“…When the firing time prolongs further, for example 120 min, the transparent glasses become opal glasses and emit red emission of Eu 3+ , indicating that a second phase appears in the glasses. The similar phenomenon of phase separation was also reported by Koudelka that two phases are produced when the melt of 0.50ZnO-0.40B 2 O 3 -0.10P 2 O 5 is cooled naturally in air, one phase is boron rich, and the other is phosphate rich, which were confirmed by Raman spectra [18]. So we hypothesize that the valence of Eu ion in borate glasses and phosphate glasses is 3.…”