Luminescence of Sn^2+ center in oxide glass with a tendency toward phase separation

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Photoluminescence (PL) of Sn2+ in oxide glasses is affected by the local coordination field because of the electrons in the outermost shell. Not only the emission energy varies depending on the local coordination, but also the transparency, and it is worth examining the local distribution of Sn2+ cations in oxide glasses, which have a tendency toward phase separation, especially in an ionic (phosphate)–covalent (borate) binary system. Here, we report the structural changes in zinc borophosphate glass and the PL properties of Sn2+ in oxide glasses. The building blocks of the main glass network vary depending on the chemical composition. We found that the Sn2+ species in B2O3-rich glasses differ from those in P2O5-rich glasses, as observed in the optical absorption, PL peaks, and PL decay constants. 119Sn Mossbauer spectra indicate that isomer shifts of Sn2+ also affect the local coordination change depending on the chemical composition. According to these results for the Sn2+ center, we conclude that Sn2+ centers are homogeneously dispersed in the borophosphate network without localization around the phosphate region.