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 cumulative pressure treatments within the 2-65 Kbar range; the metastable high-pressure phase, gamma-ZrW2O8, has been isolated by quenching from 6 Kbar. Further pressure increases up to 10 Kbar produced the volume reduction of the gamma-phase; a minimum volume was found even after having released the pressure. Otherwise, heating above 600 degrees C, followed by quenching at 77 K leads to the high-temperature phase, beta-ZrW2O8, which is stable at room temperature. Finally, when gamma-ZrW2O8 was subjected to pressure and temperature, gamma-ZrW2O8 could also be quenched with a still larger volume reduction at 6 Kbar and 600 degrees C. (C) 2000 Elsevier Science Ltd. All rights reserved.