Preparation and characterization of new microwave dielectric ceramics Ba3-nLa1+nTinNb3-nO12
(1.Department of Applied Physics, Chongqing University, Chongqing 400044, China2.State Key Laboratory of Advanced Technology for Materials Synthesis and Processing,Wuhan University of Technology, Wuhan 430070, China3.湖南省长沙市中南工业大学材料科学与工程系4.Key Laboratory of Nonferrous Materials and New Processing Technology, Ministry of Education, Guilin University of Technology, Guilin 541004, China)
Abstract: A series of new microwave dielectric ceramics Ba3？nLa1+nTinNb3？nO12 (n=0,1,2) were prepared in the BaO-La2O3-TiO2-Nb2O5 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 A4B3O12-type cation-deficient hexagonal perovskite structure, which can be described as consisting of identical perovskite-like blocks, three corner-sharing BO6 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 (τf) in the range of (-40-+6)×10-6 ℃-1. With increasing content of La and Ti, the dielectric constants slightly decrease but τf gradually increases.
Key words: Ba3-nLa1+nTinNb3-nO12; BaO-La2O3-TiO2-Nb2O5; dielectrics; dielectric resonators; microwave ceramics; hexagonal