Method for Producing Luminescent Particles with a Protective Layer and Luminescent Particles Having a Protective Layer

Abstract

In an embodiment phosphor particles include one of a Si-containing phosphor or an Al-containing phosphor, wherein a surface of the phosphor particles is coated with at least one first protective layer and a second protective layer, the first protective layer being arranged above the second protective layer, wherein the second protective layer has a content of Si which is increased at least by 40 atomic % relative to a phosphor or an Al content reduced by at least 10% relative to the phosphor, and wherein the at least one first protective layer includes a molecular monolayer of one of a metal oxide, a metal nitride, a metal sulfide or a metal oxynitride.

What is claimed is: 
     
         1 . Phosphor particles comprising:
 one of a Si-containing phosphor or an Al-containing phosphor,   wherein a surface of the phosphor particles is coated with at least one first protective layer and a second protective layer, the first protective layer being arranged above the second protective layer,   wherein the second protective layer has a content of Si which is increased at least by 40 atomic % relative to a phosphor or an Al content reduced by at least 10% relative to the phosphor, and   wherein the at least one first protective layer comprises a molecular monolayer of one of a metal oxide, a metal nitride, a metal sulfide or a metal oxynitride.   
     
     
         2 . The phosphor particles according to  claim 1 , wherein the first protective layer comprises an aluminum-containing material. 
     
     
         3 . The phosphor particles according to  claim 1 , wherein the phosphor particles comprise a plurality of first protective layers, the plurality of first protective layers having a thickness between 1 nm and 500 nm inclusive. 
     
     
         4 . The phosphor particles according to  claim 1 , wherein the phosphor particles comprise the phosphor containing an inorganic substance, which comprises in its composition at least an element D, an element A1, an element AX, an element SX and an element NX, wherein the element D is one, two or more elements from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Li, Na, K, Rb, Cs and Yb, wherein the element A1 represents one, two or more elements from divalent metals which are not included in the element D, wherein the element SX represents one, two or more elements from tetravalent metals comprising Si, wherein the element AX represents one, two or more elements from trivalent metals, and wherein the element NX represents one, two or more elements from the group consisting of O, N, S, C, Cl and F. 
     
     
         5 . The phosphor particles according to  claim 1 , wherein the phosphor particles comprise the phosphor having the general formula:
   Sr(SraM1−a)Si2Al2(N,X)6:D,A,B,E,G,L,
   wherein element M is Ca, Ba, Mg alone or in combination,   wherein element D is one, two or more elements from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Li, Na, K, Rb, Cs, Tm and Yb,   wherein element A is selected from divalent metals which are different from the element M and the element D,   wherein element B=trivalent metals,   wherein element E=monovalent metals,   wherein element G=tetravalent elements,   wherein element L=trivalent elements,   wherein element X=O or halogen, and   wherein 0.6≤a<1.   
     
     
         6 . The phosphor particles according to  claim 1 , wherein the phosphor particles comprise a phosphor that crystallizes in one of the space groups P1, P2, P 1  or P21. 
     
     
         7 . A method for producing phosphor particles with at least one first protective layer, the method comprising:
 providing the phosphor particles comprising phosphor, wherein the phosphor is one of a Si-containing phosphor or an Al-containing phosphor;   treating the Si-containing phosphor particles or the Al-containing phosphor particles with an acid solution, wherein a pH of the acid solution is kept within a range of pH 3.5 to 7 for a period of at least 1 h, and wherein a Si-containing second protective layer is formed on a surface of the phosphor particles, the second protective layer having a higher content of Si than the phosphor particles, or an Al-containing second protective layer is formed on the surface of the phosphor particles, the second protective layer having a modified content of aluminum on the surface compared with the phosphor particles; and   applying the at least one first protective layer to the surface of the phosphor particles, wherein applying the at least one first protective layer comprises:
 depositing a first starting compound by a first atomic layer deposition on the surface of the phosphor particles; and 
 depositing a second starting compound by a second atomic layer deposition on the surface of the phosphor particles. 
   
     
     
         8 . The method according to  claim 7 , wherein the first starting compound is selected from the group consisting of organometallic compounds and metal halides, and wherein the second starting compound is selected from a group consisting of H2O, H2S, NH3 and O3. 
     
     
         9 . The method according to  claim 7 , wherein a metal of an organometallic compound or of a metal halide is selected from the group consisting of boron, aluminum, silicon, tin, zinc, titanium, zirconium, tantalum, niobium and hafnium. 
     
     
         10 . The method according to  claim 7 , wherein the first starting compound comprises MClx, MBrx, M(CH3)x, M(CH2—CH3)x, M(CH2—CH2—CH3)x, M(OCH3)x, M(OCH2—CH3)x or M(OCH2—CH2—CH3)x, wherein M is one of B, Al, Si, Sn, Zn, Ti, Zr, Ta, Nb or Hf, and wherein x corresponds to a valence of M. 
     
     
         11 . The method according to  claim 7 , wherein the first starting compound comprises AlCl 3 , AlBr3, Al(CH3)3, Al(CH2—CH3)3, Al(CH2—CH2—CH3)3, Al(OCH3)3, Al(OCH2—CH3)3 or Al(OCH2—CH2—CH3)3. 
     
     
         12 . The method according to  claim 7 , wherein several first protective layers are applied to the surface of the phosphor particles such that the surface of the phosphor particles is coated with a plurality of first protective layers. 
     
     
         13 . The method according to  claim 7 , further comprising, after applying the at least one first protective layer to the surface of the phosphor particles, tempering the phosphor particles coated with the at least one first protective layer at a temperature between 200° C. and 500° C., inclusive. 
     
     
         14 . The method according to  claim 13 , wherein tempering the phosphor particles comprises tempering the phosphor particles under an inert gas atmosphere, an oxygen-containing atmosphere or an H2-containing atmosphere. 
     
     
         15 . The method according to  claim 13 , wherein tempering the phosphor particles coated with the at least one first protective layer comprises tempering with an oxygen-containing atmosphere or an H2-containing atmosphere. 
     
     
         16 . The method according to  claim 7 , further comprising after treating the Si-containing phosphor particles or the Al-containing phosphor particles with the acid solution, tempering the treated phosphor particles at a temperature of at least 100° C.