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 ε^T ₁₁/ε₀ and ε^T ₃₃/ε₀ were determined to be 16.3 and 11.8, while the piezoelectric coefficients d_15, d_31, 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 s₅₅ ^E (= s^E ₄₄) 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. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.