JPS62292672A - Ceramic composition for magnetic head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Application This invention relates to a non-magnetic material used for structural parts of a magnetic head, and the present invention relates to a non-magnetic material used for structural parts of a magnetic head, and in particular to the construction of various magnetic heads such as computers, particularly ferrite magnetic heads for digital recording. The present invention relates to a ceramic composition for magnetic heads used in sliders or spacers essential for use in magnetic heads.

BACKGROUND ART Generally, ferrite magnetic heads are assembled by glass welding a core made of a magnetic material such as l'vin-Zn ferrite or Ni-Zn ferrite and structural parts made of a non-magnetic material. As the magnetic material, Mn--Zn ferrite having high saturation magnetic flux density and magnetic permeability is used, and as the non-magnetic structural component material, TiO2CaO ceramic having a coefficient of thermal expansion equivalent to that of the ferrite is used.

In other words, if the core material and the non-magnetic structural component have different coefficients of thermal expansion, stress is applied to the ferrite core during glass welding, which not only causes deterioration of magnetic properties.
Since cracks, peeling, etc. occur, which poses a serious problem in assembling the magnetic head, the material composition is selected so that the coefficients of thermal expansion of the magnetic material and the nonmagnetic material match.

In addition, if there are many falling crystals or microcracks in this non-magnetic structural component material, the magnetic powder coated on the recording medium may adhere to the defects or cause chipping when the magnetic head and the recording medium run in contact with each other. The material must not be susceptible to such defects during machining, since such defects may damage the magnetic head or recording medium.

Furthermore, as an important factor in terms of appearance, there is the problem of the color tone of the nonmagnetic material.

In general, TiO2-CaO ceramics exhibits a white color when sintered in the atmosphere, but due to lack of oxygen supply or hot pressing for high density, it is partially reduced and easily darkens. There was a problem that not only the color tone was not constant but also lacked uniformity.

Darkening due to reduction as described above affects grain boundary strength and is unfavorable in terms of machinability. In addition, although any color may be used functionally, if the color tone is not constant and uniform, the commercial value will be significantly lowered.

Purpose of the Invention In view of the above-mentioned problems, this invention has a thermal expansion coefficient equivalent to that of Mn-Zn ferrite, a very dense crystal structure, and extremely few microcracks or crystal dropouts during machining. Ti02 exhibits stable black color
-CaO-based porcelain compositions are intended.

Structure and Effect of the Invention The conventional Ti02-CaO ceramic composition is composed of CaO・Ti
Within the two-phase mixed structure of O2 and TiO2, Ca
It is known that the coefficient of thermal expansion increases linearly with the amount of O-TiO2, and the Mn-Zn core material mentioned above
The thermal expansion coefficient of ferrite is fixed by the composition determined by the required electromagnetic properties, but it is 105 to 120
10-7/"C, it is necessary to match the thermal expansion coefficient of the non-magnetic structural component material to that of ferrite, and in order to suppress the difference in thermal expansion coefficient to 2 x 10-77"C or less.
, TiO250-75wt%, CaO25-50wt%
A porcelain composition consisting of the composition was used.

The present invention provides a Ti02-CaO based porcelain composition which has a very uniform and dense crystal structure, has very few microcracks or crystals falling off during machining, and exhibits a stable black color. As a result of various studies on the purpose, it was found that the above purpose can be achieved by containing CeO2 and ZrO2.

That is, this invention consists of TiO250wt%~75wt%, CaO25wt%~50wt%, TiO2, C
CeO22wt%~10 with respect to the total amount of aO 100
This is a ceramic composition for a magnetic head, which contains 1 wt% to 5 wt% of ZrO2 and ZrO2.

The porcelain composition according to the present invention consists of phases such as TiO2, CaO-TiO2, etc.
By adding O2 and ZrO2, uniform blackening is achieved, the size of these crystals becomes uniform and small, the generation of cracks due to machining with diamond abrasive grains, etc. is suppressed, and the porosity is reduced, resulting in flat and edge formation. The resulting material has good machining finish properties, and has excellent machinability compared to ceramic materials to which CeO2 and ZrO2 are not added, making it suitable as a material for magnetic heads.

Reasons for Limiting the Invention The reasons for limiting the components of the porcelain composition according to the present invention are as follows.

If the content of TiO2 is less than 50 wt%, the coefficient of thermal expansion is 12
The temperature exceeds 0 x 10-7/'C, and TiO2 becomes 7
If the content exceeds 5wt%, the coefficient of thermal expansion will be 105
X less than 10-7/'C, making it unsuitable as a partner material for glass welding with MnZn ferrite;
Thermal expansion coefficient of Zn ferrite 105-120 x 1
In order to maintain the same thermal expansion coefficient as 0-77'C, Ti
The content of O2 is 50 to 75 wt%.

When the CaO content exceeds 50 wt%, the thermal expansion coefficient is 1.
20 x 10-7/″C and CaO is 2
If the content is less than 5 wt%, the coefficient of thermal expansion is 105
10-7/'C, making it unsuitable as a partner material for glass welding with Mn-Zn ferrite;
Thermal expansion coefficient of ferrite 105-120X10-7/”
In order to maintain the same coefficient of thermal expansion as C, CaO25~5
The content is 0 wt%.

CeO2 is added to improve the machinability of the TiO2-CaO system and to make the color tone of the porcelain uniform black, but its content is less than 2wt% based on the total amount of TiO2 and CaO (100%). If the content exceeds 10 wt%, the crystal structure of the sintered body becomes non-uniform and the workability deteriorates, making it unsuitable as a mating material for soft ferrite. Addition.

On the other hand, ZrO2 has the effect of improving the porosity and uniformity of the crystal structure of the Ti02-CaO system due to the synergistic effect with the addition of CeO2, and its content is
If the content is less than 1 wt% with respect to the total amount of 100 O, the above-mentioned addition effect will not be obtained, and if the content exceeds 5 wt%, the porosity will tend to increase and workability will deteriorate due to changes in the crystal structure, so it is preferable. It is not necessary to add 1wt% to 5wt%.

Example The present invention will be explained below based on examples.

Commercially available TiO2, CaCO3, CeO2, Zr
Using O2, as shown in Table 1, the composition after sintering is the composition according to the present invention (No. 1 to 8) and the composition outside the scope of the present invention (No. 9 to 12), After mixing in a ball mill and drying, heat at 900℃ in air for 2 hours.
Calcination was performed for a period of time. Furthermore, the calcined raw material was again finely ground in a ball mill until the average particle size was 1.3 pm, and then 1.5 wt % of polyvinyl alcohol was added as a binder and granulated. After granulation, it was molded into a size of 40 mm x 20 mm x 20 mm at a molding pressure of 2000 Kg/cm2, and sintered in air at 1200°C for 2 hours.

The obtained porcelain was examined for properties such as density, coefficient of thermal expansion, and Vickers hardness, and the measurement results are shown in Table 2.

The Vickers hardness of the porcelain of the present invention is higher than that of ferrite materials, but lower than that of porcelain to which CeO2 and ZrO2 are not added, and free machinability is improved.

Regarding machinability, there is no physical constant that can accurately express it, but the critical stress intensity factor is currently a generally accepted parameter. A simple way to evaluate the critical stress intensity factor is to compare materials with approximately the same hardness based on the length of microcracks formed at the tip of the indentation made by the diamond indenter of a Vickers hardness tester. The standardized crack length in Table 2 shows the average value of the micro-crack lengths when a load of 500 gr is applied, and the shorter the crack length, the less chipping and micro-cracks will occur during processing. It can be said.

As is clear from Tables 1 and 2, Examples of the present invention (
Sample Nos. 1 to 8) have thermal expansion coefficients of 105 to 120.
Can be controlled between X10-7/”C,
It exhibits excellent properties such as mechanical strength and workability, and in particular, the porcelain material exhibits a black color, indicating that it is optimal as a material for magnetic head groove path components.

Margin below Table 1 Composition wt% Margin below

Claims (1)

[Claims] 1 Consisting of 250 wt% to 75 wt% of TiO and 25 wt% to 50 wt% of CaO, where CeO_2 is
2wt%~10wt% and ZrO_21wt%~5wt
A ceramic composition for a magnetic head, characterized in that it contains %.