JP2007154233A - Low-temperature operation type magnetic refrigeration working substance, and magnetic refrigeration method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-temperature operation type magnetic refrigeration working substance which shows excellent cooling capacity in a low-temperature range of 70 K or lower in particular and can be applied to hydrogen liquefaction, and to provide a magnetic cooling method. <P>SOLUTION: The low-temperature operation type magnetic refrigeration working substance can be obtained by employing NaZn<SB>13</SB>type La(Fe<SB>x</SB>Si<SB>1-x</SB>)<SB>13</SB>which is a magnetic refrigeration working substance, and replacing a part of the composition with Ce and Mn into La<SB>1-z</SB>Ce<SB>z</SB>(Fe<SB>x</SB>Mn<SB>y</SB>Si<SB>1-x-y</SB>)<SB>13</SB>. The magnetic refrigeration method includes cooling a gas by using one of the magnetic refrigeration working substance NaZn<SB>13</SB>type La<SB>1-z</SB>Ce<SB>z</SB>(Fe<SB>x</SB>Mn<SB>y</SB>Si<SB>1-x-y</SB>)<SB>13</SB>, or a plurality of substances having a composition modified from the above working substance. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a low temperature operation type magnetic refrigeration working substance NaZn ₁₃ type _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13 and a magnetic refrigeration method of operating at temperatures below 70K.

  As one of means for storing and transporting a large amount of hydrogen expected as a next-generation clean energy source, a method of cooling and liquefying hydrogen gas to about 20K, which is the boiling point, has been proposed. In order to realize this, there is a strong demand for reducing the cost required for liquefaction. Under such circumstances, magnetic refrigeration has attracted attention as a new liquefaction refrigeration technology for hydrogen gas that replaces gas refrigeration. In magnetic refrigeration, a magnetic substance is used as a refrigerant (refrigeration work substance), and its magnetocaloric effect, that is, the isothermal magnetic entropy change that occurs when the magnetic order of the magnetic substance is changed in the isothermal state, and the magnetic field is changed in the adiabatic state. The adiabatic temperature change that occurs in the event is used. In magnetic refrigeration using a solid refrigerant, the compression loss of conventional gas refrigeration is reduced, and since there is no vibration of the compressor, a decrease in refrigeration efficiency due to a decrease in cooling temperature can be suppressed. For this reason, the stable and high refrigeration efficiency of magnetic refrigeration is optimal for refrigeration technology for hydrogen storage. Further, the hydrogen gas evaporated in the cryogenic liquid hydrogen storage container can be liquefied on the spot safely and easily. In order to realize hydrogen liquefaction by magnetic refrigeration, it is desired to develop a highly efficient low-temperature operation type magnetic refrigeration working material that exhibits a large magnetocaloric effect at a low magnetic field in the vicinity of 20K.

La (Fe _x Si _1-x ) ₁₃ having a cubic NaZn ₁₃ type structure has an itinerant electron metamagnetic transition (paramagnetic to ferromagnetism primary phase transition by applying a magnetic field) just above the Curie temperature of about 180K. Show. Since the magnetization changes greatly with the transition, a giant magnetocaloric effect occurs. (For example, see Patent Document 1) In addition, by absorbing hydrogen into La (Fe _x Si _1-x ) ₁₃ , the Curie temperature rises from about 180 K to about 340 K, and after absorption of hydrogen, the metamagnetism is just above the Curie temperature. Metastasis occurs. Therefore, by controlling the hydrogen concentration of hydrogen _- absorbing La (Fe _x Si _1-x ) ₁₃ H _y , a giant magnetocaloric effect due to the metamagnetic transition can be obtained in an arbitrary temperature range of about 180 K to 340 K. (For example, see Patent Document 2)

Recently, the Curie temperature has decreased due to the Ce partial substitution of La in La (Fe _x Si _1-x ) ₁₃ (see, for example, Non-Patent Document 1) and the Mn partial substitution of Fe (see, for example, Non-Patent Document 2). It became clear to do. Furthermore, the composition of _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13 that Ce and Mn partially substituted, 0.86 ≦ x ≦ 0.88,0.0 ≦ y ≦ 0.03 and 0 By controlling between 0.0 ≦ z ≦ 0.35, the Curie temperature can be controlled in any temperature range from 70K to 180K. Even after partial substitution of Ce and Mn, the metamagnetic transition occurs just above the Curie temperature, so that a giant magnetocaloric effect due to the metamagnetic transition is obtained in an arbitrary temperature range of 70K to 180K. (For example, see Non-Patent Document 3)

However, this up, _{La (Fe x Si 1-x} ) 13 based reduction control of the Curie temperature 70K to the following compounds, and _{La (Fe x Si 1-x} ) 13 compounds giant magneto below 70K using No low temperature operation type magnetic refrigeration work material which shows a caloric effect has been developed. Therefore, La (Fe _x Si _1-x ) ₁₃ -based compounds cannot cope with magnetic refrigeration technology that requires low-temperature operation such as hydrogen liquefaction around 20K.

JP 2002-356748 A JP 2003-96547 A S. Fujieda, et.al., Materials Transactions, Vol. 45, No. 11 (2004) pp. 3228-3231. F. Wang, et.al., Journal of Physics D: Applied Physics, Vol. 36, No. 1 (2003) pp. 1-3. Toshie Fujieda et al., 135th Annual Meeting of the Japan Institute of Metals (2004) pp. 416.

As described above, NaZn ₁₃ type La (Fe _x Si _1-x ) ₁₃ exhibits a giant magnetocaloric effect just above the Curie temperature of about 180 K, and the Curie temperature is lowered to about 70 K by Ce and Mn partial substitution. The invention, of the Curie temperature of _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13 that Ce and Mn partially substituted performs further reduction control, showing the giant magnetocaloric effect in the following temperature range 70K It is an object of the present invention to provide a high-performance low-temperature operation type magnetic refrigeration working material and a refrigeration method using them.

According to the present invention, in the NaZn ₁₃ type _{La (Fe x Si 1-x} ) 13 which is a magnetic refrigerant material, partially replaced by Ce and Mn, La _1-z of the composition Ce _z (Fe _x Mn _y Si _1-xy ) ₁₃ , and the x value is 0.84 to 0.86, the y value is 0.030 to 0.050, and the z value is 0.0 to 0.5. Low temperature operation type magnetic refrigeration working material is obtained.

Furthermore, a plurality of ones the cold operation magnetic refrigerant material NaZn ₁₃ type _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13 for changing one or its composition, the following strong 5 T A magnetic refrigeration method that controls cooling by applying a magnetic field

Further, a wherein using a low temperature operation type magnetic refrigeration working substance NaZn ₁₃ type _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13, to cool control range around 70K from near the temperature 0K A magnetic refrigeration method is obtained.

Further, by using the low temperature operation type magnetic refrigeration working substance NaZn ₁₃ type _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13, the magnetic refrigeration method for cooling control range around 70K from near the temperature 0K , magnetic refrigeration method being characterized in that constitute the composition of NaZn ₁₃ type _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13 as two types are obtained.

In the above configuration, La _0.65 Ce _0.35 (Fe _0.850 Mn _0.030 Si _0.120 ) ₁₃ is formed in the temperature range from about 60 K to 70 K, and La _0.75 Ce _0.25 (Fe _0.850 Mn _{0.035) in} the range from about 0 K to 60 _K. A magnetic refrigeration method characterized by comprising Si _0.115 ) ₁₃ is obtained.

According to the present invention, at any temperature 70K from 0K by controlling the Ce and Mn substitution of the magnetic refrigeration working substance NaZn ₁₃ type _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13, A low-temperature operation type magnetic refrigeration working material having excellent magnetocaloric characteristics is obtained, and a magnetic refrigeration method using them is obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The sample was prepared by the following procedure. First, La _0.65 Ce _0.35 (Fe _0.860 Mn _0.025 Si _0.115 ) ₁₃ , La _0.65 Ce _0.35 (Fe _0.850 Mn _0.030 Si _0.120 ) ₁₃ and La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ , Ce, Fe, Mn, Si raw materials were blended in predetermined amounts. Thereafter, the blended raw material was melted in an arc melting furnace. The cast alloy was taken out and transferred to an electric furnace. La _0.65 Ce _0.35 (Fe _0.860 Mn _0.025 Si _0.115 ) ₁₃ and La _0.65 Ce _0.35 (Fe _0.850 Mn _0.030 Si _0.120 ) ₁₃ were 14 days at 1423 K, La _0.75 Ce _0.25 ( Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ was subjected to homogenization heat treatment at _1373K for 10 days. In homogenization heat treatment, in order to prevent oxidation during heat treatment, a cast alloy sample is put in a quartz tube, evacuated from the open end of the quartz tube, and the quartz tube is evacuated to 5 × 10 ^-5 Torr or less, and then the quartz tube Was sealed by heating. When the sample was rapidly cooled, the NaZn ₁₃ type phase formed by the heat treatment was stably maintained, and precipitation of foreign phases could be prevented. After the heat treatment, the quartz tube enclosing the sample was quickly taken out of the electric furnace and cooled with ice water. In order to prevent oxidation of the sample, the sample was cooled to about room temperature, and then the quartz tube was broken and the sample was taken out.

Figure 1 shows the isothermal magnetic entropy changes of La _0.65 Ce _0.35 (Fe _0.860 Mn _0.025 Si _0.115 ) ₁₃ , La _0.65 Ce _0.35 (Fe _0.850 Mn _0.030 Si _0.120 ) ₁₃ and La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) _13. Show. La _0.65 Ce _0.35 (Fe _0.850 Mn _0.030 Si _0.120 ) ₁₃ shows an isothermal magnetic entropy change of −12 J / kg K with a magnetic field change of 0 to 2 T in the vicinity of about 60K.

La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ exhibits an isothermal magnetic entropy change of −5 J / kg K with a magnetic field change of 0 to 2 T in the vicinity of 20 K which is the boiling point of hydrogen. That is, by controlling the Ce and Mn concentration of _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13, even in a temperature range below 70 K, large isothermal magnetic entropy change is obtained.

  In addition to the maximum value of isothermal magnetic entropy, RCP (Relative Cooling Power) is one of the important magnetocaloric characteristics that strongly affects the refrigeration capacity of a magnetic refrigerator. RCP is defined by the following equation.

Here, ΔS _{m MAX} is the maximum value of the isothermal magnetic entropy change peak, and ΔT is the half-value width of the peak of the magnetic entropy change. From FIG. 1, the _{RCPs of} La _0.65 Ce _0.35 (Fe _0.850 Mn _0.030 Si _0.120 ) ₁₃ and La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ are 442 J / kg and 525 J / kg, which are very large.

_{Accordingly, La 1-z Ce z (} Fe x Mn y Si 1-xy) 13 , by controlling the Ce and Mn concentration, low temperature operation type magnetic illustrating the giant magnetocaloric effect at any temperature range 70K from 0K As a refrigeration material, it can be expected to be applied to magnetic refrigeration technology such as hydrogen liquefaction.

Fig. 2 shows the _{thermomagnetic curves} of La _0.65 Ce _0.35 (Fe _0.860 Mn _0.025 Si _0.115 ) ₁₃ , La _0.65 Ce _0.35 (Fe _0.850 Mn _0.030 Si _0.120 ) ₁₃ and La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ . La _0.65 Ce _0.35 (Fe _0.860 Mn _0.025 Si _0.115 ) ₁₃ and La _0.65 Ce _0.35 (Fe _0.850 Mn _0.030 Si _0.120 ) ₁₃ show a sudden change in magnetization with hysteresis with increasing temperature. That is, La _0.65 Ce _0.35 (Fe _0.860 Mn _0.025 Si _0.115 ) ₁₃ and La _0.65 Ce _0.35 (Fe _0.850 Mn _0.030 Si _0.120 ) ₁₃ exhibit a temperature-induced primary phase transition at Curie temperatures of about 100 K and 60 K. On the other hand, in La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ , no clear transition is observed, and ferromagnetism disappears. This is, by controlling the Ce and Mn concentration of _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13, the Curie temperature is lowered to below 70 K, controlled from 0 in a temperature range of 180K It means you can do it.

FIG. 3 shows the magnetization curve of La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ at 5K. After cooling in a magnetic field (first time), the magnetization curve shows a large hysteresis. In the magnetization process, an s-hour curve having an inflection point at about 3 T is shown. That is, this compound exhibits a metamagnetic transition from paramagnetism to ferromagnetism at about 3 T in the magnetization process after cooling in a magnetic field (first time). On the other hand, the magnetization curve in the demagnetization process showed ferromagnetism and no metamagnetic transition was observed. After that (second time), even when a magnetic field was applied, the magnetization curve showed ferromagnetic behavior and no metamagnetic transition was observed. In other words, La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) _{13 exhibits a metamagnetic} transition in the magnetization process when cooled in a magnetic field in the ground state, but is strong in a magnetic field after transition to a ferromagnetic state. It becomes magnetic and exhibits irreversible metamagnetic transition. _{Accordingly, La 1-z Ce z (} Fe x Mn y Si 1-xy) 13 by controlling the Ce and Mn substitution of, while maintaining the meta-magnetic transition, the Curie temperature is controlled from 0 in a temperature range of 180K I can do it.

FIG. 4 shows a _{thermomagnetic curve} of La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) _{13 after changing} the ground state to a ferromagnetic state by _metamagnetic transition. Magnetization rapidly decreases at about 15K as the temperature rises, and enters a paramagnetic state. Therefore, FIG. 5 shows a magnetization curve of La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ at ₁₅ K or more. Above 15K, metamagnetic transition is observed not only in the magnetization process but also in the demagnetization process. That is, La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ shows a reversible _{metamagnetic transition at 15} K or more.

The isothermal magnetic entropy change ΔS _m is related by the following equation from the relationship between magnetic properties and Maxwell.

Here, M is magnetization, B is an applied magnetic field, and T is temperature. That is, the above equation means that a large isothermal magnetic entropy change can be obtained if the temperature change of magnetization in a constant magnetic field is large. As shown in Fig. 2, La _0.65 Ce _0.35 (Fe _0.850 Mn _0.030 Si _0.120 ) ₁₃ has a large isothermal magnetic entropy around 60K because the magnetization changes greatly with the temperature-induced primary phase transition at the Curie temperature. It is speculated that it showed changes and RCP. In addition, La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ is an irreversible _metamagnetic transition as shown in FIG. 3 in the ground state, but is reversible at 15 K or more as shown in FIG. It is presumed that a large isothermal magnetic entropy change and RCP were exhibited in the vicinity of 20K because a large temperature change of magnetization occurred in a constant magnetic field due to a metamagnetic transition.

Isothermal magnetic entropy change of La _0.65 Ce _0.35 (Fe _0.860 Mn _0.025 Si _0.115 ) ₁₃ , La _0.65 Ce _0.35 (Fe _0.850 Mn _0.030 Si _0.120 ) ₁₃ and La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ . Δ, □ and ○ indicate data from 0 to 2T, and ▲, ■ and ● indicate data from 0 to 5T. _{Thermomagnetic curves of} La _0.65 Ce _0.35 (Fe _0.860 Mn _0.025 Si _0.115 ) ₁₃ , La _0.65 Ce _0.35 (Fe _0.850 Mn _0.030 Si _0.120 ) ₁₃ and La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) _{13 in} a 0.2 T magnetic field . Magnetization curve of La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ at 5K. The _{thermomagnetic} curve in a magnetic field of 0.2 T after La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ is converted into a ferromagnetic state by _metamagnetic transition. La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) ₁₃ magnetization curve above 15K.

Claims (5)

In NaZn ₁₃ type _{La (Fe x Si 1-x} ) 13 which is a magnetic refrigerant material, partially replaced by Ce and Mn, and the composition as _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13 , X value of 0.84 to 0.86, y value of 0.030 to 0.050, and z value of 0.0 to 0.5 material. Multiple ones of said cold operation magnetic refrigerant material NaZn ₁₃ type _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13 for changing one or its composition, a magnetic field of less intensity 5T A magnetic refrigeration method comprising applying cooling to control cooling. Claims wherein using a low temperature operation type magnetic refrigeration working substance NaZn ₁₃ type _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13, wherein the cooling control range around 70K from near the temperature 0K Item 3. The magnetic refrigeration method according to Item 2. Using said low-temperature operation type magnetic refrigeration working substance NaZn ₁₃ type _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13, the magnetic refrigeration method for cooling control range around 70K from near the temperature 0K, NaZn ₁₃ type _{La 1-z Ce z (Fe} x Mn y Si 1-xy) 13 magnetic refrigeration process according to claim 3, wherein a composition that has been configured as two. In the above configuration, La _0.65 Ce _0.35 (Fe _0.850 Mn _0.030 Si _0.120 ) ₁₃ is formed in the temperature range from about 60 K to 70 K, and La _0.75 Ce _0.25 (Fe _0.850 Mn _0.035 Si _0.115 ) is formed in the range from about 0 K to 60 _K. magnetic refrigeration process according to claim 4, characterized by being configured at) _13.

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