Crystal Structure and Electrical Properties of (1-x) (Ba_0.85Sr_0.15)TiO₃ - x(K_0.5Na_0.5)NbO₃ System

Abstract

The composition of (1-x) (Ba0.85Sr0.15)TiO3 – x (K0.5Na0.5)NbO3 (BST-KNN) for x=0.1 and x=0.2 were successfully prepared by two separate synthesis namely oxalate co-precipitation (for BST) and solid-state reaction (for KNN). Sintered pellet at 1200 °C for 2h exhibits a single phase except x= 0.2 showing a secondary phase and was identified as Ba2TiO4. KNN doped BST system show tetragonal symmetry in which higher dopant expand its tetragonality (c/a). The density of sintered samples deduced by Archimedes method are slightly higher than 90%. Permittivity measurements as function of temperature show almost similar Tc= 90 °C at frequency 1.273 kHz and shift to higher temperature as frequency increases indicating a typical relaxor characteristics. At room temperature the relative permittivity showing Debye relaxation characteristic with ωr=12560 (x=0.1) and ωr =20096 (x-0.2). Furthermore, as function of temperature the activation energy deduced from relaxation time was obtained Ea=0,564 eV for x=0.1 and 0,58 eV for x=0.2.