Growth of Shape-Controlled Ca_3NbGa_3Si_2O_(14) and Sr_3NbGa_3Si_2O_(14) Single Crystals by Micro-Pulling-Down Method and Their Physical Properties

摘要

Shape-controlled langasite-type piezoelectric single crystals, Ca_3NbGa_3Si_2O_(14) (CNGS) and Sr_3NbGa_3Si_20_(14) (SNGS), were grown by the micro-pulling-down (n-PD) method and their physical properties were investigated. Columnar-shaped CNGS and SNGS crystals with a- and c-axes in the growth direction were grown and the diameters of the grown columnar-shaped crystals were controlled to be approximately 3 mm from the initial to the later part. The grown crystals without cracks indicated relatively high crystallinities and a single phase of the langasite-type structure in the powder X-ray diffraction patterns. Meanwhile, in the outside area of the crystals, parts of second phases were detected and energy dispersive X-ray spectroscopy measurements indicated that the second phases of the CNGS and SNGS crystals were the Ca-Nb-0 and Sr-Nb-0 systems, respectively. The du of the CNGS crystal indicated 3.98 pC/N, which was coincident with those of previous reports.