Comprehensive survey of Nd 3+ substitution In La 2Mo 2O 9 oxide-ion conductor

Abstract

Differential thermal analysis coupled to temperature-controlled diffraction have given evidence of a topological metastability phenomenon in an extended compositional range of the La 2− x Nd x Mo 2O 9 solid solution. A metastable–stable phase diagram is proposed for this series of LAMOX-type fast oxide-ion conductors. In the Nd range 0< x⩽0.35, a freezing of the oxygen/vacancy disorder of the β-phase at ambient temperature can be achieved through a splat-quenching to water–ice mixture or/and shaping/sintering into pellet. In the intermediate 0.4⩽ x⩽1.2 range, the amount of β-metastable phase grows upon substitution for powders. The negative impact of β-metastable to α phase transition on conductivity tends to disappear through the partial stabilization of the β phase by shaping/sintering.