Phosphor Particle Hydrolysis Protection via Acid Leaching
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Solution Overview
Problem
Phosphors used in light apparatuses are sensitive to hydrolysis, leading to unwanted color changes and decreased conversion efficiency over time, and existing protective methods like silicon dioxide deposition are costly and time-consuming or risk disintegrating the phosphor.
Innovation Solution
A method involving treatment of silicon-containing and/or aluminum-containing phosphor particles with an acid solution at a pH range of 3.5 to 7 for at least one hour, followed by tempering at temperatures between 100°C and 450°C, to form a protective layer with a higher silicon content and reduced aluminum and alkaline earth ion content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphors are protected with silicon dioxide layers by hydrolysis of tetraethoxysilane or CVD, then hydrolysis resistance is improved, but production time and cost increase significantly
Solution Approach 1:
The phosphor particles themselves serve as the source of the protective layer material. By treating the phosphor particles with acid, silicon is leached from the phosphor particles and automatically forms a protective layer on their surface, eliminating the need for external coating materials and complex deposition processes.
Solution Approach 2:
Silicon is extracted from the bulk of the phosphor particles through acid treatment and concentrated on the particle surface. This extraction process creates a silicon-rich protective layer directly from the phosphor material itself, rather than adding external coating materials.
2Productivity
If large quantities of acid are added to form a coating, then protective layer formation is accelerated, but phosphor disintegration risk increases
Solution Approach 1:
The acid treatment process utilizes feedback control where the pH value is continuously monitored and adjusted. The pH is maintained within a specific range (3.5-7) to ensure protective layer formation while preventing excessive acid attack that would cause phosphor disintegration. This feedback mechanism balances coating formation speed with phosphor integrity.
Solution Approach 2:
The invention changes the pH parameter from highly acidic conditions (which cause disintegration) to a controlled moderate acidic range (pH 3.5-7). This parameter change enables protective layer formation while maintaining phosphor structural integrity, resolving the contradiction between coating speed and structural stability.
3Device complexity
If phosphors are left unprotected, then production cost and complexity are reduced, but color stability and conversion efficiency deteriorate over time
Solution Approach 1:
The protective layer formation is merged with the phosphor production process itself. By incorporating acid treatment as a final step in phosphor manufacturing, the protective layer is formed integrally with the phosphor particles, eliminating the need for separate coating operations and reducing overall process complexity.
Solution Approach 2:
The phosphor particles automatically form their own protective layers through acid-induced silicon redistribution. This self-service mechanism eliminates the need for external coating materials and complex deposition equipment, reducing production complexity while ensuring long-term color stability and conversion efficiency.
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 method significantly increases the stability of phosphor particles against hydrolysis, making them suitable for high-humidity environments and reducing the risk of disintegration, while being more economical and efficient than traditional methods.
Implementation Method 1
Treatment of the silicon-containing and/or aluminum-containing phosphor with an acid solution, wherein the pH value of the acid solution is maintained within a range of pH 3.5 to 7 for a period of at least one hour and wherein a silicon-containing layer is formed on the phosphor particles
Implementation Method 2
Tempering of the treated phosphor particles at a temperature of at least 100° C., producing the protective layer
Data Source
AI summary
Phospher particles with a Protective Layer and a method for producing phosphor particles with a protective layer are disclosed. In an embodiment the method includes treating Si-containing and/or Al-containing phosphor with an acid solution, wherein a pH value of the acid solution is maintained within a range of pH 3.5 to pH 7 for a period of at least 1 h, wherein an Si-containing layer is formed on the phosphor particles, wherein the Si-containing layer has a higher content of Si on a surface than the phosphor particles, and/or wherein an Al-containing layer is formed on the phosphor particles, wherein the Al-containing layer has a modified content of aluminum on the surface than the phosphor particles and tempering the treated phosphor particles at a temperature of at least 100° C. thereby producing the protective layer.