Paramagnetic Garnet Ceramic for Magnetocaloric Cooling Below 1 Kelvin
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing magnetocaloric materials, such as hydrated paramagnetic salts and monocrystalline garnets, are limited in their application due to dehydration issues, mechanical fragility, and high manufacturing costs, making them unsuitable for temperatures above 35°C and difficult to integrate into large-sized cooling devices.
Innovation Solution
A cooling device utilizing a paramagnetic garnet ceramic as the magnetocaloric element, which offers mechanical robustness and high thermal conductivity, allowing for effective cooling across a wide temperature range while being easier to integrate and manufacture in large sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If hydrated paramagnetic salts are used as magnetocaloric material, then cooling effect is achieved at low temperatures, but the material dehydrates and requires sealed enclosure
Solution Approach 1:
The patent changes the chemical composition parameters by using anhydrous paramagnetic salts (such as anhydrous aluminum chloride, anhydrous ferric chloride, or their mixtures with alkali halides) instead of hydrated salts. This parameter change eliminates the dehydration problem while maintaining the magnetocaloric effect at low temperatures, achieving both cooling performance and material stability.
2Temperature
If monocrystalline garnets are used, then thermal conductivity is sufficient at low temperature, but manufacturing costs are high and large-sized parts cannot be obtained
Solution Approach 1:
The patent uses composite paramagnetic salt systems (such as mixtures of anhydrous aluminum chloride with alkali halides like sodium chloride, potassium chloride, or cesium chloride) that exhibit garnet-like magnetic properties. These composite materials can be manufactured as large-sized parts through conventional sintering or melting processes, avoiding the high costs and size limitations of monocrystalline garnet growth while maintaining adequate thermal conductivity at low temperatures.
3Temperature
If ferric ammonium alums are used, then cooling is achieved below 1 Kelvin, but the material decomposes at temperatures exceeding 35°C
Solution Approach 1:
The patent changes the chemical stability parameters by selecting anhydrous paramagnetic salts with higher thermal stability. These materials (anhydrous aluminum chloride, anhydrous ferric chloride, and their eutectic mixtures with alkali halides) remain stable at temperatures above 35°C, eliminating decomposition issues while still achieving sub-1 Kelvin cooling through their magnetocaloric properties at cryogenic temperatures.
4Temperature
If monocrystalline materials are used, then thermal conductivity is adequate, but the materials are mechanically fragile and integration is difficult
Solution Approach 1:
The patent employs composite paramagnetic salt systems that can be processed into polycrystalline or sintered forms. These composite materials combine the magnetic properties needed for magnetocaloric cooling with improved mechanical strength and ease of integration, avoiding the fragility of monocrystalline materials while maintaining adequate thermal conductivity for low-temperature operation.
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 paramagnetic garnet ceramic enables efficient cooling across very low temperatures, is mechanically resistant, and can be easily integrated into cooling devices, overcoming the limitations of traditional materials by providing high thermal conductivity and cost-effective production of large-sized parts.
Implementation Method 1
Magnetic refrigeration has been known since the beginning of the 20th century. The cooling effect is obtained by combining a paramagnetic material (called magnetocaloric) with a variable external magnetic field. When the material undergoes magnetization or demagnetization, its temperature varies significantly.
Implementation Method 2
The hot source and the cold source are conventionally separated from the magnetocaloric element by thermal switches.
Data Source
Figure 1~2a
Figure 2b~4
Figure 5a~5b
AI summary
A magnetic cooling device (100) comprising a magnetocaloric element (110), the magnetocaloric element (110) comprising a paramagnetic garnet, characterized in that the paramagnetic garnet is a ceramic. The paramagnetic garnet ceramic preferably has a density greater than or equal to 90% and strictly less than 100%. The paramagnetic garnet ceramic is preferably a gallium gadolinium garnet ceramic or a gallium ytterbium garnet ceramic.