Variation of fluorescence intensities and lifetime of Sm³⁺ and Tb³⁺ with As₂O₃ content in arsenic borax glasses

Fluorescence spectra and lifetimes of Sm³⁺ and Tb³⁺ were measured in borax, As₂O₃ and borax containing 20, 50 and 80 wt% of As₂O₃. For all compositions, with the exception of pure As₂O₃, glasses were formed. In the latter case, a crystal of TbAsO₄ was obtained as detected by X-ray diffraction. A gradual increase, up to a factor of three, of fluorescence was observed on addition of As₂O₃ to borax glass. In addition to optical excitations, glasses of various compositions containing Tb³⁺ were excited by an electron beam source.