Enhanced thermal stability of CaAlSiN3:Eu2+ phosphors by superficial carbon modification

To satisfy increasing stringent application requirements for high power wLEDs, we propose a superficial carbon modification method to enhance thermal stability of red-emitting CaAlSiN₃:Eu²⁺ phosphor via carbon coating by mechanical mixing and thermal post-treatment at high temperature under N₂-H₂ atmosphere. The modifications on the crystal surface include (a) elimination of amorphous phase, (b) introduction of carbon and (c) inhibition of the oxidation of Eu²⁺. During the whole processing, the route of carbon and its effects on the crystal structure and luminescence properties are investigated by XPS, TEM, SEM, Raman spectra and TG-DSC analysis. After superficial carbon modification, the thermal quenching characteristic is improved by 5.7%, and the relative brightness decays more slowly during the aging test, which means that the superficial carbon modified samples still maintain good luminescence performance at high temperature and have superior performance for long-term applications. All above indicate that the superficial carbon modification method is a promising application to enhance the thermal stability for analogous Eu²⁺-activated nitride phosphors.