Optical Wavelength Conversion Ceramic for High Illuminance
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Solution Overview
Problem
Conventional optical wavelength conversion members face challenges in achieving high illuminance, high fluorescence intensity, and reduced color unevenness due to issues such as light absorption, concentration quenching, and temperature quenching, particularly in ceramic-based phosphors used in lighting applications.
Innovation Solution
A ceramic sintered body with a garnet structure represented by A3B5O12:Ce, where the area ratio of the translucent phase to the fluorescent phase and the interfacial length of the fluorescent phase are optimized within specific ranges, along with controlled grain sizes and compositions, to enhance light conversion efficiency and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If CeAl11O18 is dispersed in the phosphor matrix to prevent color unevenness due to Ce volatilization, then color unevenness is reduced, but light absorption increases causing reduction in emission intensity and illuminance
Solution Approach 1:
The patent extracts the harmful light-absorbing function from the system by removing CeAl11O18 entirely and replacing it with Al2O3 inert grains. This eliminates the light absorption problem while maintaining the protective function against Ce volatilization through a different mechanism (physical barrier rather than chemical dispersion).
Solution Approach 2:
Al2O3 inert grains are introduced as intermediary elements that serve as physical barriers to prevent Ce volatilization during firing, without interfering with light transmission. These inert grains mediate between the conflicting requirements of Ce stabilization and light transmission by providing a non-absorbing protective structure.
2Illumination intensity
If the thickness of the fluorescent body is considerably reduced to reduce light absorption, then emission intensity improves, but durability of the structure is impaired
Solution Approach 1:
The patent creates a composite ceramic structure containing fluorescent grains (YAG:Ce), inert grains (Al2O3), and binder phases. This composite material achieves optimal balance between thickness, light transmission, and structural durability through the synergistic combination of different materials with complementary properties.
Solution Approach 2:
The patent optimizes multiple parameters simultaneously: fluorescent phase content (30-70 vol%), inert phase content (10-40 vol%), grain size ratios, and sintering conditions. By changing these parameters within specific ranges, the patent achieves both sufficient light transmission and adequate structural durability without excessive thickness reduction.
3Quantity of substance
If a ceramic member contains rare earth element in amount of 1 to 50 mol% to form emission center ion, then emission center formation is achieved, but concentration quenching occurs resulting in low emission intensity
Solution Approach 1:
The patent precisely controls the Ce content parameter within the narrow range of 0.1 to 1.0 mol% (optimally 0.2 to 0.5 mol%), which is significantly lower than conventional ranges. This parameter optimization prevents concentration quenching while ensuring sufficient emission center formation, achieving high emission intensity.
4Illumination intensity
If YAG grains surrounded by unactivated YAG grains are employed to prevent reflection of excitation light, then light reflection is reduced, but temperature quenching occurs due to poor heat dissipation
Solution Approach 1:
Al2O3 inert grains serve as thermal intermediaries with high thermal conductivity, creating thermal pathways for heat dissipation from fluorescent grains. These inert grains mediate between the fluorescent phases, allowing efficient heat transfer while maintaining optimal optical properties.
Solution Approach 2:
The patent creates local heterogeneity in the ceramic matrix by distributing Al2O3 inert grains and binder phases strategically. This local quality variation provides preferential thermal conduction pathways near fluorescent grains while maintaining overall structural integrity and optical performance.
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 achieves high illuminance, high fluorescence intensity, and reduced color unevenness, while also providing excellent heat resistance and durability, resulting in improved performance of the optical wavelength conversion member and light-emitting devices.
Implementation Method 1
a fluorescent phase having a composition represented by formula A3B5O12:Ce... effective conversion of blue light into visible light
Implementation Method 2
a translucent phase containing translucent crystal grains... transmittance, illuminance, and fluorescence intensity
Data Source
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AI summary
An optical wavelength conversion member and a light-emitting device, each of which exhibits high illuminance, high fluorescence intensity, and reduced color unevenness, are provided. An optical wavelength conversion member 9 is formed of a ceramic sintered body having a fluorescent phase containing fluorescent crystal grains as a main component and a translucent phase containing translucent crystal grains as a main component. Crystal grains of the fluorescent phase have a composition represented by formula A3B5O12:Ce, and each of the element A and the element B is at least one element selected from the following element groups. Specifically, the element A is selected from "Sc, Y, and lanthanoids (except for Ce)," and the element B is selected from "Al and Ga." In the optical wavelength conversion member 9, the following relations are satisfied: 0.3 < a < 34 and 300 µm < y < 1,050 µm, wherein a represents the ratio of the area of the translucent phase to the area of the fluorescent phase in a cross section of the optical wavelength conversion member 9, and y represents the interfacial length of the fluorescent phase.