Beta-Sialon Phosphor for White LED Color Rendering and Thermal Stability
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Solution Overview
Problem
Current phosphor materials for white light emitting devices, particularly those using β-sialon, face challenges such as low color rendering index, limited color distribution, thermal instability, and compatibility issues with high-output LED chips, which restrict their application in achieving vivid and stable white light emission.
Innovation Solution
A β-sialon phosphor with a β-type Si3N4 crystal structure, incorporating strontium (Sr) or barium (Ba) and europium (Eu), optimized in composition and firing processes to enhance light emission efficiency, thermal stability, and color reproducibility, is developed. This phosphor is used in conjunction with other phosphors to create a white light emitting device with improved color rendering index and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If yellow YAG:Ce phosphor is used to convert blue LED light, then white light can be produced, but color rendering is low and color distribution is limited
Solution Approach 1:
The patent combines multiple phosphor materials (yellow YAG:Ce phosphor, green β-sialon phosphor, and red phosphor) to create a composite phosphor system. This composite approach enables broad spectrum coverage across blue, green, and red regions, significantly improving color rendering index while maintaining efficient white light emission from blue LED excitation.
2Ease of manufacture
If silicate phosphor is used for wavelength conversion, then it can be manufactured, but it is unstable when heated and vulnerable to failure with high-output LED chips
Solution Approach 1:
The patent employs β-sialon phosphor material which possesses inherent high thermal stability due to its crystal structure. This material parameter change enables the phosphor to withstand high operating temperatures and high-output LED chip conditions without degradation or failure, while remaining manufacturable through conventional ceramic processing techniques.
3Ease of manufacture
If β-sialon phosphor is used as green phosphor, then it can be manufactured, but brightness is very low and wavelength characteristics are not appropriate
Solution Approach 1:
The patent optimizes the local composition and structure of the β-sialon phosphor by controlling stoichiometry ratios and doping elements. This local quality enhancement shifts the emission wavelength to appropriate green region and significantly increases brightness through improved luminescence efficiency, while maintaining manufacturability.
4Illumination intensity
If Sr is substituted in β-sialon crystal structure to find new properties, then fluorescence can be enhanced, but phase stability is low and thermal stability is difficult to expect
Solution Approach 1:
The patent carefully controls the doping concentration of Sr in the β-sialon crystal structure and optimizes firing parameters to achieve a balance between fluorescence enhancement and phase stability. By precisely adjusting compositional parameters and thermal processing conditions, the patent maintains crystal phase stability while achieving enhanced luminescence properties.
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 optimized β-sialon phosphor significantly improves luminance by 20% and achieves excellent color characteristics, providing vivid white light with a high color rendering index, enhanced thermal stability, and improved reliability for use in various light emitting devices.
Implementation Method 1
a wavelength conversion phosphor material is used to convert a certain wavelength of light from various light sources into a desired wavelength of light
Implementation Method 2
convert a certain amount of blue light into a yellow light, such that the converted yellow light and non-wavelength converted blue light may be combined to thereby provide white light
Data Source
AI summary
There is provided a phosphor having a β-type Si3N4 crystal structure including oxynitride expressed by an empirical formula Si6-zAlzOz N8-z:Eua,Mb, M being at least one selected from among strontium (Sr) and barium (Ba), an amount (a) of europium (Eu) ranging from 0.1 to 5 mol %, an amount (b) of M ranging from 0.1 to 10 mol %, and a composition rate (z) of aluminum (Al) satisfying 0.1<z<1, and the phosphor emitting light having a peak wavelength ranging from 500 to 550 nm when excitation light is irradiated thereto.