YAG Phosphor Composition for High Luminance LED
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Solution Overview
Problem
Conventional white LED lamps, particularly those using blue light-emitting diodes and yellow phosphors like YAG or BOSS, face challenges in emission efficiency, limiting their adoption as a replacement for fluorescent lights due to inferior luminance compared to Type 1 configurations.
Innovation Solution
A phosphor composition of 1.5Y2O3·2.5aAl2O3:Ce is developed, where 'a' ranges from 1.02 to 1.1, allowing for the replacement of Y with elements like Lu, Gd, or Tb, and Al with elements like Ga, Mg, or Sc, to enhance emission efficiency and luminance, combined with a manufacturing process involving firing in a reduced oxygen atmosphere to produce high-quality phosphor powders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional phosphors like YAG or BOSS are used in white LED lamps, then the structure is simple and ease of manufacture is good, but the emission efficiency and luminance are insufficient
Solution Approach 1:
The patent modifies the chemical composition parameters of the phosphor by adjusting the molar ratio of Al2O3 to Y2O3 to be 1.02-1.20 (conventional is 1:1), and by controlling the Ce doping concentration at 0.01-0.10 mol%. These parameter changes optimize the crystal structure and electronic transitions, resulting in improved emission efficiency while maintaining manufacturability through standard ceramic processing techniques.
Solution Approach 2:
The patent creates a composite phosphor material with the chemical formula 1.5Y2O3·2.5aAl2O3:Ce (where a=1.02-1.20), combining multiple oxides in specific ratios. This composite structure leverages the complementary properties of Y2O3 (host lattice), Al2O3 (structural reinforcement and optical property modulation), and Ce (activator for luminescence), achieving superior emission efficiency compared to conventional single-phase phosphors.
2Ease of manufacture
If conventional phosphors are used, then the manufacturing process is simple, but the luminance and emission efficiency are lower than fluorescent lights
Solution Approach 1:
The patent optimizes the Al2O3 molar ratio to 1.02-1.20 times that of Y2O3, which enhances the crystal field strength and modifies the 4f-5d electronic transitions of Ce ions. This parameter optimization increases the photoluminescence quantum efficiency, thereby improving luminance output while maintaining compatibility with existing manufacturing processes.
Solution Approach 2:
The patent introduces localized structural modifications by doping Ce at controlled concentrations (0.01-0.10 mol%) within the Y-Al-O host lattice. This creates localized luminescent centers with optimized electronic structures, enhancing the overall luminance without requiring changes to the bulk manufacturing process.
3Loss of energy
If the Al2O3 to Y2O3 ratio is increased to improve emission efficiency, then the emission efficiency improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent defines a specific parameter range for the Al2O3/Y2O3 molar ratio (1.02-1.20) and Ce doping concentration (0.01-0.10 mol%), which balances emission efficiency improvement with manufacturing feasibility. Within this range, the phosphor maintains stable crystal structure formation during sintering, reducing sensitivity to compositional variations and simplifying quality control.
Solution Approach 2:
The patent employs a slight excess of Al2O3 (2-20% molar excess relative to stoichiometric 1:1 ratio), which compensates for potential Al loss during high-temperature sintering and ensures complete reaction. This partial excess approach improves emission efficiency by ensuring full incorporation of Al into the crystal lattice while maintaining manageable manufacturing precision 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 new phosphor composition achieves higher emission efficiency and luminance than conventional phosphors, enabling white LED lamps with improved performance and color rendering properties, suitable for general lighting applications while being environmentally friendly by avoiding mercury use.
Implementation Method 1
A light-emitting diode (LED, it is also called an LED chip) is a light-emitting element acting as a light source by applying a voltage. The light-emitting diode emits light due to, for example, recombination between electron and hole in a vicinity of a contact surface (pn junction) of two semiconductors.
Implementation Method 2
a manufacturing process involving firing in a reduced oxygen atmosphere to produce high-quality phosphor powders
Data Source
AI summary
A phosphor has a composition represented by Chemical formula 1: 1.5Y2O3·2.5aAl2O3:Ce where a is a number satisfying 1.02<a<1.1.