Composite Ceramic Using Core-Shell Fluorescent Powder
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Solution Overview
Problem
Conventional fluorescent conversion materials used in laser light sources face limitations due to low thermal conductivity and short service life, which are not adequately addressed by silica gel or glass encapsulation, and the existing solid phase method for preparing luminescent composite ceramics requires high sintering temperatures and longer times, affecting the integrity and performance of fluorescent powder particles.
Innovation Solution
A composite ceramic is prepared using core-shell structured fluorescent powder with an alumina matrix and a sintering aid, such as MgO or Y2O3, to improve the interface bonding between alumina and fluorescent powder particles, enhancing mechanical and optical performances without altering the sintering process conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional silica gel or glass encapsulation is used, then the fluorescent powder is protected, but the thermal conductivity is low and service life is short due to inability to withstand high temperatures
Solution Approach 1:
The patent uses alumina ceramic as the encapsulation material instead of conventional silica gel or glass. alumina ceramic provides both high temperature resistance (withstanding temperatures above 200-250°C) and high thermal conductivity, simultaneously resolving the contradiction between reliability and temperature resistance.
2Strength
If higher sintering temperature and longer sintering time are used, then the interface bonding degree between alumina and fluorescent powder is improved, but the fluorescent powder particles enter liquid phase sintering more easily causing morphology and performance changes
Solution Approach 1:
The patent optimizes sintering parameters by controlling the sintering temperature to be below the liquid phase sintering temperature of fluorescent powder while maintaining adequate bonding. It also controls particle size distribution (alumina 0.5-5 μm, fluorescent powder 1-10 μm radius) to achieve good interface bonding without excessive sintering that would damage fluorescent powder grains.
3Reliability
If the fluorescent powder particle size is much larger than alumina particles, then the fluorescent powder does not enter liquid phase sintering easily, but the interface bonding is insufficient requiring higher sintering temperature
Solution Approach 1:
The patent creates different local characteristics by using bimodal particle size distribution: fine alumina particles (0.5-5 μm) for good interface bonding and dispersion, and larger fluorescent powder particles (1-10 μm radius) for maintaining grain integrity. The sintering conditions are locally optimized to bond these different sized particles effectively without causing liquid phase sintering of the fluorescent powder.
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 improved mechanical and optical performances of the luminescent composite ceramic, with increased density and retention of original luminescent properties, effectively addressing the limitations of conventional materials.
Implementation Method 1
These powder particles would enter the liquid phase sintering to form continuous distributed crystals
Implementation Method 2
the bonding of alumina and fluorescent powder is mainly determined by a degree of surface wetting of the alumina entering the liquid phase on the fluorescent powder particles
Implementation Method 3
degrees of precipitation and recrystallization of the alumina
Data Source
AI summary
A composite ceramic with improved mechanical performance and a preparation method therefor. The composite ceramic comprises fluorescent powder, a ceramic matrix, and an optional sintering aid. The weight ratio of the fluorescent powder to the ceramic matrix is from 3:17 to 9:1, and the relative density of the composite ceramic is greater than 95%. The preparation method comprises using core shell-structured coated fluorescent powder as a raw material, and ball-milling and sintering the raw material to obtain the composite ceramic.