Comparative study of Er3+ and Tm3+ co-doped YOF and Y2O3 powders as red spectrally pure upconverters

We prepared Er3+ and Tm3+ co-doped yttrium oxyfluoride (YOF) powder by combustion synthesis and we observed that under near-infrared (λ = 980 nm) laser excitation the characteristic green (2H11/2, 4S3/2 → 4I15/2) emission of Er3+ was suppressed by energy transfer (ET) mechanisms between Tm3+ and Er3+. The ET process observed in YOF was much more efficient than that observed in standard Y2O3 powder prepared under similar conditions. YOF combines the superior mechanical and thermal properties of oxides with low phonon energy of fluorides. Our results show that this material is a serious candidate for use as a red upconversion phosphor.