Boron environments and irradiation stability of iron borophosphate glasses analysed by EELS

Abstract

The coordination and stability under electron irradiation of boron in glasses with nominal molar composition 60P 2O 5 − (40 − x)Fe 2O 3 − xB 2O 3, for which x = 0, 5, 10, 15 and 20, have been investigated for the first time by electron energy loss spectroscopy (EELS) with transmission electron microscopy (TEM). Analyses confirm that boron is present in un-irradiated samples as tetrahedral BO 4 units; there is no evidence of any trigonal BO 3 units. TEM analysis reveals no tendency for sub-micron phase separation of the as-annealed glass. Iron borophosphate glasses exhibit high resistance to structural damage by electron beam irradiation by comparison with literature values for a range of other silicate and phosphate glasses. Large doses of highly intense irradiation result in the conversion of BO 4 to BO 3 units. The high irradiation resistance of these glasses could be related to the absence of mobile classical network modifiers such as alkalis and their associated non-bridging oxygens.