Oxynitride Phosphor for High Luminance and Stability
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Solution Overview
Problem
Conventional white LED phosphors lack red and green components, resulting in deteriorated color rendering properties and reduced light intensity when excited by wavelengths exceeding 400 nm, necessitating a phosphor with improved stability and luminance.
Innovation Solution
Development of an oxynitride-based phosphor with a monoclinic crystalline structure, specifically (Ca1-xM1x)(La1-yM2y)bSicNdOe, incorporating activators like Eu, Ce, and Mn, which emits light from green to yellow with high luminance and stability, suitable for use in LEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If oxide-based phosphor is used, then color rendering is improved, but light intensity decreases when excitation wavelength exceeds 400 nm
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating nitrogen into the oxide structure to create oxynitride phosphor. This compositional parameter change enables the material to maintain high light intensity when excited by wavelengths exceeding 400 nm, resolving the contradiction between light intensity and stability.
Solution Approach 2:
The patent creates a composite oxynitride material combining oxide and nitride components. This composite structure leverages the advantages of both material types: the color rendering properties of oxides and the high efficiency under blue/UV excitation of nitrides, thereby resolving the contradiction between light intensity and stability.
2Reliability
If conventional phosphor composition is used, then manufacturing simplicity is maintained, but color rendering properties deteriorate due to lack of red and green components
Solution Approach 1:
The patent modifies the compositional parameters by introducing specific ratios of oxynitride components and activators (Eu, Ce, Mn) to generate red, green, and yellow emissions. This parameter optimization achieves improved color rendering while maintaining relatively simple manufacturing processes.
Solution Approach 2:
The oxynitride phosphor composition serves multiple functions simultaneously: it provides red, green, and yellow emission components for color rendering, maintains stability under blue/UV excitation, and can be manufactured using standard ceramic processing. This multi-functionality resolves the contradiction between color rendering and manufacturing complexity.
3Illumination intensity
If oxynitride-based phosphor is used, then light emitting efficiency is improved, but structural stability may be compromised
Solution Approach 1:
The patent optimizes compositional parameters including the ratios of metal oxides, metal nitrides, and activators to achieve a balance between light emitting efficiency and structural stability. By carefully controlling these parameters, the oxynitride phosphor maintains high efficiency while ensuring compositional stability.
Solution Approach 2:
The patent introduces local structural variations through different activator ions (Eu2+, Ce3+, Mn2+) at specific lattice sites within the oxynitride structure. Each activator provides localized emission properties while the overall oxynitride matrix maintains structural stability, resolving the contradiction between efficiency and stability.
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 oxynitride phosphor achieves enhanced light emitting efficiency and stability, particularly in environments with humidity and heat, and allows for tunable light emission from green to yellow, improving color rendering and luminance in LED applications.
Implementation Method 1
a phosphor transforming wavelengths into visible light by using the emitted light from the light emitting device as an excitation source
Implementation Method 2
absorption and reflection of the light are repeated for several times by the phosphor layer. The absorbed blue light by the phosphor may be transformed into yellow light
Data Source
AI summary
Disclosure relates to a phosphor formed by using oxynitride having a good durability and possibly emits diverse color of light from green to yellow when using a blue emitting diode or a ultraviolet emitting diode as an excitation source. The phosphor includes a host material represented by the general formula of (Ca1-xM1x)a(La1-yM2y)bSicNdOe (in which 0.5≦b/a≦7, 1.5≦c/(a+b)≦3.5, 1≦d/c≦1.8, 0.6≦e/(a+b)≦2, 0≦x≦0.5, and 0≦y≦0.5) and having a monoclinic crystalline structure, and at least one dissolved activator selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Tb, Ho, Er, Tm and Yb. M1 is at least one element selected from Ba, Mg, Sr, Mn and Zn, and M2 being at least one element selected from Y, Lu, Sc, Gd, Tb, Ce, Nd, Sm, Dy, Ho, Er, Tm, Yb, Al, Ga, Ge, Sn and In.