The Study On Low Temperature Sintering Low Loss Microwave Dielectric Ceramics

With the rapid progress in mobile telecommunication, small-size, high frequency, integratable and low cost microwave devices are urgently required. Multilayer structure based on the low temperature cofired ceramics (LTCC) technology can significantly reduce the size of microwave components. The key technology of LTCC is preparation of high performance microwave dielectric ceramics which can be co-fired with high-conductivity metal electrode, such as Ag or Cu. Although several types of excellent microwave dielectric materials have been developed, most of them need high sintering temperatures above1300℃. Therefore, it is important to lower the sintering temperatures of these materials down to the melting point of Ag(961℃) or Cu(1083℃) without deteriorating the microwave dielectric properties.Ca[(Li1/3Nb2/3)1-xZr3x]O3(CLNZ, x=0.05) ceramic is chosen as the matrix in the present thesis. Different kinds of sintering additives were doped into CLNZ ceramics, the sintering characteristics, phase composition, microstructure and the dielectric properties are investigated to reveal the relationship between these parameters and discusses the specific mechanism and densification process in the above LTCC material.1. B2O3doped CLNZ ceramic. B2O3was chosen as the sintering additive. It is found that a small amount of B2O3additive lowered the sintering temperature of CLNZ ceramic effectively from1170℃to1020℃and B3+entered into the interval of CLNZ perovskite. The optimum microwave dielectric properties of τε=29.26, Qf=13420GHz and τf=-6.52ppm/℃can be obtained in1wt%B2O3doped CLNZ ceramic when sintered at1020℃for4hr. Therefore, B2O3additive can effectively lowered the sintering temperature of CLNZ ceramic by150℃2. Li2O-B2O3-SiO2-CaO-Al2O3(LBSCA) glass doped CLNZ ceramic. LBSCA glass was chosen as the sintering additive. It is found that a proper amount of LBSCA additive can lower the sintering temperature of CLNZ ceramic effectively from1170℃to940℃. The ions of LBSCA glass can diffuse into the crystal lattice of CLNZ ceramic, which will destroy the microwave dielectric properties of CLNZ ceramic. The optimum microwave dielectric properties of εr=29.37, Qf=5420GHz and τf=-24.9ppm/℃can be obtained in5wt%LBSCA doped CLNZ ceramic when sintered at940℃for4hr.