JP6926584B2 - Magnetic refrigeration material - Google Patents

Description

The present invention relates to a magnetic refrigeration material.

Refrigerating technology using a gas compression / expansion cycle is widely used in household appliances such as refrigerators and air conditioners. However, it is said that the specific chlorofluorocarbon gas used as the refrigerant used in the compression / expansion cycle has a great influence on the environment. Therefore, an environmentally friendly and clean freezing technology is required.

Magnetic refrigeration technology is known as one of the clean refrigeration technologies. The magnetic refrigeration technology utilizes the magnetic heat quantity effect, and heats and absorbs heat by changing the magnetization in the magnetic substance. When an external magnetic field is applied and the directions of the internal magnetization are aligned, heat is generated, and when the external magnetic field is removed and the directions of the internal magnetization vary, heat is absorbed.

For example, Patent Document 1 describes a La (Fe, Si) _13- based magnetic refrigerated material _{represented by a general formula of La (Fe 1-x} M _x ) _{13 Hz.} Further, Patent Document 2 describes a magnetic refrigerated material represented by _{(Mn 1-x} A _x ) _{3 MN.}

Japanese Patent No. 3967572 JP-A-2009-54776

However, the La (Fe, Si) _13- based magnetic refrigeration material described in Patent Document 1 is excellent in magnetic refrigeration characteristics, but contains La, which is a rare earth. Therefore, it is difficult to secure a stable supply. _{Further, the (Mn 1-x} A _x ) ₃ MN described in Patent Document 2 has a low Curie point of 80K to 120K, and cannot be used for household appliances that are required to operate near room temperature.

The present invention has been made in view of the above circumstances, and an object of the present invention is _{to provide a Mn 3} SnC-based magnetic refrigeration material having excellent cooling characteristics.

_{The present inventors have focused on a Mn 3} SnC-based magnetic refrigeration material whose operating region is near room temperature. _{Then, it was found that the cooling characteristics of the Mn 3} SnC-based magnetic refrigeration material can be improved by substituting a part of the Mn site.
That is, the present invention provides the following means for solving the above problems.

(1) The magnetic refrigeration material according to the first aspect has a compound having an inverted perovskite structure represented by the general formula of _{(Mn 1-x} M _x ) _{3 SnC, and M in the general formula is Sr.} From K, Ca, Na, Mg, Ga, Ge, Al, Si, P, Ti, V, Cr, Zr, Nb, Mo, Fe, Ni, Co, Pd, Ru, Rh, Tc, Ag, Zn, Cu It is one or more elements selected from the group, and x in the general formula satisfies 0 <x <0.2.

(2) In the magnetic refrigeration material according to the above aspect, M in the general formula may be one or more elements selected from the group consisting of Ti, V, Cr, Zr, Nb, and Mo.

(3) In the magnetic refrigeration material according to the above aspect, M in the general formula is one or more elements selected from the group consisting of Fe, Ni, Co, Pd, Ru, Rh, and Tc, and the general formula is described. In, x may satisfy 0 <x ≦ 0.12.

(4) In the magnetic refrigeration material according to the above aspect, M in the general formula may be one or more elements selected from the group consisting of Ag, Zn, and Cu.

(5) In the magnetic refrigeration material according to the above aspect, M in the general formula is one or more elements selected from the group consisting of Sr, K, Ca, and Na, and x in the general formula is 0. <X ≦ 0.1 may be satisfied.

(6) In the magnetic refrigeration material according to the above aspect, M in the general formula is one or more elements selected from the group consisting of Ga, Ge, Al, Si, and P, and x in the general formula is. , 0.08 ≦ x <0.13 may be satisfied.

According to the present invention, _{it is possible to provide a Mn 3} SnC-based magnetic refrigeration material having excellent cooling characteristics.

It is a figure which shows the crystal structure of the compound of the inverted perovskite structure contained in the magnetic refrigeration material which concerns on this embodiment. It is a crystal structure of _{the Mn 3} SnC system compound used in the simulation. It is a figure which shows the fluctuation of the magnetic moment which occurs by substituting a compound with a substitution element in Example 1. FIG. It is a figure which shows the saturation magnetization at the time of substitution with the element of the 1st group shown in Example 3-1. It is a figure which shows the saturation magnetization at the time of substitution with the element of the 2nd group shown in Example 3-2. It is a figure which shows the saturation magnetization at the time of substitution with the element of the 3rd group shown in Example 3-3. It is a figure which shows the saturation magnetization at the time of substitution with the element of the 4th group shown in Example 3-4. It is a figure which shows the saturation magnetization at the time of substitution with the element of the 5th group shown in Example 3-5.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted.

"Magnetic refrigeration material"
The magnetic refrigerated material according to the present embodiment is represented by the general formula (Mn _1-x M _x ) ₃ SnC ... (1) and contains a compound having an inverted perovskite structure.

FIG. 1 is a diagram showing a crystal structure of a compound having an inverted perovskite structure contained in the magnetic refrigeration material according to the present embodiment. As shown in FIG. 1, this compound has a Mn site in which Mn can be present, a Sn site in which Sn can be present, and a C site in which C can be present, and a part of the Mn site is replaced by another element. ..

The substituents (M in the general formula (1)) that partially replace the Mn site are Sr, K, Ca, Na, Mg, Ga, Ge, Al, Si, P, Ti, V, Cr, Zr, Nb. , Mo, Fe, Ni, Co, Pd, Ru, Rh, Tc, Ag, Zn, Cu.

Substituting a part of the compound of the general formula (1) with these elements increases the saturation magnetization Ms of the compound. The reason for this is not clear, but it is thought that the contribution rate of Mn contained in the substance to the magnetization increases.

As shown in FIG. 1, a plurality of Mns are included in the unit structure of the _{Mn 3 SnC-based compound having an inverted perovskite structure.} Among these Mns, there are Mn having a high contribution rate to magnetization and Mn having a low contribution rate to magnetization, depending on the position of Mn in the unit structure, the direction of spin in the Mn element, and the like. When a part of the Mn site is replaced with the above-mentioned element, the contribution rate of Mn, which has a low contribution rate to magnetization, increases due to the interaction with the substituted element. As a result, the saturation magnetization Ms of the compound increases.

When the saturation magnetization Ms of the compound represented by the general formula (1) is increased, the cooling characteristics of the magnetic refrigerated material are improved. The magnetic refrigerated material generates heat and endothermic depending on the difference in entropy between the state where the magnetization is random and the state where the magnetization is uniform. Therefore, when the amount of change in the magnetic entropy of the magnetic refrigerated material is large, the cooling characteristics of the magnetic refrigerated material are improved.

The amount of change in magnetic entropy can be expressed by the following relational expression. In the following equation, [Delta] S _M is the magnetic entropy change, M is the magnetization, T is the temperature, H is an external magnetic field.

In the above relational expression, dM is the amount of change in magnetization. Saturation magnetization Ms is the maximum amount of magnetization that the compound can select. Therefore, as the saturation magnetization Ms increases, the range in which the amount of change in magnetization (dM) can be selected expands, and the amount of change in magnetic entropy increases. As a result, the cooling characteristics of the magnetic refrigeration material are improved.

The substitution amount x that replaces the Mn site of the compound represented by the general formula (1) is 0 <x <0.2. When the substitution amount x of the Mn site is 0.2 or more, the inverse perovskite structure may not be maintained. That is, a compound having a single-phase reverse perovskite structure may undergo a structural change to a different phase, or a heterogeneous structure may be included as a mixed phase. When the structure changes to a different phase or a mixed phase occurs, the cooling characteristics of the magnetic refrigerated material deteriorate.

Substitution elements (M in the general formula (1)) that replace a part of the Mn site are divided into several groups according to the characteristics of each element. Elements of the same group have similar interactions on the surrounding Mn after substitution and have similar effects on the cooling properties of the magnetic refrigeration material.

The first group is a group consisting of Ti, V, Cr, Zr, Nb, and Mo. These elements are Group 4 to Group 6 elements. These elements tend to affect Mn sites, which have a low contribution to magnetization. Therefore, by substituting a part of the Mn site with one or more elements selected from this group, a large saturation magnetization can be realized.

Further, unless a heterogeneous phase appears, the saturation magnetization increases as the substitution amount x increases. Therefore, precise control of the substitution amount x is not required. When the Mn site is replaced with one or more elements included in the first group, the substitution amount x is preferably 0.08 ≦ x <0.2, and 0.12 ≦ x ≦ 0.16. Is more preferable.

The second group is then a group consisting of Fe, Ni, Co, Pd, Ru, Rh, and Tc. These elements are Group 7 to Group 10 elements. Mn is a Group 7 element, and these elements are easy to replace and have excellent structural stability after replacement. In addition, these elements themselves have strong magnetization. Therefore, when a part of the Mn site is replaced with one or more elements selected from this group, the interaction given to Mn having a small contribution rate to magnetization becomes large, and a large saturation magnetization can be realized.

On the other hand, if the substitution amount x is increased too much, the saturation magnetization tends to gradually decrease. Therefore, when replacing the Mn site with one or more elements included in the second group, the substitution amount x is preferably 0 <x ≦ 0.12, and 0.02 ≦ x ≦ 0.08. It is more preferable that there is, and it is further preferable that 0.03 ≦ x ≦ 0.05.

Next, the third group is a group consisting of Ag, Zn, and Cu. These elements are Group 11 or Group 12 elements. These elements are mainly monovalent and divalent valence elements. Therefore, when a part of Mn is replaced, the electronic state of Mn other than the replaced site changes, and as a result, the contribution rate of Mn having a low contribution rate to the magnetization can be increased. These elements have little variation in saturation magnetization when the substitution amount x is changed. Therefore, precise control of the substitution amount x is not required. When the Mn site is replaced with one or more elements included in the third group, the substitution amount x is preferably 0 <x <0.16, and 0.08 ≦ x <0.16. More preferred.

The fourth group is then a group consisting of Sr, K, Ca and Na. These elements are Group 1 or Group 2 elements. Since these elements have a larger ionic radius than Mn, the Mn-Mn interatomic distance increases due to substitution. Therefore, the antiferromagnetic interaction between adjacent Mn and Mn is weakened, and the contribution rate to magnetization is improved. For these elements, the value of saturation magnetization Ms gently fluctuates according to the substitution amount x. Therefore, it is easy to control the value of the saturation magnetization Ms by the substitution amount x. When the Mn site is replaced with one or more elements included in the fourth group, the substitution amount x is preferably 0 <x ≦ 0.1, and 0.04 ≦ x ≦ 0.08. More preferred.

Finally, the fifth group is a group consisting of Ga, Ge, Al, Si, and P. These elements are Group 13 or Group 15 elements. These elements have a smaller ionic radius than Mn. Therefore, by substituting a part of Mn, the electronic state of Mn other than the mainly substituted site changes in the same manner, and as a result, the contribution rate of Mn having a low contribution rate to the magnetization increases. When the Mn site is replaced with one or more elements included in the fifth group, the substitution amount x is preferably 0.08 <x ≦ 0.13, and 0.08 ≦ x ≦ 0.12. Is more preferable.

"Manufacturing method of magnetic refrigerated material"
The magnetic refrigerated material according to this embodiment can be produced by using a known method such as a solid phase reaction method. For example, when the solid phase reaction method is used, an oxide containing Mn, Sn, C and a substituent is prepared. These are weighed according to the composition ratio and mixed. By firing at a high temperature of about 700 ° C. to 1000 ° C. after mixing, a magnetic refrigerated material containing a compound represented by the general formula (1) in which a part of Mn sites is substituted with a substituent can be obtained.

As described above, the magnetic refrigeration material according to this embodiment has a compound represented by the general formula (1). In the compound represented by the general formula (1), a part of the Mn site is substituted with a predetermined substitution element, and the contribution rate of Mn having a low contribution rate to magnetization is high. As a result, as the saturation magnetization Ms increases, the amount of change in magnetic entropy increases, and the cooling characteristics of the magnetic refrigerated material are improved.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the configurations and combinations thereof in the respective embodiments are examples, and the configurations are added or omitted within the range not deviating from the gist of the present invention. , Replacements, and other changes are possible.

"Example 1"
In Example 1, it was confirmed by simulation which Mn site was replaced to increase the saturation magnetization by using the first-principles calculation.

First-principles calculation is a general term for electronic state calculation that does not use empirical fitting parameters, etc., and enables electronic state calculation simply by inputting the atomic numbers and coordinates of each element that constitutes a unit cell, molecule, etc. It is a calculation method.

As one method of first-principles calculation, there is a calculation method called PAW (Projector Argmented-Wave) method. This method has the advantage that the calculation can be performed with high accuracy and in a relatively short time. By preparing the potential of each atom constituting the unit lattice or the like in advance and calculating the electronic state, the crystal structure can be calculated. Optimization calculations are also possible.

In addition, a calculation method called a density functional theory is also known for calculating the interaction of many electrons existing in a crystal. As one of the approximation methods using the density functional theory, there is a method called GGA (Generated Gradient Approximation). When this method is used, the electronic state can be calculated with high accuracy.

As a first-principles calculation package program including these, there is a program called VASP (the Vienna Ab-initio Simulation Package). All first-principles calculations in the following examples were performed using VASP.

FIG. 2 shows the crystal structure of _{the Mn 3 SnC-based compound used in the simulation.} FIG. 2 shows two unit structures shown in FIG. 1 arranged in the a, b, and c directions. The Mn sites shown in FIG. 2 are numbered 1 to 24, the C site is shown as a white circle, and the Sn site is shown as a circle larger than the Mn site. Each Mn site is not completely equivalent. When Fe was substituted as a substitution element at a predetermined site, it was confirmed how the magnetic moment fluctuates with respect to that before the substitution. The composition formula of the compound after the substitution was (Mn _0.96 Fe _0.04 ) ₃ SnC.

FIG. 3 is a diagram showing changes in the magnetic moment of the Mn atom before and after the replacement when the Mn site No. 8 is replaced with Fe. The horizontal axis is the Mn number, and the vertical axis is the magnetic moment of the atom at each site. As shown in FIG. 3, for example, Mn sites such as No. 2, No. 5, No. 20, and No. 23 have a small magnetic moment and a low contribution rate to magnetization before replacement. On the other hand, after replacing the Mn site of No. 8 with the Fe element, the magnetic moments of Nos. 2, 5, 20, and 23 are large. That is, by substituting the substitution element with a predetermined Mn site, the magnetic moment of the Mn site having a small magnetic moment increases, so that the saturation magnetization increases and the cooling characteristics of the magnetic refrigerated material are improved.

On the other hand, which Mn site the substitution element actually substitutes for is determined by various conditions such as the type of the substitution element and the influence of surrounding elements when the substitution element is substituted. For example, when it is replaced with Fe, it is easy to replace it with Mn sites of Nos. 8 and 11. Therefore, when the substitution is performed with Fe, the saturation magnetization of the magnetic refrigerated material is increased, and the cooling characteristics of the magnetic refrigerated material are improved.

"Example 2"
In Example 2, a substance was actually prepared, and the value of saturation magnetization before and after the substitution was measured.

(Example 2-1)
Using the solid phase reaction method (Mn _0.9 Ni _0.1 ), Mn oxide, Ni oxide, Sn oxide, and C are weighed so as to have a composition ratio of _{3 SnC, and mixed in a solvent by a ball mill.} bottom. After drying, it was formed into a plate and further baked in an Ar atmosphere at 850 ° C. for 10 hours to prepare a magnetic refrigerated material.

(Comparative Example 2-1)
Mn oxide, Sn oxide, and C were weighed using a solid phase reaction method so as to have _{a composition ratio of Mn 3} SnC, and mixed in a solvent by a ball mill. After drying, it was formed into a plate and further baked in an Ar atmosphere at 850 ° C. for 10 hours to prepare a magnetic refrigerated material.

The XRD diffraction patterns of the magnetic refrigerated materials produced in Example 2-1 and Comparative Example 2-1 were measured by CuKα1 radiation using an X-ray diffractometer (RINT-2500HK) manufactured by Rigaku Co., Ltd., respectively. The magnetic refrigerated materials of Example 2-1 and Comparative Example 2-1 both had an inverted perovskite structure. In addition, no by-products were confirmed, and all were single-phase. It was confirmed that the XRD diffraction peak was shifted to the low angle side in Example 2-1 as compared with Comparative Example 2-1 and that a part of the Mn site was replaced with Ni.

Then, the magnetization of Example 2-1 and Comparative Example 2-1 was measured. Magnetization was measured using a vibrating sample magnetometer (VSM). The magnetization-temperature curve was measured at an external magnetic field of 800 kA / m and a sample temperature of 77 K to 300 K. In any temperature range before the Curie temperature, the magnetization of Example 2-1 was larger than that of Comparative Example 2-1. The saturation magnetization of Example 2-1 was 35.7 emu / g, and the saturation magnetization of Comparative Example 2-1 was 15.2 emu / g. That is, by substituting the Mn site with Ni, the saturation magnetization was increased and the cooling characteristics of the magnetic refrigeration material were improved.

"Example 3"
In Example 3, the value of saturation magnetization when various materials were replaced by changing the amount of substitution was obtained by simulation using first-principles calculation. Substitution elements were replaced with Mn sites where each substitution element was the most stable.

(Example 3-1)
In Example 3-1 the substitution element was substituted with the first group of elements (Ti, V, Cr, Zr, Nb, Mo). The values of each saturation magnetization were obtained, and the results are shown in Table 1 and FIG. In the table below, the numerical value at the intersection of the sequence of substitution elements and the substitution amount x is the value of saturation magnetization (emu / g) when a predetermined element is substituted with a predetermined substitution amount.

As shown in Table 1 and FIG. 4, large saturation magnetization was obtained by substituting with the elements of the first group. That is, the cooling characteristics of this magnetic refrigeration material are excellent. Further, the value of saturation magnetization was saturated when the substitution amount x exceeded 0.12.

(Example 3-2)
In Example 3-2, the element was substituted with the second group of elements (Fe, Ni, Co, Pd, Ru, Rh, Tc) as the substitution element. The values of each saturation magnetization were obtained, and the results are shown in Table 2 and FIG.

As shown in Table 2 and FIG. 5, large saturation magnetization was obtained by substituting with the second group of elements. In particular, when the substitution amount was around 0.04, the value of saturation magnetization showed a maximum value. In addition, the value of saturation magnetization when Ni was replaced by 0.1 showed a value equivalent to the actually measured value shown in Example 2-1 and it was confirmed that the result of the simulation was certain.

(Example 3-3)
In Example 3-3, the element was substituted with a third group of elements (Ag, Zn, Cu) as a substitution element. The values of each saturation magnetization were obtained, and the results are shown in Table 3 and FIG.

As shown in Table 3 and FIG. 6, when replaced with the elements of the third group, a large saturation magnetization was not obtained as compared with the case of replacing with the elements of the first group and the second group, but they were not replaced. Greater saturation magnetization was obtained than in the case. Further, when the element was substituted with the element of the third group, the variation of the saturation magnetization was small with respect to the substitution amount x.

(Example 3-4)
In Example 3-4, the element was substituted with a fourth group of elements (Sr, K, Ca, Na) as a substitution element. The values of each saturation magnetization were obtained, and the results are shown in Table 4 and FIG.

As shown in Table 4 and FIG. 7, when replaced with the elements of the 4th group, a large saturation magnetization was not obtained as compared with the case of replacing with the elements of the 1st group and the 2nd group, but the substitution was not performed. Greater saturation magnetization was obtained than in the case. Further, when the element is substituted with the element of the fourth group, the variation of the saturation magnetization is gradual with respect to the substitution amount x, and it is easy to control the value of the saturation magnetization.

(Example 3-5)
In Example 3-5, the element was substituted with an element of the fifth group (Ga, Ge, Al, Si, P) as a substitution element. The values of each saturation magnetization were obtained, and the results are shown in Table 5 and FIG.

As shown in Table 5 and FIG. 8, when replaced with the elements of the fifth group, the amount of increase in saturation magnetization was small, but a larger saturation magnetization was obtained than when not replaced.

As shown in Examples 3-1 to 3-5 described above, it was confirmed that the saturation magnetization increased when replaced with any of the elements as compared with the case where the saturated magnetization was not replaced. That is, the cooling characteristics of the magnetic refrigeration material are improved by element substitution.

"Example 4"
In Example 4, the value of saturation magnetization when the element species to be replaced was replaced with a plurality of elements was obtained by simulation using first-principles calculation. The substitution element was assumed to be replaced with the Mn site where each substitution element is the most stable.

In Example 4-1, a part of the Mn site was replaced with Fe and Ni. In Example 4-2, a part of the Mn site was replaced with Ti and Co. In Example 4-3, a part of the Mn site was replaced with Zr and V. In Example 4-4, a part of the Mn site was replaced with Nb and Cr. In Example 4-5, a part of the Mn site was replaced with Fe and Ni. In Example 4-6, a part of the Mn site was replaced with Ti and Fe. In Examples 4-1 to 4-4, the substitution amount x was 0.04, and in Examples 4-5 and 4-6, the substitution amount x was 0.08. The results are shown in Table 6 below.

As shown in Table 6, the value of saturation magnetization was larger than that of Comparative Example 4-1 which was not substituted in any case. That is, the cooling characteristics of the magnetic refrigeration material were improved by element substitution.

Claims (5)

(Mn _1-x M _x ) _{3 It} has a compound having an inverted perovskite structure represented by the general formula of SnC, and has a compound having an inverted perovskite structure.
M in the general formula is one or more elements selected from the group consisting of Ti, V, Cr, Zr, Nb, and Mo.
In the general formula, x is 0 . A magnetic refrigerated material that satisfies 08 ≦ x <0.2. (Mn _1-x M _x ) _{3 It} has a compound having an inverted perovskite structure represented by the general formula of SnC, and has a compound having an inverted perovskite structure.
M in the general formula is one or more elements selected from the group consisting of Fe, Co, Pd, Ru, Rh, and Tc.
A magnetic refrigerated material in which x in the general formula satisfies 0 <x≤0.12. (Mn _1-x M _x ) _{3 It} has a compound having an inverted perovskite structure represented by the general formula of SnC, and has a compound having an inverted perovskite structure.
M in the above general formula is one or more elements selected from the group consisting of Ag, Zn, and Cu.
In the general formula, x is 0.08 ≤ x <0. A magnetic refrigeration material that satisfies 16. (Mn _1-x M _x ) _{3 It} has a compound having an inverted perovskite structure represented by the general formula of SnC, and has a compound having an inverted perovskite structure.
M in the above general formula is one or more elements selected from the group consisting of Sr, K, Ca, and Na.
A magnetic refrigerated material in which x in the general formula satisfies 0 <x≤0.1. (Mn _1-x M _x ) _{3 It} has a compound having an inverted perovskite structure represented by the general formula of SnC, and has a compound having an inverted perovskite structure.
M in the general formula is one or more elements selected from the group consisting of Ga, Ge, Al, Si, and P.
A magnetic refrigerated material in which x in the general formula satisfies 0.08 ≦ x <0.13.

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