VAPORIZATION THERMODYNAMICS OF EUROPIUM MONOXIDE

Europium monoxide prepared by the reduction of the oxide chloride with lithium hydride has been studied by the target collection Knudsen effusion technique and found to vaporize according to the reaction 4EuO(s) → Eu3O4(s) + Eu(g) (1), over the temperature range 1334-1758°K. At 1546°K, ΔH°T = 75.91 ± 0.94 kcal/ gfw and ΔS°T = 28.66 ± 0.61 eu. Heat capacity data for EuO(s) have been estimated, and second- and third-law enthalpies for reaction 1 are presented. For EuO(s), ΔHf°298 = -145.2 ± 4.1 kcal/gfw, ΔGf°298 = -139.0 ± 4.1 kcal/gfw, and S°298 = 15.0 ± 3.0 eu.