Ashutosh Prasad

Electrical Conduction in 0–3 BaTiO3/PVDF Composites

(1-x)PVDF-xBaTiO3 ceramic-polymer composites with x = 0.10, 0.20, 0.30 were prepared using melt growth technique. The crystal symmetry, space group and unit cell dimensions were determined from the XRD data of BaTiO3 using FullProf software, whereas crystallite size and lattice strain were estimated through Williamson-Hall approach. The distribution of BaTiO3 particles in the PVDF matrix were examined using a scanning electron microscope. The correlated barrier hopping model has been applied to the ac conductivity data in order to ascertain the conduction mechanism of charge transport in BaTiO3/PVDF composites. Also, the ac conductivity data have been used to estimate the apparent activation energy, density of states at Fermi level and minimum hopping length. Filler concentration dependent ac conductivity, density of states at Fermi level and minimum hopping length data followed definite trends of exponential growth/decay types of variation.

Structural and Dielectric Properties of ZnO Added (Na1/2Bi1/2)TiO3 Ceramics

Structural and dielectric properties of polycrystalline samples of lead-free (1-x)(Na1/2Bi1/2)TiO3-xZnO, prepared using a high-temperature solid-state reaction method, were investigated in the composition range of 0≤x≤0.10. Rietveld analyses of X-ray diffraction data indicated the formation of a single-phase hexagonal structure with R3c symmetry. Williamson-Hall approach was applied to estimate the apparent particle size and lattice strain of the compounds. Temperature dependence of dielectric constant showed that the addition of ZnO to (Na1/2Bi1/2)TiO3 shifted the phase transition temperature towards higher side, a property favourable for practical applications of these ceramics. Further, temperature dependent permittivity data provided low temperature coefficient of capacitance (Tcc

Electrical Conduction in Ceramic by Complex Impedance/Modulus Spectroscopy

The present work describes the piezoelectric, impedance, and conductivity studies of ; BNT-BT ceramics. The ceramics were prepared by conventional ceramic fabrication technique. X-ray diffraction data confirmed the formation of a pure compound in all the compositions. Williamson-Hall plot yielded the apparent crystallite sizes ~26–52 nm, and SEM micrograph showed grain sizes ranging between 1.8–3.5 μm for the material samples. Values of longitudinal piezoelectric charge coefficients of the samples poled under a dc electric field of about 2.5 kV/mm at 80°C/15 min indicated that their piezoelectric properties near the MPB are rather sensitive to the phase composition and reach preferred values at , where the relative content of the tetragonal phase is significantly higher than that of the monoclinic phase. Complex impedance/modulus spectroscopic analyses indicated the presence of grain-boundary effect along with the bulk contribution and also confirmed the presence of non-Debye type of multiple relaxations in the materials. The temperature dependent electrical conductivity data suggest the negative temperature coefficient of resistance behaviour. The activation energy studies allow insight into the nature of the conduction mechanisms occurring in the materials system which are explained on the basis of hopping model of charge carriers.

Electrical conduction in (Bi0.5Na0.5)0.94Ba0.06TiO3-PVDF 0-3 composites by impedance spectroscopy

The present work describes the use of ac complex impedance and electric modulus spectroscopy techniques to obtain the electrical parameters like electrical conductivity and activation energy of (Bi0.5Na0.5)0.94Ba0.06TiO3 (BNBT06)-PVDF 0-3 composites with (a) 10, (b) 20 and (c) 30 vol. percentage of BNBT06 in the frequency range 100 Hz-5MHz over a temperature range of 35 o C-150°C. SEM micrographs showed almost homogeneous distribution of grains with less porosity for all the compositions and the EDAX patterns confirmed the presence of different constituent elements of the composite samples. Complex impedance spectroscopic analysis indicated the presence of non-Debye type dielectric relaxation in the composites. The bulk resistance showed the NTCR character of the composite materials and the presence of grain-boundary effect along with the bulk contribution, especially in the lower frequency and higher temperature regime, was indicated by the modulus spectroscopic analyses, thus confirming the non-Debye type of multiple relaxations in the system. The ac electrical conductivity data as a function of temperature also endorsed the NTCR character of BNBT06-PVDF 0-3 composites. The ac conductivity based activation energy data allowed insight into the mechanism of the occurring conduction processes in the composite system which are explained on the basis of hopping model of charge carriers. Keywords- Ceramic-polymer 0-3 composites; Grains /grain-boundaries; Hopping conduction; Complex impedance/ modulus spectroscopy; Ac conductivity; Activation energy

MICROWAVE DENSITY—INDEPENDENT PERMITTIVITY FUNCTIONS AS SPRING OATS KERNELS' MOISTURE CALIBRATORS: A NEW APPROACH

The present work makes use of experimental data for real part of microwave complex permittivity of spring oats (Avena sativa L.) at 2.45 GHz and 24 °C as a function of moisture content, as extracted from the literature. These permittivity data were individually converted to those for solid materials using seven independent mixture equations for effective permittivity of random media. Moisture dependent quadratic models for complex permittivity of spring oats (Avena sativa L.), as developed by the present group, were used to evaluate the dielectric loss factor of spring oats kernels. Using these data, seven density—independent permittivity functions were evaluated and plotted as a function of moisture content of the samples. Second and third order polynomial regression equations were used for curve fittings with these data and their performances are reported. Coefficients of determination (r2) approaching unity (∼ 0.95–0.9999) and very small Standard Deviation (SD) ∼0.001–8.87 show good acceptability for t...