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: La(2)O(3), NH(2)O(3), Sm(2)O(3), Eu(2)O(3), Gd(2)O(3), Dy(2)O(3), Ho(2)O(3), Y(2)O(3), Er(2)O(3), Tm(2)O(3), Yb(2)O(3), and Lu(2)O(3). In air PdO dissociates to Pd metal at 800 °C. The dissociation of PdO is apparently a reversible process. The Nd(2)O(3)-PdO and Sm(2)O(3)-PdO systems were studied in detail inasmuch as they typified several of the Ln(2)O(3)-PdO systems. Three compounds, 2Nd(2)O(3) · PdO, metastable Nd(2)O(3) · PdO, Nd(2)O(3) 2PdO occur in the Nd(2)O(3)-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, Nd(2)O(3) and Pd. No further reactions occur between Nd(2)O(3) and Pd up to 1300 °C Three compounds, 2:1, metastable 1:1, and 1:2 occur in the Sm(2)O(3)-PdO and Eu(2)O(3)-PdO systems. Two compounds, 2:1 and 1:2 occur in the La(2)O(3)-PdO system. Other compounds detected were the 1:1 and 1:2 in the Gd(2)O(3)-PdO system and the metastable 1:1 in the Dy(2)O(3)-PdO system. Each of these compounds subsequently dissociated upon heating. No apparent reaction occurred between PdO and either Ho(2)O(3), Y(2)O(3), Er(2)O(3), Tm(2)O(3), Yb(2)O(3), or Lu(2)O(3).