Thermochemistry of a New Class of Materials Containing Dinitrogen Pairs in an Oxide Matrix

A series of N 2 -containing perovskite phases was prepared in the La−(Ba)−Ti−O system in order to study the dinitrogen retention phenomenon from a thermochemical viewpoint. High-temperature oxide melt solution calorimetry was undertaken to determine the energetics of the corresponding starting oxynitrides, intermediate phases, and oxides. Calorimetric results show that nitrogen is weakly bound within the oxide matrix and most of the enthalpy of oxidation of the intermediate phase is devoted to its structure change between the starting perovskite structure and the formation of a layered-perovskite La 2 Ti 2 O 7 oxide.