Piezoelectric, impedance, electric modulus and AC conductivity studies on (Bi0.5Na0.5)0.95Ba0.05TiO3 ceramic

Abstract

Lead-free piezoelectric perovskite ceramic (Bi0.5Na0.5)0.95Ba0.05TiO3 (BNT-BT0.05), prepared by conventional high temperature solid state reaction technique at 1160 °C/3h in air atmosphere, is investigated by impedance and modulus spectroscopy in a temperature range 35–400 °C, over a frequency range 100 Hz–1 MHz. The crystal structure, microstructure, and piezoelectric properties as well as the AC conductivity of the sample were studied. Powder X-ray diffraction pattern derived from the resulting data at the room temperature subjected to Rietveld refinements and Williamson-Hall plot analysis confirmed the formation of phase pure compound with monoclinic unit cells having a crystallite-size ~33.8 nm. Observed SEM micrograph showed a uniform distribution of grains inside the sample having an average grain size ~3 mm. Longitudinal piezoelectric charge coefficient of the sample poled under a DC electric field of ~ 2.5 kV/mm at 80 °C in a silicone oil bath was found to be equal to 95 pC/N. The frequency and temperature dependent electrical data analysed in the framework of AC conductivity, complex impedance as well as electric modulus formalisms showed negative temperature coefficient of resistance (NTCR) character of the material and the dielectric relaxation in the material to be of non-Debye type. Double power law for the frequency-dependence of AC conductivity and Jump Relaxation Model (JRM) were found to explain successfully the mechanism of charge transport in BNT-BT0.05

Structure and electrical properties of lead-free Bi0.5Na0.5TiO3-based ceramics for energy-storage applications

“…Additionally, the exponent s 2 in all the samples reached a minimum at ~400ºC, which was the onset of the sharp rise in temperature-dependent dielectric loss curves (Fig. Within the same temperature region, E a reduced with frequency, which is also observed in other systems [48,62]. Within the same temperature region, E a reduced with frequency, which is also observed in other systems [48,62].…”

Optical and Microwave Dielectric Properties of Phase Pure (K0.5Na0.5)NbO3 Thin Films Deposited by RF Magnetron Sputtering

“…The increment in s 1 with increasing of OMP may be due to the enhancement in the short‐range hopping process, which corresponds to the grain‐boundary conduction. However, the reduction in s 2 value with an increase in OMP can be attributed to the reduction in charge defects presented in the samples …”

Comments on frequency dependent AC conductivity in polymeric materials at low frequency regime

“…We now consider a situation where, apart from DC conductivity σ ο , two dielectric loss mechanisms are also present: the first one at the low frequency regime having a characteristic frequency,  minimum, the high frequencies slope can take values higher than 1. It is observed that, with decreasing value of the shape parameter α, the superlinear value of the apparent n exponent, which is calculated in the frequency range of the one order of magnitude lower 16 than HN f , gradually decreases. The high frequencies slope of the AC conductivity is mainly formed from the contribution of slower components of the molecular dipolar relaxation at this frequency range.…”