Fe—Si—La alloy having excellent magneto-caloric properties

1. An Fe—Si—La alloy comprising:

(La 1-a-a′ M m a TR a′ ) 1 [(Fe 1-b-b′ CO b M b′ ) 1-x (Si 1-c X c ) x ] 13 (C d N e H 1-d-e ) y (R) z (I) f ,

wherein Mm represents a mixture of lanthanum, cerium, neodymium and praseodynium in the weight proportion of 22 to 26% La, 48 to 53% Ce, 17 to 20% Nd, and 5 to 7% Pr, said mixture comprising up to 1% by weight of impurities;

TR represents at least one rare earth family element other than lanthanum;

M represents at least one type d transition element of the 3d, 4d, or 5d layers;

X represents a metalloid element selected from the group consisting of Ge, Al, B, Ga, and In;

R represents at least one element selected from the group consisting of Ca, Mg, K, and Na; and

I represents one or two elements selected from the group consisting of O and S;

0≦ a< 0.5 and 0≦ a′< 0.2;

0≦ b≦ 0.2 and 0≦ b′< 0.4;

0≦ c≦ 0.5 and 0≦ d≦ 1;

0≦ e≦ 1 and f≦ 0.1;

0.09≦ x≦ 0.13 and 0.002≦ y≦ 4;

0.0001≦ z≦ 0.01; and

subscripts b, d, e, x and y are such that:

6.143 b (13(1− x ))+4.437 y[ 1−0.0614( d+e )]≧1, and

d×y≧ 0.005.

2. The Fe—Si—La alloy according to claim 1 , wherein M represents at least one element selected from the group consisting of nickel, manganese, and chromium.

3. The Fe—Si—La alloy according to claim 1 , wherein R represents calcium.

4. The Fe—Si—La alloy according to claim 1 , wherein a=0, a′=0, b=0, b′=0, and c=0.

5. The Fe—Si—La alloy according to claim 1 , wherein TR represents cerium and/or yttrium.

6. The Fe—Si—La alloy according to claim 1 , wherein d<0.01.

7. The Fe—Si—La alloy according to claim 1 , wherein d≧0.7.

8. A powder of the Fe—Si—La alloy according to claim 1 , having an average grain size smaller than 1000 μm.

9. The powder of the Fe—Si—La alloy according to claim 8 , wherein the average grain size is smaller than 500 μm.

10. A method for fabricating a powder of the alloy according to claim 1 , comprising:

preparing a precursor of the alloy comprising:

(La 1-a-a′ M m a TR a′ ) 1 [(Fe 1-b-b′ CO b M b′ ) 1-x (Si 1-c X c ) x ] 13 (C d N e H 1-d-e ) y (R) z (I) f ,

wherein Mm represents a mixture of lanthanum, cerium, neodymium, and praseodynium in the weight proportion of 22 to 26% La, 48 to 53% Ce, 17 to 20% Nd, and 5 to 7% Pr, said mixture comprising up to 1% by weight of impurities;

TR represents at least one rare earth family element other than lanthanum;

M represents at least one type d transition element of the 3d, 4d, or 5d layers;

X represents a metalloid element selected from the group consisting of Ge, Al, B, Ga, and In;

R represents at least one element selected from the group consisting of Ca, Mg, K, and Na;

I represents one or two elements selected from the group consisting of O and S;

0≦ a< 0.5 and 0≦ a′< 0.2;

0≦ b≦ 0.2 and 0≦ b′< 0.4;

0≦ c≦ 0.05 and 0≦ d≦ 0.99;

0≦ e≦ 1 and f≦ 0.1;

0.09≦ x≦ 0.13 and 0.002≦ y≦ 0.7;

0.0001≦ z≦ 0.01; and

subscripts b, d, e, x and y are such that the alloy further satisfies:

6.143 b (13(1− x ))+4.437 y[ 1−0.0614( d+e )]≧1;

d×y≧ 0.005;

casting the precursor and solidifying the precursor in ingot form;

optionally, carrying out an electroslag remelting or vacuum remelting;

comminuting the ingot into a powder of particles,

carrying out a homogenizing heat treatment with air or under blanket gas on the alloy either just before, or just after the comminuting, and

carrying out a diffusion treatment on the powder with at least one element selected from the group consisting of carbon, hydrogen, and nitrogen, to obtain an alloy powder having a composition according to claim 1 .

11. The method for fabricating an alloy powder according to claim 10 , comprising:

casting and solidifying the precursor in ingot form, further comprising at least one of the group consisting of:

maintaining the freshly solidified ingot at a temperature above 1300° C. but lower than the melting point, for less than 24 hours;

carrying out an electromagnetic agitation during the ingot casting and during the solidification; and

heating the ingot after its first solidification to a temperature above 1300° C. so that it returns at least partially to liquid state, and then solidifying it again;

comminuting the ingot into a powder of particles; and

carrying out a diffusion treatment on the powder with at least one element selected from the group consisting of carbon, hydrogen, and nitrogen, to obtain an alloy powder having a final target composition.

12. The method for fabricating an alloy powder according to claim 10 , comprising:

comminuting the ingot into a powder of particles having a size smaller than 10 mm;

carrying out a fine comminution and homogenizing treatment in hydrogen at a temperature lower than 300° C. to obtain a powder of particles having a size smaller than 1000 μm;

carrying out a diffusion treatment on the powder at a temperature lower than 400° C., with at least one element selected from the group consisting of carbon, hydrogen, and nitrogen, to obtain an alloy powder having a final target composition.

13. The method for fabricating a powder of an alloy according to claim 1 , comprising:

preparing a precursor of the alloy comprising:

(La 1-a-a′ M m a TR a′ ) 1 [(Fe 1-b-b′ CO b M b′ ) 1-x (Si 1-c X c ) x ] 13 (C d N e H 1-d-e ) y (R) z (I) f ,

wherein Mm represents a mixture of lanthanum, cerium, neodymium, and praseodynium, in the weight proportion of 22 to 26% La, 48 to 53% Ce, 17 to 20% Nd, and 5 to 7% Pr, said mixture comprising up to 1% by weight of impurities,

TR represents at least one rare earth family element other than lanthanum;

M represents at least one type d transition element of the 3d, 4d, or 5d layers;

X represents a metalloid element selected from the group consisting of Ge, Al, B, Ga, and In;

R represents at least one element selected from the group consisting of Ca, Mg, K, and Na;

I represents one or two elements selected from the group consisting of O and S;

0≦ a< 5 and 0≦ a′< 0.2;

0≦ b≦ 0.2 and 0≦ b′< 0.4;

0≦ c≦ 0.05 and 0≦ d≦ 0.99;

0≦ e≦ 1 and f≦ 0.1;

0.09≦ x≦ 0.13 and 0.002≦ y≦ 0.7;

0.0001≦ z≦ 0.01;

subscripts b, d, e, x and y are such that the alloy further satisfies:

6.143 b (13(1− x ))+4.437 y[ 1−0.0614( d+e )]≧1;

d×y≧ 0.005;

atomizing the precursor in molten form, without prior solidification, to obtain a powder of particles; and

carrying out a diffusion treatment on the powder with at least one element selected from the group consisting of carbon, hydrogen, and nitrogen, to obtain an alloy powder having a final target composition.

14. The method for fabricating an alloy according to claim 1 , comprising:

preparing a precursor of the alloy comprising:

(La 1-a-a′ M m a TR a′ ) 1 [(Fe 1-b-b′ CO b M b′ ) 1-x (Si 1-c X c ) x ] 13 (C d N e H 1-d-e ) y (R) z (I) f ,

wherein Mm represents a mixture of lanthanum, cerium, neodymium, and praseodynium, in the weight proportion of 22 to 26% La, 48 to 53% Ce, 17 to 20% Nd, and 5 to 7% Pr, said mixture comprising up to 1% by weight of impurities;

TR represents at least one rare earth family element other than lanthanum;

M represents at least one type d transition element of the 3d, 4d, or 5d layers;

X represents a metalloid element selected from the group consisting of Ge, Al, B, Ga, and In;

R represents at least one element selected from the group consisting of Ca, Mg, K, and Na;

I represents one or two elements selected from the group consisting of O and S;

0≦ a< 0.5 and 0≦ a′< 0.2;

0≦ b≦ 0.2 and 0≦ b′< 0.4;

0≦ c≦ 0.05 and 0≦ d≦ 0.99;

0≦ e≦ 1 and f≦ 0.1;

0.09≦ x≦ 0.13 and 0.002≦ y≦ 0.7;

0.0001≦ z≦ 0.01;

subscripts b, d, e, x and y are such that the alloy further satisfies:

6.143 b (13(1− x ))+4.437 y[ 1−0.0614( d+e )]≧1;

d×y≧ 0.005;

solidifying the precursor in form of a strip, wire, or powder of particles by overhardening; and

carrying out a diffusion treatment on said strip, wire, or powder with at least one element selected from the group consisting of carbon, hydrogen, and nitrogen, to obtain an alloy strip, wire or powder having a final target composition.

15. A powder of Fe—Si—La alloys according to claim 1 , comprising at least two different alloys A 1 and A 2 , selected so that the transition temperatures, Ttr 1 of A 1 , and Ttr 2 of A 2 , and the peak widths at mid-height, ΔT LMH1 of A 1 , and ΔT LMH2 of A 2 , of respective curves of variation in magnetic entropy, ΔS m1 (T) of A 1 , and ΔS m2 (T) of A 2 , are such that respective working zones, Ttr 1 −ΔT LMH1 and Ttr 1 +ΔT LMH1 of A 1 , and, Ttr 2 −ΔT LMH2 and Ttr 2 +ΔT LMH2 of A 2 , overlap.

16. The alloy powder according to claim 15 , in which the at least two different alloys, A 1 and A 2 , are obtained from a same precursor material P subjected to at least two different diffusion treatments of at least one element selected from the group consisting of carbon, hydrogen, and nitrogen.

17. The method as defined in claim 10 , wherein the precursor comprises:

(La 1-a-a′ M m a TR a′ ) 1 [(Fe 1-b-b′ CO b M b′ ) 1-x (Si 1-c X c ) x ] 13 (C d N e H 1-d-e ) y (R) z (I) f ,

wherein Mm represents a mixture of lanthanum, cerium, neodymium, and praseodynium, in the weight proportion of 22 to 26% La, 48 to 53% Ce, 17 to 20% Nd, and 5 to 7% Pr, said mixture comprising up to 1% by weight of impurities;

TR represents at least one rare earth family element other than lanthanum;

M represents at least one type d transition element of the 3d, 4d, or 5d layers;

X represents a metalloid element selected from the group consisting of Ge, Al, B, Ga, and In;

R represents at least one element selected from the group consisting of Ca, Mg, K, and Na;

I represents one or two elements selected from the group consisting of O and S;

0≦ a< 0.5 and 0≦ a′< 0.2;

0≦ b≦ 0.2 and 0≦ b′< 0.4;

0≦ c≦ 0.05 and 0≦ d≦ 0.99;

0≦ e≦ 1 and f≦ 0.1;

0.09≦ x≦ 0.13 and 0.002≦ y≦ 0.7;

0.0001≦ z≦ 0.01; and

subscripts b, d, e, x and y are such that the alloy further satisfies:

6.143 b (13(1− x ))+4.437 y[ 1−0.0614( d+e )]≧1; and

d×y≧ 0.005.

18. A method of manufacturing refrigerating equipment, comprising fabricating at least one part of the refrigerating equipment from the alloy according to claim 1 .

19. A method of manufacturing a heat pump, comprising fabricating at least one part of the heat pump from the alloy according to claim 1 .

20. A method of manufacturing refrigerating equipment or a heat pump, comprising fabricating at least one part of the refrigerating equipment or the heat pump from the powder according to claim 8 .

21. The Fe—Si—La alloy of claim 1 , wherein X represents a metalloid element selected from the group consisting of Ge, B, Ga, and In.

22. The Fe—Si—La alloy of claim 1 , comprising an effective amount of the at least one element selected from the group consisting of Al, Ca, Mg, K, and Na to hinder oxidation of the rare earth elements during electric arc melting or induction melting of the alloy.