Top-Seeded Solution Growth, Structure, Morphology, and Functional Properties of a New Polar Crystal  Cs2TeW3O12

Single crystals of the polar material Cs2TeW3O12 (CTW) with dimensions up to 26 × 18 × 4 mm3 were successfully grown using a top-seeded solution growth method. The morphologies of the as-grown crystals have been described and compared with that obtained from the Bravais–Friedel and Donnay–Harker (BFDH) method. The crystal structure of CTW has been solved for the first time using single-crystal X-ray diffraction: the compound crystallizes in polar hexagonal space group P63 (No. 173) with cell parameters a = b = 7.3279(3) Å, c = 12.4075(5) Å, Z = 2, and V = 577.00(4) Å3. Thermal analysis shows that CTW is thermally stable up to 820 °C, at which it melts incongruently. Further high-resolution X-ray diffraction experiments gave a full-width at half-maximum of the rocking curve of 33″, indicating a good crystalline quality for the as-grown crystals. Optical transmittance spectra of CTW show a broad transmission range from 410 to 5310 nm. Powder second-harmonic generation (SHG) measurements with a 1064 nm laser indicates that CTW exhibits a strong SHG efficiency of about 1.5 the one of KTiOPO4. Polarization measurements indicate that CTW is not ferroelectric; i.e., the polarization is not “switchable”. In addition, CTW is nonhygroscopic and resistant to diluted HNO3 aqua-solution.