Insights into the HfₙNb₂O₂ₙ₊₅ homologous phases from experimental, first-principle, and force-field studies

Abstract

Different outcomes have been presented on the preparation of high-temperature ceramic AnB2O2n+5 (A = Hf, Zr and B = Nb, Ta). Considering the importance of these materials as refractories, the stability range of the A = Hf and B = Nb compound is experimentally determined by preparing ceramics via solid-state synthesis and analyzing their phase compositions. Then, the density functional theory was used to study the stability of the homologous series versus decomposition to the parent compounds of HfO2 and Nb2O5. A good agreement with the experimental values is found. In order to improve the theoretical data further, an interatomic potential based on the first-principle calculations is developed and applied to larger supercell structures. These force-field calculations confirm the stability of the homologous series versus a solid solution. The calculations also allow us to study cation order and periodic compositional modulation.