类钙钛矿新铌酸盐Ba_4LaTiNb_3O_(15)的合成、结构与介电特性

Synthesis, Crystal Structure and Dielectric Properties of a New Perovskite-like Niobate Ba_4LaTiNb_3O_(15)

A new niobate compound Ba4LaTiNb3O15 has been synthesized and characterized. Through Rietveld refinement of X-ray powder diffraction data, Ba4LaTiNb3O15 is identified as the A5B4O15 type cation-deficient perovskites with space group of P3m1(164) and lattice constants a=0.572 38(1) nm, c=1.169 48(1) nm, V=0.331 81(1) nm3, and Z=1. The crystal structure can be described as consisting of identical perovskite-like blocks, four corner-sharing (Ba,La)O6 octahedra thick, separated by layers of vacant octahedral. The (Ba,La)-O bond lengths range from 0.267 to 0.321 nm and the (Ti,Nb)-O bond lengths range from 0.175 to 0.213 nm. The Ba4LaTiNb3O15 ceramic has a high dielectric constant of 53.3, high quality factors (Q) 3 650 (at 6.402 5 GHz), and low temperature variation of resonant frequency (τf) +69.3 × 10-6 K-1.

A new niobate compound Ba4LaTiNb3O15 has been synthesized and characterized. Through Rietveld re- finement of X-ray powder diffraction data, Ba4LaTiNb3O15 is identified as the A5B4O15 type cation-deficient perovskites with space group of P3^-ml（164） and lattice constants a=0.57238（1） nm, c=1.16948（1） nm, V=0.331 81（1） nm3, and Z=1. The crystal structure can be described as consisting of identical perovskite-like blocks, four corner-sharing （Ba,La）O6 octahedra thick, separated by layers of vacant octahedral. The （Ba, La）-O bond lengths range from 0.267 to 0.321 nm and the （Ti,Nb）-O bond lengths range from 0.175 to 0.213 nm. The Ba4LaTiNb3O15 ceramic has a high dielectric constant of 53.3, high quality factors （Q） 3 650 （at 6.402 5 GHz）, and low temperature variation of resonant frequency （τf） ＋69.3× 10^-6 K^-1.