Browning of bismuth borate glass by heat treatment under vacuum

Abstract

Browning after heating under vacuum has been studied on bismuth borate glasses. It was found that the reaction of water with glass surfaces was a necessary step for browning and that browning occurred at the surface of glass. The fraction of Bi atoms forming Bi metal was about 1%. It was deduced that browning was caused by the formation of Bi metal particles through the dehydration of hydrated layer of the glass surface.