Growth of Shape-Controlled Ca₃NbGa₃Si₂O₁₄ and Sr₃NbGa₃Si₂O₁₄ Single Crystals by Micro-Pulling-Down Method and Their Physical Properties

Shape-controlled langasite-type piezoelectric single crystals, Ca₃NbGa₃Si₂O₁₄ (CNGS) and Sr₃NbGa₃Si₂O₁₄ (SNGS), were grown by the micro-pulling-down (µ-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–O and Sr–Nb–O systems, respectively. The d₁₁ of the CNGS crystal indicated 3.98 pC/N, which was coincident with those of previous reports.