Beta-Sialon Phosphor Brightness Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current phosphors used in display and lighting applications, such as plasma displays and white LEDs, face challenges in maintaining high brightness and durability due to degradation when exposed to high-energy excitation sources, and there is a demand for a green phosphor with high brightness and durability.
Innovation Solution
A β-Si3N4 crystal structure-based sialon phosphor doped with divalent Eu ions, synthesized at temperatures above 1820°C, which achieves high brightness and chromatic purity in the green wavelength region of 500-600 nm, utilizing specific composition ranges and solid solution states to ensure effective solid solution of Eu ions within the host crystal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional phosphors are used in display and lighting applications, then they can be excited by high-energy sources, but their brightness degrades over time due to exposure to excitation sources
Solution Approach 1:
The patent changes the chemical composition parameters of the phosphor by incorporating specific ratios of Si, Al, Ca, and Eu elements in a sialon crystal structure. This compositional modification enables the phosphor to maintain high brightness stability while withstanding prolonged exposure to ultraviolet excitation sources, directly resolving the contradiction between reliability and service life
Solution Approach 2:
The patent creates a composite phosphor material combining multiple elements (Si, Al, Ca, Eu, O, N) in a sialon crystal structure. This composite approach leverages the synergistic effects of different elements to achieve both high initial brightness and excellent long-term stability under excitation, solving the contradiction between reliability and duration
2Illumination intensity
If synthesis temperature is increased to improve phosphor performance, then brightness and chromatic purity are enhanced, but manufacturing complexity and energy consumption increase
Solution Approach 1:
The patent optimizes the synthesis temperature parameter to a specific range (1700-2000°C) and maintains precise control over composition ratios (Si:Al:Ca:Eu). By carefully adjusting these parameters, the patent achieves high emission intensity and chromatic purity without requiring excessively complex synthesis equipment or multi-step processes, thus resolving the contradiction between performance and manufacturing complexity
3Illumination intensity
If Eu ion concentration is increased to enhance green emission, then brightness is improved, but chromatic purity decreases due to concentration quenching
Solution Approach 1:
The patent precisely controls the Eu ion concentration parameter within an optimal range and balances it with other elemental ratios (Si, Al, Ca). This precise parameter control prevents concentration quenching while maintaining high green emission intensity, achieving both brightness and chromatic purity simultaneously
Solution Approach 2:
The patent optimizes the local distribution and concentration of Eu ions within the sialon crystal structure. By controlling the local quality of Eu doping rather than uniform concentration, the patent maximizes green emission while minimizing concentration quenching effects, thus resolving the contradiction between intensity and chromatic purity
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 resulting phosphor exhibits enhanced emission intensity and stability, maintaining high brightness even when exposed to excitation sources, making it suitable for applications in VFD, FED, PDP, CRT, and white LEDs.
Implementation Method 1
a phosphor which emits a green fluorescent light having an emission peak in a wavelength region that is at least 500 nm and does not exceed 600 nm upon irradiation of an ultraviolet ray or a visible light
Implementation Method 2
upon irradiation of an ultraviolet ray or a visible light having a wavelength of 250 nm to 500 nm or an electron beam
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A green phosphor that exhibits a green luminance higher than those of conventional rare-earth-activated sialon phosphors, having durability higher than those of conventional oxide phosphors, and that emits light by ultraviolet or visible light. There is provide a phosphor comprising a crystal of oxynitride or nitride with β-type Si3N4 crystal structure and, solid dissolved therein, Eu, which phosphor emits a fluorescence having a peak at a wavelength falling within the wavelength region of 500 to 600 nm upon excitation source irradiation. The luminous intensity within the wavelength region of 500 to 600 nm is high, so that the phosphor is excellent as a green phosphor.