We report on multiphoton white-light upconversion in vacuum for Pechini synthesis (YbAG) and combustion synthesis nanopowders under IR excitation. Their intense white-light upconversion is attributed to charge transfer luminescence superimposed upon a broadband emission. Unlike common nanoscale phosphors, which show low luminescence efficiency, the intensity of white-light upconversion for nanopowders is similar to that of their bulk counterparts. The luminary efficacy of the upconversion is estimated to be , and the Commission Internationale d’Eclairage (CIE) coordinates can be widely tuned by the excitation power, pressure, and codoping ratio. The nano-YbAG sample exhibits a longer buildup time for emission, a higher excitation threshold, and a wider CIE range than the oxide nanopowders.
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