SYNTHESIS AND THERMAL-DECOMPOSITION OF SOME RARE-EARTH TETRAMETHYLAMMONIUM DOUBLE SULFATES

When reaction mixtures of rare earth(III) sulphates and tetramethylamm onium sulphate in molar ratios of from 1:4 to 1:12 were evaporated at ambient temperature and the concentrated reaction mixture was treated with ethanol, double sulphates with general empirical formula (CH3)(4) NLn(SO4)(2) . 2H2O (Ln = Ho-Lu and Y) were obtained as reaction produc ts. The crystalline products were identified by quantitative analysis, X-ray powder diffraction patterns and TG, DTG and DTA analysis. They were found to be isostructural. Their thermal decomposition look place in three stages. The temperature range of the dehydration mainly decr eased from Ho to Lu. The thermal decomposition in the second and third stages occurred with many thermal events. As final product, Ln(2)O(SO 4)(2) was obtained.