Abstract

Mechanisms of upconversion luminescence (UCL) of SrF₂:Er phosphors corresponding to the G4_11/2→I4_15/2, H2_9/2→I4_15/2, F4_5/2→I4_15/2, F4_7/2→I4_15/2, H2_11/2→I4_15/2, S4_3/2→I4_15/2, F4_9/2→I4_15/2, and I4_9/2→I4_15/2 transitions upon excitation of the I4_11/2 level of Er³⁺ ions were investigated. Energy transfer upconversion processes are responsible for the populating of the H2_9/2, H2_11/2, S4_3/2, and F4_9/2 levels. Cooperative process is the dominant mechanism of luminescence from S4_3/2 and F4_9/2 levels for SrF₂:Er with high concentrations of Er³⁺ ions. The UCL from G4_11/2 and F4_5/2 is explained by excited-state absorption. Cross-relaxation processes take part in the population of F4_9/2 and I4_9/2 levels. For quantifying material performance, the Er³⁺-concentration dependence of UCL and the absolute quantum yields of SrF₂:Er were studied. The most intensive visible luminescence was obtained for SrF₂:Er (14.2%) with 0.28% maximum quantum yield.

© 2018 Chinese Laser Press

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