The effect of ion-bombardment on the structure of bi₂O₃, moo₃, teo₂, and v₂o₅

Abstract

Abstract The four oxides Bi2O2, MoO3, TeO2, and : 2O5 we characterized by high values for the ratio (crystallization temp.)/(melting temp.), as well as by low ionicities. They would therefore be expected to amorphize on ion impact. Such amorphization is shown to occur readily following the impact of 10–40 ke V Kr ions. This was demonstrated firstly in that the gas-release spectra contained components having a dose dependence and temperature width suggestive of out-diffusion due to crystallization. Secondly, the amorphization was revealed by reflection electron diffraction at 60 or 80 kV. The doses for amorphization were lowest with TeO2 and V2O5, and these, along with U3O8 and SiO2, must be regarded as the substances most prone to bombardment-induced amorphization. The crystallization temperatures in °C were 260 for Bi2O3, 250 for MoO3, 260 for TeO2, and 310 for V2O5 and are thus amongst the lowest known with oxides. Bi2O3 crystallizes homogeneously to a cubic phase (δ-Bi2O3) different from the original, whereas MoO3, TeO2, and V2O5 crystallize by interface motion to the original structures. Very high dose bombardment of MoO3 and V2O5 : eads to preferential oxygen loss with resultant formation of MoO2 and V2O3 as thin surface layers. Such oxygen loss does not occur with Bi2O3 and TeO2