Structural and dielectric properties of La and Nb co-substituted Bi0.5(Na0.84K0.16)0.5TiO3-SrTiO3 ceramics

摘要

In this article La and Nb co-substitution effect on the crystal structure, microstructure, ferroelectric and dielectric properties of 0.96[{Bi (Na K)}La(Ti Nb)O]-0.04SrTiO (BNKLTN-ST, where (x=y) = 0.00 - 0.020) ceramics has been investigated. The ceramics with x,y ≤ 0.010 have pure perovskite structure, while a secondary phase appears in the sample with x=y = 0.020. X-ray diffraction patterns revealed that La and Nb co-doping resulted in a transition from coexistent rhombohedral and tetragonal phases to pseudocubic symmetry. The co-doping of La and Nb slightly increased the average grain size. The maximum permittivity temperature (T) increased with increasing La and Nb contents, but the values of depolarization temperature (T) as well as maximum dielectric constant (ε) decrease gradually. La and Nb addition interrupted the polarization and reveals that the ferroelectric (FE) order of unmodified BNKT-ST ceramics lead to a declination of remnant polarization along with coercive field. The results shows that La and Nb co-doping into BNKT-ST ceramics induces a phase transition from relaxor FE to ergodic relaxor phase with a substantial deterioration of the long-range FE order.