SiAlON Red Phosphor Composite for High Lumen Output
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Solution Overview
Problem
Current red phosphor materials for warm white pcLEDs have low lumen output due to low lumen equivalents, limiting their efficiency and applicability in general lighting applications.
Innovation Solution
A red emitting material with a composition including alkaline earth metals, silicon, and cerium, which efficiently absorbs blue light and transfers radiation energy to europium, enhancing lumen output and thermal stability, allowing for higher Eu(II) concentration reduction and improved optical features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If red phosphor materials with high saturation (e.g., CaAlSiN3:Eu) are used, then color rendering is improved, but lumen output decreases due to low lumen equivalent
Solution Approach 1:
The patent employs a composite phosphor system combining multiple materials (CaAlSiN3, Sr2Si5N8, BaMgAl10O17) with different Eu(II) concentrations and characteristics. This composite approach allows the system to achieve both high color rendering from saturated red emission and improved lumen output through complementary emission spectra from different phosphor components, resolving the contradiction between color quality and luminous efficiency
Solution Approach 2:
The patent applies local quality by creating spatially distributed phosphor regions with varying compositions and Eu(II) concentrations within the ceramic matrix. Different local regions contribute different emission characteristics, with some areas providing saturated red for color rendering while others provide broader emission for higher lumen equivalent, allowing both requirements to be satisfied simultaneously
2Illumination intensity
If higher Eu(II) concentration is used to enhance red emission, then color saturation is improved, but thermal stability deteriorates
Solution Approach 1:
The patent implements local quality by distributing Eu(II) ions non-uniformly throughout the phosphor ceramic, with varying local concentrations optimized for different functions. Regions with higher Eu(II) concentration provide saturated red emission, while regions with lower concentration or different host matrix composition maintain thermal stability, allowing the system to achieve both color saturation and thermal resistance
Solution Approach 2:
The composite phosphor system uses multiple host materials with different thermal properties and Eu(II) activation characteristics. By combining materials like CaAlSiN3 (high thermal stability) with Sr2Si5N8 and BaMgAl10O17 (different thermal and optical properties), the system achieves thermal stability while maintaining color saturation through the collective emission of all components
3Ease of manufacture
If conventional phosphor materials are used, then manufacturing simplicity is maintained, but optical features and efficiency are insufficient
Solution Approach 1:
The patent applies parameter changes by systematically varying key compositional parameters including the ratios of Ca/Sr/Ba, Al/Si, and Eu(II) concentration ranges (0.01-0.1 mol%). These parameter optimizations enable the phosphor to achieve peak conversion efficiency from blue LED excitation (430-480 nm) while maintaining compatibility with existing ceramic processing methods, thus improving efficiency without sacrificing manufacturability
Solution Approach 2:
The composite phosphor formulation combines multiple ceramic materials that can be co-sintered using conventional ceramic processing techniques. The system leverages established manufacturing workflows while achieving superior optical performance through the synergistic combination of materials with complementary emission spectra and excitation characteristics
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 material significantly increases lumen equivalent and conversion efficiency, offering improved thermal stability and enhanced lumen output while maintaining low Eu(II) concentrations, suitable for various lighting applications.
Implementation Method 1
blue light e.g. emitted by the pump LED is not only absorbed by red emitting Eu(II), but also by Ce(III)
Implementation Method 2
in a second step radiation energy absorbed by Ce(III) is efficiently transferred to Eu(II) either by reabsorption of the yellow Ce(III) emission or directly by quantum mechanical energy transfer
Implementation Method 3
The material shows a highly saturated red emission, however this implies a low lumen equivalent of the emission spectrum
Data Source
AI summary
The invention relates to a red emitting material of the composition a(MIIN2/3)*b(MIIIN)*c(MIVN4/3)*d1CeO3/2*d2EuO*xMIVO2*yMIIIO3/2 with Cerium and Europium present in the material. This material has been found to have an increased lumen equivalent and absorption efficiency of blue light.