Blue photoluminescence in Ti-doped alkaline-earth stannates

Blue photoluminescence properties of Ti-doped alkaline-earth stannates, A2(Sn1−xTix)O4 (A=Ca, Sr, Ba) (x=0.005–0.15), were examined at room temperature. These stannates showed intense broad emission bands peaking at 445 nm for Ca2SnO4, at 410 nm for Sr2SnO4, and at 425 nm for Ba2SnO4 under UV excitation. Emission intensities were relatively insensitive to Ti concentration and no sharp concentration quenching was observed. Mixing alkaline-earth ions in the crystal structures did not increase the emission intensities in the A2(Sn1−xTix)O4 system. The excitation spectra of these stannates exhibited broad bands just below the fundamental absorption edges, implying that luminescence centers do not consist of the component elements in the host materials. It was suggested that the isolated TiO6 complexes are possible luminescence centers in these materials, as previously proposed in other Ti-doped stannates such as Mg2SnO4 and Y2Sn2O7.