Beta-Sialon Phosphor Surface Composition for Higher Luminance
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Solution Overview
Problem
There is a need for further improvement in luminance for β-sialon phosphors and light emitting devices.
Innovation Solution
A europium-doped β-sialon phosphor is developed, where the ratio of aluminum at specific depths from the surface, as determined by X-ray photoelectron spectroscopy, satisfies P(Al)8/P(Al)80 ≤ 0.9, and a light emitting device incorporating this phosphor is used.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional β-sialon phosphors are used, then the phosphor structure is stable, but the luminance is insufficient
Solution Approach 1:
The patent applies local quality by creating a specific aluminum concentration gradient within the phosphor particle structure. The surface region (0-8 nm depth) has a controlled aluminum ratio P(Al)8 that differs from the bulk material (80 nm depth) with ratio P(Al)80, where P(Al)8/P(Al)80 ≤ 0.9. This localized compositional variation at the surface improves luminance while the bulk maintains structural stability and heat resistance.
Solution Approach 2:
The patent utilizes parameter changes by precisely controlling the aluminum element ratio at different depths from the phosphor surface. By adjusting the P(Al)8/P(Al)80 ratio to ≤ 0.9, the invention optimizes the balance between luminance enhancement and structural stability, achieving improved performance without sacrificing reliability.
2Illumination intensity
If the output of light emitting devices is increased, then the luminance improves, but the heat resistance and durability requirements increase
Solution Approach 1:
The patent addresses the temperature challenge by implementing local quality through a controlled aluminum gradient. The surface region with modified aluminum ratio P(Al)8 optimizes light emission efficiency for high luminance, while the bulk material with ratio P(Al)80 maintains the stable crystal structure necessary for heat resistance and durability under increased output conditions.
Solution Approach 2:
The patent effectively creates a composite structure within the single phosphor material by establishing distinct compositional regions. The surface layer (0-8 nm) with aluminum ratio P(Al)8 and the bulk material (80 nm) with ratio P(Al)80 form a composite-like structure that combines high luminance properties with thermal stability, enabling the phosphor to withstand increased device output.
3Illumination intensity
If the aluminum ratio at the surface is increased, then the luminance improves, but the structural stability may be compromised
Solution Approach 1:
The patent resolves this contradiction by applying local quality with precise control over aluminum distribution. The surface region (0-8 nm depth) has aluminum ratio P(Al)8 optimized for luminance, while the bulk material (80 nm depth) with ratio P(Al)80 maintains crystal structure stability. The constraint P(Al)8/P(Al)80 ≤ 0.9 ensures that the surface modification does not compromise overall structural integrity.
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 approach results in a β-sialon phosphor and light emitting device with improved luminance.
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
Implementation Method 2
when a ratio of an aluminum element at a depth of 8 nm from a surface of the phosphor, which is obtained by X-ray photoelectron spectroscopy, is indicated by P(Al)8
Data Source
AI summary
A europium-doped β-sialon phosphor, in which, when the ratio of an aluminum element at a depth of 8 nm from the surface of the phosphor, which is obtained by X-ray photoelectron spectroscopy, is indicated by P8 [at %], and the ratio of an aluminum element at a depth of 80 nm from the surface of the phosphor is indicated by P80 [at %], P8/P80≤0.9 is satisfied. A light emitting device containing this β-sialon phosphor.