Growth of substituted langasite-type Ca/sub 3/NbGa/sub 3/Si/sub 2/O/sub 14/ single crystals, and their dielectric, elastic and piezoelectric properties

It has been attempted to grow new langasite crystals. Ba/sub 3/Nb/sub 2/Ga/sub 4/O/sub 14/, Ba/sub 3/NbGa/sub 3/Si/sub 2/O/sub 14/ and Ba/sub 3/Nb/sub 0.5/Ga/sub 2.5/Si/sub 3/O/sub 14/ have been synthesized by solid state reaction and then grown by the Czochralski method. Among them, only Ba/sub 3/NbGa/sub 3/Si/sub 2/O/sub 14/ is a langasite structure and its melting temperature is 1260/spl deg/C. Growth of this crystal has been attempted, but a single phase Ba/sub 3/NbGa/sub 3/Si/sub 2/O/sub 14/ could not be grown because Ba ion is too large for A site in this system. Further, by substitution of Ba with Ca in Ba/sub 3/NbGa/sub 3/Si/sub 2/O/sub 14/, transparent and colorless Ca/sub 3/NbGa/sub 3/Si/sub 2/O/sub 14/ crystals have been successfully grown at the melting point of 1325/spl deg/C.