JPH0540917A - Production of nonmagnetic substrate for magnetic head - Google Patents

Abstract

PURPOSE:To provide the process for production of the nonmagnetic substrate for magnetic heads particularly consisting of CoO and NiO or the NiO as its basic compsn. relating to the process for production of the nonmagnetic substrate for magnetic heads for vapor deposition of magnetic metallic films. CONSTITUTION:The heating up rate up to 800 deg.C in an atm. atmosphere is set at <=30 deg.C/h at the time of sintering a molding under atm. pressure in the process for production of the nonmagnetic substrate for magnetic heads consisting of the CoO and the NiO or the NiO as its basic compsn. The molding can be sintered in the atm. without cracking the sintered body at the time of sintering in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a non-magnetic magnetic head substrate for depositing a metallic magnetic film.

[0002]

2. Description of the Related Art Barium titanate, calcium titanate, alumina, etc. have hitherto been used for such applications. However, since the coefficient of thermal expansion was largely different from that of the magnetic film structure, the vapor-deposited magnetic film structure was easily peeled off, and stress was generated due to the difference in the coefficient of thermal expansion, and cracks were sometimes generated.

The present inventors have conducted research on oxide-based ceramics in order to solve the above-mentioned drawbacks, and have studied CoO and Ni.
It has already been disclosed that an oxide having a basic composition of O or NiO is effective. (JP-A-01-287811, JP-A-02-1686
02, Japanese Patent Application 01-214206)

Further, it has already been disclosed that a manufacturing method comprising the following steps is effective as a manufacturing method of a non-magnetic substrate for a magnetic head having a basic composition of CoO and NiO or NiO. (Japanese Patent Laid-Open No. 02-94407) That is, (1) a mixing step of mixing raw material powders and sieving, (2) a calcination step of calcination of the CIP-molded mixed powders, crushing and sieving, (3) 1 μm of calcined powder
Finely pulverizing the following, (4) Granulating the finely pulverized powder into spherical particles of 20 μm or more, (5) CIP molding the granulated powder, (6) Sintering the compact, (7) H for the sintered body
This is a process of IP processing.

Regarding the step of sintering the molded body, it is decided to use atmospheric pressure sintering or hot pressing. However, if this sintering process is performed in the atmosphere, the volume expansion of CoO when it changes from room temperature to Co ₃ O ₄ at around 600 ° C., or at a temperature higher than that, Co ₃ O ₄ is reduced to CoO again. There was a problem that the sintered body was cracked due to the generation of O ₂ . Therefore, CoO and NiO
Alternatively, when a non-magnetic substrate for a magnetic head having a basic composition of NiO is sintered, the low temperature region is vacuum or an inert gas atmosphere such as nitrogen, and the high temperature region is an oxidizing atmosphere for sintering. That is, in the conventional method, it was necessary to switch the atmosphere during the sintering, and the operation was complicated.

[0006]

In order to solve the above problems, the following inventions have been made.

[0007]

That is, according to the present invention, in a method for manufacturing a non-magnetic substrate for a magnetic head having a basic composition of CoO and NiO or NiO, the atmosphere during sintering is atmospheric air, and the temperature rising rate from room temperature to 800 ° C. To 30 ° C./h or less, and to a method for manufacturing a non-magnetic substrate for a magnetic head.

[0008]

DETAILED DESCRIPTION OF THE INVENTION Specific and detailed description will be given to facilitate understanding of the present invention. The basic composition means an oxide of NiO alone or a composite oxide of NiO and CoO. For example, CoO / NiO (molar ratio) = 0/100 to 80 /
20 and more preferably CoO / NiO (molar ratio) =
It is 3 / 97-60 / 40. Furthermore, as an additive, for example, Al ₂ O ₃ , ZrO ₂ , Y ₂ O _3, etc., 0.1 to 5 wt.
%, The non-surface area of the powder is
When it is 7 m ² / g or more, a more preferable substrate can be obtained.

According to the present invention, the powder having the above composition is uniaxially molded, C
The present invention relates to the sintering conditions for sintering at normal pressure after IP. The sintering condition is to set the temperature rising rate up to 800 ° C. to 30 ° C./h or less in the atmosphere, and if the temperature rising rate is higher than 30 ° C./h, cracks will occur in the molded body during temperature rising. .. This is due to the volume expansion of CoO oxide in the air when it changes to Co ₃ O ₄ from room temperature to around 600 ° C., and C that occurs in the temperature range of 600 ° C. to 800 ° C.
Cracking of the compact occurs due to the cause of O ₂ gas generated by the decomposition reaction of o ₃ O ₄ to CoO. On the other hand, the heating rate up to 800 ° C is 30 ° C / h.
By the following, it was possible to moderate the above-mentioned volume expansion and generation of O ₂ gas at the time of temperature rise, and to prevent cracking of the molded body at the time of temperature rise. Further, by adopting this method, it is no longer necessary to switch from the vacuum or inert gas atmosphere to the oxidizing atmosphere during the temperature rise, which was conventionally done.

No cracking was observed in the thus obtained sintered body, and the density, the structure of the sintered body, etc. were found to be different from those obtained by sintering by switching from the inert gas atmosphere to the oxidizing atmosphere. I couldn't do it.

An embodiment of the present invention will be described below.

EXAMPLE CoO and NiO were used as raw materials, and CoO / NiO (molar ratio) was adjusted to 50/50 composition, and 2 wt% of alumina was added and mixed as an additive. Mixing was carried out for 20 hours in a wet ball mill in ethanol. This mixed powder was calcined in Ar at 900 ° C., then pulverized using a coarse crusher, and sieved with a 150 μm sieve to obtain a calcined powder. This calcined powder was mixed with a wet ball mill in ethanol to 40
Crushed for hours. This crushed powder is granulated and then CIP molded, and the temperature of the molded product is increased to 800 ° C at 30 ° C / h and 20 ° C /
As a result of performing atmospheric pressure sintering at 1230 ° C. for 1 hour at 10 ° C./h for 10 hours, cracks were not observed in the sintered body and the relative density of the sintered body was 98.8%. A comparative example is shown below.

[0012]

[Comparative Example] During sintering, the temperature rising rate up to 800 ° C was 40 ° C /
When sintering was carried out under the same conditions as in the above example except that h and 50 ° C./h were used, cracks were found in the sintered body in all cases.
The relative density could not be measured due to cracking.

[0013]

EFFECTS OF THE INVENTION No cracking was observed in the sintered body obtained according to the present invention, and there is no difference in density, structure, etc. from the sintered body sintered by switching from an inert gas atmosphere to an oxidizing atmosphere. I got things. Further, according to the present invention, the sintering method of the non-magnetic substrate for the magnetic head can be performed very easily.

Claims (1)

[Claims] 1. A method of manufacturing a non-magnetic substrate for a magnetic head, which comprises CoO and NiO or NiO as a basic composition, and when a compact is sintered at atmospheric pressure, it is exposed to 800 in an air atmosphere.
A method for manufacturing a non-magnetic substrate for a magnetic head, characterized in that a temperature rising rate up to 30 ° C. is 30 ° C./h or less