New noncentrosymmetric tellurite phosphate material: synthesis, characterization, and calculations of Te2O(PO4)2.

A new noncentrosymmetric polar ternary tellurium(IV) oxide phosphate, Te(2)O(PO(4))(2), has been synthesized by a standard solid-state reaction, and the structure was determined by single crystal X-ray diffraction. The material shows a three-dimensional framework structure that is composed of slightly distorted TeO(5) square pyramids and PO(4) tetrahedra. Within the framework three-, four-, and seven-membered ring channels are observed along the [100] direction. In addition to structural characterization, second-harmonic generation (SHG) and piezoelectric measurements were performed. Powder SHG measurement on the Te(2)O(PO(4))(2), using 1064 nm radiation, indicated the material has a SHG efficiency of approximately 50 x alpha-SiO(2). Converse piezoelectric measurements revealed a d(33) value of 20 pm V(-1). Thermogravimetric analysis, UV-vis diffuse reflectance, and infrared spectroscopy were also performed, as were electronic structure calculations. Crystal data: Te(2)O(PO(4))(2), monoclinic, space group Cc (No. 9), with a = 5.3819(7) A, b = 13.6990(19) A, c = 9.5866(12) A, V = 686.73(16) A(3), and Z = 4.