Crystal growth and high temperature applications of 3” Langatate

Langasite (La₃Ga₅SiO₁₄, LGS) and its two isomorphs Langatate (La₃Ga_5.5Ta_0.5O₁₄, LGT) and Langanite (La₃Ga_5.5Ta_0.5O₁₄, LGN) belong to the same point group (32) as quartz. These LGS-type (LGX) crystals have attracted much attention over the past years and have been regarded as the new candidate materials for bulk acoustic wave (BAW), surface acoustic wave (SAW) and high temperature sensor devices, because of their outstanding properties. Firstly, the piezoelectric constants of the LGX are about two times larger than that of quartz, so they are expected to have higher electromechanical coupling coefficient than quartz; Secondly, they are reported have no phase transitions from room temperature to their melting points (about 1470°C); Thirdly, they have very low acoustic friction which is an indication of high Q factor, about twice of that of quartz; Finally, all of them can be grown by Czochralski and vertical Bridgman methods, and large size (about 3” ~4”) crystal has been obtained.