β-SiAlON Phosphor Sintering via Nitrogen Atmosphere and Open Graphite Box
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Solution Overview
Problem
Mass production of β-SiAlON phosphor often results in non-uniform luminescence intensity due to uncontrolled temperature conditions and high carbon content, affecting its luminescence properties.
Innovation Solution
The method involves sintering a mixture of silicon nitride, aluminum nitride, and optically active compounds in boron nitride vessels within a graphite box in a nitrogen atmosphere at controlled temperatures, with the top open to reduce carbon concentration and enhance luminescence intensity, and subsequent acid treatment to improve fluorescence properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mass production is performed by sintering multiple boron nitride vessels in a sintering furnace simultaneously, then productivity is improved, but luminescence intensity uniformity deteriorates due to uncontrolled temperature conditions
Solution Approach 1:
The patent applies inert atmosphere control by performing sintering in a nitrogen atmosphere within a graphite box. The graphite box is designed with a specific structure that allows nitrogen gas to circulate uniformly around all boron nitride vessels, creating a controlled inert environment that ensures uniform temperature distribution and consistent luminescence intensity across all samples produced simultaneously.
2Ease of manufacture
If conventional sintering is performed without controlled nitrogen atmosphere, then ease of manufacture is improved, but carbon concentration increases leading to reduced luminescence intensity
Solution Approach 1:
The patent implements inert atmosphere control by performing sintering in a nitrogen atmosphere within a graphite box. The graphite box is designed with a specific structure that allows nitrogen gas to circulate uniformly around all boron nitride vessels, creating a controlled inert environment that ensures uniform temperature distribution and consistent luminescence intensity across all samples produced simultaneously.
Solution Approach 2:
The patent extracts carbon from the sintering environment by using a graphite box design that facilitates nitrogen gas circulation. This extraction approach removes carbon-containing gases from contact with the starting materials, thereby preventing carbon incorporation into the β-SiAlON phosphor and achieving low carbon concentration (200 ppm or lower) while maintaining ease of manufacture.
3Ease of operation
If graphite box with closed top is used, then ease of operation is improved, but carbon concentration increases due to restricted nitrogen gas contact
Solution Approach 1:
The patent applies dynamics by designing the graphite box with a movable top portion that can be opened or closed. During the sintering process, the top is kept open to allow nitrogen gas to freely contact the starting materials, preventing carbon contamination. This dynamic design enables easy operation while maintaining low carbon concentration, as the operator can simply open the top during sintering without complex mechanisms.
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
This approach produces β-SiAlON with a carbon concentration of 200 ppm or lower, achieving high luminescence intensity and stability across a wide wavelength range, suitable for various light-emitting devices, particularly those using UV or blue LEDs, with minimal brightness reduction at high temperatures and extended service life.
Implementation Method 1
β-SiAlON starting materials, namely a mixture of silicon nitride, aluminum nitride, at least one compound selected from aluminum oxide and silicon oxide, and optically active element compound, are sintered at temperatures ranging from 1820° C. to 2200° C.
Implementation Method 2
the β-SiAlON starting materials packed in a plurality of boron nitride vessels are placed in a graphite box to allow the starting materials to easily come in contact with nitrogen gas, and sintering is performed in nitrogen atmosphere
Implementation Method 3
sintering is performed in nitrogen atmosphere with the top part of the graphite box opened
Implementation Method 4
subjecting sintered and crashed materials obtained by sintering process to acid treatment is known
Data Source
AI summary
A method of producing β-SiAlON includes a sintering process, in which β-SiAlON starting materials, a mixture of silicon nitride, aluminum nitride, optically active element compound, and at least one compound selected from aluminum oxide and silicon oxide, are sintered at temperatures ranging from 1820° C. to 2200° C. The method provides new β-SiAlON low in carbon content and having high luminescence intensity by placing a plurality of boron nitride vessels in a graphite box to allow the β-SiAlON starting materials packed in the plurality of boron nitride vessels to easily come in contact with nitrogen gas, and performing sintering in nitrogen atmosphere.