Porous Ceramic Light Converter for High-Power Reflective Lighting
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Solution Overview
Problem
Existing lighting devices with light conversion elements, such as Ce-doped garnet ceramics, face limitations in thermal conductivity, which restrict the increase in optical power and luminance due to high temperatures, and are primarily designed for transmissive applications, whereas there is a need for efficient diffuse reflective designs that can utilize materials with higher thermal conductivity.
Innovation Solution
A lighting device incorporating a light conversion unit with a substrate having thermal conductivity greater than 30 W/mK, a mixed ceramic with a high thermal conductivity second phase, and a multitude of pores for enhanced light scatter, along with a highly reflective coating and an optical separation layer, to achieve efficient light conversion and diffusion in a reflective mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If Ce-doped garnet ceramics are used as light conversion material, then light conversion efficiency is achieved, but thermal conductivity is limited (5-10 W/mK) restricting maximum optical power and luminance
Solution Approach 1:
The patent uses composite ceramic materials combining Ce-doped garnet (for light conversion) with high thermal conductivity materials like Al2O3, MgO, or BeO. This composite structure maintains the phosphor's light conversion efficiency while the high thermal conductivity matrix rapidly conducts heat away, enabling higher optical powers and luminances without thermal degradation.
Solution Approach 2:
The patent introduces a substrate with very high thermal conductivity (≥30 W/mK, preferably ≥100 W/mK) as an intermediary heat sink beneath the light conversion element. This substrate acts as a thermal mediator, quickly conducting heat away from the phosphor layer to prevent temperature buildup that would reduce quantum efficiency, thereby enabling higher input optical powers.
2Loss of energy
If mixed ceramic is used to increase thermal conductivity, then thermal management improves, but device complexity increases due to multiple phases and manufacturing requirements
Solution Approach 1:
The patent employs porous ceramic structures where pores (voids) are intentionally introduced into the mixed ceramic. These pores serve multiple functions: they scatter light to enhance diffuse reflective performance, and they reduce the overall density and thermal mass of the material, facilitating faster thermal response and reduced heat accumulation while maintaining structural integrity.
Solution Approach 2:
The patent applies different materials and structures to different regions: the light conversion layer contains Ce-doped garnet particles embedded in a high thermal conductivity ceramic matrix, while the substrate beneath provides additional thermal management. Each layer is optimized for its specific function, creating a functionally graded structure that manages complexity through specialization.
3Productivity
If transmissive design is used, then light conversion is efficient, but diffuse reflective performance is insufficient for certain applications
Solution Approach 1:
The patent uses porous ceramic structures with controlled pore sizes and distributions to enhance light scattering. The pores create multiple internal reflections and scattering events that diffuse light effectively while maintaining high light conversion efficiency. This porous structure enables the material to function effectively in diffuse reflective configurations.
Solution Approach 2:
The patent transitions from traditional transmissive (one-dimensional light path) to diffuse reflective (multi-dimensional light scattering) geometry. By incorporating scattering centers (pores, grain boundaries, phase interfaces) throughout the ceramic volume, light undergoes multiple scattering events in three dimensions, creating effective diffuse reflection while maintaining high conversion efficiency.
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 enables increased light scatter and irradiance, allowing for higher light output and improved efficacy in solid-state lighting applications by effectively utilizing materials with higher thermal conductivity and optimizing the light conversion process within the lighting device.
Implementation Method 1
a light conversion element which is illuminated by the primary light and emits secondary light with an altered wavelength compared to the primary light
Implementation Method 2
The substrate optionally consists wholly or predominantly of a material having a thermal conductivity greater than 30 W/mK
Implementation Method 3
The light conversion element includes a multitude of pores
Data Source
AI summary
A lighting device includes: a light source configured for emitting a primary light; a light conversion unit formed by or including: a light conversion element including a front side and a rear side, wherein the light conversion element is configured for being illuminated by the primary light on the front side and for emitting a secondary light with an altered wavelength compared to the primary light on the front side, wherein the light conversion element includes a first phase including a light-converting ceramic material and a second phase including a further ceramic material, the second phase having a higher thermal conductivity than the first phase, and wherein the light conversion element includes a plurality of pores.