Structural Evolution and Chemical Incorporation Pathways in Wadsley-Roth Oxides

Abstract We investigate solid-state reaction pathways to high-temperature phase formation in the entropy-stabilized Wadsley-Roth Ti(NbxTa1–x)2O7 phases. We analyze and discuss thermodynamic and kinetic factors governing these processes in TiNb2O7, TiTa2O7, and Ti(NbTa)2O7. Diffraction-centric experiments enable in situ phase formation studies throughout the intermediate temperature regime (600–1200 °C). We also differentiate between solid-state reaction pathways across the compositional family using both qualitative and quantitative approaches. We identify phase evolution between related Wadsley-Roth phases with different cation sublattice decorations and shear block dimensions. We observe minimum stabilization temperatures consistent with prior predictions for cation sublattice mixing, suggesting some entropic contribution to thermodynamic phase stabilization. Composition-dependent differences in reaction pathways highlight opportunities for targeting specific intermediate phases by adjusting the chemical ensemble, with possible implications for functional and extreme materials.