新铌酸盐Sr5LnTi3Nb7O30的结构与介电性能

在SrO-Ln2O3-TiO2-Nb2O5(Ln=La, Y)体系中,通过固相反应法，合成了填满型钨青铜结构新铌酸盐Sr5LaTi3Nb7O30与Sr5YTi3Nb7O30.分别采用X射线衍射分析、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, Sr5LaTi3Nb7O30室温时为四方钨青铜结构顺电相,晶胞参数a=1.233 60(4) nm, c=0.388 01(2) nm;频率为1 MHz时,其陶瓷的室温相对介电常数为466,介电损耗约为5×10－3.Sr5YTi3Nb7O30为弛豫性铁电体, 10 kHz时居里温度为260 ℃;室温时为四方钨青铜结构铁电相,晶胞参数a=1.228 80(4) nm, c=0.387 05(2) nm; 1 MHz时,陶瓷体的室温相对介电常数为290.

Structure and Dielectric Properties of New Niobates Sr5LnTi3Nb7O30

Two new niobates Sr5LaTi3Nb7O30 and Sr5YTi3Nb7O30 were synthesized by using high temperature solid state reaction in the SrO-Ln2O3-TiO2-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 Sr5LaTi3Nb7O30 belongs to paraelectric phase of fully filled tetragonal tungsten bronze structure at room temperature with unit cell parameters: a=1.233 60(4) nm, c= 0.388 01(2) nm. The room temperature dielectric constant (εr ) of Sr5LaTi3Nb7O30 ceramic reached 466 combined with a low dielectric loss of 0.005 at 1 MHz. While Sr5YTi3Nb7O30 belongs to ferroelectric phase of fully filled tetragonal tungsten bronze structure at room temperature with unit cell parameters: a=1.228 80(4) nm, c=0.387 05(2) nm. Sr5YTi3Nb7O30 has significant relaxor behaviors, and the phase transition from ferroelectric to paraelectric occurred at temperature 260 ℃ and frequency 10 kHz. The room temperature relative dielectric constant (εr) of Sr5YTi3Nb7O30 ceramic reached 290 at 1 MHz.