Stabilized Sr2Si5N8:Eu Red Luminescent Material for LEDs
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Solution Overview
Problem
Current red-emitting luminescent materials, such as Sr2Si5N8:Eu, are chemically unstable at high temperatures and under high radiation, limiting their application in thermally stressed environments, and competing materials like CaAlSiN3 have narrow emission wavelength ranges, lacking a satisfactory solution for high stability.
Innovation Solution
A modified Eu2+-doped alkaline earth nitridosilicate M2Si5N8 is stabilized by incorporating SiO2, extending the educt mixture to include additional M3N2, resulting in a novel nitridosilicate with improved stability and emission characteristics, suitable for use in conversion LEDs generating white light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Sr2Si5N8:Eu is used as a red-emitting luminescent material, then the dominant wavelength is in the optimal range of 600-610 nm, but the material exhibits chemical instability at high temperatures and under high radiation
Solution Approach 1:
The patent creates a composite luminescent material by doping Eu2+ ions into the Sr2Si5N8 host lattice, forming Sr2Si5N8:Eu. This composite structure combines the optimal 600-610 nm emission characteristics of Sr2Si5N8 with the stabilizing effect of Eu2+ doping, which enhances chemical stability while maintaining the desired emission properties.
Solution Approach 2:
The patent modifies the compositional parameters of Sr2Si5N8 by introducing Eu2+ dopants at controlled concentrations. This parameter change transforms the material from chemically unstable pure Sr2Si5N8 to a stable doped variant Sr2Si5N8:Eu, while preserving the critical 600-610 nm dominant wavelength range through optimized doping levels.
2Reliability
If CaAlSiN3 is used as a red-emitting luminescent material, then the material exhibits high stability, but the emission wavelength range is narrow and limited to 615-620 nm
Solution Approach 1:
The patent shifts the emission wavelength parameter from the narrow 615-620 nm range of CaAlSiN3 to the broader 600-610 nm range by changing the host material composition to Sr2Si5N8:Eu. This parameter change in dominant wavelength is achieved while maintaining high stability through the same doping strategy that proved effective for Sr2Si5N8.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The stabilized luminescent material maintains high quantum efficiency and emission stability under thermal stress and radiation, with improved excitability in the 410-500 nm range, enhancing the performance of conversion LEDs without compromising optical properties.
Implementation Method 1
The luminescent material will thereby ensure the provision of an efficient, stabilized emitting red luminescent material that can be excited by blue or ultraviolet light and has a dominant wavelength in the 600-nm range
Data Source
AI summary
A red-emitting luminescent material that belongs to the class of nitridosilicates and is doped with at least one activator D, in particular Eu, wherein the material is a modified D-doped alkaline earth nitridosilicate M2Si5N8, where M=one or more elements belonging to the group Sr, Ca, Ba, with the nitridosilicate having been stabilized by an oxidic or oxinitridic—in particular alkaline earth—phase.