance was modeled with an equivalent circuit, enabling identification of the dominant contribution of grain boundary resistance (272.3 MΩ) and capacitance (7.16 pF). Full article

(This article belongs to the Special Issue Ferroelectric Materials)

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15 pages, 5685 KiB

Open AccessArticle

Properties and Potential Application of Lead-Free (BaZr_0.2Ti_0.8O₃) and Lead-Based (PbZr_0.52Ti_0.48O₃) Flexible Thick Films

by Jelena Bobić, Nikola Ilić, Željko Despotović, Adis Džunuzović, Robertas Grigalaitis, Ivan Stijepović, Biljana Stojanović and Mirjana Vijatović Petrović

Crystals 2023, 13(8), 1178; https://doi.org/10.3390/cryst13081178 - 28 Jul 2023

Cited by 3 | Viewed by 866

Abstract

For the last several decades, energy harvesters based on piezoelectricity from mechanical vibration have emerged as very promising devices that are being explored extensively for their functionality in energy technologies. In this paper, a series of flexible lead-free BaZr_0.2Ti_0.8O [...] Read more.

For the last several decades, energy harvesters based on piezoelectricity from mechanical vibration have emerged as very promising devices that are being explored extensively for their functionality in energy technologies. In this paper, a series of flexible lead-free BaZr_0.2Ti_0.8O₃ (BZT)/PVDF and lead-based PbZr_0.52Ti_0.48O₃ (PZT)/PVDF piezocomposites with variable filler content up to 50 vol% were prepared by a hot pressing method. The structure and morphology of the BZT and PZT powders, as well as the distribution of the piezo-active filler in the obtained flexible films were characterized by XRD and SEM analysis. In addition, the remnant polarization (P_r) and leakage current were also investigated to evaluate the breakdown strength in both types of flexible films. The calculations of storage energies and output voltage obtained for the investigated materials revealed an increasing trend with an increasing amount of BZT and PZT active phases. The maximum storage energy of 0.42 J/cm³ (and energy efficiency of 40.7 %) was obtained for the PZT–PVDF (40–60) films, while the maximum output voltage of about 10 V (~10 μA) was obtained for the PZT–PVDF (50–50) flexible film. In addition, a comparison between the properties of the lead-based and lead-free flexible films, as well as the potential use of these films as energy storage and energy harvesting systems were analyzed. Full article

(This article belongs to the Special Issue Ferroelectric Materials)

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8 pages, 2009 KiB

Open AccessArticle

Frustrated Magnetism and Ferroelectricity in a Dy³⁺-Based Triangular Lattice

by Xianghan Xu, Choongjae Won and Sang-Wook Cheong

Crystals 2023, 13(6), 971; https://doi.org/10.3390/cryst13060971 - 19 Jun 2023

Viewed by 1251

Abstract

Triangular lattice magnets have attracted extensive research interest because they are potential hosts for geometrically frustrated magnetism and strong quantum fluctuations. Here, utilizing a laser floating zone technique, we report the first-time successful growth of a DyInO₃ sizable crystal, which contains Dy [...] Read more.

Triangular lattice magnets have attracted extensive research interest because they are potential hosts for geometrically frustrated magnetism and strong quantum fluctuations. Here, utilizing a laser floating zone technique, we report the first-time successful growth of a DyInO₃ sizable crystal, which contains Dy³⁺-based triangular layers. The fine-tuning of Indium stoichiometry was found to be the key factor in the stabilization of the desired hexagonal phase. The X-ray diffraction study of the crystal structure reveals a non-centrosymmetric P6₃mc space group. Switchable polarization, i.e., ferroelectricity, and ferroelectric domain configuration are experimentally demonstrated at room temperature. Anisotropic magnetic and thermodynamic measurements unveil antiferromagnetic interactions, the absence of long-range ordering down to 0.1 K, and a possible doublet ground state, indicating a strongly frustrated magnetism. Our findings suggest that the DyInO₃ crystal is an excellent platform for studying emergent phenomena and their interplay with coherent topological defects in the quantum realm. Full article

(This article belongs to the Special Issue Ferroelectric Materials)

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13 pages, 4494 KiB

Open AccessArticle

Additive Manufacturing of Piezoelectric Niobium-Doped Lead Zirconate Titanate (PZT-N) by Binder Jetting

by Marco Mariani, Elisa Mercadelli, Laura Cangini, Carlo Baldisserri, Carmen Galassi, Claudio Capiani and Nora Lecis

Crystals 2023, 13(6), 883; https://doi.org/10.3390/cryst13060883 - 27 May 2023

Cited by 1 | Viewed by 1308

Abstract

Binder jetting is an emerging indirect additive manufacturing technique for ceramic materials, which could be employed to produce application-oriented designed components impossible to achieve with traditional processes and featuring enhanced performances. In our study, niobium-doped lead zirconate titanate (PZT-N) powder, usually processed through [...] Read more.

Binder jetting is an emerging indirect additive manufacturing technique for ceramic materials, which could be employed to produce application-oriented designed components impossible to achieve with traditional processes and featuring enhanced performances. In our study, niobium-doped lead zirconate titanate (PZT-N) powder, usually processed through the standard press-and-sinter route, was employed as the raw material. First, the powder was characterized in terms of granulometry and flowability to assess its suitability for the printing process. Then, shaping by binder jetting was studied, and the effect of three levels of binder saturation (75–90–105%) on the green bodies was assessed. Finally, the microstructure of the sintered samples was studied using SEM, to investigate the effect of thermal treatments on the grain size distribution and residual porosity (~40%). The piezoelectric properties were measured and compared to those of conventionally processed material. The piezoelectric charge and voltage constants (d₃₃ and g₃₃) were evaluated to determine the possible use of printed parts as porous piezoelectric components to be exploited in hydrophones in the direct mode. Full article

(This article belongs to the Special Issue Ferroelectric Materials)

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20 pages, 2019 KiB

Open AccessArticle

Phase Transition and Dynamics of Defects in the Molecular Piezoelectric TMCM-MnCl₃ and the Effect of Partial Substitutions of Mn

by Francesco Cordero, Floriana Craciun, Francesco Trequattrini, Simona Ionita, Daniel Lincu, Raul-Augustin Mitran, Victor Fruth, Simona Brajnicov, Antoniu Moldovan and Maria Dinescu

Crystals 2023, 13(3), 409; https://doi.org/10.3390/cryst13030409 - 27 Feb 2023

Cited by 1 | Viewed by 1520

Abstract

We present dielectric and anelastic spectroscopy measurements of the molecular piezoelectric TMCM-MnCl

_{3}

and TMCM-Mn

_{0.95}

M

_{0.05}

Cl

_{3}

(M = Cu, Fe, Ni; TMCM = trimethylchlorometylammonium), whose powders were pressed into discs and bars and deposited as films on Si by [...] Read more.

We present dielectric and anelastic spectroscopy measurements of the molecular piezoelectric TMCM-MnCl

_{3}

and TMCM-Mn

_{0.95}

M

_{0.05}

Cl

_{3}

(M = Cu, Fe, Ni; TMCM = trimethylchlorometylammonium), whose powders were pressed into discs and bars and deposited as films on Si by Matrix-Assisted Pulsed Laser Evaporation (MAPLE). As in other molecular ferroelectrics, the dielectric permittivity

ϵ^{'}

drops at the structural transition temperature

T_{C}

, below which the number of directions that the polar TMCM molecules visit is reduced, with the formation of ferroelectric domains. Concomitantly, the Young’s modulus E starts increasing and the elastic energy loss has a step-like increase, attributable to the motion of the domain walls. Both the dielectric and elastic anomalies indicate the improper character of the ferroelectric transition, where the ordering of the molecular orientations is not driven by the cooperative interaction of their electric dipoles. Below room temperature, at least two thermally activated relaxation processes appear both in the dielectric and anelastic spectra, whose real and imaginary parts measured at several frequencies can be fit with the Havriliak–Negami formula. The microscopic parameters so-obtained indicate that they are due to point defects, and it is argued that they are Cl vacancies and their complexes with TMCM vacancies. The considerable width of these relaxation maxima is explained by the geometry of the hexagonal perovskite structure. The partial substitution of Mn with 5% Ni has little effect on the anelastic and dielectric spectra, while Cu and, especially, Fe cause a large enhancement of the losses attributed to domain wall relaxation, with substantial contributions also above

T_{C}

. The condensation of water from the humidity in the powders compacted by cold pressing was observed and discussed. The piezoelectric activity of the films was assessed by PFM. Full article

(This article belongs to the Special Issue Ferroelectric Materials)

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11 pages, 2445 KiB

Open AccessArticle

Termination Control of (001) and (110) NdGaO₃ Single-Crystal Substrates by Selective Chemical Etching

by Victor Leca

Crystals 2022, 12(12), 1791; https://doi.org/10.3390/cryst12121791 - 9 Dec 2022

Viewed by 1497

Abstract

Controlling the surface morphology and composition of the perovskite substrates is a critical aspect in tuning the final properties of the deposited films and of their interfaces. The paper reports on a chemical etching method developed for (110) and (001) NdGaO₃ single [...] Read more.

Controlling the surface morphology and composition of the perovskite substrates is a critical aspect in tuning the final properties of the deposited films and of their interfaces. The paper reports on a chemical etching method developed for (110) and (001) NdGaO₃ single crystal substrates in order to obtain a well-defined GaO_2−x-terminated surface. The etching process is based on a HF + NH₄OH solution and includes an annealing step performed in air or under O₂ flow at temperatures of 800–1000 °C. In order to obtain the desired composition and surface morphology, the etching procedure was optimized for the vicinal step density at the surface and substrate crystal orientation. Growth nucleation studies of one-unit-cell MeO films (Me = Ti, Sr, Ba) on chemically etched and on only annealed substrates were performed in order to determine the composition of the substrate topmost layer. The results indicate that the chemically etched NdGaO₃ substrate surface has a predominantly GaO_2−x termination, with a lower free surface energy compared to the NdO_1+x termination. Full article

(This article belongs to the Special Issue Ferroelectric Materials)

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15 pages, 5055 KiB

Open AccessFeature PaperReview

Impact of Structural Strain in Perovskite Epitaxial Thin Films on Their Functional Properties

by Florin Andrei, Maria Dinescu, Valentin Ion, Floriana Craciun, Ruxandra Birjega and Nicu Doinel Scarisoreanu

Crystals 2023, 13(12), 1686; https://doi.org/10.3390/cryst13121686 - 14 Dec 2023

Viewed by 999

Abstract

The strain engineering effects induced by different means, e.g., the substrate lattice mismatch and/or chemical doping, on the functional properties of perovskite thin films have triggered interest in the use of these materials in different applications such as energy storage/generation or photonics. The [...] Read more.

The strain engineering effects induced by different means, e.g., the substrate lattice mismatch and/or chemical doping, on the functional properties of perovskite thin films have triggered interest in the use of these materials in different applications such as energy storage/generation or photonics. The effects of the film’s thickness and strain state of the structure for the lead-free perovskite ferrite-based materials (BiFeO₃-BFO; Y-doped BiFeO₃-BYFO; LaFeO₃-LFO) on their functional properties are highlighted here. As was previously demonstrated, the dielectric properties of BFO epitaxial thin films are strongly affected by the film thickness and by the epitaxial strain induced by the lattice mismatch between substrate and film. Doping the BiFeO₃ ferroelectric perovskite with rare-earth elements or inducing a high level of structural deformation into the crystalline structure of LaFeO₃ thin films have allowed the tuning of functional properties of these materials, such as dielectric, optical or photocatalytic ones. These changes are presented in relation to the appearance of complex ensembles of nanoscale phase/nanodomains within the epitaxial films due to strain engineering. However, it is a challenge to maintain the same level of epitaxial strain present in ultrathin films (<10 nm) and to preserve or tune the positive effects in films of thicknesses usually higher than 30 nm. Full article

(This article belongs to the Special Issue Ferroelectric Materials)

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14 pages, 5094 KiB

Open AccessReview

Preparation, Properties, and Applications of Near Stoichiometric Lithium Tantalate Crystals

by Xuefeng Xiao, Jiashun Si, Shuaijie Liang, Qingyan Xu, Huan Zhang, Lingling Ma, Cui Yang and Xuefeng Zhang

Crystals 2023, 13(7), 1031; https://doi.org/10.3390/cryst13071031 - 28 Jun 2023

Cited by 3 | Viewed by 1481

Abstract

Lithium tantalate crystal is widely used in optical devices, infrared detectors and surface acoustic wave devices because of its excellent piezoelectric, acousto-optic and nonlinear optical properties. The Li content of near stoichiometric lithium tantalate (NSLT) crystal is higher than that of congruent lithium [...] Read more.

Lithium tantalate crystal is widely used in optical devices, infrared detectors and surface acoustic wave devices because of its excellent piezoelectric, acousto-optic and nonlinear optical properties. The Li content of near stoichiometric lithium tantalate (NSLT) crystal is higher than that of congruent lithium tantalate (CLT) crystal. Therefore, the performance of NSLT crystal is better than that of CLT crystal in some aspects. This article reviews the physical properties, preparation methods and current research status in acoustics and optics of NSLT crystals. It also looks forward to the improvement of NSLT crystal preparation methods and their applications in surface acoustic wave (SAW) filters and optics. With the increase of Li content, the acoustic performance of NSLT crystals is expected to be comprehensively improved, achieving the application of SAW filters in 5G communication. Full article

(This article belongs to the Special Issue Ferroelectric Materials)

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