The Preparation And Properties Of Bi-layer Structure Cay Ca_yBi_y+2Ti_2y+1O_6y+6 Microwave Dielectric Ceramics

The Bi-layer structure CayBiy+2Ti2y+1O6y+6(y=1, 1.5, 2 and 2.5) ceramics were synthesized by the conventional solid-state reaction method. The crystal structure and microwave dielectric properties were investigated by bulk density, XRD, SEM, and dielectric measurements. The micro-structure and microwave dielectric properties were studied by doping modification and process optimization.In this paper, the structure and dielectric properties of Ca2Bi4Ti5O18 were studied by changing quantity of Sr-doped, synthesis temperature, second milling time and sintering process. The excellent microwave dielectric properties were obtained for Ca2Bi4Ti5O18 sintered at lower temperature(1175°C) by process optimization : ?r=170,Q×f=868GHz(at 4.7GHz). With increasing levels of Sr2+ ions additions, the relative permittivity from 170 to 202 and Q×f from 868 GHz to 428 GHz change in the opposite trend simultaneously. The microwave dielectric properties were obtained for Ca1.8Sr0.2Bi4Ti5O18 ceramics(x=0.2): ?r=180, Q×f=768GHz(at 4.7GHz),?f=+366ppm/°C.In this paper, the micro-structure and microwave dielectric properties CayBiy+2Ti2y+1O6y+6(y=1, y=1.5 and y=2)ceramics were also investigated. Sintering temperature, dielectric constant and dielectric loss( in the frequency of 1 MHz) of CayBiy+2Ti2y+1O6y+6(y=1, y=1.5 and y=2)ceramics increase with increasing y. So, in the frequency of 1 MHz, CaBi3Ti3O12 ceramics possess lower sintering temperature and dielectric loss than Ca2Bi4Ti5O18 ceramics. The microwave dielectric properties were obtained for CaBi3Ti3O12 ceramics sintered at 950°C for 5h: ?r=151,Q×f=370GHz and the value of Q×f of CaBi3Ti3O12 ceramics is lower than the value of Q×f of Ca2Bi4Ti5O18 ceramics. About dielectric loss, the change rule of dielectric loss of CaBi3Ti3O12 and Ca2Bi4Ti5O18 ceramics which was obtained in the microwave frequency is different from the change rule in the frequency of 1 MHz. In general,CaBi3Ti3O12 ceramics possess a lot of advantages, for instance low sintering temperature(950°C) and high dielectric constant(?r=151) and so on. But their valueof Q×f(370GHz) is low. If their value of Q×f would become higher, they will have more practicability and economic value.