Preparation and characterization of new microwave dielectric ceramics Ba 3− nLa 1+ nTi nNb 3− nO 12

Abstract

A series of new microwave dielectric ceramics Ba 3− n La 1+ n Ti n Nb 3− n O 12 ( n=0,1,2) were prepared in the BaO-La 2O 3-TiO 2-Nb 2O 5 system by high temperature solid-state reaction route. The phase and structure of the ceramics were characterized by X-ray diffraction, scanning electron microscope, and microwave dielectric properties measurements. These samples were identified as single phase and adopted A 4B 3O 12-type cation-deficient hexagonal perovskite structure, which can be described as consisting of identical perovskite-like blocks, three corner-sharing BO 6 octahedra thick, separated by layers of vacant octahedral. These ceramics have high dielectric constants in the range of 48–42, high quality factors ( Q×f) up to 38 000 GHz, and low temperature coefficient of resonant frequencies (τ f) in the range of (−40–+6)×10 −6 °C −1. With increasing content of La and Ti, the dielectric constants slightly decrease but τ f gradually increases.