Bridgman growth of new piezoelectric single crystal Sr3Ga2Ge4O14

A new langasite structure piezoelectric single crystal Sr3Ga2Ge4O14 (SGG) had been grown by the vertical Bridgman method for the first time. Polycrystalline SGG powder was synthesized prior to growth and [0 0 0 1] oriented La3Ga5SiO14 (LGS, langasite) crystal was used as the seeds. SGG crystals up to 28 mm in diameter and 80 mm in length were grown reproductively. X-ray fluorescence spectrum showed that only negligible amount of La3+ and Si4+ ions appeared in as-grown SGG crystals. Differential thermal analysis (DTA) and thermal gravity (TG) curves presents the melting point of SGG crystal at 1404.5 °C. The average thermal expansion coefficients along the crystallographic a- and c-axes from 293 to 973 K were measured to be 6.5×10−6 and 5.8×10−6 K−1, respectively. The transmittance spectra from 250 to 2500 nm were measured and the transmittance of SGG crystal exceeds 80% above 350 nm. The density was measured to be 5.112 g/cm3.