JPS5926993A - Preparation of oxide single crystal - Google Patents

Abstract

PURPOSE:To obtain a single crystal having little deviation in composition and uniform controlled crystal orientation in high yield, by joining an oxide single crystal to an oxide polycrystal, and heating the joined material in a specific atmosphere at a high temperature. CONSTITUTION:An oxide polycrystal 2 having composition the same as or close to that of a pair of oxide single crystals, e.g. thin plate ferrite magnetic materials, is inserted between the pair of the oxide single crystals 1 and joined by a suitable method. The joined material is then heat-treated in an atmosphere consisting of at least one of argon gas or nitrogen gas as a main component at a temperature higher than the temperature for starting the growth of giant crystalline grains to convert the oxide polycrystal into the aimed single crystal. The growth rate for the forming the single crystal is increased by the method.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for producing an oxide single crystal.

Structures of conventional examples and their problems At present, oxide single crystals include ferrite single crystals for magnetic head materials for magnetic recording, crystal oscillation elements, YAG single crystals for lasers, sensors, and LiNbO3 and LiT for surface wave devices.
AO3 single crystals and the like are widely used in the fields of electronic and mechanical industries. For example, especially among single crystal ferrites, Mn
-Zn-ferrite makes effective use of its mechanical properties (abrasion resistance, surface roughness, etc.) and magnetic properties due to the difference in crystal orientation, and is used for magnetic applications such as audio/video tape recorders and magnetic disks for computers. Widely used as head material. In particular, single crystal ferrite
Compared to polycrystalline ferrite, there are fewer chips, chips, etc. that occur during magnetic head processing, and it can be produced at a high yield.

Conventional single crystal manufacturing methods include the Czochralski method, Bridgman method, Beinoulli method, flux method, hydrothermal synthesis method,
There are various methods such as high temperature and high pressure reaction method.

By the way, conventionally, single crystal ferrite has generally been manufactured by the Bridgman method. This Bridgman method heats the raw material ferrite once above the imitation point and melts it.
Next, by gradually passing through a low temperature section, in-phase precipitation is performed from the liquid phase, and a single crystal is obtained. Therefore, a crucible for melting raw materials that can withstand high temperatures is required, and in the case of producing ferrite single crystals, platinum crucibles are used. The use of this platinum crucible makes single crystal ferrite expensive. Furthermore, with the usual Bridgman method, it is difficult to control the crystal orientation;
When processing a single crystal, the usable portion decreases, causing a decrease in yield.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned drawbacks of the conventional Bridgman method. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing large amounts of single crystals with low compositional segregation and uniformly controlled crystal orientation with high yield. The method for producing an oxide single crystal involves joining an oxide single crystal to a rimmedium polycrystal which has the same composition as, or close to, the oxide single crystal and the same crystal structure as the oxide single crystal. and heat-treating the bonded body in an atmosphere containing at least one of argon gas or nitrogen gas as a main component at a temperature higher than the temperature at which giant crystal grains begin to form,
The oxide polycrystal is a single crystal.

The manufacturing method of the present invention will be explained in more detail. Figure 1 shows
This is one of the outlines of the conjugate used in the present invention. FIG. 1(a) shows the external appearance, and FIG. 1(b) schematically shows the cross section at the center of the joined body after single crystallization heat treatment.
1) is a pair of thin plate-shaped tun crystals, (2) is a ryosha crystal (1)
A polycrystal which is sandwiched in between and undergoes single crystallization heat treatment,
(3) is the part that has been made into a single crystal from polycrystal (2), (L) is the length of the part (3) that has been made into a single crystal measured from the junction boundary between the single crystal (υ and polycrystal (2)), ( 4) are giant crystal grains grown from the polycrystalline (2) surface.

In FIG. 2, curve (B) shows the average grain size of the polycrystal as a function of the heating temperature when the polycrystal used in the present invention is heated for 6 hours in an atmosphere mainly composed of Ar gas or FiNt gas. This shows the diameter.

Further, curve (A) shows the growth of polycrystalline grains in ferrite, for example, due to "abnormal grain growth" as referred to in Japanese Patent Application Laid-Open No. 162496/1983.

Note that the heating time of 6 hours is the heat treatment time during actual manufacturing.

Figure 6 shows the grain growth of the polycrystalline grains shown by the curve (B) in Figure 2. The planes are schematically represented in order from (a) to ((L). Here, To is the temperature at which the polycrystal used in the present invention starts grain growth of giant crystals, and TI is Tc
At a temperature 20 to 50°C lower than T2, which is approximately halfway between TC and Ts, the entire surface of the polycrystal is covered with giant crystal grains.
The temperature is 70 degrees. However, Ts is the temperature at which the entire polycrystal is composed of giant crystal grains. The appearance of polycrystals at these temperatures can be easily understood by referring to FIG.

The abnormal grain growth polycrystal shown by curve (A) in Fig. 2 hardly causes grain growth until the temperature reaches Tc, and when it reaches To,
Suddenly, some giant crystals eat the surrounding microcrystals and become extremely large. This giant crystal is the 6th
The generation is not limited to the surface of the polycrystal as shown in the figure, but it also occurs uniformly from within.

The present invention proposes a new method for manufacturing oxide single crystals by using normal polycrystals as shown in curve (B) instead of using abnormally grown polycrystals as shown in curves (A) and K in Figure 2. It is something to do.

Furthermore, in addition to using polycrystals that exhibit grain growth as shown in curve (B) in FIG.
The heat treatment is carried out in a temperature range from c to Ts, preferably T3 or less, and the heat treatment atmosphere is controlled appropriately.

By the way, when manufacturing a bonded single crystal in which a single crystal and a polycrystal are bonded and heat-treated to form a single crystal, curve lf in FIG.
In the case of using abnormally grown polycrystals shown in @(A), by heating at a temperature below T0, the single crystals grow from the bonding interface between the single crystal and the polycrystal toward the polycrystal side. Crystallization progresses. On the other hand, if heat treatment is performed at a temperature higher than T0, giant crystal grains will occur and grow inside the polycrystal, inhibiting single crystallization, or even after single crystal formation, island-like crystal grains may remain inside the polycrystal. As a result, a homogeneous single crystal cannot be obtained. usually,
When manufacturing bonded single crystals, the smaller the polycrystalline grain size, the greater the driving force received when the single crystallization interface moves from the bonding interface toward the center of the polycrystal. The grains and diameter of the crystals are required to be small and constant during heat treatment. Therefore, it is necessary to perform heat treatment at a temperature lower than TO.

Since the polycrystal used in the present invention is a polycrystal that undergoes normal grain growth as shown by curve (B) in Figure 2, it is not necessary to perform the heat treatment at a temperature of less than 10°C, but at a temperature of 70°C or higher. Heat treatment increases the single crystallization rate (single crystal-polycrystal interface movement rate). However, if the heat treatment temperature is raised too much and the temperature exceeds T3, crystal grains grow inside the polycrystal, and for the reasons mentioned earlier, single crystallization may be inhibited or islands of crystals may form. Because the grains are left behind in the single crystallized area, it is difficult to obtain a homogeneous single crystal.
'< becomes. Therefore, in the present invention, the heat treatment is carried out in a temperature range of 70°C or higher, preferably 100°C, 200°C, 200°C, 200°C, 200°C, 200°C, 200°C, 200°C, 200°C, 250°C, and 200°F to TI. At this temperature, the giant crystal grains that appear on the surface are
It does not occur at the joint interface between a single crystal and a polycrystal, but only at the end face other than the joint interface. However, in the production method of the present invention, the single crystallization rate is significantly higher than the growth rate of giant crystal grains, so the single crystallization progresses as shown in FIG. 1 (1)).

When the polycrystal used in the present invention is heat-treated in an atmosphere of at least one of Ar gas and N2 gas, the single crystallization rate increases. When this polycrystal is heat-treated in another atmosphere, such as air, single crystallization from the bonding interface toward the center of the polycrystal does not occur, or even if single crystallization progresses, it grows significantly (1150 to 1/100). It's the one that reduces the speed! 7'c
HNt if IC some (,0,001~1.[1
When N2 gas (volume %) is mixed, the rate of single crystallization increases for some polycrystals.

As mentioned above, in the present invention, within a certain heating time (1
~12 hours of heat treatment), curve (B) in Figure 2
As shown in
Polycrystals are used that have regions where giant crystal grains occur and grow. In such cases, it is better to set the heat treatment temperature to a temperature at which giant crystal grains are generated on the polycrystalline surface, so that crystallization progresses in a short time, and by removing the giant crystals on the periphery, the center The single crystallized portion of can be effectively used.

The present inventors set Tl before setting the heat treatment temperature.

At each temperature of TC+T2+T3, an experiment was conducted under the same conditions such as atmosphere, type of polycrystal, heat treatment time, etc., and the single crystallization length L) shown in FIG. 1(b) was measured.

The length L) was measured by cutting the heat-treated joined body at the center, mirror-polishing the cut surface, and then etching it with strong acid.
1 by inspecting its surface.

The ratio of the length ζ (L) values when heat treated at each temperature Ts+Ta+T21 Tl was 1:L:10:4. However, 'r,, TO+ Tt+ TIf are each at intervals of 60°C, and T in the polycrystal used in this experiment.

=1600°C. In T, the polycrystal after heat treatment consisted of a single crystallized portion and a portion consisting of microcrystalline particles, and no giant crystals were found. , To, there are some giant crystal grains (4) in the periphery, as shown in Figure 1(b).
However, the generation of giant crystal grains (4) was hardly found in the single crystallized portion (3). For confirmation, the bonded body was cut into thin strips at several locations and the single crystallized portions were observed in the same manner, but giant crystal particles (4) were found. The case of T2 was similar to the case of To. In T3, a giant crystal 75 was present in front of the interface of the single crystallized portion, blocking movement of the interface. The maximum length of the peripheral giant crystal grain (4) portion in TO and T2 is 1/10 to 1/20 of the single crystallization length L), and by cutting and removing it, the subsequent single crystal There are no problems in terms of utilization, and therefore, it has been found that the most efficient method is to perform Calo heat treatment at a temperature near T.

When the single crystal produced by the present invention is compared with that produced by the ordinary Bridgman method, there are differences in magnetic properties (magnetic permeability, saturation magnetic flux density, coercive force, etc.), electrical properties (electrical resistance), etc. This method was superior to the Bridgman method in terms of yield, as there was no variation in characteristics even when mass-produced. Thus, it is clear that the manufacturing method of the present invention is extremely valuable as a method for manufacturing oxide single crystals.

Description of Examples Example-1 Composition ratio is 52 mol q6 Fe2O, 2 mol q6 Mn
A method for creating ceramics using 16 molt ZnO and crystalline Mn-Zn-ferrite with grain growth as shown in curve (B) in Figure 2. Created by molding → final firing). In this example, the main firing and the hot pressing method (1270°C - 300°C - 6 hours) were used. The obtained polycrystal had a porosity of 0.01% and an average grain size. The diameter was 20 μm. This was cut into a rectangular parallelepiped of 30 x 20 x 15 wttt.
The two surfaces of the 0×20 shoulder and shoulder 2 were polished to a mirror finish using EliC abrasive grains of +2000 mesh and +4000 mesh and diamond abrasive grains of 6 μm in diameter. On the other hand, a single crystal having the same composition ratio and made by the Bridgman method was prepared with a thickness of 1.0 to 1.5 W'IR so that the 30X20jr&2 plane became the [1003 plane and the side faces became the (110) plane. It was then cut into thin plates.

This single crystal thin plate also has SiC abrasive grains, 3
Polished with μm diamond abrasive grains to a mirror finish.

After cleaning both the polycrystalline rectangular parallelepiped and the single crystal thin plate,
Apply dilute nitric acid to the joint surfaces of the "X 20 ffm" joints, stick them together to form a joint, wrap this in Avena powder, place it in a mold, and heat it perpendicular to the joint surfaces in an atmosphere with N2 gas flowing. Pressurize and hot press (1250℃-30k
y/crtt” -30 minutes). Through this hot press, the single crystal and polycrystal were completely fixed together at the bonding surface by a solid phase reaction. In this hot press heat treatment, single crystallization did not occur, and the polycrystal and polycrystal did not form grains. It wasn't growing.

In advance, this polycrystal was heat treated in N2 gas for a period of time, the temperature at which giant crystals were generated on the surface was checked, and To=
Confirm that 1300℃, T, = 1360℃,
After that, the previously bonded body was placed in an N2 gas atmosphere.
Heat treatment was performed at 1620° C. for filtration time. After heat treatment, cut the center part of the joined body with a diamond cutter and take it out 7
, the cut surface was mirror polished and heated to 50°C.

Etching was performed for 2 to 3 minutes with 8N hydrochloric acid, and the cut surface was observed. The single crystallized length is L) halo ~ 4 h,
The length of the giant crystal at the periphery extending toward the center of the polycrystal is 0.2 to 0. It was a struggle.

For comparison, the bonded body after hot pressing was subjected to the same heat treatment with only the heat treatment temperature changed to 1270℃ and 1660℃.As a result, in the case of the heat treatment temperature of 1270℃, single crystallization The length (L) was 0.2 to 0.3 mm, and it was hardly single crystallized. On the other hand 1360
In the case of heat treatment temperature of °C, single crystallization length L) V
The diameter of the polycrystal was approximately 100 nm, and the inside of the polycrystal had grown into giant crystal grains with a grain size of approximately 0.1 to 1°O. Next, the heat treatment temperature was kept constant at 1320° C., and the heat treatment υψ atmosphere was changed to Ar gas, Co2 gas, or air. As a result, N
Single crystallized to the same extent as t gas 7'I; obtained, C
In O2 gas or air, the reduction was too strong or the total thermal single crystallization did not proceed.

Zarani1 Single crystal Mn-Zn- produced according to the present invention
7 Elite was cut out and its magnetic properties were measured.

Magnetic permeability is approximately 8000 at frequency 1, and coercive force is 0.
．． 0500 and was the same as the single crystal of the seed - Example 2 Composition ratio was 51 mo/l/% Fe20B, 25-E
/L/% Mn0, 21 L mol LIIZnO, second
Those that grow grains like curve (B) in the figure (hereinafter referred to as “B”)
(hereinafter referred to as "A polycrystal"), and those with abnormal grain growth as shown in curve (A) with the same 11 formation (hereinafter referred to as "A polycrystal").
Two types of polycrystals were prepared in the same manner as in Example-1. We hope to create a single crystal with the same composition ratio as the above,
Example - A bonded piece was obtained by hot pressing in the same manner as IJ. Both of these B polycrystals and A polycrystals have an atomization rate of o, oi%, an average crystal grain size of 15 μm,
The temperature T0 at which each giant crystal grain starts to generate and grow was the same, 1310°C. In the B polycrystal, the temperature Tsij11 was 60° C. when the whole consisted of giant crystal grains.

A plurality of these two types of bonded bodies were prepared and heated at 1280°C, 1610°C, and 1640°C in an Ar gas atmosphere.
After heating for 6 hours, the joined body was cut at the center and taken out. The steel surface was polished and etched, and the state of single crystallization was observed. For those using A polycrystal, 128
The single crystallization length L) when heat treated at 0°C is 2. Q
lll#, and the same 2. when using B polycrystal. O
It was ym. At this time, the average crystal grain size of the polycrystals was almost the same, 15 μm. A giant crystal of the fighting diameter is generated, and the single crystal length L) is 1. He was stationed at Qgx. On the other hand, in the case of using B polycrystals, giant crystals were observed in the peripheral area other than the bonding interface, but the size was about 0.2 mm, and the single crystal length L) was 2.5 ~ 3. It was a Q fight.

In the case of heat treatment at 1540° C., almost no single crystallization was observed in those using crystal A, and the sample consisted only of giant crystals with an average crystal grain size of Q and 5ff. On the other hand, in the case of using B polycrystal, the single crystallization length L) is about 5~
Ii, Qtsm, and the size of the surrounding giant crystal grains is
It was about 0.6 to 0.4.0 Effect of the Invention As described above, according to the present invention, the reaction occurs from the solid phase to the same phase without going through the process of precipitation from the liquid phase to the same phase. Therefore, it is possible to obtain a single crystal with less compositional segregation and a homogeneously controlled crystal orientation, and it is also possible to increase the growth rate of this single crystal, making it possible to produce this single crystal in large quantities with high yield. Not only can it be used, but also the high temperature (1/)00~1750℃) in the conventional Bridgman method
Therefore, there is no need to use an expensive container such as a platinum crucible, and a firing furnace for ordinary ceramics can be used.

[Brief explanation of the drawing]

FIG. 1(a) is a diagram showing the appearance of an example of a single-crystal-polycrystal bonded body used in the present invention, FIG. 1(b) is a schematic cross-sectional view of the central part of the bonded body after heat treatment, and FIG. Figure 6 is a diagram showing grain growth with respect to processing temperature, and Figure 6 is a diagram showing grain growth of polycrystals used in the present invention.・'4 crystal, (3)・
... Single crystallized part, (4) ... Giant crystal particle agent Yoshihiro Morimoto Figure 1 (,Z)

Claims (1)

[Claims] l. An oxide single crystal and an oxide polycrystal having the same composition or a composition close to that of the oxide single crystal and the same crystal structure as the oxide single crystal, In an atmosphere containing at least one of argon gas and nitrogen gas as a main component, the bonded body is heat-treated at a temperature higher than the temperature at which giant crystal grains begin to grow, so that the oxide multilayer A method for producing an oxide single crystal, characterized in that the crystal is a single crystal. 2. Claim 1 characterized in that a ferrite magnetic material is used as the oxide single crystal and the oxide polycrystal.
A method for producing an oxide single crystal as described in Section 1.