EFFECT OF GLASS ADDITIONS ON BAO-TIO2-WO3 MICROWAVE CERAMICS

The effect of glass addition on the properties of BaO-TiO2-WO3 microwave dielectric material N-35, which has Q = 5900 and K = 35 at 7.2 GHz for samples sintered at 1360-degrees-C, was investigated. Several glasses including B2O3, SiO2, 5ZnO-2B2O3, and nine other commercial glasses were selected for this study. Among these glasses, one with a 5 wt% addition of B2O3 to N-35, when sintered at 1200-degrees-C, had the best dielectric properties: Q = 8300 and K = 34 at 8.5 GHz. Both Q and K increased with firing temperature as well as with density. The Q of N-35, when sintered with a ZnO-B2O3 glass system, showed a sudden drop in the sintering temperature to about 1000-degrees-C. The results of XRD, thermal analysis, and scanning electron microscopy indicated that the chemical reaction between the dielectric ceramics and glass had a greater effect on Q than on the density. The effects of the glass content and the mixing process on the densification and microwave dielectric properties are also presented. Ball milling improved the densification and dielectric properties of the N-35 sintered with ZnO-B2O3.