JP2009221494A - Magnetic refrigerating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic refrigerating material which is inexpensive, is excellent in magnetic refrigeration performance, and is wide in an operating temperature range. <P>SOLUTION: The magnetic refrigerating material is a material whose temperature changes based on a change in a magnetic field. The related magnetic refrigerating material is composed of a compound expressed by the following general formula (1):(1) La(Fe<SB>1-x-y</SB>Co<SB>y</SB>Si<SB>x</SB>)<SB>13</SB>, where x is 0.05 to 0.16, y is 0.04 to 0.10, and 1-x-y is 0.74 to 0.91. The composition range is a range shown by slash lines of Fog. 1. In the general formula (1), x is preferably 0.06 to 0.12; y is 0.04 to 0.08, and 1-x-y is 0.82 to 0.88. The amount of change of the magnetic entropy of the magnetic refrigerating material (-▵S<SB>M</SB>) is preferably 5 to 11 J/kg K; the relative cooling power (RCP, Relative Cooling Power) indicating the magnetic refrigeration performance is preferably 140 to 180 J/kg. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic refrigeration material suitably used for home appliances such as a freezer and a refrigerator, a gas liquefaction industry, a superconducting element, and the like.

  In recent years, a new magnetic refrigeration system has been proposed in place of the conventional gas refrigeration system that uses chlorofluorocarbon-based gases that cause environmental problems such as global warming and ozone layer destruction as refrigerants. In this magnetic refrigeration system, the magnetic material is a refrigerant (magnetic refrigeration material), and the magnetocaloric effect, that is, the magnetic entropy change that occurs when the magnetic order of the magnetic material is changed by a magnetic field in an isothermal state and the magnetic properties of the magnetic material in an adiabatic state The adiabatic temperature change that occurs when the order is changed by a magnetic field is used. Therefore, according to this magnetic refrigeration method, refrigeration can be performed without using chlorofluorocarbon gas, and there is an advantage that the refrigeration efficiency is higher than that of the conventional gas refrigeration method.

  As a magnetic refrigeration material used in such a magnetic refrigeration system, an efficient material that exhibits a large magnetocaloric effect at a low magnetic field has been searched. As such a magnetic refrigeration material, gadolinium (Gd) or a compound thereof is known. This gadolinium or a compound thereof is excellent in magnetic refrigeration performance, but gadolinium is an expensive element, so that there is a drawback that the cost of the magnetic refrigeration material increases.

Therefore, as the magnetic refrigeration _{materials, La (Fe x Si 1-} x) 13 becomes compound has been proposed (e.g., see Patent Document 1). That is, magnetic refrigeration materials, NaZn ₁₃ type _{La (Fe x Si 1-x} ) 13 in _{H y,} partial substitution of Ce, to absorb H, the composition of the NaZn ₁₃ type _{La 1-z Ce z (Fe} x Si _1-x) is obtained by a 13 _{H y.} According to this magnetic refrigeration material, the magnetocaloric effect can be improved at a temperature of 170 to 340K.
JP 2006-89839 A (pages 2 and 4)

However, in the magnetic refrigeration material described in Patent Document 1, the maximum value of the magnetic entropy change (ΔS _M ) representing the magnetic refrigeration performance is large, but the operation temperature range of the magnetic refrigeration material is narrow, so that handling is difficult. There was a problem. Accordingly, there is a need for a magnetic refrigeration material that is inexpensive and excellent in magnetic refrigeration performance and that has a wide operating temperature range.

  The present invention has been made paying attention to such problems existing in the prior art, and the object thereof is to provide a magnetic refrigeration material that is inexpensive and excellent in magnetic refrigeration performance and has a wide operating temperature range. There is to do.

  In order to achieve the above object, the magnetic refrigeration material according to claim 1 is a magnetic refrigeration material whose temperature changes based on a change in a magnetic field, and from a compound represented by the following general formula (1): It is characterized by becoming.

La (Fe _1-xy Co _y Si _x ) ₁₃ (1)
Here, x is 0.05 to 0.16 and y is 0.04 to 0.10.
The magnetic refrigeration material according to claim 2 is characterized in that, in the invention according to claim 1, 1-xy in the general formula (1) is 0.82 to 0.90.

  The magnetic refrigeration material according to claim 3 is the invention according to claim 1 or claim 2, wherein x in the general formula (1) is 0.06 to 0.12, y is 0.04 to 0.08, and 1 -Xy is 0.82 to 0.88.

The magnetic refrigeration material according to claim 4 is characterized in that, in the invention according to any one of claims 1 to 3, the amount of change in magnetic entropy is 5 to 11 J / kg · K.
The magnetic refrigeration material according to claim 5 is the invention according to any one of claims 1 to 4, wherein a relative cooling power (RCP, Relative Cooling Power) indicating magnetic refrigeration performance is 140 to 180 J / kg. It is characterized by.

According to the present invention, the following effects can be exhibited.
The magnetic refrigeration material of Claim 1 consists of a compound represented by the said General formula (1). The compound represented by the general formula (1) is inferior to conventional gadolinium in terms of the maximum value of the magnetic entropy change amount indicating the magnetic refrigeration performance and the relative cooling power. Further, the compound represented by the general formula (1) according the maximum value of the conventional _{La (Fe x Si 1-x} ) of the magnetic entropy compared to ₁₃ comprising a compound change amount slightly decreases, but the operating temperature range Expanding. In addition, the compound represented by the general formula (1) can be obtained at a lower cost than conventional gadolinium and its compounds. Therefore, it is possible to provide a magnetic refrigeration material that is inexpensive and excellent in magnetic refrigeration performance and has a wide operating temperature range.

In the magnetic refrigeration material according to claim 2, 1-xy in the general formula (1) is 0.82 to 0.90. For this reason, the effect of the invention according to claim 1 can be further improved.
In the magnetic refrigeration material according to claim 3, x in the general formula (1) is 0.06 to 0.12, y is 0.04 to 0.08, and 1-xy is 0.82 to 0.88. It is. Therefore, in addition to the effect of the invention according to claim 1 or 2, the magnetic refrigeration performance can be enhanced most, and the magnetic refrigeration effect can be exhibited most efficiently.

  In the magnetic refrigeration material according to claim 4, the amount of change in magnetic entropy is 5 to 11 J / kg · k. For this reason, in addition to the effect of the invention according to any one of claims 1 to 3, the amount of change in magnetic entropy can be increased as compared with conventional gadolinium.

  In the magnetic refrigeration material according to claim 5, the relative cooling power (RCP) indicating the magnetic refrigeration performance is 140 to 180 J / kg. Therefore, in addition to the effect of the invention according to any one of claims 1 to 4, RCP can be sufficiently increased as compared with conventional gadolinium, and magnetic refrigeration performance can be improved.

In the following, embodiments that are considered to be the best of the present invention will be described in detail.
The magnetic refrigeration material (magnetic working substance) of this embodiment is a magnetic refrigeration material whose temperature changes based on a change in magnetic field. That is, the temperature of the magnetic refrigeration material is increased by increasing the magnetization, and the temperature is decreased by demagnetizing. The magnetic refrigeration material is composed of a compound (intermetallic compound) of lanthanum (La), iron (Fe), cobalt (Co) and silicon (Si) represented by the following general formula (1).

La (Fe _1-xy Co _y Si _x ) ₁₃ (1)
However, x is 0.05-0.16 and y is 0.04-0.10.
In this case, 1-xy is 0.74 to 0.91.

  FIG. 1 shows a ternary phase diagram of iron (Fe), cobalt (Co), and silicon (Si), and the composition of the compound represented by the general formula (1) is in a range indicated by oblique lines. By setting the composition of the magnetic refrigeration material within this range, the magnetic refrigeration performance (magnetocaloric effect) of the magnetic refrigeration material can be enhanced and the operating temperature range can be expanded. If the composition of any of iron, cobalt, and silicon constituting the magnetic refrigeration material is out of the above range, the magnetic refrigeration performance of the magnetic refrigeration material is reduced or the operating temperature range is narrowed.

  1-xy in the general formula (1) is preferably 0.82 to 0.90. In that case, the magnetic refrigeration performance can be further enhanced and the operating temperature range can be further expanded. Furthermore, x in the general formula (1) is most preferably 0.06 to 0.12, y is 0.04 to 0.08, and 1-xy is 0.82 to 0.88. In this case, the magnetic refrigeration performance can be enhanced most, and the magnetic refrigeration effect can be exhibited most efficiently. In general formula (1), x can be set to 0.06 to 0.11, y can be set to 0.05 to 0.08, and 1-xy can be set to 0.81 to 0.89. Also in this case, the most excellent effect similar to the above can be exhibited.

The compound represented by the general formula (1) is a material that exhibits a metamagnetic transition from a paramagnetic state to ferromagnetism, and whose physical properties such as magnetization and specific heat change greatly. For this reason, the maximum value (−ΔSmax) and the relative cooling power (RCP) of the magnetic entropy change amount (−ΔS _M ) indicating the magnetic refrigeration performance are equal to or higher than those of conventional gadolinium.

Here, ΔS _M indicating the amount of change in magnetic entropy (−ΔS _M ) can be obtained from the magnetization temperature curve using the following relational expression (2) of Maxell.

但し、Ｍは磁化（磁界の強さ）、Ｔは温度、Ｈは印加磁場を表す。

However, M represents magnetization (magnetic field strength), T represents temperature, and H represents applied magnetic field.

Further, the relative cooling power (RCP) is defined by the following equation (3).
RCP = −ΔSmax × δT (3)
However, -DerutaSmax represents the maximum value of -ΔS _M, δT denotes a half-value width of the peak of -ΔS _M.

Further, the compound represented by the general formula (1), the maximum value of the variation of the magnetic entropy slightly decreases as compared with conventional _{La (Fe x Si 1-x} ) 13 comprising a compound, but the operating temperature range Shows the expanding nature. In addition, the compound represented by the general formula (1) can be obtained at a lower cost than conventional gadolinium and its compounds. Therefore, the magnetic refrigeration material is inexpensive and excellent in magnetic refrigeration performance, and the operating temperature range can be expanded.

The amount of change in magnetic entropy indicating magnetic refrigeration performance −ΔS _M (J / kg · K) is preferably 5 to 11 J / kg · K in order to increase the amount of change over conventional gadolinium, More preferably, it is 11 J / kg · K. When the amount of change in magnetic entropy is lower than 5 J / kg · K, the magnetic refrigeration performance is insufficient and the efficiency of magnetic refrigeration decreases. On the other hand, if it is higher than 11 J / kg · K, the operating temperature range becomes narrow and the handling property tends to deteriorate, which is not preferable.

The temperature (Curie temperature) showing the maximum value of the magnetic entropy variation −ΔS _M (J / kg · K) is preferably 273 K (0 ° C.) to 308 K (35 ° C.). If the temperature showing the maximum value of the change in magnetic entropy is near room temperature, the magnetic refrigeration material can be easily operated near room temperature.

  Further, the relative cooling power (RCP) showing the magnetic refrigeration performance can be sufficiently increased as compared with the conventional gadolinium, and in order to improve the magnetic refrigeration performance, it is preferably 140 to 180 J / kg, 150 to More preferably, it is 180 J / kg. When RCP is less than 150 J / kg, the cooling capacity by the magnetic refrigeration material is insufficient, which is not preferable. On the other hand, when it exceeds 180 J / kg, the amount of change in magnetic entropy becomes too high, or the operating temperature is not preferable because it is out of the normal temperature.

Next, the structure of the magnetic refrigeration apparatus using the magnetic refrigeration material will be described.
FIG. 3 is a diagram schematically showing the magnetic refrigeration apparatus 10. As shown in FIG. 3, a pair of pairs of the magnetic refrigeration apparatus 10 are arranged at positions facing each other at 180 degrees inside the cylindrical stator 11. Magnetic working bodies 12a and 12b are arranged. A permanent magnet 13 as a rotor is disposed inward of the magnetic working bodies 12a and 12b, and a magnetic field is generated in the magnetic working bodies 12a and 12b by the rotation of the permanent magnet 13.

  Magnetic refrigeration materials 14a and 14b are accommodated in the magnetic working bodies 12a and 12b. The magnetic working bodies 12a and 12a are respectively connected with low-temperature pipes 15a and 15a led out of the stator 11 and high-temperature pipes 16a and 16a to form a water circulation path as a cooling medium. Here, the low temperature pipes 15a, 15a and the high temperature pipes 16a, 16a are connected between the pair of magnetic working bodies 12a, 12a, and the low temperature pipes 15b, 15b and the high temperature are connected between the other pair of magnetic work bodies 12b, 12b. The pipes 16b and 16b are connected to each other.

  On the other hand, between the adjacent magnetic working bodies 12a and 12b, the low-temperature pipes 15a and 15b are connected to each other via a cooling device 18 for cooling the object 17 to be cooled. Further, the high-temperature pipes 16 a and 16 b of the other pair of adjacent magnetic working bodies 12 a and 12 b are connected to the circulation device (pump) 20 and the exhaust heat exchanger 21 via the rotary valve 19. In the rotary valve 19, the cooling water supplied from the circulation device 20 is alternately supplied to the high temperature pipes 16a and 16b.

Operation | movement of the magnetic refrigeration apparatus 10 comprised in this way is demonstrated.
When the permanent magnet 13 is at the positions of 0 ° and 180 °, the magnetic refrigeration materials 14a, 14a of the magnetic working bodies 12a, 12a at the opposing positions are magnetized and the temperature rises. On the other hand, the magnetic refrigeration materials 14b and 14b of the magnetic working bodies 12b and 12b at 90 ° and 270 ° positions that are 90 ° out of phase with each other are demagnetized to lower the temperature.

  At this time, as shown by the solid line arrow in FIG. 3, the cooling water is passed through the rotary valve 19, the high temperature pipe 16 b of the magnetic working body 12 b at a position 90 ° from the circulation device 20, the magnetic working body 12 b at that position, the low temperature The pipe 15b is circulated to the high temperature pipe 16b of the magnetic working body 12b at the 270 ° position, the magnetic working body 12b at that position, the low temperature pipe 15b, and the cooling device 18. At this time, the object to be cooled 17 is cooled in the cooling device 18 by the cooling water cooled by the magnetic refrigeration material 14b whose temperature has decreased.

  Further, the low temperature pipe 15a of the magnetic working body 12a at the 180 ° position, the magnetic working body 12a at the position, the high temperature pipe 16a, the low temperature piping 15a of the magnetic working body 12a at the 0 ° position, the magnetic working body 12a at the position, The high-temperature pipe 16a, the rotary valve 19, the exhaust heat exchanger 21 and the circulation device 20 are circulated. At this time, the cooling water from the cooling device 18 cools the magnetic refrigeration material 14 a whose temperature has been increased and the temperature has risen, and returns to the exhaust heat exchanger 21 to release the heat of work.

  Subsequently, when the permanent magnet 13 is rotated by 90 °, the magnetic refrigeration material 14a of the magnetic working body 12a at the positions of 0 ° and 180 ° is demagnetized to lower the temperature, and at the positions of 90 ° and 270 °. The magnetic refrigeration material 14b of a certain magnetic working body 12b is magnetized and its temperature rises. At this time, since the valve body of the rotary valve 19 is also rotated by 90 °, the cooling water is circulated from the magnetic refrigeration material 14a of the magnetic working body 12a at the 0 ° position, as shown by the broken arrow in FIG. I will let you.

  By repeating the rotation of the permanent magnet 13, the temperature on the low temperature pipe 15b connection side of each magnetic working body 12b is lowered to a temperature at which the refrigerating capacity and the thermal load are balanced. On the other hand, the temperature on the high temperature pipe 15a connection side of each magnetic working body 12a reaches a substantially constant temperature due to the balance between the exhaust heat capacity and the refrigeration capacity of the exhaust heat exchanger 21.

The effects exhibited by the embodiment described in detail above will be collectively described below.
-Magnetic refrigeration material 14a, 14b in this embodiment is comprised from the compound represented by the said General formula (1). The compound represented by the general formula (1) has the maximum value of the magnetic entropy change amount (−ΔS _M ) indicating the magnetic refrigeration performance and the relative cooling power (RCP) equal to or higher than that of the conventional gadolinium (Gd). Show. Further, the compound represented by the general formula (1) according the maximum value of the conventional _{La (Fe x Si 1-x} ) of the magnetic entropy compared to ₁₃ comprising a compound change amount slightly decreases, but the operating temperature range Expanding. In addition, the compound represented by the general formula (1) can be obtained at a lower cost than conventional gadolinium. Therefore, it is possible to provide a magnetic refrigeration material that is inexpensive and excellent in magnetic refrigeration performance and has a wide operating temperature range. Therefore, by using this magnetic refrigeration material, it is possible to realize a magnetic refrigeration system refrigeration air conditioning system that is highly efficient, energy-saving, and friendly to the global environment.

-By said 1-xy in the said General formula (1) being 0.82-0.90, said effect can be improved further.
-In the general formula (1), x is 0.06-0.12, y is 0.04-0.08, and 1-xy is 0.82-0.88. The magnetic refrigeration effect can be exhibited most efficiently.

-The amount of change in magnetic entropy is 5 to 11 J / kg · k, so that the amount of change in magnetic entropy can be higher than that of conventional gadolinium.
-By the relative cooling power (RCP) which shows magnetic refrigerating performance being 140-180 J / kg, RCP can fully be raised compared with the conventional gadolinium, and magnetic refrigerating performance can be improved.

Hereinafter, although the embodiment will be described more specifically with reference to examples, the present invention is not limited to the scope of these examples.
Example 1
In Example 1, La (Fe _0.86 Co _0.06 Si _0.08 ) ₁₃ which is a compound of lanthanum (La), iron (Fe), cobalt (Co) and silicon (Si) is used as the magnetic refrigeration material. It was. Here, x = 0.08, y = 0.06, and 1-xy = 0.86. The composition of the magnetic refrigeration material is shown in FIG. 1 representing a ternary phase diagram. This magnetic refrigeration material was manufactured by arc melting lanthanum (La), iron (Fe), cobalt (Co), and silicon (Si), followed by annealing at 1050 ° C. for 2 weeks. With respect to La (Fe _0.86 Co _0.06 Si _0.08 ) ₁₃ which is the obtained magnetic refrigeration material, the amount of change in magnetic entropy with respect to temperature T (K) −ΔS _M (J / kg · K) was measured. The results are shown in FIG. For conventional gadolinium (Gd), the amount of change in magnetic entropy −ΔS _M (J / kg · K) was also measured and is shown in FIG.

As shown in FIG. 2, the magnetic refrigeration material of Example 1 showed a maximum value of about 277 K (about 4 ° C.) and a magnetic entropy change amount of 9.9 (J / kg · K). This maximum value was sufficiently larger than the maximum value of gadolinium (Gd) of about 4.7 (J / kg · K). The relative cooling power (RCP) was 167 (J / kg), which was equivalent to that of conventional gadolinium (Gd).
(Example 2)
In Example 2, La (Fe _0.86 Co _0.07 Si _0.07 ) ₁₃ which is a compound of lanthanum (La), iron (Fe), cobalt (Co) and silicon (Si) is used as the magnetic refrigeration material. It was. Here, x = 0.07, y = 0.07, and 1-xy = 0.86. The composition of the magnetic refrigeration material is shown in FIG. 1 representing a ternary phase diagram. This magnetic refrigeration material was produced in the same manner as in Example 1 except that the composition was slightly changed. With respect to La (Fe _0.86 Co _0.07 Si _0.07 ) ₁₃ which is the obtained magnetic refrigeration material, the amount of change in magnetic entropy with respect to temperature T (K) −ΔS _M (J / kg · K) was measured. The results are shown in FIG.

As shown in FIG. 2, the magnetic refrigeration material of Example 2 showed a maximum value of about 288 K (about 15 ° C.) and a magnetic entropy change amount of 6.9 (J / kg · K). This maximum value was sufficiently larger than the maximum value of gadolinium (Gd) of about 4.7 (J / kg · K). The relative cooling power (RCP) was 151 (J / kg), which was equivalent to that of conventional gadolinium (Gd).
(Example 3)
In Example 3, La (Fe _0.84 Co _0.06 Si _0.10 ) ₁₃ which is a compound of lanthanum (La), iron (Fe), cobalt (Co) and silicon (Si) is used as the magnetic refrigeration material. It was. Here, x = 0.10, y = 0.06, and 1-xy = 0.84. The composition of the magnetic refrigeration material is shown in FIG. 1 representing a ternary phase diagram. This magnetic refrigeration material was produced in the same manner as in Example 1 except that the composition was slightly changed. With respect to La (Fe _0.84 Co _0.06 Si _0.10 ) ₁₃ which is the obtained magnetic refrigeration material, the amount of change in magnetic entropy with respect to temperature T (K) −ΔS _M (J / kg · K) was measured. The results are shown in FIG.

  As shown in FIG. 2, the magnetic refrigeration material of Example 3 showed a maximum value of about 6.8 (J / kg · K) at about 304 K (about 31 ° C.). This maximum value was sufficiently larger than the maximum value of gadolinium (Gd) of about 4.7 (J / kg · K). The relative cooling power (RCP) was 166 (J / kg), which was equivalent to that of conventional gadolinium (Gd).

It should be noted that the embodiment described above can be modified and embodied as follows.
Regarding the composition of the magnetic refrigeration material, one of the compositions of iron (Fe), cobalt (Co), and silicon (Si) is specifically set as appropriate within the range indicated by the oblique lines in the ternary phase diagram shown in FIG. be able to.

  ・ The composition of the magnetic refrigeration material can be set with emphasis on any component of iron (Fe), cobalt (Co), and silicon (Si) according to requirements such as magnetic refrigeration performance, operating temperature range, and cost. it can.

・ With regard to the composition of the magnetic refrigeration material, any component of iron (Fe), cobalt (Co), and silicon (Si) is required according to the requirements such as magnetic entropy change (−ΔS _M ) and relative cooling power (RCP). Can be set with emphasis.

Next, the technical idea that can be grasped from the embodiment will be described below.
The x in the general formula (1) is 0.06 to 0.11, y is 0.05 to 0.08, and 1-xy is 0.81 to 0.89. Item 4. The magnetic refrigeration material according to Item 3. When comprised in this way, in addition to the effect of the invention which concerns on Claim 3, magnetic refrigeration performance can be improved most and the magnetic refrigeration effect can be exhibited most efficiently.

  The magnetic refrigeration material according to claim 4, wherein a temperature indicating a maximum value of the amount of change in the magnetic entropy is 0 to 35 ° C. When constituted in this way, in addition to the effect of the invention according to claim 4, the operation of the magnetic refrigeration material can be easily performed in the vicinity of normal temperature.

The ternary phase diagram about three components of iron (Fe), cobalt (Co), and silicon (Si). Graph showing the relationship between temperature (T) and magnetic entropy change and (-ΔS _M). Explanatory drawing which shows typically the magnetic refrigeration apparatus in embodiment.

Explanation of symbols

14a, 14b ... magnetic refrigeration materials, T ... temperature, -ΔS M _... magnetic entropy change.

Claims (5)

A magnetic refrigeration material whose temperature changes based on a change in a magnetic field,
A magnetic refrigeration material comprising a compound represented by the following general formula (1):
La (Fe _1-xy Co _y Si _x ) ₁₃ (1)
Here, x is 0.05 to 0.16 and y is 0.04 to 0.10. The magnetic refrigeration material according to claim 1, wherein 1-xy in the general formula (1) is 0.82 to 0.90. The x in the general formula (1) is 0.06 to 0.12, y is 0.04 to 0.08, and 1-xy is 0.82 to 0.88. The magnetic refrigeration material according to claim 1 or 2. 4. The magnetic refrigeration material according to claim 1, wherein the amount of change in magnetic entropy is 5 to 11 J / kg · K. 5. The magnetic refrigeration material according to any one of claims 1 to 4, wherein a relative cooling power (RCP, Relative Cooling Power) indicating magnetic refrigeration performance is 140 to 180 J / kg.

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