Ce-based Phosphor Composition for High-Efficiency Red Emission
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Solution Overview
Problem
Current red phosphors with Eu as the emission center suffer from decreased quantum efficiency under high-output excitation due to long emission lifetimes, leading to brightness saturation, whereas phosphors with Ce as the emission center are more efficient but limited in their application.
Innovation Solution
A phosphor with a crystal phase having a chemical composition Ce x M 3-x-y β 6 γ 11-z, where M is a rare-earth element, β includes Si and Al/Ga, y consists of N and O, and z is optimized to achieve a maximum emission peak in the 600-800 nm range and excitation peak in the 500-600 nm range, enhancing quantum efficiency and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Eu is used as the emission center in red phosphors, then color rendering properties are improved, but quantum efficiency decreases under high-output excitation due to long emission lifetimes causing brightness saturation
Solution Approach 1:
The patent changes the emission center element from Eu to Ce, fundamentally altering the emission mechanism. Ce-based phosphors exhibit shorter emission lifetimes and higher quantum efficiency under high-output excitation while maintaining desirable red emission characteristics through controlled composition and crystal structure
Solution Approach 2:
The patent creates a composite phosphor system with formula Ce x M 3-x-y β 6 γ 11-z, combining Ce as the primary emission center with rare-earth elements M and controlled substitutions in the β 6 γ 11 matrix. This composite approach optimizes both quantum efficiency and color rendering by leveraging Ce's efficient emission and the host lattice's structural stability
2Loss of energy
If Ce is used as the emission center in phosphors, then quantum efficiency is improved, but emission wavelength control in the red region (600-800 nm) is limited
Solution Approach 1:
The patent systematically varies compositional parameters (x, y, z values and element selections) to tune the Ce emission characteristics. By controlling the substitution levels and host lattice composition, the emission wavelength is precisely controlled within the 600-800 nm red region while preserving Ce's high quantum efficiency
Solution Approach 2:
The patent introduces local structural modifications through element substitutions in the β 6 γ 11 matrix surrounding the Ce emission centers. These local changes in the crystal environment affect the Ce 5d-4f transition energy levels, enabling precise control of emission wavelength without compromising the overall quantum efficiency
3Illumination intensity
If high-output excitation is applied to Eu-based phosphors, then brightness is improved, but brightness saturation occurs due to long emission lifetimes
Solution Approach 1:
The patent changes the emission center from Eu to Ce, fundamentally altering the emission lifetime characteristic. Ce-based phosphors exhibit shorter emission lifetimes that prevent accumulation of excited states under high-output excitation, thereby eliminating brightness saturation while maintaining high brightness output and improving reliability
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 phosphor exhibits high quantum efficiency even under high-output excitation, preventing brightness saturation and improving color rendering properties and color reproducibility in light-emitting applications.
Implementation Method 1
A phosphor with a crystal phase having a chemical composition Ce x M 3-x-y β 6 γ 11-z... excitation peak in the 500-600 nm range, enhancing quantum efficiency... The phosphor exhibits high quantum efficiency even under high-output excitation
Data Source
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AI summary
A phosphor contains a crystal phase having a chemical composition CexM3-x-yβ6γ11-z. M is one or more elements selected from the group consisting of Sc, Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. β contains Si in an amount of 50 mol% or more of a total mol of β. γ contains N in an amount of 80 mol% or more N of a total mol of γ. x satisfies 0 < x ≤ 0.6. y satisfies 0 ≤ y ≤ 1.0. z satisfies 0 ≤ z ≤ 1.0. The phosphor has a maximum peak of an emission spectrum in a wavelength range of 600 nm or more and 800 nm or less and a first peak of an excitation spectrum in a wavelength range of 500 nm or more and 600 nm or less.