Alpha-SiAlON Phosphor Particle Size Control for LED Luminance
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Solution Overview
Problem
Current α-SiAlON phosphors have limitations in light-emitting efficiency, particularly in achieving high luminance and uniformity in light-emitting devices such as LEDs, due to suboptimal particle size distributions and crystallinity, which affect their fluorescence characteristics.
Innovation Solution
The development of α-SiAlON with a specific particle size distribution, where the 50% mean area diameter of primary particles is 5 µm or more, and a ratio of primary to secondary particle diameters optimized to enhance light-emitting efficiency, combined with the use of β-SiAlON and CaAlSiN3 to improve fluorescence properties, is employed in light-emitting devices using near-ultraviolet to blue LED light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If classification treatment is applied to select α-SiAlON with particular average particle diameter, then fluorescence characteristics are improved, but manufacturing complexity increases
Solution Approach 1:
The invention changes the particle diameter parameter to specific ranges (D50 between 5-20 μm, with primary particle 50% mean area diameter ≥5 μm) to optimize fluorescence characteristics. This parameter optimization resolves the contradiction by providing precise particle size control through defined ranges rather than complex classification processes.
Solution Approach 2:
The invention uses composite material composition with specific elements (Ca, Li, Mg, Y, or lanthanide metals) doped into the α-SiAlON crystal lattice to enhance fluorescence characteristics. This composite approach improves optical properties while avoiding complex classification treatments.
2Productivity
If primary particle size is increased to 5 μm or more, then light-emitting efficiency improves, but particle size uniformity becomes harder to control
Solution Approach 1:
The invention optimizes the particle size parameter by specifying that the 50% mean area diameter of primary particles should be 5 μm or more, while controlling the ratio of primary to secondary particle diameters to be 0.56 or more. This parameter optimization achieves high light-emitting efficiency while maintaining manufacturable particle size distribution.
Solution Approach 2:
The invention applies partial classification by focusing on key particle size parameters (primary particle 50% mean area diameter ≥5 μm and D50 of secondary particles between 13-30 μm) rather than attempting to control all particle size aspects, thus achieving high efficiency with manageable manufacturing precision.
3Stability of the object's composition
If element substitution is performed to maintain electric neutrality, then crystal structure stability improves, but manufacturing complexity increases
Solution Approach 1:
The invention optimizes the composition parameters by specifying exact element ratios in the general formula (M)x(Eu)y(Si)12-(m+n)(Al)m+n(O)n(N)16-n, where M includes Ca, Li, Mg, Y, or lanthanide elements. This parameter optimization maintains crystal structure stability while simplifying the manufacturing process by providing clear compositional guidelines.
Solution Approach 2:
The invention applies local quality by selectively substituting specific elements (Ca, Li, Mg, Y, or lanthanide metals) at specific positions in the crystal lattice to maintain electric neutrality. This targeted element substitution stabilizes the crystal structure without requiring complex multi-element processes.
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
This approach results in a significant increase in light-emitting efficiency and luminance of light-emitting devices, providing high-quality yellow to orange light emission with improved color consistency and dispersion in resin applications.
Implementation Method 1
α-SiAlONs activated by a particular rare-earth element, as nitride or oxynitride phosphors, have been known to have useful fluorescence characteristics
Implementation Method 2
a phosphor for absorbing near-ultraviolet to blue light generated by the light-emitting light source to generate fluorescence
Data Source
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AI summary
Provided are an α-SiAlON activated by Eu, which can realize a higher luminance in a light-emitting device such as a white LED, and also a light-emitting device. The α-SiAlON is represented by the general formula: (M)x(Eu)y(Si)12-(m+n)(Al)m+n(O)n(N)16-n (wherein M denotes one or more elements including at least Ca, selected from the group consisting of Li, Mg, Ca, Y and lanthanide elements (except for La and Ce)), and is constituted by an α-SiAlON having Eu in the form of a solid solution. The 50% mean area diameter of primary particles of the α-SiAlON is 5 µm or more, and the ratio of the 50% mean area diameter of primary particles to the 50% mean area diameter of secondary particles of the α-SiAlON is preferably 0.56 or more. A light-emitting device 10 includes a light-emitting light source 12 and a wavelength conversion member 15, wherein the wavelength conversion member 15 includes a α-SiAlON 18 for absorbing near-ultraviolet to blue light generated by the light-emitting light source 12 to generate yellow to orange light.