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Multiferroic composites with the composition (1 − x) BaTi0.8Sn0.2O3–(x) La0.5Ca0.5MnO3 (x = 0, 0.3, 0.5, 0.7, 0.9 and 1) were prepared by sol–gel techniques. Rietveld refinements of the composites with 0–3 and 3–0 type connectivities exhibit the formation of pure phases and confirm the fraction of the composite samples. It was found that the composites grain size decreases slightly with increasing the La0.5Ca0.5MnO3 content. Magnetic measurements of the composite ceramics exhibit a gradual increase in saturation and remanent magnetization with increasing La0.5Ca0.5MnO3 content. Dielectric data demonstrate that the composite materials show high values of the dielectric constant in comparison with the parent compound BaTi0.8Sn0.2O3 (BTSO). In addition, an attempt is made to measure the magnetoelectric coupling coefficient and to explain the negative permittivity and losses occurring in these materials at a certain frequency and temperature conditions. [ABSTRACT FROM AUTHOR]

High-performance lead-free multiferroic composites are desired to replace the lead-based ceramics in multifunctional device applications. Laminated compounds were prepared from ferroelectric and ferromagnetic materials. In this work, we present the laminated ceramics compound by considering the ferromagnetic La0.5Ca0.5MnO3 (LCMO) and the ferroelectric BaTi0.8Sn0.2O3 (BTSO) in two different proportions. Compounds ($1-x$) LCMO–($x$) BTSO with $x = 1$ and 0 (pure materials) were synthesized by the sol–gel method, and $x = 0.7$ and 0.5 (laminated) compounds were elaborated by welding appropriate mass ratios of each pure material by using the silver paste technique. Structural, dielectric, ferroelectric, microstructure, and magnetic characterizations were conducted on these samples. X-ray scattering results showed pure perovskite phases confirming the successful formation of both LCMO and BTSO. Scanning electron microscope (SEM) images evidenced the laminated structure and good quality of the interfaces. The laminated composite materials have demonstrated a multiferroic behavior characterized by the ferroelectric and the ferromagnetic hysteresis loops. Furthermore, the enhancement of the dielectric constant in the laminated composite samples is mainly attributed to the Maxwell–Wagner polarization. [ABSTRACT FROM AUTHOR]

Glass-ceramics in the system xBaTiO3-(1-x)NaPO3 (0 ≤ x ≤ 14, x in mol%) have been prepared and characterized. The structural organization of the glass-ceramics has been studied using XRD diffraction and infra-red (FTIR), 31P Magic angle spinning (MAS-NMR) and dielectric spectroscopies. Results suggest two distinct regions comprising the glass structure, one with low-BaTiO3 content and the other with higher content of the ferroelectric compound BaTiO3. The depolymerisation effects and the structure changes, promoted by BaTiO3 addition, are evidenced by means of the IR and NMR results. Dielectric permittivity shows that the ferroelectric-paraelectric transition temperature of each glass-ceramic appears at the same temperature for a pure BaTiO3 ceramic. [ABSTRACT FROM AUTHOR]

Substitution of Pb with Gd in the Pb 2 KNb 5 O 15 phases leads to a new composition of solid solution with chemical composition Pb 2(1 - x ) Gd x K 1 + x Nb 5 O 15 (0 ≤ x ≤ 1) which crystallizes with TTB type structure. Powders are pressed and heated into ceramics and their compaction is about 90%. Thermal evolution of the real part of the dielectric permittivity presents different behavior according to the composition. The dielectric permittivity of compounds with Gd composition above x = 0.30 shows two anomalies. The first one appears at T C and is associated to the ferroelectric-paraelectric phase transition. The origin of the last one at which occurs at T 1 is up to now unknown. Domain structure should exhibit strong changes both with temperature and composition. [ABSTRACT FROM AUTHOR]

A series of Pb-free ferroelectric materials Ba 0.9 Sr 0.1 Ti 1-x Sn x O 3 (BSTS-x) with 0 ≤ x ≤ 0.15 was successfully prepared via solid-state reaction method. The effect of Sn substitution on the crystal structure, microstructure, dielectric behavior, ferroelectric and tunable features of BSTS-x ceramics were systematically investigated. Room temperature (RT) x-ray diffraction (XRD) analysis using the Rietveld refinement method reveals that all the synthesized BSTS-x ceramics were well crystallized into single perovskite structure. The results show a tetragonal phase for 0.00 ≤ x ≤ 0.02, which evolves to orthorhombic and tetragonal coexisting phases for 0.05 ≤ x ≤ 0.07. The composition x = 0.10 showed a mixture of tetragonal, orthorhombic and rhombohedral phases at RT, while a single cubic phase is observed for x = 0.15. The crystal phases determined by XRD were confirmed by Raman spectroscopy. Enhanced dielectric permittivity with a maximum value of ε ' ~35000 is observed for x = 0.10 at RT. The ferroelectric behavior of BSTS-x ceramics was investigated through polarization hysteresis loops and tunability measurements. High tunability of 63% at RT and under the low DC-applied electric field of 1.40 kV/cm is achieved for x = 0.10. [ABSTRACT FROM AUTHOR]

By using the semi-wet synthesis method, lead-free ferroelectric materials Ba 0.9 Sr 0.1 Ti 1-x Sn x O 3 with x = 0, 0.02, 0.05, and 0.10 (abbreviated as BSTS) were prepared and their structural, electric and electrocaloric properties were investigated. The X-ray diffraction (XRD) patterns show that the samples calcined at 950 °C have well crystallized into perovskite structure suggesting the substitution of Ti4+ by Sn4+ in BST lattice. With increasing content of Sn, the enhancement of the dielectric permittivity was observed for (0 ≤ x ≤ 0.05) and the ferroelectric transition temperature (T C) was found to shift towards the room temperature (T C = 20 °C for x = 0.10). Direct measurements of the electrocaloric effect (ECE) were performed on all samples by using the high-resolution calorimeter. It is found that Ba 0.9 Sr 0.1 Ti 0.95 Sn 0.05 O 3 exhibits a high ECE temperature change of ΔT EC = 0.188 K at an applied electric field of only 7 kV/cm. Impedance spectrum analysis of all the samples performed in the temperature range of 300–360 °C reveals the existence of two relaxation contributions related to the grain and grain boundaries that are well separated in frequency. Activation energies of conduction and relaxation processes were deduced for both contributions in order to determine the conduction mechanism of the studied compositions. • Semi-wet synthesis method is used to prepare the ferroelectric Ba 0.9 Sr 0.1 Ti 1-x Sn x O 3 (BSTS) with x = 0, 0.02, 0.05, and 0.10. • This work shows the effect of Sn on electrocaloric, structural, dielectric and electric of BSTS. • Direct electrocaloric measurements show that BSTS (x = 0.05) exhibits the highest value of EC responsivity (ξ = 0.027 K cm/kV). • Enhancement of dielectric permittivity is observed for (0 ≤ x ≤ 0.05). • Impedance spectroscopy shows that the conduction and relaxation processes can be described by the same activated mechanism. [ABSTRACT FROM AUTHOR]

This study investigates the impact of incorporating Eu into 0.8BiFeO 3 -0.2BaTiO 3 ceramics (0.8 (Bi (1-x) Eu x FeO 3) - 0.2BaTiO 3 for x = 0 and 0.05) through cost-effective solid-state sintering. Analyzing structural, microstructural, optical, ferromagnetic, and dielectric properties, it confirms pure perovskite structures exclusively crystallizing in the rhombohedral phase. Eu3+ integration yields homogeneous distribution, reduced grain size (1.57 μm–1.40 μm), and a decreased optical band gap (2.06 ± 0.02 eV to 1.65 ± 0.02 eV). Ferromagnetic properties improve, with remnant magnetization rising from M r = 0.4406 emu/g to M r = 0.5096 emu/g. Dielectric analysis identifies grain contributions, and Jonsher low analysis indicates the dominance of the Model of Correlated Barrier Hopping in conduction. The study emphasizes the potential technological applications of Eu-modified 0.8BiFeO 3 -0.2BaTiO 3 ceramics, offering valuable insights into their physical properties. [ABSTRACT FROM AUTHOR]

The Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 (BCZT) ceramics were successfully prepared by the sol-gel process and sintered at 1420 °C. The effect of sintering times (2, 4 and 6 h) on structural, microstructural, electric properties, energy storage, and electrocaloric effect was systematically examined. X-ray diffraction (XRD) results show that all the samples crystallize in the pure perovskite structure. The morphotropic phase transition from the tetragonal to the orthorhombic phase (T-O) was identified and confirmed by Rietveld refinement. The BCZT ceramic sintered at 1420 °C for 4 h possesses a good relative density of 98% and exhibits optimal properties with a high dielectric permittivity (ε r,max) ~16310, a large electrocaloric effect coefficient (ξ) ~ 0.244Kmm/kV and a high energy storage efficiency of 63.65%. [ABSTRACT FROM AUTHOR]

We prepared BiFe 0.95 (Ni 0.5 Ti 0.5 ) 0.05 O 3 by the conventional solid-state reaction method. X-ray diffraction along with the Rietveld-refinement revealed the existence of a rhombohedral R 3 c symmetry in BiFe 0.95 (Ni 0.5 Ti 0.5 ) 0.05 O 3 . The dielectric permittivity was investigated over a wide range of temperatures at 1 kHz. During its evolution, an anomaly was observed at 520 K, which corresponds to T N (antiferromagnetic transition temperature). The prepared ceramic exhibited a considerable improvement in dielectric properties compared to pure BiFeO 3 . From the magnetization dependence at room temperature, BiFe 0.95 (Ni 0.5 Ti 0.5 ) 0.05 O 3 enhanced magnetization ( M r ≈ 0.026 emu/g) and reduced the coercive field ( H c ˜ 110 Oe) compared to BiFeO 3 . BiFe 0.95 (Ni 0.5 Ti 0.5 ) 0.05 O 3 ceramic is ferromagnetic with a cluster-glass state unlike the antiferromagnetic BiFeO 3 -based compounds. The Raman study confirmed the X ray diffraction analysis, the dielectric measurement and magnetic one. [ABSTRACT FROM AUTHOR]

Abstract: Polycrystalline samples of Ba1−x Nd2x/3(Ti0.9Zr0.1)O3 (0≤x≤0.125) have been synthesized by high-temperature solid-state reaction technique. These ceramics were characterized by X-ray diffraction as well as dielectric permittivity measurements and Raman spectroscopy. The ceramic samples crystallize in the tetragonal perovskite structure for x=0 and in cubic for 0.025≤x≤0.125. Dielectric measurements showed that prepared compositions exhibit an evolution from a classical ferroelectric to a relaxor ferroelectric with rising substitution rate x. T C or T m decreases when neodymium (Nd) is introduced in the lattice of Ba(Ti0.9Zr0.1)O3. A relaxor character with ΔT m =12K and ε' r about 11.650 at 1kHz with T m =212K was found for Ba0.9Nd0.06(Ti0.9Zr0.1)O3 composition. The evolution of the Raman spectra was studied as a function of compositions and temperatures. The results of the Raman spectroscopy studies confirm our dielectric measurements. [Copyright &y& Elsevier]

Abstract: The polycrystalline samples of (1− x)BiFeO3–xBa0.8Sr0.2TiO3 (x =0, 0.1, 0.2, 0.25, 0.3, 0.4 and x =1) were prepared by the conventional solid state reaction method. The effect of substitution in BiFeO3 by Ba0.8Sr0.2TiO3 on the structural, dielectric and magnetic properties was investigated. X-ray diffraction study showed that these compounds crystallized at room temperature in the rhombohedral distorted perovskite structure for x ≤0.3 and in cubic one for x =0.4. As Ba0.8Sr0.2TiO3 content increases, the dielectric permittivity increases. This work suggests also that the Ba0.8Sr0.2TiO3 substitution can enhance the magnetic response at room temperature. A remanent magnetization M r and a coercive magnetic field H C of about 0.971emu/g and 2.616kOe, respectively were obtained in specimen with composition x =0.1 at room temperature. [Copyright &y& Elsevier]

Abstract: Ferroelectric ceramics Pb2−x K1+x Li x Nb5O15 (PKLN), with , having the tetragonal tungsten bronze (TTB) structure, were synthesized using a solid-state reaction and characterized by X-ray diffraction. The temperature dependence of dielectric permittivity was measured from 35 to 550 °C in the frequency range from 20 Hz to 1 MHz. These measurements permit us to present the phase diagram of this family and the evolution of the transition temperature as function of the chemical composition. [Copyright &y& Elsevier]

Abstract: (Pb1− y La y )(Zr0.52Ti0.48)O3 (PLZT y ) powders were prepared using sol–gel process and their structural and dielectric properties were investigated. Increasing La content is shown to transform the average symmetry to a tetragonal one in the calcined ones and to lower the temperature of the maximum of the dielectric constant. One anomaly is observed on the real part of the permittivity on the sample with ; this anomaly located at about 180°C was interpreted as a transition from ferroelectric-rhombohedral phase to ferroelectric-quadratic phase. [Copyright &y& Elsevier]

A new ferroelectric rare earth family Pb1.6K1.2R0.2Nb5O15 with R=La, Nd, Sm, Eu and Gd (PKRN) of tetragonal tungsten bronze type ferroelectrics was synthesized. The ferroelectric transition with nonuniform distribution of critical temperature over a ceramic sample was found from dielectric measurements. According to X-ray diffraction measurements, the ferroelectric phase has an orthorhombic symmetry. The transition temperature was shown to decrease weakly with increasing radius of the rare earth ion R. [Copyright &y& Elsevier]