Crystal Structure and Electrical Properties of (1-x)(Ba_(0.85)Sr_(0.15))TiO_3-x(K_(0.5)Na_(0.5))NbO_3 System

摘要

The composition of (l-x)(Ba_(0.85)Sr_(0.15))TiO_3-x(K_(0.5)Na_(0.5))NbO_3 (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 for x= 0.2 showing a secondary phase which was identified as Ba_2TiO_4. KNN doped BST system show tetragonal symmetry in which higher dopant expand its tetragonality (c/a). The densities 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 of 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 ω_r= 12560 (x= 0.1) and ω_r= 20096 (x= 0.2). Furthermore, as function of temperature the activation energy deduced from relaxation time was obtained to be E_a= 0,564 eV for x= 0.1 and 0,58 eV for x=0.2.