Mn4+ Red Phosphor Synthesis for Sub-10 μm Color-Stable Particles
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Solution Overview
Problem
Current processes for preparing red-emitting phosphor particles based on complex fluoride materials result in particles larger than 10 μm with broad size distributions, which can cause manufacturing issues in LED packaging and reduce efficiency due to total internal reflection.
Innovation Solution
A process involving the combination of a source of A and a source of H2MF6 in the presence of Mn, with a Hammett acidity function of at least −0.9, to produce Mn+4 doped phosphors with a D50 particle size of less than 10 μm and a narrow size distribution, and the use of microemulsion methods to create coated phosphors with a manganese-free shell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional processes are used to prepare red-emitting phosphor particles, then the phosphor material can be produced, but the particle size becomes greater than 10 μm with broad distribution
Solution Approach 1:
The patent applies parameter changes by controlling the Hammett acidity function (Ho ≥ -0.9) of the reaction medium and adjusting stoichiometric ratios of reactants to achieve precise particle size control below 10 μm with narrow distribution, while maintaining high manufacturing efficiency through optimized reaction conditions
2Manufacturing precision
If high aspect ratio nanorods are synthesized, then small particle size can be achieved, but manufacturing problems occur in LED packaging
Solution Approach 1:
The patent changes the aspect ratio parameter by controlling reaction conditions (Hammett acidity function and stoichiometry) to produce particles with aspect ratio of 3/1 or less, making them suitable for LED packaging manufacturing while maintaining small particle size below 10 μm
Solution Approach 2:
The patent applies local quality by creating monodisperse particle populations with uniform size and controlled aspect ratio, ensuring consistent performance in LED packaging applications
3Manufacturing precision
If particles with high aspect ratio are used, then small size can be achieved, but total internal reflection reduces efficiency
Solution Approach 1:
The patent changes the geometric parameter of aspect ratio to 3/1 or less, reducing total internal reflection losses and improving luminous efficiency while maintaining small particle size below 10 μm
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 yields monodisperse phosphor particles with a D50 size of less than 10 μm, improving manufacturing efficiency and reducing internal reflection, leading to enhanced performance in lighting and display applications.
Implementation Method 1
wherein a value of a Hammett acidity function of the first solution is at least −0.9
Implementation Method 2
The method includes combining a first microemulsion comprising a phosphor of formula I with a second microemulsion comprising a precursor for a metal fluoride compound, and isolating the coated phosphor
Data Source
AI summary
A process for preparing a Mn+4 doped phosphor of formula IAx[MFy]:Mn+4 Iincludes combining a first solution comprising a source of A and a second solution comprising H2MF6 in the presence of a source of Mn, to form the Mn+4 doped phosphor;whereinA is Li, Na, K, Rb, Cs, or a combination thereof;M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or a combination thereof;x is the absolute value of the charge of the [MFy] ion;y is 5, 6 or 7; andwherein a value of a Hammett acidity function of the first solution is at least −0.9.Particles produced by the process may have a particle size distribution with a D50 particle size of less than 10 μm.