Phase Relations Between Palladium Oxide and the Rare Earth Sesquioxides in Air.

Abstract

The equilibrium phase relations were determined in an air environment between PdO and each of the following: La2O3, NH2O3, Sm2O3, Eu2O3, Gd2O3, Dy2O3, Ho2O3, Y2O3, Er2O3, Tm2O3, Yb2O3, and Lu2O3. In air PdO dissociates to Pd metal at 800 °C. The dissociation of PdO is apparently a reversible process. The Nd2O3-PdO and Sm2O3-PdO systems were studied in detail inasmuch as they typified several of the Ln2O3-PdO systems. Three compounds, 2Nd2O3 · PdO, metastable Nd2O3 · PdO, Nd2O3 2PdO occur in the Nd2O3-PdO system. The 2:1, 1:1, and 1:2 compounds, of unknown symmetry, dissociate or decompose at 1135, 860, and 1085 °C, respectively. The 2:1 compound dissociates to the solid phases, Nd2O3 and Pd. No further reactions occur between Nd2O3 and Pd up to 1300 °C Three compounds, 2:1, metastable 1:1, and 1:2 occur in the Sm2O3-PdO and Eu2O3-PdO systems. Two compounds, 2:1 and 1:2 occur in the La2O3-PdO system. Other compounds detected were the 1:1 and 1:2 in the Gd2O3-PdO system and the metastable 1:1 in the Dy2O3-PdO system. Each of these compounds subsequently dissociated upon heating. No apparent reaction occurred between PdO and either Ho2O3, Y2O3, Er2O3, Tm2O3, Yb2O3, or Lu2O3.