SrGa2S4:Eu Green Phosphor Crystallinity Control
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Solution Overview
Problem
Conventional green phosphors excited by blue LEDs have insufficient conversion efficiency, necessitating a higher efficiency phosphor for effective light emission.
Innovation Solution
A green phosphor with the composition formula (Sr1-yCay)1-xGa2S4:Eu x (0.03 ≤ x ≤ 0.20 and 0 < y ≤ 1) is developed, where the full width at half maximum of the diffraction peak corresponding to the (422) plane in the XRD pattern is less than 0.18, enhancing crystallinity and conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional green phosphors are used, then the phosphor can be excited by blue LED, but the conversion efficiency is insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the full width at half maximum (FWHM) of the diffraction peak corresponding to the (422) plane in the XRD pattern to be less than 0.18 degrees. This specific parameter control optimizes the crystallinity and phase purity of the SrGa2S4:Eu phosphor, thereby improving its conversion efficiency from blue LED excitation to green light emission. The narrow FWHM indicates high crystallinity which directly enhances the phosphor's optical performance and energy conversion efficiency.
2Stability of the object's composition
If the full width at half maximum of the diffraction peak is reduced, then crystallinity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent establishes a specific parameter range for the FWHM of the (422) diffraction peak (less than 0.18 degrees) as a critical quality indicator. By setting this precise parameter threshold, the patent enables manufacturers to control crystallinity through measurable and controllable parameters during the firing process, transforming the abstract concept of crystallinity into a quantifiable manufacturing specification.
Solution Approach 2:
The patent implements a feedback mechanism by using XRD pattern analysis, specifically the FWHM of the (422) peak, as a quality control metric. Manufacturers can measure the diffraction peak width and adjust firing conditions accordingly to achieve the target FWHM value, creating a closed-loop control system that ensures consistent high crystallinity while managing manufacturing precision requirements.
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 phosphor achieves high conversion efficiency, with absorptance, internal quantum efficiency, and external quantum efficiency improved, producing green light with high color purity and a wide color gamut when used in illumination devices.
Implementation Method 1
A SrGa2S4:Eu (hereinafter, written as SGS) phosphor is attracting attention as a green light emitting phosphor to be excited by a blue LED
Implementation Method 2
when a full width at half maximum of a diffraction peak corresponding to a (422) plane in an XRD pattern is less than a predetermined value
Implementation Method 3
full width at half maximum of a diffraction peak corresponding to a (422) plane in an XRD pattern
Data Source
Figure 1
Figure 2(A)~2(D)
Figure 3~4
AI summary
Provided is a green phosphor having high conversion efficiency. The green phosphor is represented by the composition formula (Sr1-yCay)1-xGa2S4:Eux (0.03 ≤ x ≤ 0.20 and 0 < y ≤ 1). A full width at half maximum of a diffraction peak corresponding to a (422) plane in an XRD pattern is less than 0.18.