Abstract: A coated phosphor may comprise: phosphor particles comprised of a phosphor with composition (M)(A)2S4:Eu, wherein: M is at least one of Mg, Ca, Sr and Ba; and A is at least one of Ga, Al, In, Y; a dense impermeable (pinhole-free) coating of an oxide material encapsulating individual ones of the phosphor particles. The coated phosphor is configured to satisfy one or more of the conditions: (1) under excitation by blue light, the reduction in photoluminescent intensity at the peak emission wavelength after 1,000 hours of aging at about 85° C. and about 85% relative humidity is no greater than about 30%; (2) the change in chromaticity coordinates CIE(y), ?CIE y, after 1,000 hours of aging at about 85° C. and about 85 % relative humidity is less than about 5×10?3; (3) said coated phosphor does not turn black when suspended in a 1 mol/L silver nitrate solution for at least two hours at 85° C.

Abstract: A coated phosphor comprises: phosphor particles comprised of a phosphor with composition MSe1?xSx:Eu, wherein M is at least one of Mg, Ca, Sr, Ba and Zn and 0<x<1.0; and a coating on individual ones of the phosphor particles, the coating comprising a layer of oxide material encapsulating the individual phosphor particles; wherein the coated phosphor is configured such that under excitation by a blue LED the reduction in photoluminescent intensity at the peak emission wavelength after 1,000 hours of aging at about 85° C. and about 85% relative humidity is no greater than about 15%; and wherein the coated phosphor is configured such that the change in chromaticity coordinates CIE(x), ?x, after 1,000 hours of aging at about 85° C. and about 85% relative humidity is less than or equal to about 5×10?3.