Effects of gallium substitution on crystal growth and properties of gehlenite single crystal

Gehlenite crystal, Ca2Al2SiO7 (CAS) crystal is found to be appropriate material to high temperature piezoelectric sensors, for its high electrical resistivity and high temperature stability of piezoelectric coefficients. But the challenges of growing high quality single crystal and the fragile characteristics limited its broad application and mass production in future. In this paper, a new member of the melilite family, bulk Ca2Al2-xGaxSiO7 (CAGS) single crystal, was successfully grown by the Czochralski (Cz) method, without any bubble, inclusion and cracking. By a small fractional of gallium substitution, we obtained a new potential high temperature piezoelectric single crystal CAGS with larger pulling rate (more than twice that of CAS), and better quality of single crystal. Furthermore, the dielectric and piezoelectric properties of CAS and CAGS single crystals were measured and compared. The measured piezoelectric coefficient d(14) of CAGS single crystal is 10.52 pC/N which is much higher than that of CAS (6.68 pC/N). The electrical resistivity of CAGS was found to be remarkably high, reaching a value of similar to 2.3 x 10(9) Omega cm at 600 degrees C. (C) 2020 Elsevier B.V. All rights reserved.