Thermolysis of Hydrated Antimony Pentoxide

The thermolysis of hydrated antimony pentoxide (HAP) has been studied in the temperature range from 25 to 1000 degrees C using a variety of experimental techniques: thermogravimetry, X-ray diffraction, pycnometry, elemental microanalysis, and mass spectrometry. The composition and structure of the forming phases have been determined. It has been shown that the initial stages of HAP thermolysis, in the temperature range 24-500 degrees C, include dehydration processes and the formation of anhydrous antimony pentoxide, Sb2O5. At temperatures above 500 degrees C, the process includes oxygen removal, the reduction of Sb(V) to Sb(III), and the formation of Sb6O13 and Sb2O4. The pyrochlore structure of HAP (sp. gr. Fd3m) has been shown to persist in the course of the phase transformations at temperatures below 700 degrees C. Analysis of our experimental data has allowed us to propose a model for crystallographic site occupancies in the pyrochlore-type structure of the phases obtained and determine their temperature stability ranges.