Alpha-Sialon Phosphor Composition for Stable Yellow-Green LED Emission
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Solution Overview
Problem
Conventional phosphors used in white color LEDs, such as Ca-α-sialon doped with Eu2+, suffer from low emission intensity and significant temperature-dependent fluctuations in emission color, making them unsuitable for applications requiring stable and high-intensity yellow-green light emission.
Innovation Solution
A phosphor with an α-type sialon crystal host doped with specific optically activating metals like Eu, which emits a high-intensity yellow-green light with minimal temperature fluctuation, achieved by optimizing the composition and manufacturing process to include Li, Si, Al, O, and N, with specific parameters for x1, x2, and x3, and firing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional phosphors like Ca-α-sialon doped with Eu2+ are used in white color LEDs, then the device structure is simple and manufacturing is easy, but the emission intensity is low and temperature-dependent fluctuations in emission color are significant
Solution Approach 1:
The patent changes the chemical composition parameters of the phosphor by incorporating specific ratios of Li, Ca, Si, Al, O, and N elements in the formula Li1-x-yCaxSi12-(m+n)Alm+nOnN16-n. By optimizing the values of x, y, m, and n, the phosphor achieves high emission intensity in the yellow-green region (530-585 nm) while maintaining manufacturability through standard ceramic processing techniques.
Solution Approach 2:
The patent creates a composite phosphor material combining multiple elements (Li, Ca, Si, Al, O, N) in a specific crystalline structure. This composite approach allows the material to exhibit superior optical properties (high emission intensity and temperature stability) that cannot be achieved with single-element phosphors, while still being manufacturable using established ceramic synthesis methods.
2Ease of manufacture
If conventional phosphors like Ca-α-sialon doped with Eu2+ are used in white color LEDs, then the manufacturing process is simple, but the emission color fluctuates significantly with temperature changes
Solution Approach 1:
The patent optimizes the compositional parameters (x, y, m, n) to achieve a balance between manufacturability and temperature stability. The specific formula Li1-x-yCaxSi12-(m+n)Alm+nOnN16-n with controlled element ratios creates a phosphor whose emission color remains stable across temperature variations, as the optimized composition reduces thermal excitation effects that cause color shifting.
Solution Approach 2:
The patent introduces localized compositional variations within the phosphor crystal structure by controlling the distribution of Li and Ca elements at specific lattice sites. This local quality control allows different regions of the crystal to contribute differently to the overall emission, with the optimized local composition providing temperature compensation that stabilizes the emission color while maintaining ease of manufacturing.
3Illumination intensity
If phosphors with optimized composition for high emission intensity are used, then the emission intensity is enhanced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges for the compositional variables (x, y, m, n) that optimize emission intensity while remaining compatible with standard manufacturing tolerances. By establishing these parameter windows, the patent achieves high emission intensity (530-585 nm yellow-green region) without requiring extreme manufacturing precision, as the optimized composition is robust to normal variations in ceramic processing.
4Stability of the object's composition
If phosphors with reduced temperature dependence are used, then the emission color stability is improved, but the emission intensity may be compromised
Solution Approach 1:
The patent identifies an optimal parameter space where both temperature stability and emission intensity are maximized simultaneously. The specific compositional formula Li1-x-yCaxSi12-(m+n)Alm+nOnN16-n with controlled element ratios achieves this dual optimization: the Li and Ca content is tuned to provide temperature compensation for color stability, while the Si-Al-O-N matrix composition maintains high emission intensity in the yellow-green region, resolving the trade-off between these two competing requirements.
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 resulting phosphor exhibits enhanced emission intensity and stability, producing a yellow-green light with reduced temperature-dependent fluctuations, suitable for applications in white color LEDs and image display devices.
Implementation Method 1
a phosphor comprising: an inorganic compound as a main component, wherein the phosphor has a property to emit fluorescence of rather long wavelength from 530 nm to 585 nm
Implementation Method 2
doping an optically-activating ion as a luminescence center
Data Source
AI summary
A fluorophor includes: α-type sialon crystal which is expressed by a general formula: (Lix1, Eux2)(Si12−(m+n)Alm+n)(OnN16−n), wherein x1 is an amount of solid solution of Li in a sialon unit cell, and x2 is an amount of solid solution of Eu in the sialon unit cell, wherein the parameters x1, x2, m, and n satisfy: 1.6≦x1≦2.4 (1), 0.001≦x2≦0.4 (2), 1.8≦m≦2.4 (3), 0.8≦n≦1.2 (4), wherein the α-type sialon crystal emits fluorescence with a peak in a wavelength region of from 550 nm to 575 nm upon irradiation of an excitation source.