Ceramics-Silikáty 52 (3) 190-200 (2008)

Structure, Dielectric and Impedance Properties of Barium Strontium Samarium Bismuth Niobate Ceramic

K. S. Rao , D. M. Prasad , P. M. Krishna, T. S. Latha

Frequency and temperature dependence of dielectric permittivity, impedance and electric modulus of Barium Strontium Samarium Bismuth Niobate, (Ba_0.1Sr_0.81Sm_0.06Bi₂Nb₂O₉, BSSBN) ceramics have been studied in frequency and temperature range of 45 Hz - 5 MHz and 31-595°C respectively. Simultaneous substitution of Ba and Sm in SBN increases the phase transition temperature of SBN. Cole-Cole plots of impedance in BSSBN ceramic suggest the relaxation to be non Debye type. Variation of grain and grain boundary resistance with temperature reflects the conduction in BSSBN is through grain. Variation of M" with frequency at different temperatures in the material results that M"_max shifts to higher frequency side indicates the presence of temperature relaxation process in the material. The value of stretched exponential parameter,  showed a minimum at T_C and on either side it gives higher values revealing the transverse mode (soft mode) is weakened and restoring force tends to become zero at ferroelectric - paraelectric transition. Near TC, in ferroelectric region, the activation energies obtained from complex impedance, electric modulus measurements and ac conductivity at 1 KHz are 0.61eV, 0.60eV and 0.63eV respectively. These are typical values for anionic conduction in BSSBN material.

Keywords: Bismuth layer structured ferroelectrics, Dielectric, impedance, electric modulus