JPS6230840A - Working substance for magnetic refrigerator and its production - Google Patents

Abstract

PURPOSE:To obtain a working substance for magnetic refrigerators having high magnetic entropy at 20-300K and excellent in magnetic refrigerating performance by providing an amorphous alloy or polyphase microcrystalline aggregate alloy having a composition consisting of, each by specific atom%, 1 or >=2 elements among Gd, Tb, Dy, Ho and Er, 1 or >=2 elements among Zr, Hf, Al, Si and Ge and 1 or >=2 elements among Cu, Ni and Ag. CONSTITUTION:A melt has a composition consisting of, by atomic, 20-80% of 1 or >=2 elements among Gd, Tb, Dy, Ho and Er, 10-40% of 1 or >=2 elements among Zr, Hf, Al, Se and Ge and 10-60% of 1 or >=2 elements among Cu, Ni and Ag. The above melt is subjected to rapid cooling in vacuum or in an inert atmosphere by means of a Cu or Ag cooling body of a temp. between room temp. and 850K.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic refrigeration working material for a magnetic refrigerator and a method for producing the same.

BACKGROUND OF THE INVENTION In recent years, the scope of low-temperature utilization has expanded significantly, and there has been a demand for the development of efficient refrigerators.

In conventional refrigeration methods that repeatedly compress and expand gas, the efficiency decreases as the temperature decreases. Therefore, magnetic refrigeration, which is based on a completely new principle, has attracted attention.

Generally, when a magnetic material is inserted into a strong magnetic field and its magnetic spins are aligned, heat is generated. After removing this heat to the outside, the magnetic material is pulled out of the strong magnetic field and the magnetic spin is disturbed, causing heat absorption, which takes heat from the external object to be frozen and freezes it. Magnetic refrigeration uses this principle,
Mechanistically, disturbances in the alignment of magnetic spins in magnetic refrigeration correspond to compression and expansion of gas in gas refrigeration. 20
At temperatures lower than K (Kelvin), the inverse Carnot cycle can be used, but at temperatures above 20, the lattice specific heat becomes large, so the Ericsson cycle using a regenerator can be used.
A;i must be scarce.

These magnetic refrigeration methods, compared to conventional gas 14p;
It has many excellent features such as high refrigeration efficiency, no need for a compressor, less vibration and noise, compact size, and computer control. In order to put such an excellent magnetic refrigeration method into practical use, it is essential to develop high-performance magnetic refrigeration materials.

Currently, as a magnetic refrigeration working material in the lower temperature range than 20, Gds Gas 01! , Gd5(Ga
Garnet single crystals such as + -x Al x )s O+s are said to have excellent properties, and magnetic refrigeration tests are being conducted using them.

In the above-mentioned garnet system, the Neel temperature of the antiferromagnetic-paramagnetic transition is near IK, and this transition can be utilized at a temperature of 20°C or higher, but when the temperature exceeds 20°C, the change in magnetic entropy due to an external magnetic field becomes small. Refrigeration capacity decreases significantly.

In magnetic refrigerators in the temperature range of 20° to 300° C., it is advantageous to utilize the large magnetic entropy change caused by an external magnetic field near the Curie temperature of the ferromagnetic-paramagnetic transition. This magnetic refrigeration working material is required to have a Curie temperature within the working temperature range.

Furthermore, it is required to have a large magnetic moment, a small lattice specific heat, and a high thermal conductivity, but currently no material with excellent properties in this temperature range has been obtained.

OBJECTS OF THE INVENTION An object of the present invention is to provide a working material for a magnetic refrigerator that has a large magnetic entropy and excellent magnetic refrigeration performance in a temperature range of 20 to 300 degrees Celsius, and a method for manufacturing the same.

Cd, a rare earth element with a large magnetic moment 1. Tb'
14 Dys Has Er alone or two or more, Zr s Hf s Al as an amorphous element, 85% Ge alone or two or more, and Cu Nix Ag as an element that increases affinity with the cooling body Cu and Ag. The melt is heated at room temperature to 850°C in vacuum or in an inert gas atmosphere.
Amorphous alloys or multi-phase microcrystalline aggregate alloys produced by rapid cooling with a Cu or Ag cooling body controlled at a temperature of
It has been found that a working material with large magnetic entropy over a wide temperature range and excellent magnetic refrigeration performance can be obtained. The present invention was completed based on this knowledge.

The gist of the present invention is to combine 20 to 80 atomic % of one or more elements selected from the following elements: Gdx Tb% Dy% Ho1 and Er; Zr;
Hf% Single or two or more selected from the elements Ai, Si and Ge, 10 to 4o atomic%5CuNi and Ag
A magnetic refrigeration working material of an amorphous alloy or a multiphase microcrystalline aggregate alloy consisting of 10 to 60 atoms of one or more elements selected from the following.

Further, there is a manufacturing method characterized in that the melt having the above composition is rapidly cooled in vacuum or in an inert gas atmosphere with a Cut or Ag cooling body to a temperature of room temperature to 850°C.

Gd, Tb%Dy, Ho, and Er are rare earth elements with a large magnetic moment, and if their components exceed 80 atoms, an amorphous alloy or a multiphase microcrystalline aggregate alloy cannot be obtained, and it becomes almost a single-phase alloy. crystal structure, and the refrigeration capacity is significantly reduced. On the other hand, if the amount is less than 20 atoms, the magnetic moment decreases, so the magnetic entropy decreases rapidly, and the refrigerating ability is no longer exhibited.

Zr % Hf S Al, 51nGe is an amorphous element, and when its component exceeds 40 atoms, non-magnetic Z
Compounds such as r, Cu, Zr, and Ni are formed, making it difficult for amorphization to occur. On the other hand, if the amount is less than 10 atoms, it becomes difficult to obtain an amorphous alloy.

In addition, in order to obtain a high-density, multi-phase microcrystalline aggregate alloy,
It is necessary to contain an amorphous element.

When the amorphous element component exceeds 40 atoms, non-magnetic Zr
Compounds such as Cu, Zr and Ni are formed, making it impossible to obtain a microcrystalline aggregate alloy. In addition, the amorphous element component is 10
If the amount is less than atomic, the crystal grains become coarse and it becomes difficult to obtain a microcrystalline aggregate alloy.

Cu and Nis Ag increase the affinity with the cooling body, and when the content exceeds 60 atoms, the amorphous alloy or the multiphase microcrystalline aggregate alloy becomes particularly hard and brittle. On the other hand, if the amount is less than 10 atoms, Cu
, kg, the affinity of the cooling body becomes small, making it difficult to amorphize or microcrystallize.

If the temperature of the molten Cu or Ag cooling body is 300 to 670, it becomes amorphous. 670 to 850, an alloy consisting of a collection of high-density, multiphase microcrystals is obtained. However, if the temperature exceeds 850K, each crystal grain becomes coarse and brittle, so it is necessary not to exceed 850K.

Although a multiphase microcrystalline aggregate alloy can be obtained by heat treating the amorphous alloy described above, those obtained by controlling the temperature of a cooling body often require heat treatment. The Curie temperature of this amorphous alloy can be easily controlled depending on the composition, and furthermore, the magnetic entropy is large over a wide temperature range centered around the Curie temperature. In addition, in a multiphase microcrystalline aggregate alloy, the Curie temperature of each phase can be controlled to be distributed between 300 and 20 K depending on the composition, and the magnetic entropy is large in this temperature range, and the change in magnetic entropy due to temperature is gradual. Both are working materials with excellent magnetic refrigeration performance.

In addition, in order to prevent oxidation of the melt, the process is carried out in a vacuum or in an inert gas atmosphere.

Example 1 An ingot with the composition shown in Table 1 prepared in advance by an arc melting method was melted in vacuum by a levitation method, and the melt was rapidly cooled from a fine-hole nozzle onto a Cu cooling body at room temperature to form an amorphous material. An alloy was made.

Changes in magnetization of these alloys due to temperature were measured in a magnetic field H up to 7.5 T (Tesla), and magnetic entropy ΔSM, which is the main magnetic refrigeration performance, was determined. Table 1 shows the temperature range ΔToo in which 68M has a value of 60 degrees or more with respect to the temperature Tmax1ΔSMmax which indicates the maximum value ΔSMmaX%ΔSMmax of the obtained magnetic entropy.

An example of the relationship in Table 1 is shown. This amorphous alloy has a smaller ΔSMmax than the already known D)'A1g crystal, but its change with temperature is gradual, and ΔT9 is as wide as 70. In addition, as shown in Table 1, ΔS
Mmax%TmaxsΔT0 can be easily controlled by changing the type of rare earth element and its content. Using this amorphous alloy magnetic refrigeration material,
This makes it possible to create a magnetic refrigerator that exhibits high refrigeration capacity over a wide temperature range.

Example 2゜Table 2 A melt obtained by melting the composition shown in Table 2 in the same manner as in Example 1 was quenched with a Cu cooling body heated to 750K to produce a multiphase microcrystalline aggregate alloy.

An example of the results is shown in Figure 4. This microcrystalline aggregate alloy consists of GdCu (Te = 90K) with different Curie temperatures Tc.
, GdCuA1 (Tc=67K), GdAlx(-Tc
= 168 K) s GdS+ (Tc = 50 K
) and DyN1 (Tc=48K), DyNiA1
(Tc = 39K), DVAh (Tc = 68K), D7
Since it is made of microcrystals such as Siz (Tc = 17 K), the change due to temperature of 68M is very gradual,
ΔT6° is wide. %TmaXt as shown in Table 2
ΔToo can be easily controlled by changing the type of rare earth element and its content. Use of this multiphase microcrystalline aggregated alloy magnetic refrigeration material enables a magnetic refrigerator that exhibits high refrigeration capacity over a wide temperature range.

Effects of the Invention The amorphous alloy and multiphase microcrystalline aggregate alloy of the present invention can easily control the Curie temperature depending on the composition.
It has a large magnetic entropy over a wide temperature range centered around the Curie temperature, and the magnetic entropy changes slowly with temperature, making it a magnetic refrigeration material with a large magnetocaloric effect.

Therefore, a magnetic refrigerator for generating a low temperature environment from room temperature to 20 degrees is possible. This magnetic refrigerator has higher efficiency than conventional gas refrigerators, and can be made smaller and lighter.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between magnetic entropy ΔSM and temperature T. Patent applicant: Ryu Kawa, Director, Research Institute for Metals, Science and Technology Agency −

Claims (1)

[Claims] 1) 20 to 80 atomic % of one or more elements selected from Gd, Tb, Dy, Ho, and Er; Zr, Hf;
, Al, Si and Ge alone or two selected from the elements
Magnetic refrigeration of an amorphous alloy or a multiphase microcrystalline aggregate alloy consisting of 10 to 40 atomic % of one or more species and 10 to 60 atomic % of one or more elements selected from Cu, Ni, and Ag. working substance. 2) 20 to 80 atomic % of one or more elements selected from the elements of Gd, Tb, Dy, Ho and Er, Zr, Hf
, Al, Si and Ge alone or two selected from the elements
A melt consisting of 10 to 40 at. % of one or more elements and 10 to 60 at. A method for producing a magnetically frozen working material, characterized by rapid cooling with a Cu or Ag cooling body at ~850K.