In-situ observation of first-order phase transition in BaLn₂Mn₂O₇

Abstract

BaLn₂Mn₂O₇ has a Sr₃Ti₂O₇-type layered perovskite structure with double-block oxygen octahedra. In-situ transmission electron microscopy observation revealed that BaLn₂Mn₂O₇ undergoes several transitions upon heating. In the case of BaPr₂Mn₂O₇, the tetragonal P4₂/mnmphase was transformed into a tetragonal phase I4/mmm phase at 373 K by in-situ single X-ray diffractometory. At 1040K, split reflections appeared along the c-axis in which two phases were coexisted, and the transition was of the first order.