New Polymorphs of Ternary Sodium Tellurium Oxides: Hydrothermal Synthesis, Structure Determination, and Characterization of β-Na2Te4O9 and Na2Te2O6•1.5H2O

Two new sodium tellurium oxide materials, beta-Na2Te4O9 and Na2Te2O6 center dot 1.5H(2)O, have been synthesized through hydrothermal reactions using Na2CO3, TeO2, and H2TeO4 center dot 2H(2)O as reagents. The structures of the novel materials have been determined by single crystal X-ray diffraction. beta-Na2Te4O9 is a new polymorph of ternary tellurite that is showing a three-dimensional framework structure containing only TeO4 polyhedra. Na2Te2O6 center dot 1.5H(2)O reveals an anionic layered backbone composed of Te6+O6 octahedra and Te4+O5 polyhedra. Thermogravimetric analyses and powder X-ray diffractions at different temperatures suggest that the frameworks of beta-Na2Te4O9 and Na2Te2O6 center dot 1.5H(2)O are thermally stable up to 480 and 400 degrees C, respectively. The Na+ cations in between the anionic layers in Na2Te2O6 center dot 1.5H(2)O are completely replaced by Li+ cations through an ion-exchange reaction. The UV-vis diffuse reflectance and infrared spectra, elemental analyses, and local dipole moment calculations are also reported.