JPH0633166B2 - Porcelain composition for magnetic head - Google Patents

Description

The present invention relates to a porcelain composition for a magnetic head porcelain (hereinafter referred to as a slider) for supporting a magnetic pole piece (ferrite core) used in a porcelain head such as a floppy disk. And more particularly to a porcelain composition of a magnetic head slider suitable for Mn-Zn ferrite.

(Background Art) As shown in the figure, the slider 1 is generally a ferrite core 2
Are bonded by heat treatment through the adhesive glass 3 to form a magnetic head. Therefore, if each of the slider 1 and the ferrite core 2 has a large thermal expansion or the like, a thermal history during heat treatment causes cracks or residual strains in these materials, causing glass peeling or the like during the assembling process. Therefore, the slider 1 must select its porcelain composition and composition ratio to match the thermal expansion coefficient of the ferrite core 2.

There are various grades of ferrite cores depending on their use, and the thermal expansion coefficient is 105 to 140 depending on this grade.
It needs to be applied to a wide range of × 10 ^-7 / ° C. Therefore, by changing the composition ratio of the slider, 105
It is desired to easily select a wide range of thermal expansion coefficient of ˜140 × 10 ⁻⁷ / ° C.

Further, the slider is required to have as few pores as possible in the porcelain sintered body. If there are many pores on the surface of the sintered body that comes into contact with the floppy disk, the magnetic powder coded on the disk surface will easily adhere to the pores, and the presence of the adhered magnetic powder will impair the magnetic characteristics during recording and reproduction. Bring

Further, the slider must have its porcelain sufficiently sintered and densified. If the sintering is insufficient and the strength and toughness are inferior, chipping and cracks will occur in the porcelain, leading to a serious defect that the disk itself will be damaged when running on a floppy disk.

On the other hand, Ni-Zn ferrite has been conventionally used as the core of the magnetic head, but Mn-Zn ferrite has better magnetic characteristics, especially coercive force than Ni-Zn as the ferrite core for the prop disk. Since then, it is shifting to Mn-Zn ferrite.

(Explanation of Prior Art) Forsterite or barium titanate having a thermal expansion coefficient of about 90 to 98 × 10 ⁻⁷ / ° C. is known as a slider composition conventionally applied to Ni—Zn ferrite. .
However, when these porcelains are applied to Mn-Zn ferrite, the thermal expansion coefficient of Mn-Zn ferrite is 105 to 140 ×
Since it is 10 ⁻⁷ / ° C. and the difference in thermal expansion is too large, it is difficult to apply these porcelains.

On the other hand, as a slider composition applied to Mn-Zn ferrite, for example, calcium titanate, magnesium titanate, and strontium titanate, which mainly contain a titanate compound, have the same thermal expansion coefficient as that of Mn-Zn ferrite. It is known to be degree. However, Mn-Zn ferrite is 105 to 140 × depending on the required characteristics.
There are a wide variety of grades in a wide range of 10 ^-7 / ° C. Conventionally, the thermal expansion coefficient of this wide range can be linearly changed by simply changing the composition ratio and easily match the thermal expansion coefficient of various grades. No magnetic head slider composition has been found.

On the other hand, recently, in order to reduce the generation of pores in the porcelain sintered body for sliders, especially pores of large diameter, the sintered body obtained by normal pressure firing or hot pressing is further subjected to HIP (hot isostatic pressing) treatment. Is being tested. However, in the composition mainly containing the titanate compound, the color tone of the porcelain is extremely changed because Ti ions are reduced when firing in argon gas, for example. In this case, it is necessary to restore the changed color of the porcelain.

(Problems to be solved by the present invention) As a result of earnest research in view of the above-mentioned present situation, the present inventors have found that BaO and SiO
₂ is the main component, on the other hand, a ceramic composition for a magnetic head containing a small amount of an additive selected from TiO ₂ , MgO, ZnO and ZrO ₂ has a thermal expansion coefficient of 105 to 140 × 10 ^-7 / ° C. It was found that they can be freely selected, have an excellent void generation rate and excellent sinterability, and have little change in color tone when subjected to HIP treatment.

(Object of the Invention) The present invention can be easily adapted to a wide range of the thermal expansion coefficient of the porcelain head of Mn-Zn ferrite according to various required characteristics, has less voids and is excellent in sinterability, and when subjected to HIP treatment. Another object of the present invention is to provide a porcelain composition for a magnetic head, in which the color tone of the sintered body is small.

(Means for Solving the Problem) The present invention is based on 100 parts by weight of a main component consisting of 37 to 50 mol% of BaO and 50 to 63 mol% of SiO ₂ , TiO ₂ , MgO, ZnO and ZrO ₂ 15 parts by weight or less (0
A ceramic composition for a magnetic head is provided.

The thermal expansion coefficient can be freely selected within the range of 105 to 140 × 10 ^-7 / ° C by changing the composition ratio of BaO and SiO ₂ within the above range.

In addition, BaO and S are less susceptible to changes in valence depending on the atmosphere.
Since iO ₂ is the main component, there is no change in color tone due to HIP processing.

The reason for limiting the amount ratio of BaO and SiO ₂ to the above range is that when BaO exceeds 50 mol%, unreacted BaO in the porcelain is present.
Is easily present, and the moisture resistance of the porcelain itself is deteriorated, which makes it unstable as a slider porcelain. When BaO is less than 37 mol% and SiO ₂ is more than 63 mol%, a SiO ₂ phase is formed and the thermal expansion coefficient is greatly reduced.

Although the addition of at least one of TiO ₂ , MgO, ZnO and ZrO ₂ promotes the sinterability of the BaO-SiO ₂ system,
By adding these, the firing temperature can be lowered,
The generation of pores can be reduced. However, when at least one of the above additives is added in excess of 15% by weight,
The coefficient of thermal expansion is less than 105 × 10 ⁻⁷ / ° C. and is excluded from the present invention.

Hereinafter, the present invention will be described in detail with reference to examples.

In the present invention, the method of manufacturing a slider for a magnetic head is to weigh raw materials in a predetermined composition ratio, mix and pulverize, and then calcine,
Next, it is preferable to employ a usual method in which the calcined product is finely pulverized, an organic binder is added to granulate, and the mixture is molded into a predetermined size and then fired, since a denser sintered body can be obtained.

Example 1 Commercially available BaCo ₃ , SiO ₂ , TiO ₂ , Mg (OH) ₂ and CoCO ₃
The porcelain composition after sintering was weighed as shown in Table 1 using ZrO ₂ and ZrO ₂ , and wet-mixed using a ball mill. This is dried, and the raw material after drying is heated in the temperature range of 950 to 1150 ° C.
It was calcined for 2 hours. After the calcination, the raw material was finely pulverized so that the mixture of impurities was suppressed and the average particle diameter was about 1.5 μm or less.
After adding an organic binder to this and granulating, 1.0 ~
Molded at a pressure of 2.0 ton / cm ² . Main firing is 1200-1450 ℃
Samples Nos. 1 to 9 shown in Table 1 were obtained by performing the heating in the atmosphere in the temperature range of 1.0 to 2.0 hours.

Proper firing temperature, bulk specific gravity, 40-400 for the obtained porcelain
The average coefficient of thermal expansion at ℃, pore distribution and sinterability were investigated and listed in Table 1. The appropriate firing temperature was the temperature at which the bulk specific gravity was maximum. The pore generation rate was evaluated by measuring the area occupied by pores in the final lap surface (mirror surface) formed by 1 μm crushed diamond particles. The measurement was performed using an image analyzer under a magnification of (× 200), and it was shown as the ratio of the area occupied by pores to the total measured area. When this value is 2% or more, x is shown, 1-2% is indicated by Δ, 0.1-1% is indicated by o, and 0.1% or less is indicated by o. Regarding sinterability, water absorption of 2% or more is ×,
The symbol 0 indicates 0% and the middle symbol indicates Δ.

As can be seen from Table 1, Sample Nos. 3 to 7 are within the scope of the present invention, and the thermal expansion coefficients thereof are 105 to 140 × 10 5, respectively.
It is selected in the range of ^-7 / ° C, and the rate of pore generation and sinterability are good. On the other hand, sample Nos. 1 and 2 are TiO ₂ , Mg
When O, ZnO, ZrO ₂ or CaO was not added, the pore generation rate and sinterability deteriorate. Sample No. 1 is B in the main component
In the case where aO is a little large, the moisture resistance deteriorates and the slider becomes unstable, so that the thermal expansion coefficient is as large as 143 × 10 ⁻⁷ / ° C. Sample No. 8 had a large amount of SiO ₂ and had a large decrease in the coefficient of thermal expansion. Sample No. 9 had a large addition of TiO ₂ and had a low coefficient of thermal expansion.

Example 2 The samples shown in Table 1 were subjected to HIP treatment. HIP
Regarding the treatment, it was baked at 1000 to 1200 ° C. and 2000 kg / cm ² in an argon atmosphere for 1 to 2 hours. The specific gravity after HIP, the up ratio with respect to the specific gravity before HIP and the rate of change in color tone were calculated and visually observed, and the pore generation rate was evaluated in the same manner as in Example 1 and shown in Table 2.

The specific gravity of each sample after HIP has improved by about 2%.
Except for o.1 and 2, the pore generation rate is very small and good. However, in Sample No. 9, the color tone of the sintered body after HIP changed from white to blue because TiO ₂ was added in a large amount.

Example 3 A mixed powder mainly composed of a titanate compound in which 64% by weight of TiO ₂ and 36% by weight of CaO are mixed is calcined by the same method as in Examples 1 and 2 -normal firing- When HIP processing was performed, the color tone of the sintered body after HIP changed from light brown to black.

As described above, the BaO—SiO ₂ porcelain composition of the present invention contains TiO ₂ , Mg
By mixing a small amount of at least one sintering promoter of O, ZnO and ZrO ₂ , a thermal expansion coefficient of 105 to 140 × 10 ^-7 /
A wide range of ° C can be arbitrarily selected, the pores are small and the sinterability is good. Further, even if HIP treatment is performed to reduce the pore diameter of the sintered body or reduce the pores, the color tone of the sintered body does not change and the commercial value is not reduced.

[Brief description of drawings]

The drawing is a perspective view of a magnetic head used for a floppy disk.

Claims (1)

[Claims] 1. TiO ₂ , MgO, Z based on 100 parts by weight of the main component consisting of 37 to 50 mol% of BaO and 50 to 63 mol% of SiO _2.
A porcelain composition for a magnetic head, comprising 15 parts by weight or less (not including 0) of at least one selected from nO and ZrO ₂ .