A new class of ordered langasite structure compounds

Abstract

Langasite (LGS) and its isomorphs are only a few piezoelectric crystals which have the unique temperature compensation property. But most of the known langasite structure compounds are disordered. Disorder causes higher acoustic losses and also nonuniform mechanical properties. We reported a new class of langasite isomorph which has all the cations totally ordered. They are CNGS (Ca/sub 3/NbGa/sub 3/Si/sub 2/O/sub 14/), CTGS (Ca/sub 3/TaGa/sub 3/Si/sub 2/O/sub 14/), SNGS (Sr/sub 3/NbGa/sub 3/Si/sub 2/O/sub 14/) and STGS (Sr/sub 3/TaGa/sub 3/Si/sub 2/O/sub 14/). They all melt congruently. High quality single crystals were produced by Czochralski melt pulling technique. They have the advantages of low Ga/sub 2/O/sub 3/ content, high acoustic velocity and low acoustic loss.