Thermal decomposition of europium sulfates Eu2(SO4)3•8H2O and EuSO4

Reactions of europium sulfates Eu-2(SO4)(3)center dot 8H(2)O and EuSO4 complete decomposition were studied by Simultaneous Thermal Analysis. It was revealed that one-step dehydratation of Eu-2(SO4)(3)center dot 8H(2)O crystallohydrate is accompanied by the formation of amorphous anhydrous europium sulfate Eu-2(SO4)(3). Crystallization of amorphous europium (III) sulfate occurs at 381.1 degrees C (in argon) and 391.3 degrees C (in air). The average enthalpy values for dehydratation reaction of Eu-2(SO4)(3)center dot 8H(2)O (Delta H degrees = 141.1 kJ/mol), decomposition reactions of Eu-2(SO4)(3) (Delta H = 463.1 kJ/mol), Eu2O2SO4 (Delta H = 378.4 kJ/mol) and EuSO4 (Delta H = 124.1 kJ/mol) were determined. The step process mechanisms of thermal decomposition of europium (III) sulfate in air and europium (II) sulfate in inert atmosphere were established and justified. The kinetic parameters of complete thermal decomposition of europium (III) sulfate octahydrate were calculated by Kissinger model. The standard enthalpies of compound formation were calculated using thermal effects and formation enthalpy data for binary compounds.