Sr-Ba Oxynitride Phosphor Thermal Stability
Solution Overview
Problem
There is a lack of high-efficiency yellow-emitting phosphors that are insensitive to external influences and can be easily excited by blue or UV radiation, limiting their application in LED lighting and other light sources.
Innovation Solution
A highly efficient oxynitride phosphor with the formula Sr1-xBa x Si2O2:Eu is developed, where x ranges from 0.42 to 0.70, specifically designed to have a dominance wavelength shifted towards longer wavelengths by at least 6 nm compared to pure Sr-Sion, achieved through a manufacturing process involving the mixing of carbonates, SiO2, and Si3N4 in a reducing atmosphere, allowing for enhanced stability and excitation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional YAG:Ce phosphors are used, then broad spectral coverage is achieved, but efficiency at high temperature (150°C) is reduced due to temperature quenching
Solution Approach 1:
The patent changes the chemical composition parameters of the phosphor by creating a mixed ion system (Sr1-xBax)2Si2O2N2:Eu with specific ratios (0.42 ≤ x ≤ 0.70) and europium doping content (5 ≤ c ≤ 12 mol%). This compositional parameter change results in a new phase with dominant emission wavelength ≥570 nm that exhibits superior thermal stability and maintains high efficiency at 150°C, achieving a 20% efficiency advantage over traditional YAG:Ce phosphors.
Solution Approach 2:
The patent employs a composite material strategy by combining Sr and Ba ions in specific proportions within the phosphor structure, along with Eu dopant. This composite approach creates a new phase with enhanced properties: the mixed ion system provides both the structural framework and the optical characteristics needed to resist temperature quenching while maintaining high quantum efficiency and stability at elevated temperatures.
2Illumination intensity
If pure Sr-Sion or Ba-Sion is used, then specific emission characteristics are achieved, but the dominance wavelength cannot be shifted sufficiently towards longer wavelengths
Solution Approach 1:
The patent applies local quality by selectively substituting Ba ions into the Sr-Sion lattice at controlled positions and concentrations (0.30 ≤ x ≤ 0.70). This localized substitution at specific compositional ratios creates the new phase with the desired long-wavelength emission (≥570 nm), allowing precise control over the dominance wavelength while maintaining the overall phosphor structure and properties.
3Productivity
If garnet phosphors are replaced, then manufacturing complexity increases, but efficiency and visual effect are improved
Solution Approach 1:
The patent achieves improved efficiency (20% advantage at 150°C) and visual effect by optimizing key parameters: the Ba content ratio (x), europium doping concentration (c), and resulting dominant wavelength (≥570 nm). These parameter optimizations are achieved through a systematic manufacturing process that, while requiring precise control, provides a clear recipe for reproduction and scaling, balancing complexity with performance gains.
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 new phosphor exhibits improved efficiency and stability, with a 20% efficiency advantage over YAG:Ce-based solutions at 150°C, and can replace traditional garnet phosphors, offering superior performance in white LEDs and other light sources by emitting a narrower band with higher visual effect and reduced temperature quenching.
Implementation Method 1
The phosphor can be easily excited by both blue and UV radiation... completely or partially converted into longer-wave radiation by such a phosphor
Implementation Method 2
an orthosilicate is synthesized from them... this mixture is then ignited in a slightly reducing atmosphere
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to an illuminant from the class of oxynitridosilicates, doped with bivalent europium and comprising a cation M2+, said illuminant corresponding to the basic formula M(1-c) Si202N2: Dc wherein the following holds good: M = Sr (1-x) Bax where 0,3 < x < 0,7.