Detailed Studies Of Dielectric Parameters Research Articles

RETRACTED ARTICLE: Study of effect of Gd substitution at the Fe site on structural, dielectric and electrical characteristics of BiFeO3

In this communication, the effect of gadolinium (Gd) substitution on structural, microstructural, electrical and dielectric properties of bismuth ferrite BiFeO3 (i.e. Bi(Fe0.95Gd0.05)O3 abbreviated as BFGO5) has been reported. The development of an environment-friendly lead-free multiferroic material by substituting a rare earth element at the uncommon site of BiFeO3 (BFO) (i.e. Gd at the Fe site rather than commonly preferred Bi site) for the tailoring of its multiferroic properties has been attempted in this study. The present studied material has been fabricated through a conventional standard solid-state reaction (SSR) method using carbonates and high-quality oxides in a stoichiometric amount. The phase formation and basic crystal data were analysed by X-ray diffraction technique which shows a single-phase formation of BFGO5 material in orthorhombic symmetry. The average crystallite size was calculated using Scherrer’s formula and found to be 84 nm. The surface morphology and compositions examined by FE-SEM, EDX, FT-IR and TEM show the formation of highly compact sample with uniform distribution of grains. Detailed studies of dielectric parameters (dielectric constant and tangent loss) in a selected frequency range (1–1000 kHz) at different temperatures (273–773 K) clearly exhibit enhancement on dielectric properties of BFO. Studies of its impedance spectroscopy, electrical modulus and electrical conductivity confirm the semiconductor behaviour [negative temperature coefficient of resistance (NTCR)] and non-Debye type relaxation process of the material. The polarization versus electric field (P–E) analysis of BFGO5 shows an improvement in remnant polarization as compared to the parent compound BFO. Therefore, based on the several investigations of results, the BFGO5 material could be considered as a favourable candidate for electronic device applications.

Structural, dielectric, electrical and magnetic characteristics of lead-free multiferroic: Bi(Cd0.5Ti0.5)O3[sbnd]BiFeO3 solid solution

This communication provides the detailed description of the synthesis and characterization of a lead-free multiferroic solid solution of Bi(CdTi)O3 and BiFeO3 of a general chemical composition Bi(Cd0.45Ti0.45Fe0.10)O3 (abbreviated as BCTFO). The material has been synthesized via a solvent-free solid-state reaction approach by utilizing high-purity oxides and carbonate in appropriate stoichiometric amount. The structural, morphological, molecular structure, electrical and magnetic characteristics of as-synthesized electronic system were examined by the powder X-ray diffraction, field emission scanning electron microscopy, vibrating sample magnetometer and impedance spectroscopy techniques respectively in different experimental conditions. Analysis of X-ray diffraction data of BCTFO shows a single-phase formation of the material in orthorhombic crystal symmetry with very fine powder (average linear crystallite dimension = 30 nm). Detailed studies of dielectric parameters (dielectric constant, tangent loss and polarization) in a selected frequencies (1 kHz–1.5 MHz) and temperatures (300 K–773 K) clearly exhibit one of the important components of multiferroics (i.e., ferroelectricity). Studies of some components of electrical parameters (dielectric, impedance, electric modulus and conductivity) of complex spectroscopy confirmed the existence of non-Debye type and other type of dielectric relaxation process in the material. The correlation between the real and idealized circuit response at several temperatures has been investigated by using ZSIMP WIN software and impedance data. Study of another component of multiferroics (i.e., field dependent magnetization) of BCTFO shows the significantly higher value of remnant and spontaneous magnetization. Thus, the existence of dielectric polarization and magnetization is single phase (orthorhombic) in a distorted perovskite confirms the multiferroicity of bismuth ferrite modified bismuth cadmium titanate (BCTFO) at room temperature, and hence the material can be used for some multifunctional applications.

Dielectric response and pyroelectric properties of lead-free ferroelectric Ba3(VO4)2

The current paper presents results of dielectric response, pyroelectric behavior and conductivity study of lead-free ferroelectric barium orthovanadate ( Ba 3( VO 4)2 or Ba 3 V 2 O 8) 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 (εr 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 Ba 3 V 2 O 8 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.

Pyroelectric Response and Conduction Mechanism in Highly Crystallized Ferroelectric Sr3(VO4)2 Ceramic

We present a study on the ferroelectric phase transition, pyroelectric properties, and conduction mechanism of highly crystallized strontium orthovanadate (Sr3V2O8) ceramic, prepared by a solid-state reaction technique. X-ray diffraction studies show the formation of a single-phase compound in trigonal crystal system. Detailed studies of dielectric parameters (er and tan δ) of the compound as a function of temperature and frequency reveal their independence over a wide range of temperature and frequency. An anomaly in er suggests the possible existence of a ferroelectric–paraelectric phase transition of diffuse type in the material, which is confirmed by electric polarization and pyroelectric studies. The low dielectric loss and moderate relative permittivity make this material (with suitable modifications) a potential candidate for use in microwave applications. The low leakage current and negative temperature coefficient of resistance (NTCR) behavior of the sample have been verified from J–E plots. The nature of the variation of the direct-current (DC) conductivity with temperature confirms the Arrhenius and NTCR behavior of the material.

Dielectric and electrical properties of gadolinium-modified lead-zirconate-titanate system

The gadolinium (Gd) modified lead zirconate titanate (PbZr,TiO3) ceramics with Zr/Ti=48/52 (i.e., near morphotropic phase boundary (MPB)) in a general chemical formula Pb1−xGdx (Zr0.48Ti0.52)1−x/4 O3 (PGZT; x=0, 0.07, 0.10 and 0.12) have been synthesized using a high-temperature solid-state reaction method. Preliminary structural analysis using X-ray powder diffraction (XRD) shows the formation of a single-phase tetragonal structure of the compounds. Detailed studies of dielectric parameters of PGZT exhibit the diffuse phase transition but non-relaxor characteristics in the material for the higher concentration of gadolinium. The ac conductivity spectra of PGZT are found to obey Jonscher’s universal power law. The electrical impedance parameters of PGZT (near MPB) were obtained in a wide range of temperature (25–500°C) and frequency (1–1000kHz) using complex impedance spectroscopy (CIS) technique. Detailed analysis of these parameters shows that bulk (grain) and grain boundary resistance have significant effect on the total impedance of the materials. Temperature dependence of hysteresis characteristics of PGZT confirms that the phase transition parameter of the material is strongly affected by the substitution of Gd at the Pb-sites.

Pyroelectric and dielectric properties of lead-free ferroelectric Ba3Nb2O8 ceramic

The present study highlights ferroelectric phase transition, dielectric, pyroelectric properties and conduction mechanism of highly crystallized barium orthoniobate (Ba3Nb2O8) ceramic, prepared by a solid-state reaction technique. X-ray diffraction studies show the formation of a single-phase compound in hexagonal crystal system. Detailed studies of dielectric parameters (εr and tanδ) of the compound as a function of temperature and frequency reveal their independence over a wide range of temperature and frequency. An anomaly in εr suggests the possible existence of a ferroelectric–paraelectric phase transition of diffuse-type in the material. The low dielectric loss and moderate relative permittivity make this material (with certain modification) a potential candidate for microwave applications. Studies of pyroelectric properties reveal that the materials have reasonably high figure of merit useful for fabrication of pyroelectric detectors. The low-leakage current and negative temperature coefficient of resistance (NTCR) behavior of the sample have been verified from J–E plots. The nature of variation of dc conductivity with temperature confirms the Arrhenius and NTCR behavior of the material.

Dielectric and impedance spectroscopy of Sr(Bi0.5Nb0.5)O3 ceramics

A lead free polycrystalline material Sr(Bi0.5Nb0.5)O3 was prepared using a high-temperature solid-state reaction technique. Preliminary X-rays diffraction studies exhibit the formation of a single-phase compound in the orthorhombic crystal system. The study of microstructure of gold-coated pellet by scanning electron microscopy (SEM) shows well-defined and homogeneous distribution of grains on the surface of the sample. Detailed studies of dielectric parameters (i.e., εr and tanδ) of the compound as a function of temperature at selected frequencies reveal that the values of these parameters are almost independent of temperature. Studies of impedance and related parameters exhibit that these electrical properties of the material are strongly dependent on temperature, and bear a good correlation with the microstructure of the material. The decrease in value of bulk resistance on increasing temperature suggests the existence of negative temperature co-efficient of resistance (NTCR) in the material. Studies of electric modulus show the presence of hopping conduction mechanism in the material with non-exponential-type of relaxation. The nature of variation of dc conductivity with temperature confirms the Arrhenius- and NTCR- types of behaviors of the material. The ac conductivity spectrum provides a typical-signature of an ionic conducting system, and is found to obey Jonscher′s universal power law.

Studies of dielectric, pyroelectric and conduction mechanism of Sr3Ta2O8

Abstract The current research work reports on structural, dielectric, pyroelectric and conduction properties of strontium orthotantalate, prepared by using a high-temperature solid-state reaction technique. Preliminary x-rays structural study of the material confirms the formation of a single-phase compound with trigonal crystal structure. The microstructure of gold-coated pellet sample recorded by scanning electron microscopy (SEM) shows well-defined and homogeneously distributed grains. Detailed studies of dielectric parameters ( e r and tan δ ) of the compound as a function of temperature at some selected frequencies reveal that these parameters are invariant in a wide range of frequency and temperature (room temperature to about 400 °C). Studies of pyroelectric properties reveal that the materials have reasonably high figure of merit useful for fabrication of pyroelectric detector. The ac conductivity spectra show a typical-signature of an ionic conducting system, and are found to obey Jonscher's universal power law. The low leakage current and negative temperature coefficient of resistance (NTCR) behavior of the sample have been verified from J ~ E plots. The nature of variation of dc conductivity with temperature confirms the Arrhenius and NTCR behavior in the material.

Phase transition and electrical properties of strontium orthovanadate

Abstract The current research work reports the study of phase transition and transport mechanism in lead-free strontium orthovanadate (Sr3V2O8), prepared using a high-temperature solid-state reaction technique. Preliminary X-rays diffraction studies exhibit the formation of a single-phase compound in the trigonal crystal system. Study of microstructure of gold-coated pellet by scanning electron microscopy (SEM) shows well-defined and homogeneous grains in the morphology. Detailed studies of dielectric parameters (er and tan δ) of the compound as a function of temperature at some selected frequencies reveal their independence for a wide range of temperatures. An anomaly in relative permittivity (er) suggests the existence of a ferroelectric–paraelectric phase transition of diffuse-type in the material that confirms through the detailed studies of its electric polarization. Detailed studies of impedance and related parameters exhibit that the electrical properties of the material are strongly dependent on temperature, and bear a good correlation with its microstructure (i.e., bulk, grain boundary, etc.). The decrease in value of bulk resistance on increasing temperature suggests the negative temperature co-efficient of resistance (NTCR) behavior of the material. Studies of electric modulus indicate the presence of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation. The nature of variation of dc conductivity with temperature confirms the Arrhenius and NTCR type of behavior in the material. The ac conductivity spectrum shows a typical-signature of an ionic conducting system, and is found to obey Jonscher’s universal power law.

Dielectric and electrical properties of Na2Pb2La2W2Ti4Ta4O30 electroceramics

The polycrystalline sample of complex tungsten-bronze type compound (Na2Pb2La2W2Ti4Ta4O30) was prepared by a high-temperature solid-state reaction technique. Room temperature preliminary structural study using X-ray diffraction (XRD) data exhibits the formation of a single-phase new compound. The SEM micrograph of the compound exhibits non uniform rectangular grains distributed throughout the sample surface. Detailed studies of dielectric parameters (ɛr, tan δ) as a function of temperature and frequency, and P-E hysteresis (spontaneous polarization) confirmed the existence of ferroelectricity in the material. Complex impedance spectroscopy analysis, carried out as a function of frequency at different temperatures, established a correlation between the microstructure and electrical properties of the material. The electrical relaxation process occurring in the material is temperature dependent. The activation energy found from the Arrhenius plot that the conduction process in the material is of mixed type. The nature of frequency dependence of ac conductivity suggests that the material obeys Jonscher’s universal power law.

Effect of doping Ca ions on structural and electrical properties of Ba(Zr0.05Ti0.95)O3electroceramics

Polycrystalline samples of (Ba1−zCaz)(Zr0.05Ti0.95)O3 (z=0, 0.03, 0.06 and 0.09) (BCZT) belonging to perovskite ferroelectric were prepared by a high-temperature solid-state reaction technique. Preliminary room temperature X-ray study confirmed the formation of a single phase compound in orthorhombic crystal structure. Detailed studies of dielectric parameters as a function of temperature at 10 kHz suggests that the substitution of Ca2+ ion at the Ba-site and Zr4+ at Ti-site has a strong effect on the dielectric properties of BaTiO3.

Ferroelectric phase transition in sol-gel derived Bi-doped PLZT ceramics

Polycrystalline samples of Bi-modified PLZT, [Pb0.92(La1−zBiz)0.08][Zr0.60Ti0.40]0.98O3 (abbreviated as PLBZT) for z = 0.0, 0.3, 0.6, 0.9 and 1 were prepared through a metal-alkoxide/sol-gel route. Preliminary X-ray diffraction study of the compounds confirmed the formation of single-phase tetragonal compounds. Scanning electron-microscopic (SEM) study of pellet samples of PLBZT shows uniform distribution of grains (spherical) throughout the sample surfaces. Detailed studies of dielectric parameters (dielectric constant, tangent loss) of PLBZT as a function of temperature (30 to 450°C) at 10 kHz reveal that the compounds have diffuse phase transitions. Large variation (first increase and then decrease) in dielectric constant and shift of transition temperature towards higher temperature side with increasing Bi concentration was also observed in PLBZT. The nature of variation of dc resistivity shows that the titled compounds have negative temperature coefficient of resistance (NTCR). Pyroelectric coefficient of the PLBZT compound (z = 0.0 to 1.0) increases with increase of Bi content in PLZT. The transition temperature obtained in this study is very much consistent with that obtained from our dielectric studies. Piezoelectric d33 coefficient of the compound at 100 Hz was found to be 385, 272, 301, 248 and 291 pc/N for z = 0.0, 0.3, 0.6, 0.9 and 1 respectively.

Structural dielectric and electrical conducting properties of KB′B″O 6 (B′=Nb, Ta; B″=W, Mo) ceramics

The polycrystalline samples of the defect pyrochlore-type KB′B″O 6 (B′=Nb, Ta; B″=W, Mo) compounds were prepared by solid-state reaction technique. The formation of the compounds was checked by X-ray diffraction (XRD) technique. All the compounds have cubic crystal structure at room temperature. Detailed studies of dielectric parameters ( ϵ, tan δ) in wide frequency (10 3–10 6 Hz) and temperature (300–600 K) range reveal that the compounds do not have any dielectric anomaly in the studied frequency and temperature range. Detailed studies of electrical properties (viz. ac and dc conductivity, transference number) as functions of various parameters, e.g. frequency, biasing de electric field, temperature, etc., are carried out.