Photoluminescence processes in τ-phase Dy3+/Tb3+-codoped Ba1.3Ca0.7SiO4 phosphors for solid-state lighting

The τ-phase-Ba1.3Ca0.7SiO4 phosphors co-doped with 3 mol% Dy3+ and ~1-5 mol% Tb3+ trivalent rare-earth ions were prepared by the gel-combustion method. The structure-property relation of the samples was examined by X-ray diffraction, scanning electron microscopy, and spectrophotometer. Here, the effect of Tb3+’s concentration on the spectroscopic properties of Dy3+/Tb3+ co-doped Ba1.3Ca0.7SiO4 phosphors was explored by using the photoluminescence excitation, emission, and decay curves. Importantly, the photonic energy transfer from (Dy3+: 4F9/2 + Tb3+: 7F6) to (Dy3+: 6H15/2 + Tb3+:5D4) was observed, in which the Dy3+ ions acts as a light-emitting donor whereas the Tb3+ ions as a light-absorbing acceptor, resulting in an enhanced emission from the co-doped Ba1.3Ca0.7SiO4: Dy3+/Tb3+ phosphors. Finally, the chromaticity coordinates were determined from the measured emission spectra, locating at the green and white light regions. This observation indicates that the characteristic emission c...