  An experimental and theoretical study of the structural properties of
monoclinic bismuth oxide (alfa-Bi2O3) under high pressures is here reported.
Both synthetic and mineral bismite powder samples have been compressed up to 45
GPa and their equations of state have been determined with angle-dispersive
x-ray diffraction measurements. Experimental results have been also compared to
theoretical calculations which suggest the possibility of several phase
transitions below 10 GPa. However, experiments reveal only a pressure-induced
amorphisation between 15 and 25 GPa, depending on sample quality and deviatoric
stresses. The amorphous phase has been followed up to 45 GPa and its nature
discussed.
