Beta-Sialon Phosphor Composition With Si Gradient for Higher Luminance
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Solution Overview
Problem
Existing β-sialon phosphors and light emitting devices require further improvement in luminance.
Innovation Solution
A europium-doped β-sialon phosphor particle with a specific Si concentration gradient, where the surface Si concentration (Ps) is lower than the center Si concentration (Pc) by 3% or more, achieved through a two-stage firing process and acid treatment, ensuring appropriate raw material composition and particle size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional β-sialon phosphors are used, then the light emitting device can operate with basic luminance, but the luminance is insufficient for further improvement
Solution Approach 1:
The patent applies local quality by creating a Si concentration gradient within the phosphor particle, where the surface region has lower Si concentration (Ps) and the center region has higher Si concentration (Pc). This spatial variation in composition optimizes different regions for different functions: the surface region with lower Si concentration enhances light emission efficiency, while the center region with higher Si concentration maintains structural stability and heat resistance. The specific requirement that Pc-Ps ≥ 3 at% ensures sufficient gradient to achieve both improved luminance and maintained reliability.
2Illumination intensity
If the Si concentration is increased to improve luminance, then light emission efficiency improves, but the crystal structure stability may be compromised
Solution Approach 1:
The patent resolves this contradiction by applying local quality through spatially varying Si concentration. The surface region (lower Si concentration, Ps) provides enhanced light emission efficiency due to reduced non-radiative recombination centers, while the center region (higher Si concentration, Pc) maintains crystal structure stability and prevents degradation. The gradient structure allows both regions to coexist with optimal properties.
Solution Approach 2:
The patent applies parameter changes by controlling the Si concentration gradient parameter (Pc-Ps ≥ 3 at%) during the two-stage firing process. By adjusting firing temperature, holding time, and raw material composition in different stages, the patent creates the desired Si concentration distribution that optimizes both light emission efficiency and crystal structure 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 luminance of the β-sialon phosphor particle and the light emitting device is significantly improved, with enhanced light emission efficiency in the green wavelength range.
Implementation Method 1
A phosphor Eu2+ doped in the crystal structure of β-sialon is a phosphor which is excited by ultraviolet to blue light and emits green light having wavelengths of 520 nm or more and 550 nm or less
Data Source
AI summary
A europium-doped β-sialon phosphor particle. When the element concentration of a Si atom on the surface portion of the particle that is obtained by analyzing a cross section of the phosphor particle by the energy dispersive X-ray analysis method is indicated by Ps [at %], and the element concentration of a Si atom near the center of the particle that is obtained by an analysis by the same method is indicated by Pc [at %], the Pc-Ps value is 3 at % or more.