Beta-Sialon Fluorescent Material Cooling Rate Control
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Solution Overview
Problem
Current β-sialon fluorescent materials have limitations in emission intensity and full width at half maximum (FWHM) of light emission spectrum, which affect their performance in light-emitting devices, particularly in liquid crystal display backlighting.
Innovation Solution
A method involving a heat-treatment process of silicon nitride with aluminium and europium, followed by controlled temperature decrease steps, to produce a β-sialon fluorescent material with improved emission intensity and a narrower FWHM, optimizing the crystal structure and europium placement for enhanced light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional heat treatment at high temperature (1800°C or more) is used to produce β-sialon fluorescent material, then the material can be formed with proper crystal structure, but the emission intensity is insufficient and the full width at half maximum (FWHM) is too wide
Solution Approach 1:
The patent changes the heat treatment temperature parameter from conventional 1800°C or more to a lower range of 1300-1600°C, and introduces a specific cooling rate parameter (1.5-200°C/min) to control crystal growth. This parameter optimization resolves the contradiction by achieving narrow FWHM and high emission intensity simultaneously through controlled crystallization at lower temperatures with regulated cooling rates.
Solution Approach 2:
The patent introduces dynamic control of the cooling process by specifying a controlled cooling rate from the heat treatment temperature to room temperature. This dynamic parameter allows precise control over crystal formation, enabling the material to achieve optimal crystal structure and europium distribution that simultaneously improves emission intensity and narrows FWHM.
2Stability of the object's composition
If heat treatment temperature is increased to improve crystal structure formation, then material stability improves, but emission intensity decreases and FWHM increases
Solution Approach 1:
The patent optimizes the heat treatment temperature parameter to a specific range (1300-1600°C) that is lower than conventional temperatures but sufficient for forming stable β-sialon crystal structure. Combined with controlled cooling rate (1.5-200°C/min), this parameter change achieves both crystal structure stability and high emission intensity, resolving the contradiction between stability and emission performance.
3Ease of manufacture
If conventional single-step cooling is used after heat treatment, then the process is simple, but the emission properties (intensity and FWHM) cannot be optimized
Solution Approach 1:
The patent segments the cooling process into a controlled cooling stage (from heat treatment temperature to room temperature at 1.5-200°C/min) that follows heat treatment. This segmentation of the thermal process allows independent optimization of crystal formation and emission properties, achieving high emission intensity and narrow FWHM while maintaining reasonable process simplicity through a single controlled cooling step.
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 method results in a β-sialon fluorescent material with higher emission intensity and a narrower FWHM, leading to improved color reproducibility and efficiency in light-emitting devices, specifically in liquid crystal display backlighting.
Implementation Method 1
heat-treating the composition at a temperature in a range of 1300° C. or more and 1600° C. or less to obtain a heat-treated product
Implementation Method 2
subjecting the heat-treated product to a temperature decrease from the heat treatment temperature to 1000° C. as a first temperature-decrease step, and subjecting the heat-treated product to a temperature decrease from 1000° C. to 400° C. as a second temperature-decrease step
Data Source
AI summary
Provided is a method for producing a β-sialon fluorescent material, comprising preparing a composition containing a silicon nitride that contains aluminium, oxygen, and europium; heat-treating the composition at a temperature in a range of 1300° C. or more and 1600° C. or less to obtain a heat-treated product; subjecting the heat-treated product to a temperature-decrease of from the heat treatment temperature to 1000° C. as a first temperature-decrease step; and subjecting the heat-treated product to a temperature-decrease of from 1000° C. to 400° C. as a second temperature-decrease step. The first temperature-decrease step has a temperature-decrease rate in a range of 1.5° C./min or more and 200° C./min or less, and the second temperature-decrease step has a temperature-decrease rate in a range of 1° C./min or more and 200° C./min or less.