Effect of temperature and frequency on electrical properties of composite multiferroic of lead titanate and strontium hexaferrite (PbTiO3 – SrFe12O19)

Abstract

The work describes the use of dielectric and ac complex impedance and modulus spectroscopy techniques to obtain the electrical parameters like electrical conductivity and activation energy of composite multiferroic having composition (x) PbTiO3 – (1-x) SrFe12O19; where x = 0.10, 0.30, 0.50 in the frequency range 10–1000 KHz over a temperature range of 30–550 °C. The coexistence of low dielectric constant region with high dielectric constant region results in Maxwell – Wagner (M-W) polarization in the composite. Complex impedance and modulus spectroscopic analysis indicated the presence of non-Debye type dielectric relaxation in the composites. The grain (Rg) and space charge polarization resistance (RSCP) decreases with increase in temperature providing convincing evidence that the electrical properties of composite are temperature as well as microstructure dependent. The ac conductivity of composite calculated from dielectric loss and it shows an increase with increasing temperature suggesting semiconductor behavior. The hopping rate and concentration of charge carriers was calculated using Almond and West formalism based on Jonscher's universal power law. The activation energy of the ion migration and conduction was determined from temperature dependence of the hopping rate and dc conductivity respectively. For all compositions, the activation energy of dc conductivity is greater than that of hopping; i.e., Ea > Em. The increase in drift mobility represents enhanced mobility of the charge carriers due to thermal activation.