类钙钛矿新铌酸盐Ba_3La_2Ti_2Nb_2O_(15)的合成、结构与介电特性

Synthesis,Structure and Dielectric Properties of a New Pervoskite-related Niobate Ba_3La_2Ti_2Nb_2O_(15)

为满足现代通信技术的小型化、集成化与高可靠性的迫切要求，探索具有高介电常数、低介电损耗与低温度系数的微波介电材料引起了材料科学、化学、物理和电子学等领域科学工作者的广泛关注，并已开发出复合钙钛矿结构［Ba(Zn1/3Ta2/3)O3］和钨青铜结构［Ba6-3xLn8+2xTi18O54］等实用化的高性能材料［1～5］.

A new niobate Ba3La2Ti2Nb2O15 was synthesized by high temperature solid state reaction in the BaO-La2O3-TiO2-Nb2O5 system. The chemical compositions, crystal structure, microstructure, density and melting point of the new compound were characterized by EPMA, XRD, SEM, DTA and so on. Ba3La2Ti2Nb2O15 crystallizes in the hexagonal system with unit cell parameters a = 0. 568 2(1) nm, c -1.165 7(1) nm, and space group P3m1, Z = l. The structure may be described as four (Nb,Ti)O6 octa-hedra corner-sharing to form hexagonal perovskite layer, while Ba or La occupying the interstices. The Ba3La2Ti2Nb2O15 ceramic exhibits a high dielectric constant of 90. 04, a low dielectric loss of 4. 5 × 10-4 and a small temperature coefficient of dielectric constant of -65 × 10-6 K-1 at 1 MHz due to its close structure and relative high dielectric polarizabilities of Ba2+, La3+, Ti4+ and Nb5+. Ba3La2Ti2Nb2O15 might be a suitable candidate of high er microwave dielectric ceramics.