The temperature-stable piezoelectric material GaPO 4 and its sensor applications

Gallium (ortho) phosphate (GaPO4) has a similar structure as quartz, but the high thermal stability up to 970 °C and the high sensitivity make it a very attractive choice for a wide range of uncooled high temperature applications. Furthermore it shows no pyroelectricity, no outgassing and a high electric resistance to guarantee high precision piezoelectric measurements. GaPO4 offers good temperature compensation for a new generation of crystal microbalances operating at temperatures up to at least 700 °C as shown in thermogravimetric and film thickness measurements. It also allows the production of SAW sensors with a very high thermal stability.