The magnetization reversal and high temperature dielectric response in Y1−xHoxFe0.5Cr0.5O3

The structural, magnetic, and dielectric properties of the Y_1−xHo_xFe_0.5Cr_0.5O₃ (x=0, 0.05, 0.1, 0.3, and 0.5) compounds have been investigated. Rietveld refinement of the XRD patterns shows that the compounds possess orthorhombic perovskite structure. The dual magnetization reversal is observed in the samples with x=0.05 and 0.1, and it vanishes when x≥0.3. Ferromagnetic-like behavior with large coercive fields is observed in all Ho³⁺ doped YFe_0.5Cr_0.5O₃ samples, indicating a doping induced metamagnetic behavior. This abnormal magnetization behavior can be explained by the antiparallel magnetic coupling between the Ho³⁺ and the canted Cr³⁺/Fe³⁺ moments, as well as the Ho–O–Ho magnetic interaction. The dielectric behavior in the frequency range from 100 Hz to 10 MHz is investigated. The low doped samples (x=0, 0.05, and 0.1) exhibit relaxation-like dielectric behavior and colossal dielectric constant in a wide temperature and frequency range. The dual magnetization reversal under low magnetic field makes these materials attractive candidates for the magnetic dual sensor devices.     

Structure refinement,defects evolution and calcium doping of Sr2CeO4 microwave dielectric ceramics with high quality factor

Sr_2-2xCa_2xCeO₄ (x = 0, 0.025, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8) ceramics were synthesized through cold isostatic pressing and solid-state reaction. The microstructure, defects, microwave dielectric properties, and the effect of Ca²⁺ doping of Sr₂CeO₄ ceramics were systematically investigated. As the sintering temperature increased, the densities of Sr₂CeO₄ ceramics rose, the content of oxygen vacancies increased, and Ce⁴⁺ reduction would be enhanced. In addition, the Sr₂CeO₄ structure had poor compatibility with Ca²⁺. The major phase could be kept unchanged only when x ≤ 0.1. The reason was that the doping of Ca²⁺ intensified the distortion of the CeO₆ octahedron and induced the structural transformation of the common edges (Sr₂CeO₄) to the common angles (SrCeO₃). With the increase of dopant, the densities of Sr_2-2xCa_2xCeO₄ ceramics increased significantly, while the content of oxygen vacancies also increased. The microwave dielectric properties were mainly influenced by the density, structural symmetry, defects, and the second phase SrCeO₃. The dielectric permittivity (ε_r) of 13.4–15, the quality factor (Qf) of 118,580–52,170 GHz, and the temperature coefficient of resonant frequency (τ_f) of ?58.3 ～ ?47.5 ppm/°C were obtained for Sr_2-2xCa_2xCeO₄ ceramics When x ≤ 0.1. This work has provided a foundation for further research on cerate microwave dielectric ceramics.     

Band gap engineering and microwave dielectric properties evolution of mixed (Sr,La, Ce) TiMgO3 titanate–aluminate system

A mixed perovskite titanate-aluminate [(1-x)(Sr_0.6La_0.2Ce_0.2Ti_0.8Mg_0.2O₃)-xNdAlO₃ for x = 0.1 to 0.4] solid solution was successfully synthesized. X-ray diffraction patterns (XRD) and Rietveld refinement results indicated a stable perovskite phase with a cubic structure, in which Nd³⁺ occupies the A-site randomly while Al³⁺ occupies the B-site. No additional reflection spots (superlattice reflections) were detected in the HRTEM pattern (see SAED), confirming the cubic symmetry. All samples showed small Urbach tails, mainly due to compositional disorder. Microstructural analysis based on atomic force microscopy (AFM) showed no traces of impurity phases. For x = 0.4, excellent microwave dielectric properties (MWD) are obtained with a quality factor (Q × f) of 37,131 GHz at f = 5.2801 GHz, relative permittivity (ε_r) of 43, and temperature coefficient of resonant frequency (τ_f) of +1.3 ppm/°C. Variations in ε_r, Q × f values, and τ_f may be related to changes in relative density (ρ_rel), ion polarizability, optical band gap, and tolerance factor, respectively.     

Ca-doped PrBa1-xCaxCoCuO5+δ (x = 0–0.2) as cathode materials for solid oxide fuel cells

Ca-doped perovskite oxides PrBa_1-xCa_xCoCuO_5+δ (PBCCCO, x = 0–0.2) were prepared and investigated as SOFC cathode materials. PBCCCO samples are single perovskite structure with P4/mmm space group. Pr, Cu and Co ions in PBCCCO samples exist in the form of Pr³⁺/Pr⁴⁺, Cu²⁺/Cu⁺ and Co³⁺/Co⁴⁺ multi-valence states. The average TECs of PBCCCO samples were reduced from 17.4 × 10^?6 K^?1 (x = 0) to 16.7 × 10^?6 (x = 0.1) and 16.1 × 10^?6 K^?1 (x = 0.2) whin RT-900°С. The electrical conductivity and electrochemical catalytic activity of PBCCCO perovskites was enhanced obviously by Ca doping. The ASR values decreased by 60.1% (@650 °C), 68.9% (@700 °C), 71.0% (@750 °C) and 72.8% (@800 °C) respectively when Ca doping content increased from x = 0 to 0.2. These results suggest PBCCCO sample with Ca doing content x = 0.2 can be a promising cathode for IT-SOFC.     

Enhanced Curie temperature and superior temperature stability by site selected doping in BCZT based lead-free ceramics

In this work, Bi³⁺ doped Ba_0.98-3x/2Bi_xCa_0.02Zr_0.02Ti_0.976Cu_0.008O₃ [0 ≤ x ≤ 0.03] lead free ceramics, to be employed for structural, dielectric and ferroelectric studies, have been synthesized via conventional solid state reaction method. Rietveld refinement of the X-ray diffraction (XRD) data evidences the existence of a pure perovskite phase with tetragonal symmetry for all ceramics. The Scanning Electron Microscopy (SEM) reveals that the grain size, which is 16.14 μm for x = 0 reduced to 2.11 μm for x = 0.03. Dielectric studies demonstrate excellent dielectric behavior with high Curie temperature (T_C ～159 °C), high dielectric constant (ε_r ～834, ε_max ～ 3146), and a low dielectric loss (tanδ ～ 0.019), for an optimum value of x = 0.02. The analysis of temperature coefficient of the dielectric permittivity indicates the applicability of these materials in multilayer ceramic capacitors. Impedance studies, conducted to understand the underlying physical mechanisms, are found to be in good agreement with the results of structural and dielectric studies. Furthermore, the ferroelectric measurement confirms the ferroelectric nature for all samples with an energy storage efficiency (η) of ～42% for x = 0.02 composition.     

Study of physical properties of cobalt substituted Pr0.7Ca0.3MnO3 ceramics

An investigation on single phase semiconducting polycrystalline Pr_0.7Ca_0.3MnO₃ and Pr_0.7Ca_0.3MnCo_0.1O₃ crystallized in the orthorhombic system with Pnma space group is reported. We found that σ_DC increases when introducing Co for T<110 K but for T>110 K, it decreases. Also, the contribution of hopping process in conduction mechanism was in agreement with the Jonscher law and Mott theory. Capacitance was extensively dependent on temperature and frequency. A dielectric transition was observed at T=150 K for the doped compound. The temperature dependence of dielectric permittivity is well described by Curie–Weiss law. The parameter of deviation from Curie–Weiss behavior to modified Curie–Weiss law is found to be ΔT_m=30 K. The substitution of Mn by Co was found to destroy the charge order state observed in the parent compound and to induce a ferromagnetic phase at low temperature. The cobalt-substituted sample exhibits a maximum value of magnetic entropy change |∆S^max|=3.2 J kg⁻¹ K⁻¹and a large relative cooling power with a maximum value of 301 J/kg under an applied field of 5 T. Technically, these large values make the prepared material very promising for magnetic refrigeration.     

The microstructure and magnetic properties of Ca2+ ion doped GdCrO3

In this paper, the crystal structure, vacancy defect, local electron density and magnetic properties of Gd_1-xCa_xCrO₃ (0 ≤ x ≤ 0.3) polycrystalline samples were investigated systematically. The crystal structural analyses show that all the samples are orthorhombic phase and a structural distortion happens around x = 0.3. Due to the formation of Cr⁴⁺ ions, both the lattice constant and the Cr–O bond length decrease. The results of positron annihilation spectrum reveals that the vacancy defect concentration increases and the local electron structure changes with the introduction of Ca²⁺ ions. The field-cooled (FC) and zero-field cooled (ZFC) curves of Gd_1-xCa_xCrO₃ samples measured under H = 100 Oe exhibits negative magnetization characteristics due to the interaction between Gd³⁺ and Cr³⁺ ions, and the magnetism can be affected by the structural distortion.     

Fabrication of high-efficiency dielectric patch antennas from temperature-stable Sr3−xCaxV2O8 microwave dielectric ceramic

A novel high-efficiency dielectric patch antenna was fabricated using Sr_3-xCa_xV₂O₈ ceramics. A typically temperature-stable Sr_3-xCa_xV₂O₈ was achieved by tailoring the Ca²⁺ substitution to 30 mol% (x = 0.3), where well-balanced microwave dielectric properties were obtained (a near-zero value of +5.2 ppm/°C, a low ε_r ～ 13.4, and a moderate Q×f ～ 18,500 GHz). To manifest the application potentiality in wireless communication, a patch antenna was fabricated from the x = 0.3 ceramic based on the simulated result using the CST Microwave Studio software, and it showed a high simulated radiation efficiency (99.7%) and a gain (5.35 dBi) at 3.421 GHz. All results indicate that the Sr_3-xCa_xV₂O₈ ceramics have promising application potential for 5 G technology due to their prominent microwave dielectric properties, lightweight, and low cost.     

Microwave dielectric characterization of Ca0.6(La1-xYx)0.2667TiO3 perovskite ceramics with high positive temperature coefficient

Solid solution Ca_0.6(La_1-xY_x)_0.2667TiO₃ dielectric ceramic systems with various x values were studied, which were prepared using a solid-state reaction method. X-ray diffraction and X-ray spectroscopy analyses showed that the crystal structure of these samples was orthorhombic perovskite. The microstructures with the substitution amount of Y³⁺ and the dielectric performances of the Ca_0.6(La_1-xY_x)_0.2667TiO₃ ceramics were also explored. With x = 0.1, the Ca_0.6(La_0.9Y_0.1)_0.2667TiO₃ ceramic could be sintered at 1350 °C, and the microwave dielectric performance was found to be strongly correlated with the sintering temperature. A maximum Qf value of 23,100 (GHz), dielectric constant (ε_r) of 111, and temperature coefficient (τ_f) of 374.6 ppm/°C were achieved for samples sintered at 1350 °C for 4 h. This dielectric ceramic possessed good potential as a τ_f compensator to obtain a near-zero τ_f mixture for high-quality substrates for use in wireless communication systems.     

Structure,dielectric and optical properties of Bi1.5+xZnNb1.5O7+1.5x pyrochlores

Non-stoichiometric pyrochlore ceramics with formula Bi_1.5+xZnNb_1.5O_7+1.5x were systematically investigated. Crystal structures of the compounds were studied by X-ray diffraction (XRD) technique. The structures were identified as pure cubic pyrochlores when |x| < 0.1. Dielectric and optical properties of the compositions when x = −0.1, 0 and 0.1 were studied. All samples have high resistivities and low dielectric loss. With increasing x in Bi_1.5+xZnNb_1.5O_7+1.5x, the lattice constant, permittivity, temperature coefficient of permittivity and thermal expansion coefficient increased, while dielectric loss decreased. Raman spectra indicated that the intensity of Bi–O stretching become stronger with increasing x. A vibration mode emerging at 861 cm⁻¹ when x = −0.1 means that the B–O coordination environment is significantly more disordered. Absorption spectra suggested that the bandgap energy become lower from 2.86 to 2.70 eV as lattice constants increased. Strong absorption occurs at wavelengths from 433 to 459 nm, shows that samples have the ability to respond to wavelengths in the visible light region.     

Abnormal variation of microwave dielectric properties in A/B site co-substituted (Ca1−0.3xLa0.2x)[(Mg1/3Ta2/3)1−xTix]O3 complex perovskite ceramics

A/B site co-substituted (Ca_1?0.3xLa_0.2x)[(Mg_1/3Ta_2/3)_1?xTi_x]O₃ ceramics (0.1 ≤ x ≤ 0.5) were prepared by solid state reaction and the structures, microstructures and dielectric properties were investigated. B site 1:2 cation ordering and oxygen octahedra tilting lead to monoclinic symmetry with space group P2₁/c for x = 0.1. For x above 0.1, the ordering was destroyed and the crystal structure became orthorhombic with space group Pbnm. The B site 1:2 cation ordering tended to be destroyed to form 1:1 ordering by the A site La³⁺ substitution. The dielectric constant increased linearly with increasing content of Ti⁴⁺ as the increasing second Jahn–Teller distortion enhanced the B site cation rattling. The temperature coefficient of resonant frequency and Qf values showed abnormal variations, which were refined to be caused by the increasing A site cation vacancy and diffused distribution of small size ordering domains respectively. Good combination of microwave dielectric properties was obtained at x = 0.5, where ?_r = 48, Qf = 21,000 GHz and τ_f = 2.2 ppm/°C.     

Lead-free high-temperature dielectrics with wide temperature stability range induced from BiFeO3-BaTiO3-based system

Lead-free BNSTNZ ((Bi,Na,Ba,Sr)(Ti,Nb,Zr)O₃)-modi?ed BF35BT (0.65BiFeO₃-0.35BaTiO₃) dielectrics were investigated by conventional solid-state reaction method. Dielectric permittivity of BFBT-BNSTNZ ceramics was suppressed through addition of BNSTNZ content, while dielectric temperature stability range was expanded from 105 °C to 412 °C as BNSTNZ content increases from 0.025 to 0.1, due to the ferroelectric-relaxor phase transition. In particular, x = 0.10 exhibits the widest stability temperature range from 88 °C to 500 °C having small variation of (Δε_m/ε_{m 150 °C} ≤ 15%) with high dielectric permittivity (> 1000) and low dielectric loss (tan? ≤ 0.1) in temperature range from 50 °C to 250 °C. Moreover, high room temperature energy storage density (W_store) of 0.75 and 0.57 J/cm³ with energy storage efficiency (?) of 57% and 78% for x = 0.03 and x = 0.10, respectively, was achieved. These results indicate that BFBT-BNSTNZ can be a promising system for high-temperature dielectric and energy storage applications.     

Gd3+ doping induced microstructural evolution and enhanced visible luminescence of Pr3+ activated calcium fluoride transparent ceramics

Transparent Pr³⁺ doped Ca_1-xGd_xF_2+x (x = 0, 0.01, 0.03, 0.06, 0.10, 0.15) polycrystalline ceramics with fine-grained microstructures were prepared by the hot-pressing method. The dependence of microstructure, optical transmittance, luminescence performances and mechanical properties on the Gd³⁺ concentrations for Pr³⁺:Ca_1-xGd_xF_2+x transparent ceramics were investigated. The Gd³⁺ ions show positive effects on the microhardness of Pr³⁺:Ca_1-xGd_xF_2+x transparent ceramics as a result of the decrease in the grain sizes. Excited by the Xenon lamp of 444 nm, typical visible emissions located at 484 nm, 598 nm and 642 nm were observed. Furthermore, the incorporation of Gd³⁺ ions can greatly enhance the photoluminescence performance owing to the improvement in the concentration quenching effect. The quenching concentration of Pr³⁺ ions in CaF₂ transparent ceramics increased to 1 at.% as a result of the positive effect of Gd³⁺ codoping. The energy transfer mechanism of Pr³⁺ in the Pr³⁺:Ca_1-xGd_xF_2+x transparent ceramics has been investigated and discussed.     

A/B-site cosubstituted Ba4Pr28/3Ti18O54 microwave dielectric ceramics with temperature stable and high Q in a wide range

High permittivity Ba₄(Pr_1-xSm_x)_28/3Ti_18-yAl_4y/3O₅₄(0.4≤x ≤ 0.7, 0≤y ≤ 1.5) ceramics were synthesized using a standard solid-state method. The effects of Sm³⁺ substitution into the A-site and Sm³⁺/Al³⁺ cosubstitution into the A/B-sites on the microstructure, crystal structure, Raman spectra, infrared reflectivity (IR) spectra and dielectric characteristics were investigated in a Ba₄Pr_28/3Ti₁₈O₅₄ solid solution. In the ceramic samples of Ba₄(Pr_1-xSm_x)_28/3Ti₁₈O₅₄(0.4≤x ≤ 0.7), Sm³⁺ partial substitution for Pr³⁺ could improve the quality factor (Qf) value and reduce the TCF value. Nevertheless, the quality factor (Qf~10,000GHz) needed further improvement and the TCF values (+12.3~+35.4 ppm/°C) were still too large. Therefore, Al³⁺ was introduced for further optimization of the TCF values and Qf values of the Ba₄(Pr_1-xSm_x)_28/3Ti₁₈O₅₄ ceramics. Sm/Al cosubstitution led to a good combination of high ε_r (ε_r ≥ 70), high Qf (Qf ≥ 12,000 GHz), and near-zero TCF (−10 < TCF < +10 ppm/°C) in a wide range (0.4≤x ≤ 0.7). Infrared reflectivity (IR) spectra indicated that A-TiO₆ vibration modes gave the primary contribution rather than Ti–O bending and stretching modes. The decrease in the degree of B-site cations order could be confirmed by Raman spectra. XPS results demonstrated that the improvement of quality factor (Qf) value was strongly related to the suppression of Ti³⁺. Excellent dielectric properties were achieved in Ba₄(Pr_1-xSm_x)_28/3Ti_18-yAl_4y/3O₅₄ microwave ceramics with x = 0.5 and y = 1.25: ε_r = 72.5, Qf = 13,900GHz, TCF = +1.3 ppm/°C.     

Enhanced dielectric and piezoelectric properties in Na0.5Bi4.5Ti4O15 ceramics with Pr-doping

The bismuth layer-structured Na_0.5Bi_4.5-xPr_xTi₄O₁₅ (x?=?0, 0.1, 0.2, 0.3, 0.4, and 0.5) (NBT-xPr³⁺) ceramics were fabricated using the traditional solid reaction process. The effect of different Pr³⁺ contents on dielectric, ferroelectric and piezoelectric properties of Na_0.5Bi_4.5Ti₄O₁₅ ceramics were investigated. The grain size of Pr³⁺-doping ceramics was found to be smaller than that of pure one, the maximum dielectric constant and Curie temperature T_c gradually decreased with increasing Pr³⁺ contents, and the dielectric loss decreased at high temperature by Pr³⁺-doping. Moreover, the activation energy (E_a), resistivity (Z’), remanent polarization (2P_r) and piezoelectric constant (d₃₃) increased by Pr³⁺-doping. The NBT-xPr³⁺ ceramics with x?=?0.3 achieved the optimal properties with the maximum dielectric constant of 1109.18, minimum loss of 0.00822 (250?kHz), E_a of 1.122?eV, Z’ of 7.9?kΩ?cm (725 ºC), d₃₃ of 18 pC/N, 2P_r of 12.04 μC/cm². The enhancement was due to the addition of Pr³⁺ which suppressed the decreasing of resistivity at high temperature and made it possible for NBT-xPr³⁺ ceramics to be poled in perpendicular direction, implying that it is a great improvement for Na_0.5Bi_4.5Ti₄O₁₅ ceramics in electrical properties.     

Thermal stability of dielectric and energy storage performances of Ca-substituted BNTZ ferroelectric ceramics

In this study, we synthesized [Ca_x(Bi₀.₅Na_0.5)_1?x](Ti₀₈₅Zr_0.15)O₃ (Ca-substituted BNTZ) ferroelectric ceramics with x = 0–0.15 using a solid-state reaction technique. The structural evolution of Ca-substituted BNTZ was revealed by X-ray diffraction combined with Rietveld crystal structure refinement. A pseudocubic structure with P4bm symmetry is suggested for all Ca-substituted BNTZ samples. Temperature-dependent dielectric properties show a clear and broad dielectric peak of approximately 340 °C. The dielectric peak becomes even wider, and the thermal stability of the permittivity is dramatically improved when x gradually increases. In the x = 0.10 composition, the permittivity at 25–450 °C varies between +5% and ?14.5%. A recoverable energy storage density (W_rec) of 2.79 J/cm³ with an energy storage efficiency (η) of 76% was achieved in the x = 0.07 composition, which suggests superior properties over other BNT-based systems. In addition, the compositions of x = 0.07, 0.10 and 0.15 show excellent thermal stability of W_rec and η. This work proves that the thermal stability of dielectric and energy storage performances in BNT-based ferroelectric ceramics can be achieved by introducing ions without contributing to the polarization.     

Ferroelectric,dielectric, and impedance properties of Sm-modified Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 ceramics

To investigate the effect of Sm doping on the electrical properties of Ba(Zr_0.2Ti_0.8)O₃-x(Ba_0.7Ca_0.3)TiO₃ (BZT-xBCT) (x = 40, 50, 60) ceramics, three Sm-modified ceramics were prepared using the conventional solid-state reaction method. Related electrical measurements, including ferroelectric and dielectric investigations and impedance spectroscopy, were recorded for these ceramics. It was found that a tilted morphotropic phase boundary resulted from the addition of Sm, which induced the best piezoelectric properties and insulating behaviour in the Sm-BZT-60BCT sample. An abnormal P-E loop shrinkage appeared in the Sm-BZT-50BCT sample but not in the other two samples. This could be attributable to the different electronegativities between Ca²⁺ and Ba²⁺ and between Zr⁴⁺ and Ti⁴⁺, whose contents are different in varied samples and have an effect on defect-dipole alignment as well as spontaneous polarization. The activation energies for the bulk conductivity in the three composites were calculated to be 0.28 ± 0.01, 0.08 ± 0.01, and 0.36 ± 0.01 eV, confirming the existence of oxygen vacancies in our samples. The Sm dopant is responsible for the oxygen vacancies. This also leads to an increased Curie temperature in the three composites.     

Enhanced magnetodielectric properties of Co2Z ferrite ceramics for ultrahigh frequency applications achieved via Cr3+ ion doping

Phase formation, microstructure, magnetic properties, and dielectric properties of Ba_1.5Sr_1.5Co₂Fe₍₂₃−_x)Cr_xO₄₁ (0.0 ≤ x ≤ 1.0) ceramics, in which Fe³⁺ ions were substituted by Cr³⁺ ions, were systematically investigated. X-ray diffraction results reveal that Z-type hexagonal ferrite was formed by sintering at 1250 °C, and Cr³⁺ ions successfully enter lattice without destroying crystal structure. Analysis of the microstructure reveals that Cr³⁺ ion doping has significant effect on crystal micromorphology. Samples with x = 0.4 have the most homogeneous micromorphology and the highest sintering density of 5.12 g/cm³. In addition, under the influence of external magnetic field, all samples exhibit typical soft magnetic character and hysteresis characteristics, with saturation magnetization up to 63.86 emu/g (x = 0.6). Particularly, compared with undoped sample, Cr-doped samples have outstanding magnetic–dielectric properties. Firstly, with increasing Cr³⁺ amount, real part of the permeability (μ′) reaches the maximum value of 10.70 at x = 0.4, while cutoff frequency exceeds 2 GHz, and Snoek constant reaches ∼19.50 GHz. Furthermore, due to more homogeneous microstructure, samples with x = 0.4 have low magnetic loss and can maintain high quality factor (Q) over a broad frequency range. Moreover, real part of the permittivity (ε′) reaches the maximum value of 16.90 at x = 0.6, and dielectric loss remains lower than 0.013 for frequencies below 0.7 GHz. Consequently, magnetic–dielectric materials prepared in this work are expected to have extensive application prospects for ultrahigh-frequency devices.     

Frequency and temperature dependent electrical properties of Ni0.7Zn0.3CrxFe2−xO4 (0 ≤ x ≤ 0.5)

Series of the ferrite samples with a chemical formula Ni_0.7Zn_0.3Cr_xFe_2?xO₄ (x = 0.0–0.5) were prepared by a sol–gel auto-combustion method and annealed at 600 °C for 4 h. The prepared samples have the cubic spinel structure with no impurity phase. As the Cr³⁺ content x increases, the unit cell dimensions decrease with an increase in Cr³⁺ content x. The crystallite size is decreases from 37 nm to 21 nm as the Cr³⁺ content increases from x = 0.0 to 0.5. Resistivity increases whereas dielectric constant decreases with an increase in Cr³⁺ content x. Maxima in the dielectric loss tangent versus frequency appear when the frequency of the hopping charge carriers coincides with the frequency of the applied alternating field. Dielectric constant and dielectric loss tangent increases with increase in temperature. Saturation magnetization of sintered samples showed higher values as compared to as-prepared sample. Curie temperature deduced from AC susceptibility data decreases with increasing x.     

Low variation in relative permittivity over the temperature range 25–450 °C for ceramics in the system (1 − x)[Ba0.8Ca0.2TiO3]–x[Bi(Zn0.5Ti0.5)O3]

The dielectric and ferroelectric properties of the ceramic system, (1 − x)Ba_0.8Ca_0.2TiO₃–xBi(Zn_0.5Ti_0.5)O₃, were investigated for compositions 0 ≤ x ≤ 0.4. X-ray powder diffraction patterns indicated tetragonal symmetry at x ≤ 0.05, switching to pseudocubic at x ≥ 0.1, with a single-phase solid solution limit at 0.2 < x < 0.3. The x = 0 and 0.05 samples were ferroelectric; a change to relaxor behaviour occurred at x ≥ 0.1, with broad frequency dependent peaks in plots of relative permittivity versus temperature. A significant reduction in the temperature dependence of relative permittivity occurred at x = 0.3, with ɛ_r = 1030 ± 15% over the temperature range ∼25–425 °C, and loss tangent, tan δ ≤ 0.01 from 110 °C to 420 °C. The dc resistivity values for x = 0.3 were ∼10⁹ Ω m at 300 °C and ∼10⁶ Ω m at 450 °C.