JPH01287206A - Porous sintered body for infiltrated complex target material and manufacture thereof - Google Patents

Abstract

PURPOSE:To easily manufacture a porous sintered body having fixed porous ratio at good productivity by forming a ground sheet in slurry containing transition metal powder and binder and sintering under reducing atmosphere after laminating this under semidrying condition. CONSTITUTION:By adding and mixing the binder of CMC, etc., and water or organic solvent with the transition metal powder or rare earth metal having about 10-150mum particle size and the rare earth metal-transition metal alloy powder containing <=10 atom %, the slurry is prepared. This slurry is spread to flattened plane to form the ground sheet having the fixed thickness.When this ground sheet is under semi-drying condition, the above slurry is again spread on this and the same operation is repeated and laminated, to form the green compact having the desired thickness. Successively, after drying this green compact, this is sintered at 1,000-1,400 deg.C under reducing atmosphere. By this method, the high density porous sintered body having the fixed porous ratio, such as 40-90%, which is suitable to obtain an infiltrated complex target material infiltrating the transition metal-rare earth metal alloy, is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a porous body used for manufacturing a composite target material comprising a rare earth metal and a transition metal, and a method for manufacturing the porous body. The composite target is used when forming a perpendicularly magnetized film for magneto-optical recording by sputtering.

(Prior Art) Conventionally, as a Kukerat material for forming a perpendicular magnetization film for magneto-optical recording consisting of a rare earth metal and a transition metal by sputtering, the two metals are melted in a vacuum or an inert gas atmosphere. There are composite targeters 1 to 1) A in which other metal chips are placed on the fabricated alloy target layer, transition metal plate or rare earth metal plate.

However, the former alloy targent is brittle and easily damaged, and has almost no thermal shock resistance, so there is a risk of cracking during sputtering. In addition, since it is difficult to arrange the chips in the latter composite target material in a uniform state, the magnetic field during sputtering becomes non-uniform, and the film composition becomes non-uniform in a plane.

Therefore, a sintered composite target material that eliminates these drawbacks is disclosed in Japanese Patent Application Laid-Open No. 119648/1983. This composite target material is made by mixing, molding, and sintering transition metal powder and rare earth metal powder, and the rare earth metal powder particles and transition metal powder particles are uniformly distributed in the target material and react at the interface between the two. A diffusion layer is formed and integrated to improve strength and thermal shock resistance.

(Problems to be Solved by the Invention) However, in the sintered composite target material, a weak intermetallic compound exists in the reaction diffusion layer throughout the structure, so it is difficult to impart sufficient strength to the composite material. Furthermore, since it is necessary to suppress the formation of the fragile diffusion layer as much as possible, strong sintering conditions cannot be selected, making it difficult to obtain a high-density composite material. Therefore, gas is likely to be generated during sputtering, and abnormal discharge is likely to occur. Furthermore,
It also has a drawback that it has a high oxygen content, making it difficult to obtain desired magnetization characteristics.

Therefore, the applicant proposed a target material capable of eliminating these drawbacks in Japanese Patent Application No. 62-215736. This target material contains 45 to 98 at% of a rare earth metal in a porous body formed of a rare earth metal-transition metal alloy containing 10 at% or less of a transition metal or a rare earth metal under vacuum or an inert gas atmosphere. A composite material in which a transition metal-rare earth metal alloy is infiltrated (infiltrated) in a molten state, and is characterized in that the rare earth metal content in the composite material is 20 to 45 at.%.

As a method for manufacturing the porous body, a method has been generally tried in which a transition metal powder or a rare earth metal-transition metal alloy powder is filled into a mold and fired as it is.

However, the porous sintered body produced by this method is
The packing density of the metal powder tends to be uneven, which makes the porosity unstable, and the ratio of rare earth metals to transition metals in the target material after infiltration is unstable, which in turn makes it difficult to sputter this target material. There is a problem that the characteristics of the formed perpendicularly magnetized film tend to be non-uniform.

The present invention was made in view of such problems, and an object of the present invention is to provide a porous sintered body having a constant porosity and a suitable manufacturing method thereof.

(Means for Solving the Problems) The porous sintered body for an infiltrated composite target material of the present invention, which has been made to achieve the above first object, contains 10 atomic % or less of transition metal powder or rare earth metal in the form of a slurry. Rare earth metals made by sintering of compacts formed from transition metal alloy powders
The structure of the invention is that it is magnetized.

In addition, as a manufacturing method, a binder, water, or an organic solvent is added to and mixed with transition metal powder or rare earth metal-transition metal alloy powder containing 10 at% or less of rare earth metal to prepare a slurry, and this is spread on a flat surface. to form a dough sheet of a certain thickness, and when the dough sheet is in a semi-dry state, the same operation is repeated on it to create a molded object of a predetermined thickness, and after drying, it is placed in a reducing atmosphere. The structure of the invention is to perform sintering.

(Function) 10 atomic % slurry of transition metal powder or rare earth metal
A compact formed from the rare earth metal-transition metal alloy powder contained below has high fluidity during compaction because the metal powder is in the form of a slurry, and the packing density of the metal powder in the compact becomes -like. Since the sintered body of the present invention is obtained by sintering and magnetizing such a molded body, the relative density and porosity of the sintered body are also similar.

According to the manufacturing method of the present invention, a slurry of transition metal powder or the like is spread on a flat surface to form a dough sheet of a constant thickness, and when the dough sheet 1- is in a semi-dry state, Since a molded body of a predetermined thickness is created by repeating the same operation as before, a molded body of a predetermined thickness with a metal powder packing density of - can be easily produced without using a mold and therefore without demolding. Obtainable. Since the inside of the molded body is semi-dry, it is difficult to crack during drying. After drying,
Since the compact is sintered in a reducing atmosphere, oxygen contained in the raw metal powder and oxides that may be generated during slurry formation are removed during the sintering process, and carbon, etc. in the metal powder is removed. Impurities are also removed. As a result, a homogeneous porous body made of a high purity transition metal or rare earth metal-transition metal alloy is obtained.

(Example) First, the transition metal powder used as a raw material for producing the porous sintered body of the present invention will be described.

As the transition metal powder, Fe, Co, and Ni alone or an alloy thereof (for example, Fe-12% by weight Co) powder is used, and rare earth metals such as Gd, Th, and D are used.
y.

tlo, Er and Tm alone or an alloy of these
Rare earth metal-transition metal alloy powders containing less than 0 atomic percent can also be used. The content of rare earth metals of 10% or less is allowed in the intermetallic compound TM+7R.
IE2 (TM: transition metal, RE: rare earth metal) is TM
However, at this level, the influence on deterioration of TPJJ properties is small and the wettability with the infiltrated alloy is improved.

To manufacture the sintered body of the present invention, first, a plate-shaped compact is manufactured using a slurry of transition metal powder or the rare earth metal-transition metal alloy powder (hereinafter simply referred to as metal powder).

The slurry is usually prepared by adding a binder such as carboxymethyl cellulose, water, or an organic solvent to metal powder of 10 to 150 μm and thoroughly mixing the mixture.

The molded body is usually produced by filling a flat mold with the slurry, drying it, and then removing the mold.

In this case, extreme care must be taken to ensure that the molded product is not damaged by one member during demolding.

On the other hand, the slurry was spread on the flat surface of a carrier such as polypropylene film or polyethylene film J, and in order to keep the thickness constant, an I-lid blade or the like was spread while maintaining a constant distance from the flat surface. One possible method is to move the slurry relative to each other to create a molded body (dough sheet) of a constant height. According to this method, a molded article can be obtained with high efficiency without the need for demolding.

However, although this method is suitable for forming thin-walled molded bodies with a wall thickness of approximately 1 to 2 mm or less, if the thickness exceeds that, the molded body may lose its shape due to the peripheral edges flowing out, or cracks may occur during drying. There's a problem. The standard thickness of Targutsu l-material is 5 to 6 mm, and considering the variation of several tens of percent, the thickness is 2.8 to 8 mm.

Therefore, the wall thickness of the molded body before sintering must be greater than this range, and there is a problem that the above-mentioned method cannot be applied as is.

Therefore, in the present invention, after the dough sheet is created, when the dough reaches a semi-dry state, the gap between the doctor blade and the carrier is expanded, and the slurry is poured onto the previously created dough sheet. The process of rolling out the dough again and laminating a new sheet of dough is repeated to create a molded product of the required thickness.

At this time, if another dough sheet is laminated on top of the dough sheet after it has completely dried, a gap will easily form between the two, which is not preferable. In addition, if drying is extremely insufficient,
This is not preferable because it causes flow to occur at the peripheral edge and the thickness becomes non-uniform.

Generally, when creating a porous sintered body of metal powder, it is sufficient to make the sintering gas atmosphere reducing or inert, or to sinter the metal powder compact under vacuum. Do it in an atmosphere. In particular, an atmosphere containing 11□ is good. This is because oxygen contained in the raw metal powder or oxides that may be generated during slurry creation are removed during the sintering process, and impurities such as carbon in the raw material are also removed. This is because it is possible to obtain a high-purity metal powder sintered body required as a metal powder.

In addition, in order to prevent surface oxidation of the sintered body during cooling after completion of sintering, it is preferable to use high-purity +12 in which O, L, and II□0 contained in 11□ are removed as much as possible. For this purpose, it is effective to use a noble metal deoxidizing catalyst such as palladium together with a dehumidifying agent such as molecular sieve according to a conventional method.

The sintering temperature may be lower as the particle size of the metal powder becomes smaller, but when using a particle size of about 10 to 150 μm, which is suitable for target material, the sintering temperature is 1,000 to 1,000 μm.
400'C is preferable; below this, the sintering strength will be low, and above this, shrinkage during sintering will increase, leading to a decrease in porosity, which is not preferable.

Further, a sintering time of about 5 to 60 minutes is sufficient; if it is less than this, the sintering strength may decrease, and if it is more than this, there is no effect of increasing the sintering strength, so it is not necessary.

In addition, the porosity of a sintered body is usually adjusted by the particle size and packing density of the metal powder, but in order to increase the porosity,
Particles that disappear in the slurry during firing or can be removed from the sintered body with a simple operation after sintering (called pore-forming agent).
A method can be adopted in which the traces of their disappearance are used as voids. Examples of the pore-forming agent include powders of carbon, cellulose, plastic, and the like.

The particle size of the pore-forming agent is preferably the same as the pores (gaps) between the metal powders. Since the particle size of the pore-forming agent has a large difference in specific gravity from the metal powder, if the particle size of the pore-forming agent is smaller than the size of the gap between the metal powders, the pore-forming agent will move and separate during the process of forming the slurry and drying the compact. Because it does.

The porosity of the sintered body is 40 to 90% (preferably 70%)
It is better to If it is less than 40%, the rare earth metal content necessary for the target material cannot be secured.

On the other hand, if it is 90% or more, the strength of the sintered body is significantly lowered, causing warping, cracking, etc. during infiltration.

For example, when producing a Fe-Tb based infiltration composite target material with the minimum required rare earth metal content (Tb: 20 atomic % or 41.6 weight %), pure Tb
For infiltration, a Fe sintered body with a porosity of 40% is required. In addition, those with the highest required content of rare earth metals (
When producing Fe-Tb co-conjugated alloy Tb: 72 at% or 88 wt%), the porosity is approximately 80%.
of Fe sintered body is required.

Next, specific examples are listed.

(1) Electrolytic iron powder (average particle size near 0μm (maximum 149μm)
mL oxygen concentration 1500 ppmw, carbon concentration 110 ppm
w) as the raw metal powder, F by the following methods
e Powder compacts Nos. 1 to 3 were produced in eight pieces each.

(2) 5 parts by weight of a binder (carboxymethylcellulose) and 90 parts by weight of water were added to 100 parts by weight of iron powder, and the mixture was mixed in a ball mill for 5 hours, and the resulting slurry was defoamed under vacuum.

Spread this slurry on a polypropylene sheet and form a dough sheet (gap of 2m between doctor blade and sheet).
m) did. After the dough sheet became semi-dry, the dough sheet was stacked on top of the dough sheet and molded again twice to obtain a molded product with a thickness of 6 mm, which was left to dry.

■ In addition to the binder, particle size 44-74μ is used as a pore-forming agent.
A sample to which 5 parts by weight of carbon (m) was added was prepared in the same manner as in (2).

(2) As a comparative example, the electrolyte was filled into the mold as it was.

(2) These three molded bodies were placed in an electric furnace and sintered at 1100°C for 15 minutes while flowing L gas (0□ concentration Q, 2ppmw, dew point <-80°C), and then allowed to cool to room temperature. After cooling, the sintered body was taken out, and its porosity was determined from the apparent density of the obtained sintered body. The results are shown in Table 1.

In addition, porosity - (1 - apparent density/true density) x 100'
(%).

Table 1 (Note) No. 1, No. 2 is an example, No. 3 is a comparative example. From Table 1, an example (No. 1 and 2) is a comparative example (N.
It is known that the porosity of the sintered body tends to be uniform compared to the case of 3). In addition, by using a pore-forming agent,
It is known that the porosity can be increased.

(3) The molded body prepared by the method in (1) The O and C concentrations in Fe were compared with the sintered body obtained using purity 112 gas.The results are shown in Table 2.The analyzed values are the average values of three samples.

Table 2 From Table 2, although the content is significantly lower than the concentration of each component in the raw iron powder, the influence of the purity of the 11□ gas is also recognized.

(Effects of the Invention) As explained above, the porous sintered body for infiltration composite target material of the present invention is obtained by molding a metal powder compact before sintering with a slurry of metal powder. Because of its good fluidity, it is possible to maintain a constant packing density.
This results in a sintered body with constant porosity.

Further, according to the manufacturing method of the present invention, a metal powder compact of a predetermined thickness can be produced without careful handling such as demolding.
It is easily obtained and has excellent productivity. Furthermore, since the molded body is sintered in a reducing atmosphere after drying, a highly pure metal powder sintered body can be easily obtained.

Claims (2)

[Claims] (1) The sintered body used for manufacturing an infiltrated composite target material in which a porous sintered body mainly composed of a transition metal is infiltrated with a transition metal-rare earth metal alloy, the sintered body being a slurry-like transition material. 10 atomic% metal powder or rare earth metal
A porous sintered body for an infiltrated composite target material, characterized in that a molded body formed from rare earth metal-transition metal alloy powder containing the following is sintered and integrated. (2) Prepare a slurry by adding and mixing a binder, water or an organic solvent to transition metal powder or rare earth metal-transition metal alloy powder containing 10 atomic % or less of rare earth metal, and spread it on a flat surface to a constant thickness. When the dough sheet is in a semi-dry state, the same operation is repeated on it to create a molded body of a predetermined thickness, which is dried and then sintered in a reducing atmosphere. A method for producing a porous sintered body for an infiltrated composite target material, characterized in that: