Complex thermoanalytical studies on volatile rare earth element β-diketonates

Abstract

Experimental data on the thermal characteristics of fl-diketonates of rare earth elements (REE) are discussed. Tris chelates LnL3.nH20 and tetrakis chelates Na[LnL4] (Ldifferent fl-diketones) are considered. The volatility and thermal stability of these ft. diketonates depend on several factors, e.g. the hydrate composition and the organic substituents in the ligand. Hydrolysis is possible during the dehydration of light gEE tris chelates. Increase volatility and thermal stability are maintained by the introduction of sterically hindered and fluorinated substituents onto the chelate ring of the complex.It is known that fl-diketonates containing branched and fluorinated substituents readily form volatile complexes with salts of the rare earth elements (REE). Owing to these properties, they are widely used in the separation of the REE by means of the fractional sublimation technique [1], and such REE complexes are also used in some fields of microelectronics [2,3]. In this connection, the most typical problems in studies of their physical and chemical properties are the thermal stability and volatility. The data from the literature are incomplete [4,5], which was the reason for this paper, which combines the results of earlier published articles [6][7][8] and new results.The following materials were studied: REE tris chelates, with common formula LnL3.nH20, where Ln stands for any REE, L = trifluoroacetylacetone (TFA), hexafluoroacetylacetone (HFA), pivaloyltrifluoroacetone (PTA), dimethylheptafluoroacetonedione (FOD) and dipivaloylmethane (DPM); and REE tetrakis chelates, containing an alkali metal cation, with common formula Na[LnL4].