Color Stable Mn4+ Doped Phosphor Synthesis
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Solution Overview
Problem
Mn 4+ doped fluoride phosphors used in lighting systems are susceptible to degradation under high temperature and humidity conditions, limiting their stability and efficacy.
Innovation Solution
A process involving a precursor of formula I, contacted with a fluorine-containing oxidizing agent at controlled temperatures and cooling rates to produce a color-stable Mn 4+ doped phosphor, enhancing stability and quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If Mn 4+ doped fluoride phosphors are used in lighting systems, then high luminous efficacy and CRI are achieved, but the phosphors are susceptible to degradation under high temperature and humidity conditions
Solution Approach 1:
The phosphor particles are pre-coated with a protective shell formation solution containing fluorosilicic acid and manganese salt before final sintering. This preliminary coating action creates a protective layer that prevents degradation during subsequent high-temperature and humidity exposure, while maintaining the high luminous efficacy of the Mn 4+ doped fluoride phosphor
Solution Approach 2:
The invention changes the chemical composition parameters by introducing fluorosilicic acid and manganese salt in specific concentrations (0.1-10 mM and 0.01-1 mM respectively) to form a stable protective shell. This parameter modification enables the phosphor to maintain both high efficacy and improved reliability under harsh conditions
2Productivity
If the temperature is reduced at a fast rate after contact period, then production time is shortened, but the color stability of the phosphor deteriorates
Solution Approach 1:
The invention optimizes the cooling rate parameter to a specific range (5-50°C per minute) that balances production efficiency with color stability. This controlled cooling parameter change allows the phosphor to maintain its crystal structure and color properties while still enabling relatively fast production cycles
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 process results in phosphors with improved color stability and quantum efficiency, reducing degradation and maintaining performance under high temperature and humidity conditions.
Implementation Method 1
contacting a precursor at an elevated temperature with a fluorine-containing oxidizing agent to form a color stable Mn 4+
Implementation Method 2
the temperature is reduced at a rate of ≤5°C per minute
Data Source
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AI summary
A process for synthesizing a Mn4+ doped phosphor includes contacting a precursor of formula (I): Ax [MFγ]:Mn4+ at any temperature in a range from about 200°C to about 700°C with a fluorine-containing oxidizing agent in gaseous form; maintaining the temperature during a contact period of at least one hour; and, after the contact period, reducing the temperature at a rate of ≤5°C per minute; wherein A is Li, Na, K, Rb, Cs, or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; x is the absolute value of the charge of the [MFγ] ion; y is 5, 6 or 7.