A synthetic and structural study of Tl2W3TeO12, Na2W3TeO12·2H2O and A2W3SeO12 (A = NH4, Cs, Rb, K, Tl) compounds was undertaken for a better understanding of quaternary tellurites and selenites of tungsten(VI) with [W3XO12]2- (X = Se, Te) anionic framework1-4. A2W3SeO12 (A = NH4, Cs, Rb) have noncentrosymmetric layered structure, whereas K2W3SeO12(α) and Tl2W3SeO12 have centrosymmetric and noncentrosymmetric three-dimensional structures respectively. Na2W3TeO12·2H2O, Tl2W3TeO12(β) and Tl2W3TeO12(α) compounds have noncentrosymmetric structures and show SHG responses. Tl2W3TeO12(α) possess a new structure with both intra- and inter-layer Te-O bonds and other compounds have layered and three-dimensional structures with intra- and inter- layer Se/Te-O bonds respectively.
A quaternary tellurite5 and four selenites of antimony(V), namely, CsSb3Te2O12 and ASb3Se2O12 (A = Cs, Rb, K, Tl) were synthesized and characterised. They have noncentrosymmetric layered structure.
An exploratory synthetic investigations for quaternary tellurites of A/Nb/Te/O (A = Sr and Pb) systems led to isolation of SrNb6Te3O22, PbNb6Te3O22 and SrNb2Te3O12 compounds, which have three-dimensional centrosymmetric structures6, 7.
References:
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