Journal of Advanced Dielectrics

To understand possible interaction between magnetic and electric order parameters of Fe-doped Sr_xBa_1-xNb₂O₆ (SBN), Fe-doped Sr_0.5Ba_0.5Nb₂O₆ (SBN50) and Sr_0.4Ba_0.6Nb₂O₆ (SBN40) are synthesized and investigated. Synthesis has been carried out via ceramic route. The paper reports synthesis, crystal structure, dielectric properties, P–E hysteresis loops, M–H hysteresis loops and magneto-capacitance of the Fe-doped SBN compositions. All the compositions are observed to exhibit a useful value of magneto-capacitance, especially at frequencies less than 10 kHz.

Ceramic samples of Barium Zirconium Titanate (BaZr_xTi_1-xO₃ (BZT)) were synthesized by conventional solid-state reaction method with different concentrations of x(= 0.05 (BZT1), 0.10 (BZT2), 0.15 (BZT3), 0.20 (BZT4), 0.25 (BZT5), 0.30 (BZT6)). Phase confirmation of the samples was done by X-ray diffraction (XRD) technique. All the compositions are in cubic structure. XRD pattern was recorded for samples sintered at different sintering temperatures. Lattice parameters increased with addition of Zr⁺⁴. Doping with Zr⁺⁴ into Barium titanate resulted in interesting changes of electrical properties (dielectric, impedance and ferroelectiricity). The strong influence of Zr doping on the phase transition characteristics of the BZT ceramics was studied from the dielectric response of the samples. Diffusivity of phase transition of the BZT ceramic samples increase with Zr⁺⁴ concentration, indicating changes from normal to diffuse transition to relaxor phase transition behavior. Impedance spectroscopy reveals the presence of temperature-dependent grain, grain boundary effects. Polarization–Electricfield (PE) loop measurements are also done on the samples.

This paper examines the selection and performance evaluation of a variety of piezoelectric materials for cantilever-based sensor applications. The finite element analysis method is implemented to evaluate the relative importance of materials properties such as Young's Modulus (E), piezoelectric stress constants (e₃₁), dielectric constant (ε) and Poisson's ratio (υ) for cantilever-based sensor applications. An analytic hierarchy process (AHP) is used to assign weights to the properties that are studied for the sensor structure under study. A technique for order preference by similarity to ideal solution (TOPSIS) is used to rank the performance of the piezoelectric materials in the context of sensor voltage outputs. The ranking achieved by the TOPSIS analysis is in good agreement with the results obtained from finite element method simulation. The numerical simulations show that K_0.5Na_0.5NbO₃–LiSbO₃ (KNN–LS) materials family is important for sensor application. Young's modulus (E) is most influencing material's property followed by piezoelectric constant (e₃₁), dielectric constant (ε) and Poisson's ratio (υ) for cantilever-based piezoelectric sensor applications.

A structural analysis concerning the incorporation of dysprosium into A- and/or B-sites of the lead titanate is shown. The two "boundary" refinements are presented, i.e., Dy²⁺ substitutes for Pb²⁺ (Dy³⁺ substitutes for Ti⁴⁺) and Dy³⁺ substitutes for Pb²⁺ (Dy³⁺ substitutes for Ti⁴⁺). The results offer quantitative information about the incorporation into both crystallographic sites. The increase of Dy³⁺ fraction into B-site provides the increase of the Ti⁴⁺ atomic displacement along the [001] direction and the tetragonal distortion.

A series of ceramics with a general formula, La₂Ti_2-xTa_xO₇, in which x = 0.05, 0.1, 0.2, and 0.3, were prepared by Spark Plasma Sintering (SPS). Effects of tantalum substitution for titanium on the structure, dielectric, and piezoelectric properties were studied. Results revealed that the structure changed gradually from 4-layer to 3-layer due to the higher valence of Ta. The solid solution limit of tantalum in La₂Ti₂O₇ lattice was in the proximity of x = 0.2. The ferroelectric Curie temperature (T_c) decreased with increasing tantalum doping content. dc resistivity reached a maximum value at x = 0.2 with a value of ∼ 1.0 × 10⁸Ω ⋅ cm at 600°C. The influence of texture on the piezoelectric properties of La₂Ti_2-xTa_xO₇ ceramics was also investigated. A maximum d₃₃ value ∼2.1 pC/N was obtained at x = 0.2.

The current paper presents results of dielectric response, pyroelectric behavior and conductivity study of lead-free ferroelectric barium orthovanadate (Ba₃(VO₄)₂ or Ba₃V₂O₈) ceramic, for a wide range of temperature and frequency. An X-ray diffraction study suggests the formation of a single-phase compound in trigonal crystal system. The SEM micrograph of gold-coated pellet sample shows well-defined and homogeneous morphology. Detailed studies of dielectric parameters (ε_r and tan δ) of the compound as a function of temperature and frequency reveal their independence over a wide range of temperature and frequency. The nature of Polarization versus electric field (P–E) hysteresis loop of Ba₃V₂O₈ at room temperature suggests its ferroelectric nature. The temperature dependence of pyroelectric coefficient and figure of merits of the sample support its dielectric response. The nature of variation of dc conductivity with temperature confirms the Arrhenius and negative temperature coefficient of resistance (NTCR) behavior of the material.

Polycrystalline of [(Na_0.535K_0.480)_0.966Li_0.058](Nb_0.90Ta_0.10)O₃ samples were prepared using the high-temperature solid-state reaction technique. X-ray diffraction (XRD) analysis indicates the formation of a single-phase with orthorhombic structure. AC impedance plots were used as tool to analyze the electrical behavior of the sample as a function of frequency at different temperatures. The AC impedance studies revealed the presence of grain effect, from 425°C onwards. Complex impedance analysis indicated non-Debye type dielectric relaxation. The Nyquist plot showed the negative temperature coefficient of resistance (NTCR) characteristic of NKLNT. The AC conductivity results were used to correlate with the barrier hopping (CBH) model to evaluate the binding energy (W_m), the minimum hopping distance (R_min), the density of states at Fermi level (N(E_f)), and the activation energy of the compound.

For quantitative estimation of the degree of electrical disorder (electrical inhomogeneity) in ZnO varistor ceramics caused by a variation in the barrier height at different grain boundaries in a sample, the comparison of threshold electric fields (onsets of highly nonlinear current–voltage characteristics) in ceramics and single grain boundary (GB) is suggested and approved. At dc degradation similar behavior of the current–voltage characteristics of ZnO varistor ceramics and single GB is observed. The percolation model of Shklovskii–De Gennes is applicable for the description of a disorder in ZnO varistor ceramics. The degree of the disorder in ZnO varistor ceramics is not dependent on the duration of dc degradation at least at degradation time below 60 h. At voltages close to the onset of a highly nonlinear region of current–voltage characteristic the correlation radius of infinite cluster is ∼ 5 times greater than the average grain size.

In this paper, we designed a metamaterial absorber performed in microwave frequency band. This absorber is composed of E-shaped dielectrics which are arranged along different directions. The E-shaped all-dielectric structure is made of microwave ceramics with high permittivity and low loss. Within about 1 GHz frequency band, more than 86% absorption efficiency was observed for this metamaterial absorber. This absorber is polarization insensitive and is stable for incident angles. It is figured out that the polarization insensitive absorption is caused by the nearly located varied resonant modes which are excited by the E-shaped all-dielectric resonators with the same size but in the different direction. The E-shaped dielectric absorber contains intensive resonant points. Our research work paves a way for designing all-dielectric absorber.

We have systematically studied the composition dependence of the dielectric properties of Zr_1-xAl_xO_2-x/2 and Zr_1-xSi_xO₂. An essentially linear variation of the static dielectric constant, ε_s, was observed as a function of composition, x, for compositions rich in the p-block element, i.e., x > 0.4, for both chemical systems. However an abrupt change in ε_s is found near x ≈ 0.35, associated with the onset of crystallinity in as-deposited films. Breakdown fields do not show a comparable composition dependence. Measurements of the index of refraction at optical frequencies, combined with a simple Clausius–Mossotti interpretation, indicates that low-frequency (ionic) contributions to the polarizability exhibit systematic deviation with respect to values linearly interpolated from the endmembers. These trends are not consistently affected by the presence of crystalline order, but are related to changes associated with heterogeneous local oxygen coordination and bonding.