Low-Temperature Synthesis of Tungsten Silicates with Pyrochlore and Tungsten Bronze Structure

Polyoxotungstosilicates with the general formulas Cat 4 [SiW 12 O 40 ] · m H 2 O and Cat 6 [SiW 11 O 39 Ni(H 2 O)] · n H 2 O were synthesized, where Cat = Rb + , Cs + , (CH 3 ) 4 N + . By means of IR spectroscopy and x-ray diffraction analysis, it was shown that the compounds have the Keggin anion structure. The thermolysis of the obtained compounds within the temperature range of 600 – 800°C resulted in the formation of previously unknown pyrochlore-structure phases Rb 12/13 Si 2/13 W 22/13 Ni 2/13 O 6 and Cs 12/13 Si 2/13 W 22/13 Ni 2/13 O 6 with the with the unit cell parameters a of 10.284 and 10.309 Å, as well as phases with tungsten bronze structure Rb 12/20 Si 3/20 W 36/20 O 6 and Si 3/38 W 36/38 O 3 . The synthesis of tungsten silicates with pyrochlore and tungsten bronze structure through thermolysis of polyoxotungstosilicates reduces the temperature of their preparation to 600 – 650°C and heating time to 1 h, thus extending the ranges of chemical compositions and their morphological diversity.