| With the rapid development of information technology, the electronic circuit gradually tends to miniaturization integration and high frequency. So the multilayer co-fired ceramic technology develops rapidly. Zn2 Si O4 ceramic has stable dielectric constant(εr=6.6), low medium loss, high Q(Q·f=219000GHz) and high thermal conductivity. Thus Zn2 Si O4 ceramic suits as dielectric substrate material. As its inherent sintering temperature is generally above 1300 ℃, hence, it is particularly important to reduce the sintering temperature of Zn2 Si O4 ceramic. Because it should satisfies the requirement of which co-fired with low melting point of electrode materials such as Ag(961 ℃) or Cu(1064 ℃). Ceramics dope with sintering aids by conventional solid reaction method, which can worsen microwave dielectric properties. We propose to introduce the Cu O into Zn1.8SiO3.8 through modifying the surface of Zn1.8Si O3.8 by precipitation and replacement methods, in order to lowering sintering temperature, and reducing deterioration of dielectric properties at the same time. Phase compositions, sintering characteristics, microstructures and microwave dielectric properties of Zn1.8Si O3.8 ceramics were investigated. This paper inquired low temperature sintering mechanism, densification process, distributed situation of Cu O and contrasted with solid-phase and direct coating methods. Compared with the traditional sintering, microwave sintering has advantages of overall heating, reducing the sintering temperature, shortening heating time and pollution-free. In addition, it can affect the growth of grain and control the microstructure of materials. So we researched that phase compositions, sintering characteristics, microstructures and microwave dielectric properties of Zn1.8Si O3.8 ceramics by microwave sintering. The main research results are as follows:(1) The analysis results indicated that low temperature sintering mechanism of Cu O coated Zn1.8Si O3.8 ceramics with liquid phase sintering by precipitation and replacement methods. The sintering temperature of Zn1.8Si O3.8 ceramic was effectively lowered from 1350 ℃ to 1000 ℃ with Cu O by precipitation and replacement methods. It can meet co-fire with copper and silver palladium alloy electrodes.(2) 4wt%CuO coated Zn1.8SiO3.8 ceramic was prepared by precipitation method, when the specimen sintered at 1000 ℃ for 3 h exhibited high microwave dielectric properties of εr=6.5, Q·f=63151GHz, τf=-35ppm/℃. For replacement method, when the amount of Cu O was 5wt%, microwave dielectric properties of Zn1.8Si O3.8 ceramic: εr=6.5, Q·f=63151GHz, τf=-35 ppm/℃. Their values of Q·f were much stronger than Zn1.8SiO3.8 ceramics doped CuO by solid phase mix and direct coating methods. So I think precipitation and replacement methods not only reduced sintering temperature but also lower deterioration of ceramic dielectric properties.(3) Zn1.8SiO3.8 ceramic by microwave sintering which can lowered sintering temperature about 50 ℃ and cutted down the sintering processing time. Zn1.8Si O3.8 ceramic sintered at 1300℃ for 30 min exhibited good microwave dielectric properties: εr=6.3,Q·f=83357GHz,τf=-37.7ppm/℃.(4) Main crystalline of Zn1.8SiO3.8 ceramic through microwave sintering was Zn2 Si O4, and no other phases were generated accompany the sintering temperature rising. Microstructure was homogeneous and densification. Compared with conventional sintering, microwave dielectric properties of Zn1.8Si O3.8 ceramic by microwave sintering was slightly increased, but microwave sintering did not has a major impact on microwave dielectric properties of Zn1.8SiO3.8 ceramic. |
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