Abstract
ZnSnF6·6H2O:Mn4+ red-emitting hexahydrate phosphor is synthesized by the chemical reaction method, and its unique structural and optical properties are investigated using X-ray diffraction measurement, photoluminescence (PL) analysis, PL excitation spectroscopy, and electron spin resonance (ESR) spectroscopy. The Mn4+-activated phosphor exhibits remarkable degradation in the PL intensity under Xe lamp exposure and also by the coherent laser beam irradiation with the following order of degradation: Ar+ (488nm)>He–Cd (325nm)>He–Ne laser (632.8nm). The mechanism of degradation is considered to be due to a change in the valence state of manganese ions from Mn4+ to Mn5+ by the photooxidation and/or disproportionation. The ESR measurement supports decreased Mn4+ spin density in the Xe-lamp exposed, degraded sample. The changes in the structural and PL properties are also observed after thermal annealing above ∼100°C and explained by the thermal-annealing-induced dehydration/decomposition of the host material.
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