XRD study of ZrW2O8 versus temperature and pressure

ZrW2O8 samples have been prepared from ZrO2 and WO3 precursors by a ceramic method. Different portions of this material were subjected to non cumulati ve pressure treatments within the 2-65 Kbar range; the metastable high-pres sure phase, gamma-ZrW2O8, has been isolated by quenching from 6 Kbar. Furth er pressure increases up to 10 Kbar produced the volume reduction of the ga mma-phase; a minimum volume was found even after having released the pressu re. Otherwise, heating above 600 degrees C, followed by quenching at 77 K l eads to the high-temperature phase, beta-ZrW2O8, which is stable at room te mperature. Finally, when gamma-ZrW2O8 was subjected to pressure and tempera ture, gamma-ZrW2O8 could also be quenched with a still larger volume reduct ion at 6 Kbar and 600 degrees C. (C) 2000 Elsevier Science Ltd. All rights reserved.