类钙钛矿新铌酸盐Ba_5NdTi_2Nb_3O_(18)的合成、结构与介电特性

Synthesis, Structure and Dielectric Properties of a New Pervoskite-related Niobate Ba_5NdTi_2Nb_3O_(18)

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、电子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、钨青铜结构Ba6-3xLn8+2xTi18O54等实用化的高性能材料[1-5].

A New Niobate Ba5NdTi2Nb3O18 was synthesized by high temperature solid state reaction in the BaO-Nd2O3-TiO2 -Nb2O5 system. The chemical compositions, crystal structure, microstructure, density and melting point of the new compound were characterized by EPMA, XRD, DTA and so on. Ba5NdTi2Nb3O18 crystallizes the rhombohedral system with unit cell parameters a = 0.51760 (2) nm, c = 4.2102(2) nut, and space group R(3) over bar m, Z = 3. The structure may be described as five (Nb, Ti) O-6 octahedra corner-sharing along c axis to form perovskite layer connected by Ba atoms. The Ba5NdTi2Nb3O18 ceramic exhibits high dielectric constant of 76, low dielectric loss of 5.4 x 10(-4) and small temperature coefficient of dielectric constant of - 85ppm . K-1 at 10MHz due to its close structure and relative high dielectric polarizabilities of Ba2+, Nd3+, Ti4+ and Nb5+. Ba5NdTi2Nb3O18 might be a suitable candidate of high epsilon(r) microwave dielectric ceramics.