ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 55, (1) 14 - 19 (2011)

Li Bo, Tang Bin, Zhang Shuren, Jiang Hongmei
State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, P. R China

Keywords: Willemite (Zn₂SiO₄), Microwave ceramics, Dielectric property, Microstructure, Millimeter-wave frequency, Low temperature co-sintered ceramics (LTCC)

The low-temperature sintered (ZnMg)₂SiO₄-TiO₂ microwave ceramic using CaO-B₂O₃-SiO₂ (CBS) as a sintering aid has been developed. Microwave properties of (Zn₁₋ₓMgₓ)₂SiO₄ base materials via sol-gel method were highly dependent on the Mg-substituted content. Further, effects of CBS and TiO₂ additives on the crystal phases, microstructures and microwave characteristics of (ZnMg)₂SiO₄ (ZMS) ceramics were investigated. The results indicated that CBS glass could lower the firing temperature of ZMS dielectrics effectively from 1170 to 950°C due to the liquid-phase effect, and significantly improve the sintering behavior and microwave properties of ZMS ceramics. Moreover, ZMS-TiO₂ ceramics showed the biphasic structure and the abnormal grain growth was suppressed by the pinning effect of second phase TiO₂. Proper amount of TiO₂ could tune the large negative temperature coefficient of resonant frequency (τf) of ZMS system to a near zero value. (Zn0.8Mg0.2)₂SiO₄ codoped with 10 wt.% TiO₂ and 3 wt.% CBS sintered at 950°C exhibits the dense microstructure and excellent microwave properties: εᵣ = 9.5, Q.f = 16 600 GHz and τf = −9.6 ppm/°C.

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