New double perovskites having low dielectric loss: LaBaZnTaO₆, LaSrZnNbO₆, and Ba₂Zn_0.5Ti_0.5TaO₆

Abstract

Oxides of the type LaBaZnTaO₆ and LaSrZnNbO₆ have been synthesized by the solid-state method at 1100°C. Ba₂Zn_0.5Ti_0.5TaO₆ was synthesized by the molten salt method (using NaCl-KCl as flux), the solid-state method yielding a biphasic mixture of BaTiO₃ and BaZn_1/3Ta_2/3O₃. LaBaZnTaO₆ and LaSrZnNbO₆ were found to crystallize in an ordered (cubic) double perovskite structure in the Fm3̅ m space group with A = 8.0867(8) and 8.001(1) Å, respectively. Ba₂Zn_0.5Ti_0.5TaO₆ crystallizes in the disordered cubic perovskite structure with A = 4.054(1) Å. These oxides have very low dielectric losses in the region of 0.0005 to 0.003 (500 kHz). The dielectric constants of LaBaZnTaO₆ and LaSrZnNbO₆ are low (13 and 10, respectively) while Ba₂Zn_0.5Ti_0.5TaO₆ has a high dielectric constant of 36 at 500 kHz.