Gibbs Energy of Formation of Eu₃O₄ and EuO

Abstract

Thermodynamic data for Eu3O4 are not available in standard compilations. However, data for EuO and Eu2O3 are available. Data for Eu2O3 in the compilations are in agreement while those for EuO differ significantly. Two solid–state electrochemical cells incorporating yttria–doped thoria as the electrolyte are used to measure the standard Gibbs energy of formation of Eu3O4 and EuO relative to that for Eu2O3 in the temperature range from 1000 to 1300 K. A mixture of Nb and NbO is used as the reference electrode since the oxygen chemical potential associated with the mixture is close to that of the working electrodes EuO + Eu3O4 and Eu3O4 + Eu2O3. The standard Gibbs energy of formation of Eu3O4 can be represented by the following equation: Δf G°(±860)/J·mol–1 = −2267816 + 403.18­(T/K) {1090–1300 K}. Below the melting point of Eu, the Gibbs energy of formation of Eu3O4 is given by Δf G°(±860)/J·mol–1 = −2240177 + 377.824­(T/K) {1000–1090 K}. Also, the standard Gibbs energy of formation of EuO can be represented by the equations: Δf G°(±350)/J·mol–1 = −601046 + 96.878­(T/K) {1000–1090 K} and Δf G°(±350)/J·mol–1 = −610259 + 105.33­(T/K) {1090–1300 K}. Based on these results and the Neumann–Kopp rule, a complete set of thermodynamic data for Eu3O4 is generated. The results also permit refinement of data for EuO.

Effect of carbon on the co-presence of metallic tungsten as a nucleation agent and Eu2+ in glass: crystallization of CaO–Al2O3–SiO2 glass probed with Eu2+ luminescence

“…10 This interpretation ts well with the lines in Ellingham diagrams decreasing in the order W/WO 3 , EuO/ Eu 3 O 4 , Eu 3 O 4 /Eu 2 O as reported in previous studies. 48,49 Although the co-presence of metallic W and Eu 2+ is evident in the glass specimen prepared by the conventional melting method, the reduction efficiency of this method is lower than that of the improved glass raw material addition method used in the present study, as evaluated on the bases of the coloration and the uorescence spectra of glass specimens of W-Eu-Glass-4.0C, -0.40C, and -normal (Fig. 2 and 4).…”

The electron shuffle: Cerium influences samarium 4f orbital occupancy in heteronuclear Ce–Sm oxide clusters

“…In the Ln 2 O 3 sequioxide materials favored by most lanthanoids [CeO 2 is more stable than Ce 2 O 3 ; europium favors a mixed Eu(ii, iii) oxide over Eu 2 O 3 ], the partially filled 4f band generally lies within the conventional band gaps. [50][51][52][53][54] For Ce 2 O 3 , each Ce center has a singly occupied 4f orbital, and Sm 2 O 3 has a 4f 5 occupancy (the atomic number of Sm is 62, the atomic number of Ce is 58). However, the trend from Ce 2 O 3 to Sm 2 O 3 is that the bulk 4f band energy moves closer to the valence band, and in the case of Sm 2 O 3 , the 4f band energy lies very near the valence band.…”