Double sulphates of rare earths(III) with trimethylammonium: Part 1. Synthesis and thermal behaviour of (CH 3) 3NHLn(SO 4) 2·3H 2O

Abstract

The double sulphates of some Ln(III) rare earths with trimethylammonium were obtained as crystalline products by evaporation at room temperature of an aqueous mixture of Ln(III) sulphate and trimethylammonium sulphate and treatment, in some cases, of the concentrated mixture with ethanol. After identification by means of X-ray powder diffraction patterns, it was found that three groups of double sulphates with different crystal structures were obtained. The results of the investigations of two groups with general empirical formula (CH 3) 3NHLn(SO 4) 2·3H 2O are given. They were examined by means of TG, DTG and DTA analyses, from 20 to 700° C. It was found that there is a difference in the thermal decomposition of these structurally different groups, in particular, a difference in the thermal decomposition of their anhydrous double sulphates.