Phase transition of NaGaO2 at high pressure and high temperature

This work presents a comprehensive study on phase transition in NaGaO2 under high pressure and temperature (P–T) conditions. X-ray diffraction (XRD) was used to identify the phase composition of the recovered samples. Our results revealed that NaGaO2 could undergo a structural phase transition from orthorhombic ββ- NaGaO2 to hexagonal αα- NaGaO2 under high pressure and temperature. The pressure–temperature phase boundaries of NaGaO2 were determined up to 5 GPa and 2073 K. The hexagonal αα- NaGaO2 sample recovered from higher pressure and temperature exhibited a highly (003) preferred orientation. Besides, a reversible transition from αα- to ββ- NaGaO2 was observed above 473 K under normal-pressure condition. The high-pressure melting curve of NaGaO2, for the first time, was measured by using in-situ thermal measurement.

► We present a systematic study of the phase stability of NaGaO2 at HPHT conditions. ► Pressure induced the coordination and structural changes in NaGaO2. ► The P–T phase diagram of NaGaO2 by XRD was determined up to 5 GPa and 2073 K. ►αα- NaGaO2 is stable in the atmosphere at temperatures below 473 K. ► High pressure melting curve of NaGaO2 was measured by in-situ thermal measurement.