A novel Na0.5K0.5NbO3-La(Zn0.5Ti0.5)O3 ceramics with excellent dielectric properties at wide temperature range

Ceramic-based dielectrics are considered as the best candidates for high temperature capacitors because of their outstanding mechanical and electrical properties. Nevertheless, conventional barium titanate-based capacitors show narrow operating temperature ranges owing to the low tetragonal-cubic phase transition temperature. In order to increase the working temperature and relative permittivity, a novel (1-x)Na0.5K0.5NbO3- xLa(Zn0.5Ti0.5)O-3 (NKN-xLZT) ceramics were chosen to meet the targets in this work. The NKN-xLZT ceramics with sub-micrometer grains (0.2-0.4 mu m) were synthesized via a conventional solid-state sintering route. A relative permittivity (epsilon' = 1560 +/- 15%) with low loss tangent over wide temperature range from 96 degrees C to 350 degrees C was obtained in the x = 0.02 ceramics. Additionally, the crystal structure distortion and conduction behaviors of the NKN-xLZT ceramics were systematically studied. The decrease of oxygen octahedron distortion induced a weak polarization, and the high resistance (9 x 10(6) Omega cm at 400 degrees C) greatly suppressed the long-term migration of defective ions in the ceramics. Therefore, the low loss tangent and high permittivity were still stabilized at the high temperature. It believes that the NKN-xLZT ceramic system in this work will become one of the most promising candidates for high-temperature capacitor devices.