Thermal expansion and electro-elastic features of Ba2TiSi2O8 high temperature piezoelectric crystal

A high-quality Ba2TiSi2O8 (BTS) single crystal was grown using the Czochralski (Cz) pulling method. The thermal expansion and electro-elastic properties of BTS crystal were studied for high temperature sensor applications. The relative dielectric permittivities εT11/ε0 and εT33/ε0 were determined to be 16.3 and 11.8, while the piezoelectric coefficients d15, d31, d33 were found to be 17.8, 2.9, and 4.0 pC/N, respectively. Temperature dependence of electro-elastic properties were investigated, where the variation of elastic compliance s55E (= sE44) was found to be <6% over temperature range of 20-700◦C. Taking advantage of the anisotropic thermal expansion, linear thermal expansion comparable to insulating alumina ceramic was achieved over temperature range up to 650◦C. The optimum crystal cut with large effective piezoelectric coefficient (>8.5 pC/N) and linear thermal expansion coefficient (8.03 ppm/◦C) achieved for BTS crystal along the (47◦, ϕ) direction (ϕ is arbitrary in 0-360◦), together with its good temperature stability up to 650◦C, make BTS crystal a promising candidate for high temperature piezoelectric sensors.