Atomic environment changes induced by rare earths addition to heavy metal glasses

Abstract

The study aims to evidence the local order changes in Bi2O3-GeO2 heavy metal glasses by addition of gadolinium oxide. The elemental analysis carried out by X-ray photoemission spectroscopy shows that in the first surface layers the oxygen and germanium contents are higher than the calculated values for bulk samples, while the content of gadolinium and bismuth atoms is lower than the expected values for bulk samples. Non-equivalent sites of bismuth atoms are evidenced in the glasses with low Gd2O3 content (x <= 3 mol %). The gadolinium addition to Bi2O3-GeO2 glass matrix determines the diminishing of bridging oxygens number and implicitly a depolymerisation of the glass structure. On the other hand, the decrease of full-width at half-maximum of O 1s photoelectron peaks denotes the diminishing of the structural disorder in samples. According to the values of O 1s photoelectrons binding energy, the investigated samples are a mixture of ionic and covalent oxide compounds.