Nitridation of AEAlSi for Production of AEAlSiN₃:Eu²⁺ Nitride Phosphors (AE=Ca, Sr)

Abstract

The nitridation process of Eu‐doped AEAlSi (AE=Ca and/or Sr) was investigated by thermogravimetry–differential thermal analysis to improve the method for synthesis of AEAlSiN3:Eu2+ nitride phosphors. The nitridation reactivity was dependent on alkaline earth elements. For SrxEuyCa1−x−yAlSi with a high Sr content, nitridation proceeded efficiently at 1100°–1150°C, close to the melting point of the intermetallic compounds. As nitridation of Si or Al intermetallics usually proceeds via the diffusion‐controlled surface reaction, sudden rupture of the diffusion barrier, the surface nitride layer, at the melting point could cause a marked change in the reaction rate and dependence on nitrogen partial pressure. The order of reactivity at temperatures close to the melting point agreed with the order of vapor pressure of alkaline earth elements at the melting point. A highly efficient process for large‐scale production of SrxCa1−xAlSiN3:Eu2+ phosphor was developed taking advantage of the characteristic nitridation reaction at the melting point.

The Future of Lighting

“…3), 28 and the emission maximum can be tuned down to 620 nm by Sr 2+ substitution by making phosphors using high pressure nitriding of arc-melted alloys. 29 While many of these nitride phosphors were based on known (oxy)nitride compositions, there has also been investigation of nitride and oxynitride phase diagrams to discover new phosphors. In many respects, the discovery of new (oxy)nitrides required some degree of guesswork and perseverance since the formation of condensed tetrahedral networks with N with air or moisture.…”

“…In many respects, the discovery of new (oxy)nitrides required some degree of guesswork and perseverance since the formation of condensed tetrahedral networks with N with air or moisture. There has been progress in using air-stable precursors to make nitride phosphors, 29,36 so this issue could be alleviated. However, there have also been reports in the patent literature that some of these Eu 2+ -doped nitride phosphors may lose efficiency over time in pcLED packages.…”

Photoluminescence properties and energy level locations of RE3+ (RE = Pr, Sm, Tb, Tb/Ce) in CaAlSiN3 phosphors

“…When doped with Eu 2+ or Ce 3+ , [13][14][15]25,26 it exhibits bright red or yelloworange emission respectively under blue irradiation. 27 CaAlSiN 3 is isostructural with ASi 2 N 3 (A ¼ Li, Na) and crystallizes in the Cmc2 1 space group.…”

Combustion synthesis of LaSi3N5:Eu2+ phosphor powders

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] These phosphors have excellent thermal and chemical stability which are attributed to their rigid structures built up of highly condensed [SiN4] tetrahedron-based networks. Moreover, they have long excitation/emission wavelengths and low thermal quenching which are ascribed to the high covalency of chemical bonding (nephelauxetic effect) and large crystal-field splitting due to the incorporation of nitrogen in the structure.…”