JPH11278922A - Ferrite porcelain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dense Ca-based or Ca-Zn-based ferrite porcelain scarcely causing cracking or chipping even when carrying out a grinding working or applying an impact thereto. SOLUTION: This ferrite porcelain is composed of the crystal phase in the interior thereof comprising CaFe2 O4 or the CaF2 O4 and ZnFe2 O4 and the porcelain surface layer part having Ca2 Fe2 O5 other than the crystal phase so as to provide <=1 peak ratio (I2 /I1 ) of the main intensity peak (I2 ) of the Ca2 Fe2 O5 to the main intensity peak (I1 ) of the CaFe2 O4 when measuring the porcelain surface layer part according to the X-ray diffractometry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a Ca-based or Ca-Zn-based ferrite porcelain used for a ceramic substrate for a magnetic head, a slider for a magnetic head, a spacer for a magnetic head, a magnetic tape guide, a part for a micromachine, and the like. Particularly, it is suitable as a ferrite porcelain for a slider of a magnetic head used for magnetic recording such as a hard disk, a floppy disk, and a magnetic tape of a computer.

[0002]

2. Description of the Related Art A magnetic recording apparatus using a magnetic head has been increasing in recording density and capacity, and accordingly, the magnetic head has been required to cope with higher linear density and higher track density. Has been requested.

Therefore, as a magnetic head capable of achieving high linear density and high track density, a composite type magnetic head in which a head core is bonded to a ceramic slider with glass or the like is employed. In general, Mn-Zn ferrite porcelain has been used, and calcium titanate or barium titanate has been used as a slider material. The head core and the slider were bonded by heating to a high temperature of about 400 ° C. and melting the glass interposed between the head core and the slider.

As another magnetic head, a composite core in which a part of the head core is replaced with a non-magnetic substrate and a magnetic thin film is formed on the non-magnetic substrate is also employed. Calcium titanate was used for the substrate.

[0005] Further, sliders constituting these magnetic heads have been manufactured by cutting a substrate made of various ceramics by grinding or the like. In recent years, with the miniaturization of magnetic heads, sliders having a size of 50% (1. 6 × 2 × 0.
4%) to 30% size (1 × 1.2 × 0.3mm)
In such a size, the slider has been integrally formed by press molding.

[0006]

If the coefficient of thermal expansion of the slider is different from the coefficient of thermal expansion of the head core, cracks and residual strains occur due to thermal stress when the head core is bonded to the slider, resulting in insufficient bonding. Since the head core may fall off the slider, it is necessary to make the thermal expansion coefficient of the slider match the thermal expansion coefficient of the head core.

However, the coefficient of thermal expansion of calcium titanate forming the slider is 100 to 120 × 10 ^-7.
/ ° C, and the coefficient of thermal expansion of barium titanate is 80 to 1
The thermal expansion coefficient of the Mn—Zn ferrite porcelain forming the head core is 10 × 10 ⁻⁷ / ° C.
5 to 130 × 10 ⁻⁷ / ° C., the thermal expansion coefficient of the composite core is 10
A slider made of calcium titanate or barium titanate having a temperature of 0 to 120 × 10 ⁻⁷ / ° C. could not cover all the thermal expansion coefficients of various materials forming the head core.

In a magnetic recording device for a hard disk, a CSS (Contact start / start) in which a magnetic disk rotates and a magnetic head flies.
op) is adopted, and the head comes in contact with the magnetic disk at the time of starting and stopping.
If the slider material that composes the magnetic head is not sufficiently densified, chipping or cracking occurs due to contact with the magnetic disk, and when this fragment is caught between the magnetic head and the magnetic disk, the recording medium on the magnetic disk or There is a problem that the reliability of the magnetic recording apparatus is significantly reduced because the magnetic head is destroyed.

On the other hand, the present applicant has conducted various studies to obtain a slider material for a magnetic head which can be applied to a head core having a large coefficient of thermal expansion and has excellent slidability with a magnetic disk. -Based ferrite containing Zn and Fe ₂ O ₃ in a specific molar ratio, and ZnFe ₂ O ₄
Japanese Patent Application Laid-Open No. 5-85807 proposes that if formed from a ferrite porcelain such as a Ca-Zn-based ferrite mixed with, the slidability is excellent and the thermal expansion difference between the head core and the composite core can be reduced. JP-A-8-10812
No. 0).

However, if the ferrite porcelain is subjected to HIP processing to make it denser and then subjected to grinding to cut out a slider having a predetermined shape, cracks and chips are generated. This has been a major problem because of low yield in mass production.

Further, in the case where the slider is integrally formed by press molding with the above ferrite porcelain, cracks or chips are generated in the surface layer of the slider during repeated contact with the magnetic disk, and these fragments are separated from the magnetic head. There is a problem that the recording medium or the magnetic head on the magnetic disk is destroyed when the magnetic head is sandwiched between the magnetic disk and the magnetic disk.

[0012]

Means for Solving the Problems Accordingly, the present inventor has proposed:
Repeated experiments were conducted on the causes of the breakage of ferrite porcelains made of HIP-treated Ca-based ferrite and Ca-Zn-based ferrite. An altered layer was found on the surface of the ferrite porcelain. The crystal phase inside the porcelain was CaFe
Although it is composed of ₂ O ₄ or CaFe ₂ O ₄ and ZnFe ₂ O ₄ , in addition to the above crystal phase, Ca ₂ F
e ₂ O ₅ exists as an altered layer, and the Ca ₂ Fe ₂ O ₅
Was found to be the cause of chipping and cracking.
It has been found that cracking and chipping can be significantly reduced by setting the amount of a ₂ Fe ₂ O ₅ to a specific range or less.

[0013] That is, the ferrite porcelain of the invention, porcelain internal crystal phase consists CaFe ₂ O ₄ or CaFe ₂ O ₄ and ZnFe ₂ O ₄ Prefecture, Ca ₂ Fe ₂ in the porcelain surface portion other than the crystalline phase has O _5, the peak ratio of the main intensity peak of the porcelain surface layer portion of the main intensity peak of CaFe ₂ O ₄ as measured by X-ray diffraction (I ₁₎ and _{Ca 2 Fe 2 O 5 (I} 2) (I ₂ / I ₁ ) is set to 1 or less.

According to the present invention, the crystal phase of the ferrite porcelain is CaFe ₂ O ₄ or CaFe ₂ O ₄ and ZnFe ₂
O ₄ , the coefficient of thermal expansion is 100 to 130 × 1
It can be adjusted freely within the range of 0 ^-7 / ° C. Therefore, since the thermal expansion difference with the head core made of the Mn-Zn-based ferrite porcelain can be made the same or similar, it does not cause cracks or residual strain when adhering to the head core, and can be suitably used as a slider material. it can.

When the ferrite porcelain is subjected to HIP processing to make it denser, the surface layer has a crystal phase of Ca
Fe ₂ O ₄ or CaFe ₂ O ₄ and ZnFe ₂ is O ₄ Ca ₂ Fe ₂ O ₅ in addition is being generated, the Ca ₂
If a large amount of Fe ₂ O ₅ is present, cracking and chipping are likely to occur. Therefore, the present invention provides a method for measuring the amount of Ca ₂ Fe ₂ O ₅ present in the surface layer of ferrite porcelain when measuring the amount of Ca ₂ Fe ₂ O ₅ by X-ray diffraction.
a Main intensity peak (I ₁ ) of aFe ₂ O ₄ and Ca ₂ Fe ₂
The peak ratio (I ₂ / O ₂ ) to the main intensity peak (I ₂ ) of O ₅
I ₁ ) is 1 or less.

By setting the peak ratio (I ₂ / I ₁ ) to 1 or less as described above, cracking or chipping of the ferrite porcelain can be prevented. For example, grinding is performed to cut out a slider from a plate-shaped ferrite porcelain. Yield can be improved because there is almost no chipping or cracking even after processing, and when the slider is integrally formed by press molding, chipping or cracking of the slider even after repeated contact with the magnetic disk Since no cracking occurs, the recording medium on the magnetic head or the magnetic disk is not damaged.

In measuring the main intensity peak (I ₁ ) of CaFe ₂ O ₄ , d =
In the measurement of the main intensity peak (I ₂ ) of Ca ₂ Fe ₂ O ₅ , d = 2.717 ± 0.02 corresponding to the (002) plane has a large intensity peak. Also, because the intensity peaks overlap little,
an intensity peak between d = 2.527 ± 0.01 and d
The peak ratio (I ₂ / I ₁ ) may be calculated by finding the respective intensity peaks between 2.717 ± 0.02.

By the way, in the present invention, porcelain internal crystal phase consists CaFe ₂ O _4, and the ferrite ceramic crystal phase porcelain surface layer portion consisting of CaFe ₂ O ₄ and Ca ₂ Fe ₂ O _5, Ca ferrite Wherein the molar ratio of CaO to Fe ₂ O ₃ is preferably 45/55 to 67
Those in the range of / 33 are good. This is because when the content of CaO is more than 67 mol% and the content of Fe ₂ O ₃ is less than 33 mol%, a small amount of CaO phase is generated in the ferrite porcelain and the sinterability is remarkably deteriorated.
Less, Fe ₂ O ₃ is generated a magnetic ferrite phase is more than 55 mol%, rough because not be used in a slider for a magnetic head used in a magnetic recording apparatus. The desirable molar ratio between CaO and Fe ₂ O ₃ is 50
/ 50 to 66/34 is good.

Further, in the present invention, porcelain internal crystal phase consists CaFe ₂ O ₄ and ZnFe ₂ O _4, a crystal phase of the ceramic surface layer portion CaFe ₂ O ₄ and ZnFe ₂ O _4, and C
Ferrite porcelain made of a ₂ Fe ₂ O ₅ means Ca-Z
It is made of n-based ferrite, and contains CaO and Fe ₂ O
₃ in a molar ratio of 45/55 to 67/33, and the total weight of these CaO and Fe ₂ O ₃ is 100.
It is preferable that ZnFe ₂ O ₄ be contained in a range of less than 170% by weight based on the weight%. The content of ZnFe ₂ O ₄ is 1
If it exceeds 70% by weight, the coefficient of thermal expansion becomes 100 × 10 ^−7.
/ ° C, which may cause breakage at the time of glass bonding with the head core.

The ferrite porcelain contains MnO, SiO _{2 and the} like as impurities, but if it is 3% by weight or less, there is no adverse effect on the porcelain characteristics.

In order to obtain these ferrite porcelains, for example, Fe ₂ O ₃ having a purity of 99.9% or more and C ₂
CaCl ₂ , CaCO ₃ , CaFe ₂ O ₄ as aO source
After weighing these in a predetermined amount, the mixture is wet-mixed using a ball mill or the like, and dried, and then the raw material is calcined at 800 ° C. to 1200 ° C. for about 2 to 10 hours in the air or an oxidizing atmosphere. Then, the obtained raw material is finely pulverized so as to have an average particle diameter of 1 μm or less, and then a binder is added to produce a slurry, which is formed into a predetermined shape by a tape forming method such as a doctor blade method or an extrusion forming method. Alternatively, the above-mentioned slurry is dried to produce a granulated body, filled in a mold, and formed into a predetermined shape by a uniaxial pressing method, an isopressing method, or the like. In addition, when forming by the uniaxial pressure molding method,
It is preferable to apply pressure at a pressure of 0.8 to 2.0 ton / cm ² .

Next, the obtained compact is fired in the atmosphere or in an oxidizing atmosphere under a normal pressure of 1150 to 1350 ° C. to produce a Ca-based ferrite porcelain having a relative density of 95% or more.

To produce a Ca—Zn ferrite porcelain, a ZnFe ₂ O ₄ raw material is added in a predetermined range to a raw material obtained by mixing the above-mentioned Fe ₂ O ₃ and CaO source and calcining the mixture. A Ca—Zn having a relative density of 95% or more is fired in the air or an oxidizing atmosphere under normal pressure at 1000 to 1200 ° C.
What is necessary is just to manufacture a system ferrite porcelain.

Next, the calcined Ca-based or Ca-Zn-based ferrite porcelain is placed in an inert gas atmosphere at 1000 to 1%.
By performing hot isostatic pressing (HIP) at a temperature of 200 ° C., a ferrite porcelain having a pore diameter of 1 μm or less is obtained. It is important to store it in a case made of ceramics. That is, when the ferrite porcelain containing calcium is exposed to an inert gas atmosphere, the surface layer reacts to cause Ca ₂ Fe ₂ O ₅ which is a cause of cracking and chipping.
Is easily generated. In order to further suppress the reaction, the above case may be filled with a powder made of an oxide ceramic such as alumina, zirconia, or calcium ferrite, and a ferrite porcelain may be embedded in the powder.

If the HIP treatment is performed under these conditions, the reaction in the surface layer of the ferrite porcelain can be suppressed, and the formation of Ca ₂ Fe ₂ O ₅ as the altered layer can be suppressed. Ca as measured by diffraction
Main intensity peak (I ₁ ) of Fe ₂ O ₄ and Ca ₂ Fe ₂ O
Peak ratio to the main intensity peak (I ₂ ) of ₅ (I ₂ / I ₁ )
Can be set to 1 or less.

Thus, when the ferrite porcelain of the present invention is used, the coefficient of thermal expansion can be freely adjusted within the range of 100 to 130 × 10 ⁻⁷ / ° C., and since it is nonmagnetic, it can be used as a ceramic for magnetic heads. It can be used for various purposes such as a substrate, a slider for a magnetic head of a porcelain recording device, a spacer for a magnetic head, a magnetic tape guide, and a part for a micromachine. Moreover, cracking and chipping hardly occur even when cutting or applying an impact. The yield can be improved, and the slider integrally formed by press molding does not cause chipping or cracking of the slider even after repeated contact with the magnetic disk. Does not damage the recording medium.

Example 1 Fe _{2 having a} purity of 99.9% or more
O ₃ and CaCl ₂ and CaCO ₃ were used as CaO sources, and the composition ratio of the ferrite porcelain after firing was weighed so as to be as shown in Table 2, wet-mixed using a ball mill, and dried, and then dried in an oxidizing atmosphere. At about 1000 ° C. for about 2 hours. Then, the calcined raw material is finely pulverized so that the average particle diameter is 1 μm or less, and a binder is added to produce a granulated body, and the granulated body is filled in a mold, and is charged to 1 ton / cm ^2. A plate-like molded body was formed by a uniaxial pressure molding method under the pressure of

Next, the obtained compact is fired at a temperature of 1150 ° C. in an oxidizing atmosphere at normal pressure to obtain a 2 × 3
× 1.2mm substrate is manufactured and HIP
Although the substrate is densified by performing the processing, in the case of using and not using the case in the HIP processing,
Further, when a case was used, an experiment was conducted by changing the material of the case. In the experiment, 101 substrates manufactured for each condition were prepared.

The obtained ferrite porcelain was subjected to X-ray diffraction under the conditions shown in Table 1, and the main intensity peak (I ₁ ) of CaFe ₂ O ₄ present on the surface of the ferrite porcelain and the Ca ₂ Fe ₂ O ₅ C along with measuring the main intensity peak (I _2), a main intensity peak of CaFe ₂ O ₄ by cutting the ferrite porcelain inside porcelain (I ₁₎
The main intensity peak (I ₂ ) of a ₂ Fe ₂ O ₅ was measured, and the peak ratio (I ₂ / I ₁ ) was calculated.

The remaining 100 ferrite porcelains were subjected to surface grinding using a diamond wheel to a thickness of 3 mm to measure the occurrence of cracks and chips. It was evaluated as good.

The results are as shown in Table 2.

[0032]

[Table 1]

[0033]

[Table 2]

As a result, in all ferrite porcelains, the crystal phase inside the porcelain is substantially composed of only CaFe ₂ O _4, but in the case where no case was used at the time of the HIP treatment, Ca ₂ Fe ₂ O ₅ was contained on the porcelain surface layer. As a result, Ca ₂ Fe ₂ O ₅ was generated to such an extent that it could not be evaluated by X-ray diffraction. When the case was not used, the densification in the surface layer of the porcelain was not so advanced, and the pore diameter was 1 μm.
m or less.

Therefore, when this ferrite porcelain was subjected to surface grinding, cracks or chips occurred in 33 out of 100 pieces.

On the other hand, in the case where the case was used at the time of the HIP treatment, the peak ratio (I ₂ / I ₁ ) in X-ray diffraction was less than 1 and Ca ₂ Fe ₂ O ₅
The amount could be reduced, and the pore diameter could be reduced to 1 μm or less.

Therefore, even if these ferrite porcelains were subjected to surface grinding, almost no cracks or chips occurred.

(Example 2) Next, CaO after firing
And Fe ₂ O ₃ composition ratio by firing a Ca-based ferrite porcelain having different experiments were conducted under the same conditions as in Example 1 to those densified by using a zirconia casing during HIP processing.

The results are shown in Table 3.

[0040]

[Table 3]

As a result, the sample No. having a molar ratio of CaO to Fe ₂ O ₃ of more than 67/33. Any Ca-based ferrite porcelain except 1 can be sintered, and the crystal phase inside the porcelain is CaFe ₂ O ₄ , and the peak ratio (I ₂ / I ₁ ) of the surface layer of the porcelain by X-ray diffraction is less than 1. And Ca ₂ Fe ₂
The amount of O ₅ could be reduced, and as a result, cracking and chipping hardly occurred even when surface grinding was performed.

Example 3 Next, the CaO after firing was
And a Ca—Zn-based ferrite porcelain having different contents of Fe ₂ O ₃ and ZnFe ₂ O ₄ were fired and densified using a zirconia case during HIP processing under the same conditions as in Example 1. Experiments.

The results are as shown in Table 4.

[0044]

[Table 4]

As a result, the sample No. having a molar ratio of CaO to Fe ₂ O ₃ larger than 67/33. Any Ca except 7
-Zn-based ferrite porcelain also has a CaFe crystal phase inside.
It consists of ₂ O ₄ and ZnFe ₂ O _4, and the peak ratio (I ₂ / I ₁ ) of the surface layer of the porcelain by X-ray diffraction is less than 1 and Ca ₂ Fe
_The amount of ₂ O ₅ could be reduced, and as a result, cracking and chipping hardly occurred even when surface grinding was performed.

[0046]

As described above, according to the ferrite porcelain of the present invention, the crystal phase inside the porcelain is composed of CaFe ₂ O ₄ or CaFe ₂ O ₄ and ZnFe ₂ O _4, and Despite having Ca ₂ Fe ₂ O ₅ in addition to the phase, when the surface of the porcelain is measured by X-ray diffraction,
Main intensity peak (I ₁ ) of Fe ₂ O ₄ and Ca ₂ Fe ₂ O
Peak ratio to the main intensity peak (I ₂ ) of ₅ (I ₂ / I ₁ )
Is set to 1 or less, the coefficient of thermal expansion is set to 100 to 1
Since it can be adjusted freely within the range of 30 × 10 ⁻⁷ / ° C., Mn−
Since the difference in thermal expansion from the magnetic head core made of Zn-based ferrite can be made extremely small, the head core can be securely joined to the slider without causing cracks or residual distortion when bonding the head core and the slider.

Further, even if grinding is performed to cut out the slider from the ferrite porcelain, cracking and chipping hardly occur, mass production is possible, and even if the slider is integrally formed by press molding, Since cracking and chipping do not occur due to repeated contact with the magnetic disk, it is possible to provide a highly reliable magnetic recording device without damaging the magnetic head or the recording medium on the magnetic disk.

Claims (1)

[Claims] 1. A crystal phase in a porcelain is composed of CaFe ₂ O ₄ or CaFe ₂ O ₄ and ZnFe ₂ O _4, and the surface layer of the porcelain has Ca ₂ Fe ₂ O ₅ in addition to the above crystal phase. CaFe ₂ when the surface layer of porcelain was measured by X-ray diffraction
Ferrite porcelain O ₄ main intensity peak (I ₁₎ and Ca ₂ Fe ₂ O ₅ main intensity peak (I ₂₎ the peak of the ratio (I ₂ / I ₁₎ is characterized in that 1 or less.