We report the effects of Sr or Ba substitution on the crystal growth and electrical and mechanical properties of Ca 2 Al 2 SiO 7 (CAS) piezoelectric single crystals, which are suitable for use in high-temperature pressure sensors. Ba was scarcely incorporated in the crystal lattice of CAS. Strontium-substituted CAS single crystal with a nominal chemical composition Ca 0.75 Sr 1.25 Al 2 SiO 7 (CSAS125) was grown by the Czochralski method. Although the piezoelectric modulus d¤ 31 of CSAS125 is a bit lower than that of the CAS crystal, the rupture strength of the (XYt)45°rotation cut substrate of CSAS125 crystal was 170 MPa, which was 1.2 times higher than that of CAS crystal. By considering the rupture strength and the apparent piezoelectric d à 31 coefficient calculated for the crystal rotation cut of CAS crystal, the CSAS125 crystal substrate with a rotation cut of (XYt)25°was found to indicate a rupture strength of 220 MPa and a piezoelectric d¤ 31 coefficient of approximately 2 pC/N.

Electroacoustical constants (, , and dij) of calcium aluminate silicate Ca2Al2SiO7 piezoelectric single crystals, which have the tetragonal structure with the point group , were evaluated. The normalized first-order temperature coefficients of all the constants were determined between −30 and 120 °C at 10 kHz frequency, e.g., for and were 69.3 and 87.6, and for d14 and d36 were −338.4 and 552.4 ppm/°C, respectively. The Rayleigh surface acoustic wave (SAW) velocities for the fundamental X- and Z-cuts of the crystals were theoretically calculated. The results were supported by the SAW velocities measured for the Z-cut of the crystal, proving the accuracy of the electroacoustic constants determined in this study.