Top-Seeded Solution Growth, Morphology, and Properties of a Polar Crystal Cs₂TeMo₃O₁₂

Abstract

Single crystals of the polar hexagonal tungsten oxide (HTO) material Cs2TeMo3O12 with dimensions up to 20 × 20 × 16 mm3 were grown successfully through a top-seeded solution growth (TSSG) method using a TeO2−MoO3 mixture as a self-flux. The Cs2TeMo3O12 crystals grown from a solution with a low concentration exhibit {0002}, {101̅0}, and {101̅1̅} facets, which are in good accordance with the predicted growth morphology based upon the Bravais−Friedel and Donnay−Harker (BFDH) methods. However, the crystals grown from solution with a high concentration show additional {101̅2̅} facets, which are not predicted. Crystals grown by using the [0001]-oriented seed have more regular shapes as compared with those grown by using the [21̅1̅0]-oriented seed. Cs2TeMo3O12 crystallizes in the polar hexagonal space group P63 (no. 173). The result of the high-resolution X-ray diffraction indicates that the full-width at half-maximum (fwhm) of the rocking curve is 18.96′′. Thermal analysis and powder X-ray diffraction demonstrate that Cs2TeMo3O12 melts incongruently at 494.95 °C. Optical measurements indicate that the Cs2TeMo3O12 crystal has a broad transmission window range from 0.43 to 5.38 μm. In addition, polarization measurements indicate that although Cs2TeMo3O12 is polar, the material is not ferroelectric.