Blue photoluminescence of germania-stabilized benitoite

Benitoite (BaTiSi₃O₉) phases, which were partially-substituted by germania (GeO₂) in order to stabilize the phase, were synthesized, and their optical properties were examined. The benitoite phase was crystallized by a small quantity of Ge-introduction into the benitoite composition. Clear blue emission with the peak at ∼430 nm, due to the transition of ³T₁ → ¹A₁ in the TiO₆ octahedra, was observed at room temperature during the ultraviolet excitation, being sufficient for a visual confirmation. On the other hand, the reduction in blue emission intensity by the Ge-introduction was confirmed. This was qualitatively explained on the basis of configurational- coordinate mode without discrepancy.