FIELD OF THE INVENTION

The present invention relates to magnetocaloric materials based on the La—Fe—Si alloy system compositionally modified to improve mechanical stability, such as substantially reduced brittleness, improve thermal conductivity, and preserve analogous or even higher magnetocaloric effects compared to other known and commercially available La—Fe—Si based magnetocaloric materials for use as working bodies in magnetocaloric heat pumping applications, including as magnetic refrigerant materials.

BACKGROUND OF THE INVENTION

The ability of magnetic materials to change their temperature due to variation of applied magnetic field (magnetocaloric effect, MCE) is a physical phenomenon that could lead to the realization of clean, highly energy efficient refrigeration and heat pumping systems. However, for this to be realized, magnetic materials should possess (i) large MCE, both magnetic entropy change, ΔSM, and adiabatic temperature change, ΔTad, in magnetic field less than 2 Tesla, which is the current limit for permanent magnets, and (ii) Curie temperature near about 300K for room temperature application. In addition the materials should be reasonably inexpensive, mechanically and chemically stable, and contain no toxic elements.

Various alloy systems have been proposed as potential magnetocaloric materials including La(Fe,Si)13[1], Fe2P-type compounds [2], MnAs [3], Heusler alloys (MnCoGe-based alloys) [4], Fe49Rh51[5], rare earth based materials (Gd and Gd5Si2−xGex) [6,7] among other. However, all of them have one or more of the following disadvantages: contain toxic, critical, or expensive elements, exhibit small magnetocaloric effect at desired magnetic field of 2 Tesla or lower, have low Curie temperature, or poor mechanical properties, such as excessive brittleness for the La(Fe,Si)13materials, which readily suffer from decrepitation or disintegration upon handling and, especially, upon thermal and magnetic cycling during operation of a magnetocaloric heat pump.

SUMMARY OF THE INVENTION

The present invention relates to magnetocaloric materials based on the La—Fe—Si alloy system, such as for example the LaFe13-zSizsystem, where 1.1≤z≤1.9 modified by inclusion of a small but effective amount of at least one of Al, Ga, and In to improve the inherent mechanical stability of the alloy in terms of substantially reducing its brittleness and increasing its handle-ability and mechanical stability during processing and use operations, while preserving similar or providing even higher magnetocaloric effects compared to other known and commercially available La—Fe—Si based magnetocaloric materials. To this end, certain illustrative embodiments include at least one of Al, Ga, and In in an amount of 0.07 atomic % to 3.5 atomic %, individually or collectively.

A further illustrative embodiment of the present invention involves a first-order phase-transition magnetocaloric alloy represented by LaFe13-zSiz-yXywhere 1.1≤z≤1.9, and X is at least one of Al, Ga and/or In present in an amount 0.01≤y≤0.5 (i.e., from 0.07 atomic % to 3.5 atomic %) which is effective to substantially reduce alloy brittleness, enabling the alloy to be handled in one's hand and/or to serve as a working body in a magnetocaloric heat pumping device without decrepitation or disintegration. Another illustrative embodiment of the present invention involves the above first-order phase-transition magnetocaloric alloy that further includes M which is at least one of Co, Mn, Cr, and V substituted for Fe in the modified La—Fe—Si based alloy composition. Still another illustrative of the present invention involves including interstitial hydrogen in the modified La—Fe—Si based alloy composition.

The present invention envisions in certain embodiments magnetocaloric alloys, both as bulk arc-melt/drop-cast, as heat treated, and/or as rapidly solidified (using melt spinning, any method of atomization, splat cooling, or any other rapid solidification technique) having one of the following compositions:a. LaFe13-zSiz-yXy, where X=Al, Ga, In with 1.1≤z≤1.9 and 0.01≤y≤0.5b. La(Fe1-wMw)13-zSiz-yXy, where X=Al, Ga, In, and M=Co, Mn, Cr, V with 0.05≤w≤0.1, and 1.1≤z≤1.9, and 0.01≤y≤0.5c. LaFe13-zSiz-yXyHv, where X=Al, Ga, In with 1.1≤z≤1.9, 0.01≤y≤0.5, 0<v≤2.3d. La(Fe1-wMw)13-zSiz-yXyHv, where X=Al, Ga, In, and M=Co, Mn, Cr, V with 0.05≤w≤0.1, and 1.1≤z≤1.9, and 0.01≤y≤0.5, and 0<v≤2.3
and exhibiting large magnetocaloric effect tunable between about 170K and about 350 K as well as having improved mechanical stability and even some machinability.

The present invention provides a magnetic regenerator prepared from alloy compositions set forth above. The regenerator may be used in any form such as including, but not limited to, packed alloy particles, such as for example packed spheres or irregularly-shaped particles, or stacked parallel alloy plates. The regenerator can comprise 3D-printed spherical alloy particles and/or 3D-printed irregularly shaped alloy particles. The present invention also provides a magnetic refrigerator or heat pump using such regenerators.

Additional details and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein only the illustrative embodiments of the invention are shown and described. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

