新钽酸盐Ba2LnTi2Ta3O15(Ln=Y、La)的结构与介电性能

通过固相反应法合成了四方钨青铜结构新钽酸盐Ba2LaTi2Ta3O15与Ba2YTi2Ta3O15,分别进行了X射线衍射分析与介电性能测试.结果表明, Ba2LaTi2Ta3O15室温时晶胞参数为a=1.242 64(5) nm, c=0.391 57(2) nm,为四方钨青铜结构顺电相；Ba2YTi2Ta3O15室温时晶胞参数为a=1.236 46(4) nm, c=0.388 60(2) nm,为四方钨青铜结构铁电相,铁电相与顺电相转变温度为180 ℃.频率为1 MHz时, Ba2LaTi2Ta3O15陶瓷的室温相对介电常数为194,介电损耗也降低至8×10－4. Ba2YTi2Ta3O15陶瓷的室温相对介电常数为107.

Structure and Dielectric Properties of New Tantalates Ba2LnTi2Ta3O15 (Ln = Y, La)

New tantalates Ba2LnTi2Ta3O15 (Ln=Y, La) were synthesized by Ln partial substitution for Ba in the crystal structure of Ba3TiTa4O15.The crystal structure and dielectric properties were determined by X-ray powder diffraction and dielectric measurements. The results show that Ba2YTi2Ta3O15 belongs to ferroelectric phase of tetragonal tungsten bronze structure at room temperature with unit cell parameters: a=1.236 46(4) nm, c=0.388 60(2) nm. The phase transition of Ba2YTi2Ta3O15 from ferroelectric to paraelectric occurred at 180 ℃. Ba2LaTi2Ta3O15 belongs to paraelectric phase of tetragonal tungsten bronze structure at room temperature with unit cell parameters: a=1.242 64(5) nm, c=0.391 57(2) nm. At room temperature, the dielectric constant (εr) of Ba2YTi2Ta3O15 approached 107, while Ba2LaTi2Ta3O15 ceramic approached 194,combined with a low dielectric loss of 8×10－4 at 1 MHz. Ba2LaTi2Ta3O15 might be a suitable candidate of high εr microwave dielectric ceramics.