An oxynitride phosphor powder contains α-SiAlON and aluminum nitride, obtained by mixing a silicon source, an aluminum source, a calcium source, and a europium source to produce a composition represented by a compositional formula: Ca.sub.x1Eu.sub.x2Si.sub.12−(y+z)Al.sub.(y+z)O.sub.zN.sub.16−z (wherein x1, x2, y and z are 0<x1≦3.40, 0.05≦x2≦0.20, 4.0≦y≦7.0, and 0≦z≦1), and firing the mixture.

To provide a sintered material having excellent oxidation resistance, as well as excellent abrasion resistance and chipping resistance. A sintered material containing a first compound formed of Ti, Al, Si, O, and N is provided.

Provided a method of producing a β-sialon fluorescent material having excellent emission intensity. The method includes providing a first composition containing aluminum, an oxygen atom, and a europium-containing silicon nitride, heat treating the first composition, contacting the heat-treated composition and a basic substance to obtain a second composition, and contacting the second composition resulting from contacting the heat-treated composition with the basic substance and an acidic liquid medium containing an acidic substance.

A europium-doped β-sialon phosphor, in which, when the ratio of an aluminum element at a depth of 8 nm from the surface of the phosphor, which is obtained by X-ray photoelectron spectroscopy, is indicated by P.sub.8 [at %], and the ratio of an aluminum element at a depth of 80 nm from the surface of the phosphor is indicated by P.sub.80 [at %], P.sub.8/P.sub.80≤0.9 is satisfied. A light emitting device containing this β-sialon phosphor.

An α-sialon phosphor particle containing Eu. At least one minute recess is formed on a surface of the α-sialon phosphor particle. The α-sialon phosphor particle is preferably produced by undergoing a raw material mixing step, a heating step, a pulverizing step, and an acid treatment step.

This specification discloses a method of enhancing the stability and performance of Eu.sup.2+ doped narrow band red emitting phosphors. The resulting phosphor compositions are characterized by crystallizing in ordered structure variants of the UCr.sub.4C.sub.4 crystal structure type and having a composition of AE.sub.1−xLi.sub.3−2yAl.sub.1+2y−zSi.sub.zO.sub.4−4y−zN.sub.4y+z:EU.sub.x(AE=Ca, Sr, Ba; 0<x<0.04, 0≤y<1, 0<z<0.05, y+z≤1). It is believed that the formal substitution (Al,O).sup.+ by (Si,N).sup.+ reduces the concentration of unwanted Eu.sup.3+ and thus enhances properties of the phosphor such as stability and conversion efficiency.

Provided a method of producing a -sialon fluorescent material having excellent emission intensity. The method includes providing a first composition containing aluminum, an oxygen atom, and a europium-containing silicon nitride, heat treating the first composition, contacting the heat-treated composition and a basic substance to obtain a second composition, and contacting the second composition resulting from contacting the heat-treated composition with the basic substance and an acidic liquid medium containing an acidic substance.

A method of making a -SiAlON is described in involves mixing nanoparticles of AlN, Al.sub.2O.sub.3, and SiO.sub.2 with particles of Si.sub.3N.sub.4 and spark plasma sintering the mixture. The sintering may be at a temperature of 1450-1600 C. or about 1500 C. The particles of Si.sub.3N.sub.4 may be nanoparticles comprising amorphous Si.sub.3N.sub.4, or 25-55 m diameter microparticles comprising -Si.sub.3N.sub.4.

A phosphor powder including phosphor particles of a phosphor represented by a general formula M.sub.x(Si, Al).sub.2(N, O).sub.3y and in which a part of M is substituted with a Ce element, the phosphor powder includes phosphor particles in which a Si/AI atomic ratio is equal to or more than 1.5 and equal to or less than 6, an O/N atomic ratio is equal to or more than 0 and equal to or less than 0.1, 5 to 50 mol % of M is Li, and 0.5 to 10 mol % of M is Ce. In a case where a volume-based cumulative 10% particle size, a volume-based cumulative 50% particle size, and a volume-based cumulative 90% particle size of this phosphor powder measured by a laser diffraction scattering method are defined as D.sub.10, D.sub.50, and D.sub.90, respectively, (D.sub.90-D.sub.10)/D.sub.50 is equal to or more than 0.7 and equal to or less than 1.1.

This specification discloses methods of enhancing the stability and performance of Eu.sup.2+ doped narrow band red emitting phosphors. In one embodiment the resulting phosphor compositions are characterized by crystallizing in ordered structure variants of the UCr.sub.4C.sub.4 crystal structure type and having a composition of AE.sub.1xLi.sub.32yAl.sub.1+yzSi.sub.zO.sub.44yzN.sub.4y+z:Eu.sub.x (AE=Ca, Sr, Ba, or a combination thereof, 0<x<0.04, 0y<1, 0<z<0.05, y+z1). It is believed that the formal substitution (Al,O).sup.+ by (Si,N).sup.+ reduces the concentration of unwanted Eu.sup.3+ and thus enhances properties of the phosphor such as stability and conversion efficiency.