The thermal stability and decomposition pathways of six Dion-Jacobson-related double-layered perovskites, ALaNb(2)O(7) (A = H, Li, Na, Ag) and (ACI)LaNb(2)O(7) (A = Fe, Cu), are investigated. These Compounds are made by low temperature (<400 degrees C) ion exchange reactions from RbLaNb(2)O(7). 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 LaNbO(4). Results from differential scanning calorimetry and high temperature X-ray powder diffraction studies are presented and structural parameters pertinent to compound stability discussed. (C) 2008 Elsevier Ltd. All rights reserved.