Thermal stability of Dion–Jacobson mixed-metal-niobate double-layered perovskites

The thermal stability and decomposition pathways of six Dion–Jacobson-related double-layered perovskites, ALaNb2O7 (A = H, Li, Na, Ag) and (ACl)LaNb2O7 (A = Fe, Cu), are investigated. These compounds are made by low temperature (<400 °C) ion exchange reactions from RbLaNb2O7. All the compounds are low temperature phases with some of them exhibiting decomposition exotherms consistent with metastability. Decomposition temperatures and reactions pathways vary with the identity of A with most decompositions resulting in the formation of a niobate (containing A) and LaNbO4. Results from differential scanning calorimetry and high temperature X-ray powder diffraction studies are presented and structural parameters pertinent to compound stability discussed.