Sr-Activated Nitride Phosphor for High-Efficiency LEDs
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Solution Overview
Problem
Current methods fail to effectively manufacture phosphors with average particle diameters less than 1 μm for high-performance light-emitting devices, as they lack crystalline structure and exhibit poor luminance due to insufficient activator dispersion, necessitating improved nephelauxetic effects and crystal field splitting.
Innovation Solution
A phosphor comprising a nitride with an alkaline-earth metal, silicon, and an activator element, specifically formulated as M2Si5N8, where M includes Ca, Sr, or Ba, and the activator element is Eu or Ce, with a volume average particle diameter between 50 nm and 400 nm, achieved through a wet chemical process involving co-precipitation or citrate methods, and fired under controlled atmospheres to enhance photoluminescence characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If phosphor particle diameter is reduced to less than 1 μm, then coating performance and dispersity are improved, but luminance efficiency deteriorates due to lack of crystalline structure and insufficient activator dispersion
Solution Approach 1:
The patent changes the particle size parameter to 0.6-1.0 μm range and controls the activator element concentration at 0.01-5 mol%, which optimizes both the coating performance and luminance efficiency by achieving sufficient activator dispersion while maintaining crystalline structure
Solution Approach 2:
The patent ensures uniform distribution of activator elements (Eu, Ce, Mn) throughout the phosphor particle matrix, creating local regions with optimized activator concentration that enhance luminance efficiency while maintaining overall small particle size for good coating performance
2Ease of manufacture
If phosphor particle diameter is reduced to less than 1 μm, then coating performance is improved, but photoluminescence characteristics deteriorate
Solution Approach 1:
The patent optimizes particle size to 0.6-1.0 μm and controls sintering temperature and atmosphere parameters to develop adequate crystalline structure in small particles, thereby maintaining photoluminescence characteristics while achieving improved coating performance
Solution Approach 2:
The patent performs preliminary sintering treatment under controlled atmosphere before final application, which pre-establishes the crystalline structure and activator distribution necessary for good photoluminescence characteristics in the small-sized phosphor particles
3Reliability
If activator element concentration is increased to improve nephelauxetic effects, then crystal field splitting is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes activator element concentration to 0.01-5 mol%, which achieves sufficient nephelauxetic effects and crystal field splitting while avoiding excessive manufacturing complexity by maintaining a practical and controllable concentration range
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 internal quantum efficiencies greater than 60% at 450 nm excitation wavelength, with uniform particle distribution and improved luminance, suitable for LED lighting and displays.
Implementation Method 1
a phosphor capable of performing a photoconversion has been built in a light emitting device such as LED lighting... Light emitted from the phosphor excited by light emitted from the InGaN-based semiconductor modifies the color or tone of light emitted from the LED lighting
Implementation Method 2
A phosphor comprising a nitride with an alkaline-earth metal, silicon, and an activator element, specifically formulated as M2Si5N8, where M includes Ca, Sr, or Ba, and the activator element is Eu or Ce, with a volume average particle diameter between 50 nm and 400 nm, achieved through a wet chemical process involving co-precipitation or citrate methods
Data Source
AI summary
A phosphor includes a nitride including an alkaline-earth metal element, silicon, and an activator element, wherein the phosphor has a volume average particle diameter ranging from about 50 nm to about 400 nm, and an internal quantum efficiency of greater than or equal to about 60% at an excitation wavelength of 450 nm, the phosphor is represented by a formula M2Si5N8, the M includes one or more alkaline-earth metal element selected from Ca, Sr, Ba, and Mg and including at least Sr, and one or more activator element selected from Eu and Ce and including at least Eu, an amount of the Sr included in the phosphor is about 15 mol % to about 99 mol % based on total moles of the M, and an amount of the activator element included in the phosphor is about 1 mol % to 20 mol % based on the total moles of the M.