Top-Seeded Solution Crystal Growth and Functional Properties of a Polar Material—Na₂TeW₂O₉

Centimeter-size single crystals of the noncentrosymmetric and polar material Na 2 TeW 2 O 9 were successfully grown through a top-seeded solution growth (TSSG) method. Differently oriented seeds, along the [100], [010], and [001] directions, were used to grow large single crystals. The morphologies of the grown crystals with different oriented seeds are described. Na 2 TeW 2 O 9 crystallizes in the noncentrosymmetric and polar monoclinic space group Ia (No. 9). Functional properties including piezoelectricity and polarization were also measured. The d 11 and d 33 piezoelectric coefficients are 4.0 pC/N and 13.9 pC/N, respectively. Polarization measurements indicate that although Na 2 TeW 2 O 9 is polar, the material is not ferroelectric; that is, the polarization is not switchable. In addition, optical measurements indicate a UV absorption edge near 360 nm, with a transmission window up to 5 μm.