Bi2O3 under hydrostatic pressure:: observation of a pressure-induced amorphization

We report on the changes of alpha-Bi2O3 under hydrostatic pressures in excess of 30 GPa, using Raman and absorption spectroscopy. The loss of Raman signal and the change of the absorption edge indicate a substantial modification of the atomic ordering around 21 GPa, in agreement with a pressure-induced amorphization inferred by X-ray diffraction. An attempt to characterize the amorphous state of alpha-Bi2O3 as a stable or metastable one has also been made by heating the sample under pressure and at room conditions. This analysis has shown that pressure-amorphized Bi2O3 undergoes an amorphous-to-crystal line transformation when heated with an Ar+ laser at room conditions. (C) 1999 Elsevier Science Ltd. All rights reserved.