A(3)V(5)O(14) (A = K+, Rb+, or TI+), New Polar Oxides with a Tetragonal Tungsten Bronze Related Structural Topology: Synthesis, Structure, and Functional Properties

作者：Yeon Jeongho; Kim Sang Hwan; Halasyamani P Shiv^*

来源：Inorganic Chemistry, 2010, 49(15): 6986-6993.

DOI：10.1021/ic1008297

Three polar noncentrosymmetric (NCS) oxide materials, A(3)V(5)O(14) (A = K+, Rb+, or TI+), have been synthesized by hydrothermal and conventional solid state techniques. Their crystal structures and functional properties (second-harmonic generation, piezoelectricity, and polarization) have been determined. The iso-structural materials exhibit a layered structural topology that consists of corner-sharing VO4 tetrahedra and VO5 square pyramids. The layers stack parallel to the c-axis direction and are separated by the K+, Rb+,or TI+ cations. Powder second-harmonic generation (SHG) measurements using 1064 nm radiation indicate the materials exhibit moderate SHG efficiencies of similar to 100 x alpha SiO2. Additional SHG measurements, that is, particle size versus SHG efficiency, indicate the materials are type-I phase-matchable. Converse piezoelectric measurements for K3V5O14, Rb3V5O14, and TI3V5O14 revealed d(33) values of 28, 22, and 26 pm/V, respectively. Pyroelectric measurements, that is, temperature-dependent polarization measurements, resulted in pyroelectric coefficients of -2.2, -2.9, and -2.8 mu C/m(2). K at 65 degrees C, for K3V5O14, Rb3V5O14, and TI3V5O14 respectively. Frequency-dependent polarization measurements confirmed that all of the materials are nonferroelectric, consistent with our first principle density functional theory (DFT) electronic structure calculations. Infrared, UV-vis, thermogravimetric, and differential scanning calorimetry measurements were also performed. Crystal data: K3V5O14, trigonal, space group P31m (No. 157), a = 8.6970(16) angstrom, c = 4.9434(19) angstrom, V= 323.81(15), and Z= 1: Rb3V5O14, trigonal, space group P31m (No. 157), a= 8.7092(5) angstrom, c=5.2772(7) angstrom, V= 346.65(5), and Z = 1; TI3V5O14, trigonal, space group P31m (No. 157), a= 8.7397(8) angstrom, c= 5.0846(10) angstrom, V= 336.34(8), and Z = 1.