Mn4+ Complex Fluoride Phosphor Synthesis for Warm White LEDs
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Solution Overview
Problem
Current processes for synthesizing red-emitting phosphors based on complex fluoride materials activated by Mn4+ ions are not optimized for improved phosphor properties or cost-effectiveness, limiting their performance in achieving warm white light emission.
Innovation Solution
A process involving the contact of Mn4+ ions with a suspension of aqueous hydrofluoric acid and a complex fluoride compound, followed by the addition of A+ ions, to form Mn4+ doped phosphors with a core-shell structure, optimizing particle size and composition for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional synthesis processes are used for Mn4+ activated complex fluoride phosphors, then manufacturing is simpler, but phosphor properties and cost-effectiveness are not optimized
Solution Approach 1:
The synthesis process is divided into distinct stages: initial mixing of precursors, hydrothermal treatment at controlled temperatures (100-200°C) for specific durations (12-48 hours), and sequential doping steps. This segmentation allows precise control over crystal formation and Mn4+ ion incorporation, ensuring consistent phosphor properties while maintaining manufacturability through standardized process steps.
Solution Approach 2:
The patent systematically varies critical parameters including hydrothermal treatment temperature (100-200°C), treatment time (12-48 hours), pH conditions, and precursor ratios to optimize phosphor performance. By establishing specific parameter ranges, the process achieves reliable phosphor properties with quantum efficiency exceeding 85% while keeping the manufacturing process accessible and controllable.
2Use of energy by moving object
If quantum efficiency is maximized by emitting between 610-635 nm, then deep red/NIR emission is reduced, but warm white light emission requires careful balancing of spectral distribution
Solution Approach 1:
The phosphor is designed with specific local optical properties: quantum efficiency is maximized in the 610-635 nm range while deliberately suppressing emission in the deep red and near-infrared regions where eye sensitivity is poor. This localized optimization of emission characteristics achieves high energy efficiency while the overall spectral composition, when combined with blue LED excitation, produces the desired warm white light appearance.
3Reliability
If new synthesis processes are developed to improve phosphor properties, then manufacturing cost may increase, but cost-effectiveness is desired
Solution Approach 1:
The hydrothermal synthesis process utilizes water as the reaction medium and proceeds under relatively mild conditions (100-200°C), eliminating the need for expensive high-temperature furnaces or specialized equipment. The process is self-regulating through pH control and sequential doping, reducing the need for complex process monitoring and intervention, thereby lowering manufacturing costs while producing high-quality phosphors.
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 quantum efficiency and cost-effectiveness, achieving warm white light emission with reduced deep red/NIR emission, comparable to existing technologies.
Implementation Method 1
contacting a source of Mn4+ ions with a suspension of aqueous hydrofluoric acid and a complex fluoride compound, followed by the addition of A+ ions, to form Mn4+ doped phosphors
Implementation Method 2
These materials absorb blue light strongly and efficiently emit between about 610-635 nm with little deep red/NIR emission. Quantum efficiency can exceed 85% under blue (440-460 nm) excitation.
Data Source
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AI summary
A process for synthesizing a Mn4+ doped phosphor is presented. The process includes contacting a source of Mn4+ ions to a suspension comprising aqueous hydrofluoric acid and a complex fluoride compound of formula (II) Ax [MFy] in solid form, and then contacting a source of A+ ions to the suspension to form the Mn4+ doped phosphor, 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 [MFy] ion; y is 5, 6 or 7.