Syntheses, structures, and second-harmonic generating properties in new quaternary tellurites:: A2TeW3O12 (A = K, Rb, or Cs)

The syntheses, structures, and characterization of a new family of quaternary alkali tungsten tellurites. A(2)TeW(3)O(12) (A=K, Rb, or Cs), are reported. Crystals of the materials were synthesized by supercritical hydrothermal methods using 1 M AOH (A=K-1 Rb, or Cs). TeO2, and WO3 as reagents. Bulk, polycrystalline phases were synthesized by standard solid-state methods combining stoichiometric amounts of A(2)CO(3), TeO2, and WO3. Although the three materials are not iso-structural, each exhibits a hexagonal tungsten oxide layer comprised of corner-sharing W6+ O-6 octahedra. Te4+ O-3 groups connect the WO6 layers in K2TeW3O12, whereas the same groups cap the WO6 layers in Rb2TeW3O12, and Cs2TeW3O12. This capping results in non-centrosymmetric structures for Rb2TeW3O12 and Cs2TeW3O12. Powder second-harmonic generation measurements on Rb2TeW3O12, and Cs2TeW3O12 revealed strong SHG efficiencies of 200 and 400 x SiO2, respectively. These values indicate an average non-linear optical Susceptibility. <d(eff)>(exp) of 16 and 23 pm/V for Rb2TeW3O12 and Cs2TeW3O12 respectively. Crystallographic information: K2TeW3O12, monoclinic, space group P2(1)/n (No. 14). a = 7.3224(13) Angstrom, b = 11.669(2) Angstrom, c = 12.708(2) Angstrom, beta = 90.421(3)degrees. Z = 4: Rb2TeW3O12, trigonal, space group P31c (No. 159), a = b = 7.2980(2) Angstrom. c = 12.0640(2) Angstrom, Z = 2. (C) 2003 Elsevier Inc. All rights reserved.