Phase Transitions in GeTe at Hydrostatic Pressure up to 9.3 GPa

The electrical resistance of GeTe polycrystalline samples with hole concentration 3.9 × 1020 cm−3 has been measured at hydrostatic pressure up to 9.3 GPa and at temperature up to 600°C. The PT phase diagram of GeTe is presented based on the resistance peculiarities observed at the phase transitions in this material. The new γ′-phase is found to be stable at high pressure. Equilibrium lines between rhombohedral α-phase, cubic β-phase, and new γ′-phase intersect in the triple point (3.5 GPa; 300°C). The pressure coefficient of the ferroelectric α → β phase transition temperature is dTcdP = −31.6 K/GPa. The influence of shear stresses on the phase transitions in GeTe is discussed.