Nitride Phosphor Composition for Stable LED Color Conversion
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Solution Overview
Problem
Current nitride phosphors used in LED lamps to convert blue photons to red frequencies are unstable, expensive, and difficult to produce, limiting their availability and consistency in color output, which is essential for achieving warmer white light emission.
Innovation Solution
A method involving the mixing of cations like calcium, strontium, and aluminum with an activator such as europium, in a refractory crucible under controlled atmospheric conditions, to form a phosphor composition that down-converts blue and ultraviolet photons to longer wavelengths, using a forming gas to prevent decomposition and reaction with the crucible, resulting in a stable and easily manufactured phosphor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional nitride phosphors are used to convert blue photons to red frequencies, then color conversion function is achieved, but stability and manufacturability deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating oxygen into the nitride phosphor structure to form oxynitride compounds (CaAlSiN3:Eu). This compositional parameter change simultaneously improves stability and manufacturability, resolving the technical contradiction between reliability and ease of manufacture.
Solution Approach 2:
The patent creates a composite material system by combining calcium aluminate silicate nitride with oxygen to form CaAlSiN3:Eu oxynitride phosphor. This composite approach integrates multiple elements (Ca, Al, Si, N, O, Eu) to achieve both stability and ease of manufacture, resolving the contradiction between these two parameters.
2Illumination intensity
If blue light emitting diodes are combined with yellow phosphors to produce white light, then white light emission is achieved, but color temperature control deteriorates
Solution Approach 1:
The patent segments the white light generation into multiple phosphor components: a yellow phosphor (CaAlSiN3:Eu) and a red phosphor (CaAlSiN3:Eu). This segmentation allows independent optimization of each phosphor's properties and enables precise control of the overall color temperature by adjusting the ratio and characteristics of individual phosphors, resolving the contradiction between white light emission and color temperature control.
Solution Approach 2:
The patent applies local quality by assigning different functions to different phosphor components: the yellow phosphor provides broad spectrum emission while the red phosphor (with improved stability) enhances the red portion of the spectrum. This localized functional assignment enables fine-tuned color temperature control while maintaining strong white light emission.
3Illumination intensity
If red phosphors are added to enhance warmer white light, then color quality improves, but manufacturing complexity increases
Solution Approach 1:
The patent merges the yellow and red phosphor functions into a single unified material system (CaAlSiN3:Eu oxynitride). By combining multiple phosphor functions into one compound with controlled composition, the patent achieves warmer white light quality without increasing manufacturing complexity, as only one material needs to be synthesized and processed rather than multiple separate 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 method produces a phosphor composition that consistently converts blue photons to red photons, enhancing the stability and manufacturability of nitride phosphors, thereby improving the color consistency and availability of warmer white light emission in LED lamps.
Implementation Method 1
nitride phosphors that can convert blue photons from a light emitting diode into frequencies within the red portion of the visible spectrum
Implementation Method 2
heated in the presence of a forming gas at or near atmospheric pressure... to prevent decomposition and reaction with the crucible
Data Source
AI summary
A method is disclosed for forming a blended phosphor composition. The method includes the steps of firing precursor compositions that include europium and nitrides of at least calcium, strontium and aluminum, in a refractory metal crucible and in the presence of a gas that precludes the formation of nitride compositions between the nitride starting materials and the refractory metal that forms the crucible. The resulting compositions can include phosphors that convert frequencies in the blue portion of the visible spectrum into frequencies in the red portion of the visible spectrum.