Superior thermal quenching and degradation of phosphors are required for long lifetime lighting devices, such as light-emitting diodes, which can be realized through composition modification. Here, Al-N bonds in AlON: Eu²⁺ phosphors are substituted by higher bond order of Si-C. Photoluminescence (PL) results show thermal quenching (at 150 °C) and thermal degradation (after 600 °C treatment in air) are improved by 5% and 8% with a small decrease of PL intensity in 5% SiC doped AlON: Eu²⁺ phosphor. To explain these observations, first-principles computational study was performed to understand the Si and C configuration in AlON:Eu²⁺. The calculations reveal that Si and C elements are not randomly distributed in AlON lattice. It was found that Si prefers occupying tetrahedral sites (Td-Si) and the insertion of C in Td-Si is always energetically favorable, which results in the formation of SiC₄ and SiNC₃ clusters. Thus, the Al-N substitution by Si-C induces a stronger local structure, which accounts for the emission redshift and better thermal stability.

Many strategies have been adopted to improve thermal degradation of phosphors. Because of the stability and high transmittance of graphene, here we report a novel method of carbon coating on BaMgAl₁₀O₁₇:Eu²⁺ (BAM) phosphor particles through chemical vapor deposition. The chemical composition, microstructure, and luminescence performance of carbon-coated BAM were characterized carefully. This coating can be controlled within 3-10 atomic layers, depending on the reaction time. Because of the decrease of surface defects and the effective weakening effect of oxidizing Eu²⁺ to Eu³⁺ after carbon coating, different layer numbers showed an obvious effect on the optical properties of carbon-coated BAM. Carbon-coated BAM phosphors had higher emission intensity and better oxidation resistance at high temperature than uncoated BAM phosphors. These results indicate that the method of carbon coating on phosphor particles is a promising way to improve the luminescence properties of other phosphors used in lighting and display devices.