Microwave Dielectric Properties of Fused Silica Prepared by Different Approaches

Fused silica was prepared by different approaches, and the microwave dielectric properties were investigated. For the fused silica sintered at 1100°C by solid‐state sintering, the dielectric constant (ε r ) and Qf value increased with increasing the sintering time up to 5 h, while the temperature coefficient of resonant frequency (τ f ) decreased. The optimal properties with low ε r of 3.72, high Qf value of 44,300 GHz, and low τ f of −14.4 ppm/°C were achieved when sintered at 1100°C for 5 h. The microwave dielectric properties could be further improved by other preparing approaches, as listed below: ε r  = 3.90, Qf  = 63,500 GHz, τ f  = −5.7 ppm/°C for spark plasma sintering, and ε r  = 3.83, Qf  = 122,100 GHz, τ f  = −8.3 ppm/°C for melting method. The results showed that fused silica was a good candidate as a microwave substrate material.