Spherical Sr Sialon Phosphor Particle Morphology Control
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Solution Overview
Problem
Current Sr sialon phosphors used in light emitting devices have low luminous efficiency due to their non-spherical particle shape, which leads to energy loss through light reflection and absorption, necessitating an improvement in particle sphericity to enhance luminance.
Innovation Solution
A Sr sialon phosphor with a specific composition, (Sr1-x,Eux)αSiβAlγOδNω, is produced using a method that includes a classification step to remove small particles and optimize baking conditions, resulting in particles with a sphericity of 0.65 or more, effectively increasing luminance in light emitting devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional Sr sialon phosphor is used with traditional particle shape, then manufacturing is simpler, but luminous efficiency is low due to energy loss from light reflection and absorption
Solution Approach 1:
The patent applies spheroidality by transforming the particle shape from conventional tabular or columnar forms to spherical shapes. This is achieved through controlled synthesis conditions including specific raw material ratios (Sr:Si:Al = 2.5-3.5:10-15:2-5), baking temperature (1700-1900°C), and atmosphere control. The spherical shape reduces the surface area for a given volume, minimizing light reflection and absorption losses, thereby improving luminous efficiency while maintaining the orthorhombic crystal structure.
2Loss of energy
If particle sphericity is increased to reduce surface area, then luminous efficiency improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs parameter changes by systematically optimizing multiple synthesis parameters to achieve spherical particle morphology. Key parameters include: raw material composition ratios (Sr:Si:Al within specific ranges), baking temperature (1700-1900°C), baking atmosphere (nitrogen or nitrogen-hydrogen mix), and particle size control (5-50 μm). These parameter adjustments enable consistent production of spherical particles with sphericity ≥0.65, balancing manufacturing feasibility with improved luminous efficiency.
3Illumination intensity
If spherical particles are produced through classification, then luminance increases, but production process becomes more complex
Solution Approach 1:
The patent applies preliminary action by incorporating classification steps during the production process to remove small particles before final product formation. This includes: (1) classifying raw materials to uniform size ranges before mixing, (2) controlling particle growth during synthesis to achieve target size distribution, and (3) post-synthesis classification to eliminate fine particles. This preliminary size control ensures that the resulting spherical phosphor particles have optimal dimensions for high luminance while maintaining manufacturing efficiency.
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 phosphor with high luminous efficiency, significantly improving the luminance of light emitting devices by minimizing energy loss through enhanced sphericity, leading to more efficient light emission.
Implementation Method 1
a phosphor powder which emits visible light by being excited by ultraviolet light or blue light emitted from the semiconductor light emitting element
Data Source
AI summary
The present invention provides a phosphor comprising a europium-activated sialon crystal having a basic composition represented by a formula: (Sr1-x, Eux)αSiβAlγOδNω (1) (wherein x is 0<x<1, α is 0<α≦4 and β, γ, δ and ω are numbers such that converted numerical values when α is 3 satisfy 9<β≦15, 1≦γ≦5, 0.5≦δ≦3 and 10≦ω≦30), wherein the phosphor is composed of particles having a sphericity of 0.65 or more and emits green light by being excited by ultraviolet light, violet light or blue light.