Red Phosphor Composition for Stable White Light
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Solution Overview
Problem
Conventional red phosphors used in white light-emitting apparatuses face challenges in maintaining brightness and reliability under higher temperature and humidity environments, with issues related to oxygen content and particle size affecting their performance.
Innovation Solution
A red phosphor with a nitride composition of (Sr1-x-yBaxEuy)2Si5N8, where 0<x<0.7 and 0<y<0.1, is developed, with controlled oxygen content below 1 wt% and particle size between 10 μm to 25 μm, to enhance brightness and reliability. This phosphor emits light in the 600 nm to 630 nm range when excited by a blue light source, and is combined with other phosphors in a white light-emitting apparatus to achieve improved luminous flux and color rendering index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional red phosphors are used in white light-emitting apparatuses, then the apparatus can operate, but the brightness and reliability deteriorate under higher temperature and humidity environments
Solution Approach 1:
The patent changes the chemical composition parameters of the red phosphor by incorporating barium (Ba) and europium (Eu) into the Sr2Si5N8:Eu2+ lattice structure. The specific compositional range (0 < x < 0.7 and 0 < y < 0.1 in the formula (Sr1-x-yBaxEuy)2Si5N8) is optimized to enhance thermal and humidity stability while maintaining photoluminescence properties, thereby improving reliability under elevated temperature and humidity conditions
Solution Approach 2:
The patent creates a composite phosphor material by combining multiple elements (Sr, Ba, Eu, Si, N) in a specific nitride structure. The dual-doping strategy with both Ba and Eu creates a composite structure that synergistically improves both the structural stability (for temperature/humidity resistance) and the optical performance (for brightness), resolving the contradiction between reliability and environmental stability
2Illumination intensity
If oxygen content in red phosphor is not controlled, then manufacturing is simpler, but brightness and reliability deteriorate
Solution Approach 1:
The patent employs an inert atmosphere (nitrogen or argon) during the sintering process to prevent oxygen incorporation into the phosphor lattice. By conducting the high-temperature synthesis in an oxygen-free environment, the method achieves low oxygen content (<1 wt%) without requiring complex post-processing, thus maintaining brightness while managing manufacturing complexity through process atmosphere control
Solution Approach 2:
The patent controls the oxygen content parameter during manufacturing by adjusting the sintering atmosphere composition and oxygen partial pressure. This parameter control during the synthesis stage directly influences the final brightness and reliability of the phosphor, achieving high performance through precise manufacturing parameter management
3Illumination intensity
If particle size of red phosphor is not optimized, then manufacturing is easier, but brightness and color stability deteriorate
Solution Approach 1:
The patent performs preliminary particle size control during the sintering process itself, rather than relying on post-synthesis size reduction. By controlling sintering conditions (temperature, time, atmosphere) to directly produce particles within the optimal size range (10-25 μm), the method achieves both high brightness and manufacturing simplicity through advance process design
Solution Approach 2:
The patent optimizes the particle size parameter through controlled sintering conditions. The specific particle size range (10-25 μm) is achieved by adjusting sintering temperature and duration, which simultaneously affects particle growth, density, and photoluminescence efficiency, thereby improving brightness while maintaining reasonable manufacturing complexity
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 red phosphor maintains high brightness and reliability in higher temperature and humidity conditions, with reduced variations in brightness and color coordinates, resulting in a more stable and efficient white light-emitting apparatus with improved luminous flux and color rendering index.
Implementation Method 1
The red phosphor may emit light having a peak wavelength in a range of 600 nm to 630 nm when irradiated by an excitation source. The excitation source may be a blue light source having a dominant wavelength in a range of 420 nm to 470 nm.
Implementation Method 2
Phosphors that convert wavelengths of light may be used to convert light having specific wavelengths generated by a variety of light sources into light having desired wavelengths.
Data Source
AI summary
There is provided a red phosphor that may include a nitride represented by a formula of (Sr1-x-yBaxEuy)2Si5N8, wherein 0<x<0.7, and 0<y<0.1. The red phosphor may emit light having a peak wavelength in a range of 600 nm to 630 nm when irradiated by an excitation source and the excitation source may be a blue light source having a dominant wavelength in a range of 420 nm to 470 nm.