JPS61146780A - Manufacture of single crystal - Google Patents

Abstract

PURPOSE:To obtain the titled large-sized single crystal in good yield by polishing specularly the surface of a polycrystalline body and a single crystal to be joined, joining both ground surfaces to obtain a joined body, and heating the joined body in the specified temp. range and at a specified temp. increasing rate. CONSTITUTION:A mixture consisting of about 32mol% MnO, about 16mol% ZnO, and about 52mol% Fe2O3 is calcined to obtain a polycrystalline body of manganese, zinc, ferrite, etc. A ferrite single crystal having the composition almost identical to the polycrystalline body is prepared. Both polycrystalline body and single crystal are cut out into plates having about the same size, and both surfaces to be joined are ground with diamond abrasive grains. A strong acid such as hydrochloric acid is coated on both surfaces to be joined, and the polycrystal body and the single crystal are put on each other to obtain a joined body. The joined body joined as such is heated in the temp. range from 50 deg.C lower than the discontinuous grain growing temp. to 40 deg.C higher than the temp. and at the temp. increasing rate of 1-20 deg.C/hr to transform the whole polycrystalline body into a single crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to uniform single crystallization of polycrystals,
In particular, the present invention relates to a method of manufacturing single crystal ferrite useful for magnetic heads such as VTRs.

(Prior art) Conventionally, as a method for producing single crystals, the applicant has
No. 162496 discloses a single crystal production method using a solid phase reaction method. In this manufacturing method, the joint surfaces of the seed single crystal and polycrystalline material are mirror-polished, and then they are joined using a strong acid such as hydrochloric acid or nitric acid, which is lower than the discontinuous grain growth temperature of the polycrystalline material. Polycrystals were turned into single crystals by heating at a constant temperature.

FIG. 4 is a graph showing an example of a typical heat treatment schedule, where T6 indicates a temperature below the discontinuous grain growth temperature of the polycrystalline material. As shown in FIG. 4, the conventional heat treatment schedule produces a bonded body of T.

After raising the temperature to a temperature of To, heating was performed while maintaining the temperature at To to convert the polycrystal into a single crystal.

(Problems to be Solved by the Invention) In the above manufacturing method, in order to grow crystals in the direction of the polycrystal using the seed single crystal as a nucleus, the holding temperature T0 is set to be lower than the discontinuous grain growth temperature of the polycrystal. It was necessary to set the temperature 2-5° C. lower and hold the joined body precisely at that temperature. However, in heat treatment equipment such as electric furnaces used in actual production, even if the temperature distribution is good, there is a deviation of 2 to 5 degrees Celsius in the temperature distribution, and this cannot be prevented. Non-uniform temperature distribution occurs in the body itself, and even though part of the bonded body is below the discontinuous growth temperature, other parts exceed the discontinuous growth temperature, producing a single crystal with a different phase, resulting in a uniform single crystal. There was a drawback that it was not possible to obtain

Furthermore, due to slight variations in composition and subtle differences in firing conditions, the discontinuous grain growth temperature of other crystals fluctuates, making it impossible to obtain uniform single crystals simply by heating at a constant holding temperature. . Therefore, the yield of single crystals was low and large single crystals could not be obtained.

FIG. 5 is a perspective view showing the appearance of the above-mentioned single crystal with a different phase, in which 1 indicates a seed single crystal, 2 indicates a generated single crystal, and 3 indicates a single crystal with a different phase.

The purpose of the present invention is to eliminate the above-mentioned problems, improve the heat treatment schedule, prevent the appearance of single crystals of different phases, and provide a method for producing single crystals that can obtain large single crystals with good yield. It is.

(Means for Solving the Problems) The method for producing a single crystal of the present invention is to grow the single crystal in the direction of the polycrystal by contacting and heating the polycrystal and the single crystal. In the method for obtaining a polycrystal, the joint surfaces of the polycrystal and the single crystal are mirror-polished, the polycrystal and the single crystal are joined by preferably interposing an acid between the mirror-polished surfaces, and the polycrystal is bonded in the joined state. Average heating rate 1 within the temperature range of -50℃ to +40℃ before and after the discontinuous grain growth temperature point
It is characterized by heating at a rate of .degree. C./hour to 20.degree. C./hour to convert the polycrystalline body into a single crystal.

(Function) As a result of various studies on heating schedules, the present inventors found that in order to obtain a desirable single crystal by eliminating the above-mentioned non-uniform temperature distribution during heating and fluctuations in the discontinuous grain growth temperature of polycrystals. , -50 before and after the discontinuous grain growth temperature point of the polycrystal in a state where the bonded body consisting of a single crystal and a polycrystal is joined during heating.
Average heating rate 1°C/hour to 2 within the temperature range of t to +40°C
It has been found that it is good to heat at a rate of 0 t/hour, that is, to gradually raise the temperature around the above discontinuous grain growth temperature.

(Example) Hereinafter, the present invention will be explained in detail based on examples.

Although the method for producing a single crystal of the present invention can be applied to polycrystals of any composition, the following compositions are actually preferred.

I ferrite Mn0 20-40 mol% Zn0 5-
30 mol% Fe, 03 balance (preferably 48-60% li%
) ■ Ferrite Ni0 15-40 mol% Zn0
15-40 mol% Fe2O+ balance (preferably it 45-55 mol%
) ■ Garnet; 3Y21 for garnet] 3 -5
There are Fe, D3 and 3Y203.51.03, both of which can be produced by the method of the present invention.

The mixing ratio is Y2O3:Fe203=3:5 or y
, o, :^l1203・3:5.

■ Spinel; Spinel has a composition of MgO: A R2's, and the blending ratio is MgO:^β203=1:1.

First, a polycrystalline block having the composition as described above is prepared, and its joint surface is mirror-polished with diamond abrasive grains. On the other hand, a single crystal with the same composition and a bonding surface of the same size is prepared as a seed, and the bonding surface is mirror-polished in the same manner. Thereafter, a strong acid such as hydrochloric acid or nitric acid was dropped onto both bonding surfaces to bond the single crystal and polycrystalline body. At this time, if a dummy material made of a polycrystalline material that does not grow is prepared and bonded to the surface of the polycrystalline material facing the single crystal using a mirror polisher with strong acid,
More suitable for single crystallization. Next, with the bonded body bonded, -5 before and after the discontinuous grain growth temperature point of the polycrystalline body
Average heating rate of 1°C/hour within the temperature range of 0°C to +40°C
The entire polycrystal is turned into a single crystal by heating at a rate of 20° C./hour.

At this time, the relative humidity of the bonded body is 70% prior to heating at elevated temperature.
It is preferable to maintain the above atmosphere for 2 hours or more. In addition, in order to eliminate residual dalein, which is small crystals with different orientations, after single crystallization, it is preferable to maintain the temperature at a temperature higher than the discontinuous grain growth temperature after the heat treatment schedule is completed.

In addition, the discontinuous grain growth temperature in the above example is the first
Within the range shown in the table.

Table 1 Example 1 Manganese oxide obtained by roasting manganese carbonate with a purity of 99.9%, zinc oxide and ferric oxide with a purity of 99.9% are used as raw materials, and the composition is Mn O = 32 , 0 mol%.

ZnO=16, 0 mol%, Fe203=52. Q
Formulation A with MnO = 28.0 mol %, Z
Formulation B with n0 = 17.0 mol% and Fe 20 = 55.0 mol% was molded, respectively, and 1
Manganese zinc ferrite polycrystals A and B were obtained by firing at 320° C. for 4 hours.

10 x 30 x 5 mm and 10 x 30
, 5 mm plates were cut out, and the joint surfaces of each were polished using diamond abrasive grains. Thereafter, 6N hydrochloric acid was applied to each joint surface, and the polycrystalline ferrite plate and the single-crystal ferrite plate were overlapped to obtain ferrite joints A and B.

Sample Nα from each of these ferrite bonded bodies A and B
Samples Nos. 1 to 11 were prepared and heated according to different heating schedules described below to cause a solid phase reaction and obtain a single crystal according to the present invention.

1 to 3 are graphs showing the heating schedule in the present invention described above. That is, Fig. 1 shows sample N
The heating schedule for α1 to α9 is shown, and the temperature increase rate a from P to P2 in the figure is changed respectively. Figure 2 shows the heating schedule for sample Nα10, in which P1
10℃/hour from P2 to P2, 5℃/hour from P2 to P3
The average heating rate was 6.2℃/
It's time.

In addition, Fig. 3 shows the heating schedule for sample No. 11, in which the temperature was raised and held in steps for a total of 8 hours from P1 to P8 in the figure, and the average temperature increase rate was 10 ° C /
It's time. In the above-mentioned examples, the discontinuous grain growth temperature of the manganese-zinc ferrite polycrystal was about 1370°C. The results are expressed as the appearance rate of completely single crystals for each sample (
%) shown in Table 2.

Table 2 □ (Unit: %) As is clear from Table 2, sample N is within the scope of the present invention.
No. o, 1 to Nα7 and No. 10 to Nα11 have a low appearance rate of single crystals with different phases, whereas No. o is outside the scope of the present invention.

8 and Nα9 have a high incidence of single crystals with different phases.

(Effects of the Invention) As is clear from the above detailed explanation, according to the method for producing a single crystal of the present invention, a single crystal in which the entire polycrystalline body is completely single crystallized can be obtained in good yield. . Moreover, it is possible to obtain large single crystals and to improve the yield of single crystallization of polycrystals. Furthermore, the ferrite single crystal obtained by the method of the present invention can be suitably used as a VTR magnetic head.

Brief explanation of the previous aspect Figures 1 to 3 are graphs showing the heating schedule in the present invention, Figure 4 is a graph showing a typical conventional heat treatment heating schedule, and Figure 5 is a graph showing a heating schedule for a conventional heat treatment. FIG. 3 is a perspective view showing the state in which a single crystal appears.

l... Seed single crystal 2... Generated single crystal 3... Single crystal with different phase

Claims (1)

[Claims] 1. A method for obtaining a single crystal by growing the single crystal in the direction of the polycrystal by contacting and heating the polycrystal and the single crystal, comprising: The joint surfaces are mirror-polished, the polycrystalline body and the single crystal are joined together, and the average temperature increase rate is 1°C within the temperature range of -50°C to +40°C before and after the discontinuous grain growth temperature point of the polycrystalline body in the joined state. 1. A method for producing a single crystal, which comprises heating the polycrystalline substance at a rate of 20° C./hour to a single crystal. 2. Interposing an acid between the bonded bodies prior to the temperature raising heating,
2. The method for producing a single crystal according to claim 1, wherein the single crystal is maintained in an atmosphere with a relative humidity of 70% or more for 2 hours or more. 3. The method for producing a single crystal according to claim 1, wherein the average heating rate is 3°C/hour to 12°C/hour.