Alkaline earth sulfide-based red-emitting phosphor Ca0.8Sr0.2S:Eu2+, Tm3+ were coated directly by ZnO and Al2O3 Particles to prevent PL intensities degradation under the effects from moist air. The PL intensities degradation of phosphors modified with oxides particles was reduced to different extents, in comparison with that of uncoated phosphor. SEM (scanning electron microscopy), powder XRD (X-ray diffraction) and EDX (energy dispersive X-ray) methods were used to characterize the coating. (C) 2003 Elsevier B.V. All rights reserved.