Strontium-substituted calcium magnesium silicate single crystals for high-temperature piezoelectric applications

Abstract

We present a relationship between piezoelectric property and crystal structure in melilite-type crystals. Two independent piezoelectric constants, d₁₄ and d₃₆, increase and decrease with the polyhedral distortion, respectively. Based on this knowledge, single crystals made of strontium-substituted calcium magnesium silicate Ca₂MgSi₂O₇ (CMS) have been submitted to the Czochralski method, which made them grown. The CMS crystal has a high d₃₆; however, its transition temperature is around 85 °C. Therefore, the strontium substitution is conducted to decrease this phase transition temperature. A single crystal of strontium substituted CMS, with nominal chemical composition Ca_1.7Sr_0.3MgSi₂O₇ (CSMS30), shows no phase transition when temperature rises from room to melting temperature. Its piezoelectric d′₃₁ constant is 2.1 pC/N and its compressive strength is 830 MPa on crystal substrate with (ZXt)45° cut. The CSMS30 single crystal is a superior candidate material for pressure sensors at high operating temperatures.