新铌酸盐Ba5LnZnNb9O30(Ln=Y,La)的合成、结构与介电性能

在BaO-Ln2O3-ZnO-Nb2O5(Ln=Y,La)体系中通过固相反应法合成了填满型钨青铜结构的新铌酸盐Ba5YZnNb9O30与Ba5LaZnNb9O30.采用X射线衍射分析和扫描电镜进行了结构分析,并进行了介电性能测试.结果表明,Ba5YZnNb9O30为弛豫性铁电体,10kHz时的居里温度为25℃;室温时为四方钨青铜结构铁电相,晶胞参数a=1.25255(4)nm,c=0.39530(2)nm;1MHz时陶瓷体的室温相对介电常数为456.Ba5YZnNb9O30在室温下为四方钨青铜结构顺电相,晶胞参数a=1.25731(3)nm,c=0.39812(2)nm;频率为1MHz时,其陶瓷的室温相对介电常数为316.

Synthesis, Structure and Dielectric Properties of New Niobates Ba5LnZnNb9O30(Ln=Y, La)

Two new niobates Ba5YZnNb9O30 and Ba5LaZnNb 9O30 were synthesized by high temperature solid-state reaction in the BaO-Ln2O3-ZnO-Nb2O5 system. The crystal structure and dielectric properties were characterized by using X-ray powder diffraction, scanning electron microscope and dielectric measurements. The results show that Ba5YZnNb9O30 belongs to ferroelectric phase of fully filled tetragonal tungsten bronze structure at room temperature with unit cell parameters: a=1.252 55(4) nm, c=0.395 30(2) nm. Ba5YZnNb9O30 has significant relaxor behavior, and the phase transition from ferroelectric to paraelectric occurred at 25 ℃ as frequency was at 10 kHz. The room temperature dielectric constant(εr) of Ba5YZnNb9O30 ceramic reached 456 at 1 MHz. While Ba5LaZnNb9O30 belongs to paraelectric phase of fully filled tetragonal tungsten bronze structure at room temperature with unit cell parameters: a=1.257 31(3) nm, c=0.398 12(2) nm. The room temperature dielectric constant(εr) of Ba5LaZnNb 9O30 ceramic reached 316 combined with a low dielectric loss of 0.017 at 1 MHz.