Temperature Characteristics of β-phase Quartz Resonators and Their Application to Accurate Temperature Sensors in High Temperature Region

Quartz has been widely used for resonators and filters because of its excellent electromechanical characteristics. Quartz has a transition temperature, TC, at 573°C. The electromechanical characteristics of quartz have been well investigated for α-phase (below TC), however the characteristics in β-phase have not been well clarified. We investigated the piezoelectric properties of β-quartz plates from 573°C to about 1,300°C. Clear piezoelectric resonances with high quality factors were observed. By using the large frequency temperature coefficient, β-phase quartz can be applicable to temperature sensors in high temperature region above 600°C. We proposed also an unwired set-up using the β-phase quartz temperature sensor.