Phase transitions in tellurium at high pressure and temperature

The structural phase transitions in tellurium have been studied up to 21 GPa and 743 K using powder-diffraction techniques. We find the incommensurate Te-III phase to be stable up to at least 743 K, and have determined the P-T dependence of the incommensurate wave vector q. We also find that the rhombohedral beta-Po phase of Te, Te-IV, previously reported to exist at room temperature, is stable only above 315 K.