Analysis of structural phase transition behavior of Ln2NiO4 + δ (Ln: Nd, Pr) with variation of oxygen content

The orthorhombic-tetragonal structural phase transition behaviors of Pr2NiO4 (+) (delta) and Nd2NiO4 (+ delta) were investigated by DSC and TG-DTA under controlled oxygen partial pressure, P(O-2), and their difference was discussed. A discrete weight variation originating from the variation of oxide ion content, Delta delta, was observed during the phase transition in both Pr2NiO4 (+) (delta) and Nd2NiO4 (+) (delta). The Delta delta of Pr2NiO4 (+) (delta) was larger than that of Nd2NiO4 (+) (delta), and the Delta delta of Pr2NiO4 (+) (delta) increased with decreasing P(O-2), while that of Nd2NiO4 (+) (delta) was independent on P(O-2), suggesting that not only the valence of Ni but also that of Pr changed during the phase transition in Pr2NiO4 (+) (delta) (C) 2014 Elsevier B.V. All rights reserved.