High-performance (1-x)(0.2B2O3-0.8SiO2)-xTiO2 (x = 0.025-0.1) glass matrix composites for microwave substrate applications

The (1-x)(0.2B2O3-0.8SiO2)-xTiO2 (x = 0.025-0.1) glass matrix composites were prepared by a solid state sintering method, and high relative density >97% was obtained when the sintering temperature was 975-1000 °C. The rutile and amorphous phases were indicated by XRD, and no crystallization of amorphous SiO2 or chemical reaction was observed. With increasing x from 0 to 0.1, the dielectric constant (εr) increased slightly while the Qf value decreased, and the temperature coefficient of resonant frequency (τf) increased from a negative to a positive value. The optimized microwave dielectric properties were obtained as following: εr = 4.01, Qf = 66,800 GHz, τf = −2.2 ppm/oC for x = 0.025 sintered at 1000 °C, and εr = 4.22, Qf = 55,300 GHz, τf = 3.1 ppm/oC for x = 0.05 sintered at 975 °C. The ultra-low εr, high Qf value and near-zero τf indicate that the present glass matrix composites are excellent candidates as the microwave substrate materials.