High-temperature neutron diffraction study of the cation ordered perovskites TbBaMn2O5+x and TbBaMn2O5.5−y

The miscibility of TbBaMn2O5+x and TbBaMn2O5.5−y has been investigated at 100–600 °C using in situ powder neutron diffraction. No miscibility is observed, and the two phases remain oxygen stoichiometric (image) at 600 °C. Structure refinement results show that neither material undergoes a phase transition in this temperature range. TbBaMn2O5 is Mn2+/Mn3+ charge ordered and any charge melting transition is >600 °C. This symmetry-broken charge ordering is remarkably robust in comparison to that in other oxides.