Growth and Piezoelectric Properties of Melilite ABC3O7 Crystals

Single ABC 3 O 7 crystals with the melilite structure, including SrLaGa 3 O 7, SrGdGa 3 O 7, and BaLaGa 3 O 7, have been successfully grown by the Czochralski method. A complete set of room temperature elastic, dielectric, and piezoelectric constants was determined using resonance techniques and impedance analysis. Our results indicate that the crystals exhibit superior piezoelectric and elastic properties. The electrical resistivity was found to be on the order of 6 × 10 13 ohm·cm at room temperature. The dielectric permittivity ε 11, piezoelectric constant d 14, and electromechanical coupling coefficient k ′ 12 were found to be on the order of 15–17, 12–15 pC/N, and 16–19%, respectively. For an ABC 3 O 7 group member such as SrLaGa 3 O 7, the melting temperature was measured to be 1588 °C, below which the crystal maintains good thermal stability. Consequently, the piezoelectric properties were studied as a function of temperature over the range of −50 to 120 °C. The frequency vs temperature coefficient was determined to be −16 to −55 ppm/K, depending on orientation. The dielectric permittivity, piezoelectric constant, and electromechanical coupling coefficient showed good temperature stability. The absence of any phase transitions below their melting points (on the order of 1600 °C) makes the ABC 3 O 7 family promising candidate materials for high temperature piezoelectric applications.