Green Emitting Sialon Phosphor for LED Thermal Stability
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Solution Overview
Problem
Current green emitting phosphors for white LEDs lack stability, spectral sharpness, and tunability, making them unsuitable for a wide range of applications, particularly in warm white pcLEDs with optimized luminous efficiency and color rendering.
Innovation Solution
A green emitting material with the composition Sr5−y−z−aMySi23−xAl3+xOx+2aN37−x−2a:Euz:Cez1, where M is Ca, Ba, or Mg, and specific stoichiometric adjustments enhance thermal stability, spectral sharpness, and tunability, allowing for a narrow emission band and improved photothermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Sr5−y−z−aMySi23−xAl3+xOx+2aN37−x−2a:Euz:Cez phosphor material is used, then thermal stability and spectral sharpness are improved, but material composition complexity increases
Solution Approach 1:
The patent applies parameter changes by systematically varying the stoichiometric ratios of elements (Sr, Ca, Ba, Mg, Si, Al, O, N) and dopant concentrations (Eu, Ce) to optimize thermal stability and spectral properties. Specifically, controlling the ratio of (Si,N) to (Al,O) substitution and adjusting the alkaline earth cation concentration allows tuning of emission characteristics while maintaining compositional control
Solution Approach 2:
The patent employs composite material strategy by creating a multi-element phosphor system combining Sr-based SiAlON host with Ca, Ba, or Mg substitutions and dual doping with Eu and Ce. This composite approach enables simultaneous achievement of thermal stability, spectral sharpness, and color tunability through synergistic interactions between different elements in the crystal structure
2Ease of manufacture
If green emitting phosphor materials like SrSi2O2N2:Eu or (Ba,Sr)2SiO4:Eu are used, then ease of manufacture is improved, but spectral sharpness and stability deteriorate
Solution Approach 1:
The patent maintains ease of manufacture by using conventional ceramic processing techniques while achieving improved spectral sharpness and stability through precise control of composition parameters. The synthesis process involves standard solid-state reaction methods with controlled heating treatments, keeping manufacturing complexity comparable to conventional phosphors while achieving superior optical and thermal properties
Solution Approach 2:
The patent applies local quality by introducing specific dopant elements (Eu and Ce) at controlled concentrations within the crystal structure to create localized luminescent centers with enhanced spectral characteristics. The dual doping strategy allows Eu to provide sharp emission lines while Ce contributes to thermal stability and color tuning, achieving localized functional optimization within the bulk material
3Ease of manufacture
If green emitting phosphor materials like SrSi2O2N2:Eu are used, then ease of manufacture is improved, but color point saturation and spectral appropriateness worsen
Solution Approach 1:
The patent achieves color point saturation and spectral optimization through precise parameter control of the phosphor composition. By adjusting the Sr content (y parameter), substitution elements (Ca, Ba, Mg), and dopant ratios (Eu and Ce concentrations), the emission spectrum can be tuned to achieve saturated green color coordinates suitable for specific LED applications while maintaining manufacturability
Solution Approach 2:
The patent applies dynamics by enabling continuous tuning of the emission spectrum and color point through variable composition parameters. The phosphor system allows dynamic adjustment of color coordinates and spectral shape by modifying the ratios of host elements and dopants, providing adaptability for different LED chip wavelengths and application 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 material exhibits high thermal stability, a sharp emission spectrum, and tunable properties, enabling its use in various lighting applications with improved luminous efficiency and color rendering, maintaining luminescence intensity under heat and high excitation conditions.
Implementation Method 1
Phosphors comprising silicates, phosphates (for example, apatite) and aluminates as host materials, with transition metals or rare earth metals added as activating materials to the host materials, are widely known. As blue LEDs, in particular, have become practical in recent years, the development of white light sources utilizing such blue LEDs in combination with such phosphor materials is being energetically pursued.
Data Source
AI summary
The invention relates to a light emitting device, especially a LED comprising a green emitting material of the composition Sr5−y−z−aMySi23−xAl3+xOx+2aN37−x−2a:Euz:Cez1. This material has been found to have a narrow emission in the green wavelight range together with a good producibility and stability.