Abstract: A new niobate Ba₃La₂Ti₂Nb₂O₁₅was synthesized by high temperature solid state reaction in the BaO-La₂O₃-TiO₂-Nb₂O₅system. The chemical compositions, crystal structure, microstructure, density and melting point of the new compound were characterized by EPMA, XRD, SEM, DTA and so on. Ba₃La₂Ti₂Nb₂O₁₅crystallizes in the hexagonal system with unit cell parameters a=0. 5682(1) nm, c=-1.1657(1) nm, and space group P3 m1, Z=l. The structure may be described as four (Nb,Ti)O₆octa-hedra corner-sharing to form hexagonal perovskite layer, while Ba or La occupying the interstices. The Ba₃La₂Ti₂Nb₂O₁₅ceramic exhibits a high dielectric constant of 90. 04, a low dielectric loss of 4. 5 × 10^-4and a small temperature coefficient of dielectric constant of -65 × 10^-6K^-1at 1 MHz due to its close structure and relative high dielectric polarizabilities of Ba²⁺, La³⁺, Ti⁴⁺and Nb⁵⁺. Ba₃La₂Ti₂Nb₂O₁₅might be a suitable candidate of high er microwave dielectric ceramics.

Key words: Niobate, Perovskite-related structure, Dielectric property