Spectroscopic properties of Eu3+- and Eu3+:Yb3+-doped LaOF crystalline powders prepared by combustion synthesis

Highlights: ► Eu and Eu:Yb doped LaOF crystalline powders were prepared by combustion synthesis. ► The luminescence quantum efficiency was 53.8% for 1 wt% of Eu3+ doped LaOF. ► The Yb–Eu (2:1 wt%) energy transfer rate for cooperative upconversion was 740 s−1. - Abstract: Lanthanum oxyfluoride (LaOF) powders doped with Eu3+ and co-doped with Eu3+ and Yb3+ were prepared by combustion synthesis. Surface morphology and structure of the powders were investigated by scanning electronic microscopy, energy dispersive X-ray and X-ray powder diffraction. Luminescence experiments were performed in singly doped (Eu3+) samples illuminated with ultraviolet light (λ = 255 nm) and co-doped (Eu3+:Yb3+) samples exposed to near-infrared diode laser (λ = 975 nm). The characteristic red luminescence of Eu3+ corresponding to 5D0 → 7FJ transitions was observed in both cases. The Judd–Ofelt intensity parameters Ω2 and Ω4 were calculated from experimental data and luminescence quantum efficiencies were estimated. The near-infrared to visible up-conversion luminescence achieved in co-doped samples is due to energy transfer (ET) from pairs of Yb3+ to Eu3+. The ET rate was estimated by use of a rate equation model adjusted to the dynamics of up-conversion luminescence.