R. N. P. Choudhary

Erratum to: A comparative study of structural, electrical and magnetic properties rare-earth (Dy and Nd)-modified BiFeO3

The polycrystalline samples of BiFeO3 (BFO) and rare earth-modified bismuth iron oxide, Bi0.95R0.25FeO3 (R = Nd, Dy) (BNFO, BDFO) are prepared by a standard high-temperature solid-state reaction technique. A preliminary x-ray structural analysis is carried out to examine the structural deformation and stability of rare earth-modified BFO. Room temperature surface morphologies and textures of the samples are recorded by a scanning electron microscope, which reveals the uniform distribution of the plate-and rod-shaped grains. Studies of dielectric and electric properties in a wide frequency (1 kHz–1 MHz) and temperature (30–400 °C) ranges using complex impedance spectroscopic method have provided many new results. The dielectric constant is found to be increases, and the tangent loss decreases as compared to BFO. The electrical polarizations (spontaneous and remnant) is found to be enhanced on rare-earth substitutions. Studies of ac conductivity suggest that the samples obey Jonscher’s universal power law. The enhancement of magnetization was observed in rare-earth doped samples compared to pure BFO.

Structural, electrical and magnetic characteristics of improper multiferroic: GdFeO3

Studies of dielectric, impedance, conductivity, magnetic and magneto-electric (ME) properties of GdFeO3 ceramics fabricated by chemical method are reported here. The synthesized powder is phase-pure and crystallizes in the orthorhombic crystal structure. Below 50 degrees C, the impedance has only grain contribution, while at higher temperatures, it has both grain and grain boundary contributions. Based on the depression angle of the Nyquist plot, the inhomogeneity of the sample is estimated. The capacitance data reveal that at low temperatures, the sample behaves as a leaky capacitor while at higher temperatures the sample shows the effect of the diffusion of thermally excited charge carriers across a barrier. In the low-frequency domain, the dielectric characteristics were explained on the basis of the Maxwell-Wagner mechanism, while in the high-frequency range those were correlated to the grain effect. The frequency dependent characteristic of the tangent loss is explained as a combined contribution from the Debye-like relaxation and dc conductivity related mechanism at higher temperatures. The temperature dependence of the dielectric characteristic and data are found to fit with two Gaussian peaks centered at 148 degrees C and 169 degrees C. While the first peak is explained on the basis of the Maxwell-Wagner mechanism, the second has its origin in magnetic reordering and the shifting of Gd3+ ions along the c-axis. The magnetic reordering also results in a sharp decrease of conductivity between 169 degrees C and 243 degrees C. The frequency dependent ac conductivity is explained on the basis of the correlated barrier hopping model and the quantum mechanical hopping model for the different frequency domain. The existence of P-E and M-Hloops support its improper ferroelectric behavior and canted anti-ferromagnetism respectively. The ME coefficient of the sample is found to be 1.78 mV cm(-1) Oe(-1).

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.

Structural, dielectric, impedance and modulus spectroscopy of Bi2NdTiVO9 ferroelectric ceramics

Detailed studies of electrical and resistive properties of Bi2NdTiVO9 (a member of the Aurivillius family), fabricated by a method of standard high-temperature solid-state reaction, are discussed here. The compound crystallizes in the orthorhombic crystal structure. The surface morphology studies show a uniform distribution of grains. The single semicircle of the complex impedance plot and the value of the nonlinear coefficient of the J∼E graph suggest that the polarization in the material is due to grain effect only. The semiconducting nature (i.e., negative temperature coefficient of resistance) is observed in the temperature dependence of bulk resistance and J–E characteristics of the sample. The frequency dependence of impedance and electrical modulus of the material shows the existence of non Debye-type of relaxation. The activation energy obtained from the relaxation and conduction processes is found to support the activation of oxygen vacancies in the compound. An analysis of ac conductivity, based on the Jonscher’s power law, suggests that the conduction mechanism in the material can be explained using CBH model (i.e., hopping of oxygen ions between vacancies). The nature and existence of electric field dependent polarization (P–E hysteresis loop) at room temperature show that the material has ferroelectric property.

Structural, Dielectric, and Electrical Properties of BiFeWO6 Ceramic

A polycrystalline sample of BiFeWO6 was synthesized using a high-temperature solid-state reaction method. The formation of the single-phase compound was checked using an x-ray diffraction technique. The surface morphology recorded by scanning electron microscopy exhibited a uniform distribution of grains of different sizes on the surface of the sample. The existence of ferroelectric properties in the material was confirmed by temperature-dependent dielectric and polarization studies. The temperature and frequency dependence of the electrical properties (impedance, modulus, and conductivity) of the compound were studied using a complex-impedance spectroscopy technique. The frequency dependence of the modulus and impedance plots confirmed the presence of dielectric and conductivity relaxation processes of non-Debye type. The frequency dependence of the alternating-current (ac) conductivity obeys Jonscher’s universal power law.

Capacitive, resistive and conducting characteristics of bismuth ferrite and lead magnesium niobate based relaxor electronic system

The ferroelectric relaxor based BFO–PMN [bismuth ferrite (BiFeO3; BFO) and lead magnesium niobate (PbMg1/3Nb2/3O3; PMN)] binary electronic system has been synthesized making use of the solid state chemical reaction technique. The capacitive, resistive and conducting characteristics of the prepared solid solutions [((PbxBi1−x)(Mg0.33xNb0.66xFe1−x)O3) with x = 0.1, 0.2, 0.3 and 0.4] have been studied along with their structural and morphological characteristics. It has been revealed that the dielectric behaviour of BFO–PMN is modified with the addition of PMN content. The nature of phase has also been changed from a general ferroelectric towards a typical relaxor. The comprehensive experimental impedance analysis substantiates the contributions of grain boundary including the grains in the resistive and capacitive characteristics. The prepared compounds illustrate non-Debye type of dielectric relaxation behaviour. The studied material may pave the way for formulation of electronic components.

Dielectric dispersion and impedance spectroscopy of yttrium doped BiFeO3-PbTiO3 electronic system

The dielectric dispersion and impedance spectroscopy of multiferroic bismuth ferrite (BFO; BiFeO3) and lead titanate (PT; PbTiO3) electro ceramics have been altered by doping chemically with Yttrium (Y3+). The distinctive structural study including morphology as well as electrical properties of Y3+ doped BFO-PT solid composite [(Pb0.9Bi.05Y0.05) (Fe0.1Ti0.9)O3] depicts several interesting results on structure-properties correlation. The development of single phase compound with tetragonal crystal coordination is predicted from X-ray diffraction (XRD). The micrograph substantiates the development of dense grains. The chemical content and composition of the prepared solid solution is determined using the energy dispersive X-ray (EDX) technique. The impedance spectroscopy shows the evidence of grain as well as grain boundary effects leading to the subsistence of negative temperature coefficient of resistance (NTCR) in this processed material. At lower temperature region, the ac conductivity of this compound rises with the frequency. The processed electronic compound illustrates non-Debye type electrical relaxation behaviour. The preliminary study of the prepared electronic material may provide some useful information for devise of electronic components as well as gadget.

Development of ilmenite-type electronic material CdTi0 3 for devices

The correlation between structural and electrical properties of cadmium titanate (CdTiO3) ceramic was established through X-ray diffraction combined with electrical and optical characterization techniques. The compound was prepared using a high-temperature solid-state reaction technique. Preliminary study on some structural aspect of the material using X-ray diffraction pattern showed the formation of single-phase compound in orthorhombic crystal system. Some characteristics of molecular structure of the material were studied by using Fourier transform infrared spectroscopy and ultraviolet visible spectroscopy techniques. The size and distribution of grains in the scanning electron micrograph revealed the polycrystalline nature of the material with size anisotropy and small number of voids. Detailed analysis of temperature-frequency dependence of dielectric parameters (i.e. dielectric constant and tangent loss) has revealed many interesting and important results of the material. The impedance studies of CdTiO3 over a wide range of temperature and frequency in the complex plane formalism with suitable equivalent circuit have shown some correlation between microstructure and electrical properties of the material. From the impedance and dielectric measurements some electrical parameters such as bulk resistance, capacitance, relaxation time and relative dielectric constant were calculated. The variation of DC conductivity with inverse of absolute temperature follows the Arrhenius relation. The study of frequency dependence of AC conductivity suggests that the material obeys Jonschers universal power law.

Dielectric and impedance spectroscopy of (Bi0.5Li0.5)(Fe0.5Nb0.5)O3 multiferroics

The polycrystalline sample of (Bi0.5Li0.5)(Fe0.5Nb0.5)O3 was prepared by a solid-state reaction method. Preliminary X-ray structural analysis of the sample suggests the formation of a tetragonal phase with a new unit cell configuration. Dielectric, electrical, impedance and modulus properties of the material were investigated in a wide range of temperature (25–500 °C) and frequency (1 kHz–1 MHz). Two dielectric anomalies observed at 295 °C and 400 °C clearly suggest the existence of magnetic phase transition and two relaxation processes in the system. Dielectric properties have greatly been improved on addition of LiNbO3 to BiFeO3. The appearance of a hysteresis loop at room temperature confirms the ferroelectric properties of the material. The nature of the Nyquist plot confirms the presence of both bulk and grain boundary effects in the material. The ac conductivity was found to obey Jonschers power law. The dc conductivity variation with temperature follows the Arrhenius equation. The induced voltage changes with the applied magnetic field, showing that the sample is multiferroic.

Dielectric and impedance characteristics of Bi(Zn2/3Nb1/3)O3 electronic material

The capacitive, resistive and conducting characteristics of Bi(Zn2/3Nb1/3)O3 electronic material have been investigated experimentally. Detailed studies of frequency–temperature dependence of electrical parameters using impedance spectroscopy technique provide the experimental evidence of contributions of grain as well as grain boundary in the resistive and capacitive characteristics of the synthesized material. Temperature and frequency dependent ac conductivity of the compound provides the nature and conduction mechanism of the material studied. The compound illustrates its non-Debye type of dielectric relaxation behaviour. The preliminary study of the electronic material may provide some useful information for formulation of electronic components as well as gadget.