Fluorescence of Eu3+ in Sodium Phosphotungstate Glasses

Sodium phosphotungstate glasses of various ratios of P₂O₅/WO₃ were doped by 1.0 weight per cent Eu3 +. Fluorescence spectra were measured on excitation to 394 and 464 nm. On excitation to 394 nm the ratio of 5D₀ → 7F₂/ 5D_o →7F₁ emissions and the amount of splitting of the 5D_o → 7F₁ transition are dependent on composition of the glass and conditions of glass preparation. It is concluded that two different types of Eu8 + sites exist in phosphotungstate glasses. One type is this in which Eu3+ is surrounded by phosphate and tungstate tetrahedra at random. In the other type, Eu3 + is incorporated into microcrystallites. It is shown that Eu3+ may serve as a spectroscopic probe for microphase separation. It is also suggested that phosphotungstate glasses doped by Eu3+ can substitute Eu3 +-doped tungstate crystals for fluorescence purposes.