Phase transitions of LiAlO2 at high pressure and high temperature

This work presents a comprehensive study on phase transitions in LiAlO2 system at high pressures and temperatures (0.5–5.0 GPa and 300–1873 K, respectively), as well as the phase stability for polymeric phases of LiAlO2 in the studied P–T space by X-ray diffraction (XRD). Besides the previously described polymorphic hexagonal α-phase, orthorhombic β-phase and tetragonal δ-phase, a possible new phase of LiAlO2 was observed after the tetragonal γ-LiAlO2 sample was treated at 5.0 GPa and 389 K. The stable regimes of these high-pressure phases were defined through the observation of coexistence points of the polymeric phases. Our results revealed that LiAlO2 could experience structural phase transitions from γ-LiAlO2 to its polymorphs at lower pressures and temperatures compared to the reported results. Hexagonal α-LiAlO2 with highly (003) preferential orientation was prepared at 5.0 GPa and 1873 K.