Effects of CaF2 addition on the microstructure and microwave dielectric properties of ZnNb2O6 ceramics

• Published in: Ceramics international 2003, Vol.29 (5), p.555-559
• Main Authors: Zhang, YingChun, Yue, ZhenXing, Gui, ZhiLun, Li, LongTu
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Chemical industry and chemicals; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectric loss and relaxation; Dielectric properties of solids and liquids; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Electrotechnical and electronic ceramics; Exact sciences and technology; Permittivity (dielectric function); Physics; Technical ceramics
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/S0272-8842(02)00202-X

The effects of CaF2 additions on the microstructure and the microwave dielectric properties of ZnNb2O6 ceramics were investigated systematically. The sintering temperature of ZnNb2O6 ceramics with 0.5 wt.% CaF2 additions can be effectively reduced from 1150 deg C to 1080 deg C. The secondary phase CaNb2O6 was observed in sintered samples with 1-5 wt.% CaF2 additions. There was evidence of reaction between CaF2 and ZnNb2O6 during sintering. The dielectric properties at microwave frequencies (6-8 GHz) in this system were strongly dependent on the relative density, sintering temperature and CaF2 content. For 0.1-5 wt.%-CaF2-doped ZnNb2O6 ceramics, The dielectric constants (*er) of densified samples range in 28-31 which is higher than that of undoped ZnNb2O6 ceramics, However, the Qxf values decreased and ranged from 39000 GHz to 68000 GHz. The *tf values were shifted toward zero direction with the increase of CaF2 addition. ZnNb2O6 ceramics with 0.5 wt.% CaF2 addition sintered at 1080 deg C have the optimum microwave dielectric properties: *er=32, Qxf=68000 GHz and *tf=-55 ppm/ deg C. (The material is a candidate for multilayer microwave devices in satelite and mobile communications applications such as cellular phones, phasers and GPS.)