Ceramic Wavelength Converter With Lattice-Matched Grain Interfaces
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Solution Overview
Problem
Conventional Al2O3-YAG:Ce composite materials suffer from reduced internal quantum efficiency due to lattice mismatch between Al2O3 and YAG crystal grains, leading to impaired fluorescent characteristics and heat resistance issues.
Innovation Solution
A polycrystalline ceramic sintered body with Al2O3 crystal grains and X3Al5O12:Ce crystal grains, where atoms of element X (such as lanthanoids or Sc) are incorporated into Al2O3 crystal grains adjacent to the interface through atomic substitution, mitigating lattice mismatch and enhancing internal quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If Al2O3 and YAG:Ce particles are combined to form a composite phosphor, then heat resistance and thermal conductivity are improved, but lattice mismatch at the interface causes defects that reduce internal quantum efficiency
Solution Approach 1:
A third component with lattice constant between Al2O3 and YAG:Ce is introduced as an intermediary material at the interface. This mediator reduces the lattice mismatch between the two main components, preventing defect formation while maintaining the composite structure's heat resistance benefits.
Solution Approach 2:
The lattice constant parameter is modified by introducing a third component material whose lattice constant falls between those of Al2O3 and YAG:Ce. This parameter adjustment creates a gradient transition at the interface, reducing the abrupt lattice mismatch that causes defects and maintains high internal quantum efficiency.
2Stability of the object's composition
If eutectic transformation of Al2O3 and YAG is used to prepare phosphor, then composite material structure is achieved, but large lattice constant difference causes reduction in internal quantum efficiency
Solution Approach 1:
A three-component composite material system is designed where the third component is specifically selected to have intermediate lattice constant. This composite structure maintains the stability and heat resistance benefits of Al2O3-YAG while adding a lattice-matching layer that prevents interface defects.
3Ease of manufacture
If CeAl11O18 phase precipitates during production of Al2O3-YAG composite phosphor, then third component is formed, but larger lattice constant difference results in reduction of internal quantum efficiency
Solution Approach 1:
The composition parameters are precisely controlled during manufacturing to prevent the formation of CeAl11O18 phase. By adjusting the ratio and processing conditions, the third component that forms has a lattice constant between Al2O3 and YAG:Ce, whereas uncontrolled precipitation produces CeAl11O18 with excessively small lattice constant that worsens the mismatch.
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 solution significantly improves internal quantum efficiency, emission intensity, and heat resistance by reducing defects at the interface and preventing energy conversion to heat, resulting in high emission efficiency and color uniformity.
Implementation Method 1
atoms of element X are present also in an Al2O3 crystal grain adjacent to the interface between, the Al2O3 crystal grain and an X3Al5O12:Ce crystal grain
Implementation Method 2
a head lamp, a projector, a lighting apparatus, or a similar apparatus generally includes a device for achieving white light through wavelength conversion, by means of a fluorescent body (i.e., a wavelength conversion member), of blue light emitted from a light-emitting diode (LED) or a laser diode (LD)
Data Source
AI summary
In one aspect of the present disclosure, there is provided an optical wavelength conversion member including a polycrystalline ceramic sintered body containing, as main components, Al2O3 crystal grains and crystal grains represented by formula X3Al5O12:Ce. In the optical wavelength conversion member 9, atoms of element X are present also in an Al2O3 crystal grain adjacent to the interface between the Al2O3 crystal grain and an X3Al5O12:Ce crystal grain.