Study On Preparation And Properties Of Low-firing Microwave Dielectric Ceramic

In this paper, a series of microwave dielectric ceramics BaMV2O7(M=Mg, Zn)、LiMVO4(M=Mg, Zn)、Li2M2W3O12(M=Mg, Zn) and Li2W2O7 were prepared by the conventional solid-state reaction route and systematical analysis was carried out on the structure, microstructure, and microwave dielectric properties. The relationship between the microwave properties and the structure was also studies. Meanwhile, the possible applications of these materials as LTCC substrate materials was discussed.(1) Two microwave dielectric ceramics in BaMV2O7(M=Mg, Zn) system were synthesized through a solid-state reaction route. BaMgV2O7 could be well sintered at830 oC and exhibited excellent microwave dielectric properties with a εr of 8.2, a Q×f value of 37600 GHz and a negative τf of-35.2 ppm/oC. The optimum sintering temperature of BaZnV2O7 was much lower(~ 720 oC) with a higher relative density95.6% compared with BaMgV2O7. It also had promising microwave properties with aεr of 10.7, a Q×f value about 31000 GHz and a τf about-64.4 ppm/oC for sintered at720 oC.(2) LiMVO4(M=Mg, Zn) ceramics sintered at 720 oC obtained high relative density and good microwave dielectric properties: LiMgVO4 ceramic has 96.6%relative density with a εr of 9.89, a Q×f value of 30800 GHz and a negative τf of-181ppm/oC; LiZnVO4 ceramic shows 94.9% relative density with a εr of 7.15, a Q×f value of 17600 GHz and a negative τf of-114 ppm/oC.(3) Li2Mg2W3O12 ceramics sintered at the optimum sintering temperature 720 oC obtained the best microwave dielectric properties with a εr of 8.36, a Q×f value of56700 GHz and a τf of-72.8 ppm/oC. Li2Mg2W3O12 ceramics exhibit low sintering temperature and good microwave dielectric properties. This indicates these ceramics might be candidates for LTCC application in wireless communication systems.(4) The microwave dielectric properties of Li2W2O7 ceramics was affected by the density and the second phase. Li2W2O7 ceramics possesses low permittivity and high Q×f values, as well as negative τf values ceramics could be tuned nearly to zero by adding with TiO2. Li2W2O7 sintered at optimum sintering temperature 680 oC obtained the best microwave dielectric properties with a εr of 12.15, a Q×f value of 17700 GHz and a τf of-232 ppm/oC.