JPH0471036B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a gadolinium yttrium iron garnet solid solution single crystal by a floating zone method.

(Prior technology) Gadolinium yttrium iron garnet is used as a microwave ferrite with high power resistance and good temperature characteristics, and will be used in optical isolators,
It is also expected to be used as a magneto-optical element and a current magnetic field sensor.

Ceramics and single crystals grown by a flux method using a flux have been used as materials for these purposes. However, the performance of ceramics is inferior to that of single crystals, and the flux method requires a long time to grow single crystals, and it is difficult to obtain single crystals with good performance. There was also the problem that it was easy to incorporate into the solid solution, and there was also the decisive problem that solid solution single crystals with the desired composition could not be obtained.

On the other hand, the so-called floating zone method, in which a floating molten zone is formed between a raw material rod and a seed crystal, and a single crystal is precipitated on the seed crystal by moving the floating molten zone toward the raw material rod, can be applied in a relatively short time. Recently, this floating zone method has been attracting _attention as a method for _obtaining high _- quality single crystals _.
An example of producing a single crystal of Ga _0.5 O ₁₂
This is disclosed in Example 8 of Publication No. 28799.

(Problems to be Solved by the Invention) However, the method described in the above-mentioned patent publication involves incorporating a small amount of gadolinium into a raw material rod or solvent based on yttrium or iron, and reducing the gadolinium content to a low level. This is an example of manufacturing a gadolinium yttrium iron garnet solid solution single crystal in which the gadolinium content is equal to or higher than that of yttrium, for example, about 20.0 to 99.9 mol%. No examples have been disclosed to date.

In addition, when manufacturing a high-quality gadolinium yttrium iron garnet solid solution single crystal with a high gadolinium content using the floating izone method as described above, it is necessary to accurately select the composition of the solvent used. A phase equilibrium diagram of the (Gd ₂ O ₃ + Y ₂ O ₃ )-Fe ₂ O ₃ system is required, but the above patent publication does not include the phase equilibrium diagram of the (Gd ₂ O ₃ + Y ₂ O ₃ )-Fe ₂ O ₃ system. There is no mention of phase equilibrium diagrams.

Therefore, the inventors of the present application have determined the (Gd ₂ O ₃ + Y ₂ O ₃ ) − necessary for selecting the solvent composition for producing a gadolinium yttrium iron garnet solid solution single crystal with a high gadolinium content by the floating zone method.
A phase equilibrium diagram of the Fe ₂ O ₃ system was created.

FIG. 1 is a phase equilibrium diagram of the (50 mol % Gd ₂ O ₃ +50 mol % Y ₂ O ₃ )-Fe ₂ O ₃ system drawn from differential thermal analysis, heating quenching method, and X-ray diffraction of the sample.

As is clear from Figure 1, the (GdY) ₃ Fe ₅ O ₁₂ single crystal has a composition ratio of liquidus line AB, that is, Gd ₂ O ₃ + Y ₂ O ₃ .
14.1 to 21.9 mol%, _{Fe2O3 85.9} to 78.1 mol%
It is clear that precipitation occurs from solutions in the range of .

In addition, Fig. 1 and the already disclosed Gd ₂ O ₃ −
Phase equilibrium diagram of Fe ₂ O ₃ system (Fig. 2: Patent application 1986-133262)
_{Figure 3 : HJ}
Van Hook, J.Am.Ceram.Soc.44208 1961), the composition of the liquidus line AB where Gd ₃ Fe ₅ O ₁₂ and Y ₃ Fe ₅ O ₁₂ and (GdY) ₃ Fe ₅ O ₁₂ are precipitated is It is also clear that the temperature range of the liquidus line AB shown in FIG. 1 is located midway between the temperature range of the liquidus line AB in FIGS. 2 and 3.

From this, it is predicted that in the (Gd ₂ O ₃ + Y ₂ O ₃ )-Fe ₂ O ₃ system, Gd ₂ O ₃ and Y ₂ O ₃ are completely dissolved in solid solution, and a solid solution single crystal is grown. In fact, Gd ₂ O ₃
and _{Y2O3 ratio} is 75:25, 50:50, 25:75, 10:90
(GdY) ₃ Consists of Fe ₅ O ₁₂ raw material rod, a mixture of Gd ₂ O ₃ and Y ₂ O ₃ with the same ratio of Gd ₂ O ₃ and Y ₂ O ₃ as the raw material rod, and Fe ₂ O ₃ When the floating zone method was performed using a solvent in which the mixture and Fe ₂ O ₃ were in a molar ratio of 20:80, it was found that the ratio of Gd ₂ O ₃ to Y ₂ O ₃ was the same as that of the raw material rod. A thorium iron garnet solid solution single crystal was obtained.

(Means for Solving the Problems) Based on the above-mentioned findings, the present invention is based on the above-mentioned knowledge, and the present invention is based on the floating zone method for producing high-quality gadolinium yttrium iron garnet solid single crystals with a high gadolinium content, for example, about 20.0 to 99.9 mol%. The manufacturing method was completed using

That is, in this invention, for the above purpose, the solvent provided between the raw material rod and the seed crystal contains 99.9 to 20.0 mol % of gadolinium oxide and 0.1 to 0.1 mol % of yttrium oxide.
A mixture of gadolinium oxide and yttrium oxide having a predetermined composition ratio within the range of 80.0 mol%
The composition has a composition of 14.1 to 21.9 mol%, ferric oxide is 85.9 to 78.1 mol%, and the above solvent is 1450 to 1450 mol%.
A floating molten zone is formed by heating to 1550° C., and a solid solution single crystal is precipitated in the seed crystal by moving the floating molten zone in the direction of the raw material rod.

The raw material rod used in this invention contains gadolinium oxide, yttrium oxide, and ferric oxide so that a (GdY) ₃ Fe ₅ O ₁₂ solid solution single crystal with the desired composition ratio of gadolinium and yttrium can be obtained in the floating zone method. A mixture of gadolinium oxide is used, but in this case the amount of gadolinium oxide is
The blending amount of yttrium oxide is selected from the range of 99.9 to 20.0 mol%, and the blending amount of yttrium oxide is selected from the range of 0.1 to 80.0 mol%, and the molar ratio of the mixture of gadolinium oxide and yttrium oxide to ferric oxide is 3.0 to 5.0. That is, the raw material rod has the same composition as the (GdY) ₃ Fe ₅ O ₁₂ solid solution single crystal to be manufactured within the above range.

Furthermore, even if a small amount of some foreign element is mixed in at the positions of gadolinium, yttrium, and iron atoms in the (GdY) ₃ Fe ₅ O ₁₂ solid solution single crystal, the phase equilibrium diagram will qualitatively change to ( Gd ₂ O ₃ +Y ₂ O ₃ )−Fe ₂ O ₃
If it is essentially the same as the phase equilibrium diagram of the system, a small amount of a different element is mixed into the raw material rod to produce a gadolinium yttrium iron garnet solid solution single crystal mixed with a different element by the same method as above. It is also possible to do so. For example, a gadolinium yttrium iron garnet solid solution single crystal containing a small amount of different elements such as Al and Co can be produced.

On the other hand, regarding the mixing ratio of gadolinium oxide and yttrium oxide in the above solvent, (GdY) ₃ Fe ₅ O ₁₂
It is necessary to match the desired composition ratio of gadolinium and yttrium in the solid solution single crystal, but generally when obtaining a solid solution single crystal from a solution, the distribution system of each substance is different, and the grown solid solution single crystal has a composition mixed in the solution. The composition ratio is often not exactly the same as the ratio.

Therefore, the inventors investigated the relationship between the composition ratio of the solvent (Y ₂ O ₃ /Gd ₂ O ₃ + Y ₂ O ₃ ) and the composition ratio of the grown crystal (Y / Gd + Y) for gadolinium yttrium iron garnet solid solution single crystals. The results shown in Figure 4 were obtained. According to this, it is clear that yttrium is more easily mixed into the actually grown crystal than gadolinium, and therefore the amount of yttrium in the solvent is 70 to 70% of the yttrium required for the grown crystal. 110% preferably 90
~93%.

(Function) From Figure 1, the (GdY) ₃ Fe ₅ O ₁₂ solid solution single crystal is
A temperature range of about 1450°C to 1550°C from a solution with a composition ratio of liquidus line AB, that is, Gd ₂ O ₃ + Y ₂ O ₃ of 14.1 to 21.9 mol% and Fe ₂ O ₃ of 85.9 to 78.1 mol%. It is thought that it precipitates in

Therefore, in this invention, the composition of the solvent provided between the raw material rod and the seed crystal is a mixture of Gd ₂ O ₃ and Y ₂ O ₃ in a composition ratio of 14.1 to 21.9 mol %, which is selected based on the above considerations. , Fe ₂ O ₃ is 85.9 to 78.1 mol%, the solvent is heated and melted at 1450 to 1550 ° C., and moved in the direction of the raw material rod while keeping the molten composition stable,
A (GdY) ₃ Fe ₅ O ₁₂ single crystal is grown as a seed crystal.

(Example) Next, one embodiment of the present invention will be described.

Example 1 A solid solution single crystal having the composition (Gd _0.75 Y _0.25 ) ₃ Fe ₅ O ₁₂ was produced by the floating zone method.

Mix Gd ₂ O ₃ and Y ₂ O ₃ in a molar ratio of 75:25,
The mixture and a powder of Fe ₂ O ₃ mixed in a molar ratio of 3.0 to 5.0 were fired at 1150°C for 2 hours, and the powder was shaped into a cylindrical rod with a diameter of 10 mm and a length of 10 cm using a pressure molder at 1490°C. Homogeneously fired for 4 hours (Gd _0.75 Y _0.25 )
₃ Fe ₅ O ₁₂ raw material rod.

Similarly, the molar ratio of Gd ₂ O ₃ and Y ₂ O ₃ is 77:23.
The mixture was mixed with 20 mol% of the mixture and 80 mol% of Fe ₂ O ₃ was baked at 1150°C for 2 hours, then molded into a cylindrical rod shape with a diameter of 10 mm in the same manner as above, and heated at 1400°C. The mixture is baked homogeneously for 2 hours to form a solvent.

After that, this cylindrical rod-shaped solvent was cut in the radial direction to form a disk weighing 1.2 to 1.5 g (Gd _0.75 Y _0.25 ).
₃ Fused to Fe ₅ O ₁₂ raw material rod.

In this way, the cylindrical rod-shaped sample with the solvent fused to the tip of the (Gd _0.75 Y _0.25 ) ₃ Fe ₅ O ₁₂ raw material rod was placed on the upper sample rotation axis of the floating zone method single crystal production device that adopted the infrared heating method. Fix the seed crystal to the lower rotating shaft in the same way. In this case, the setting is made so that the (Gd _0.75 Y _0.25 ) ₃ Fe ₅ O ₁₂ raw material rod to which the seed crystal and solvent are attached is not eccentric with respect to the rotation axis.

Thereafter, the raw material rod and the seed crystal are rotated at 30 rpm in opposite directions.

After heating and dissolving the solvent using infrared rays, the seed crystal is brought into contact with the solvent, and the solvent is held in contact between the raw material rod and the seed crystal due to the surface tension of the liquid.

Furthermore, this melted solvent is moved toward the raw material rod, that is, upward, at a speed of 0.5 to 2 mm/hr to grow a (Gd _0.75 Y _0.25 ) ₃ Fe ₅ O ₁₂ single crystal as a seed crystal.

Note that this growth was performed under atmospheric pressure and in oxygen.

When the raw material rod was almost consumed, the grown single crystal and the raw material rod were separated and cooled to room temperature. As a result, a cylindrical bar with a diameter of 8 mm and a length of 40 mm (Gd _0.75
Y _0.25 ) ₃ Fe ₅ O ₁₂ single crystal was obtained.

Example 2 A solid solution single crystal having the composition (Gd _0.5 Y _0.5 ) ₃ Fe ₅ O ₁₂ was produced by the floating zone method.

Mix Gd ₂ O ₃ and Y ₂ O ₃ in a molar ratio of 50:50,
A mixture of this mixture and Fe ₂ O ₃ in a molar ratio of 3.0 to 5.0 was used as a raw powder powder, and in the same way, Gd ₂ O ₃ and
The same operation as in Example 1 was carried out using a powder obtained by mixing Y ₂ O ₃ in a molar ratio of 55:45, 20 mol % of the mixture, and 80 mol % of Fe ₂ O ₃ as a solvent. Through the same procedure, a round rod-shaped (Gd _0.5 Y _0.5 ) ₃ Fe ₅ O ₁₂ solid solution single crystal with a diameter of 8 mm and a length of 50 mm was obtained.

Example 3 A solid solution single crystal having the composition (Gd _0.25 Y _0.75 ) ₃ Fe ₅ O ₁₂ was produced by the floating zone method.

Mix Gd ₂ O ₃ and Y ₂ O ₃ in a molar ratio of 25:75,
A mixture of this mixture and Fe ₂ O ₃ in a molar ratio of 3.0 to 5.0 was used as a raw powder powder, and in the same way, Gd ₂ O ₃ and
The same operation as in Example 1 was carried out using a powder obtained by mixing Y ₂ O ₃ in a molar ratio of 30:70, 20 mol % of the mixture, and 80 mol % of Fe ₂ O ₃ as a solvent. Through the same procedure, a round rod-shaped (Gd _0.25 Y _0.75 )Fe ₅ O ₁₂ solid solution single crystal with a diameter of 8 mm and a length of 40 mm was obtained.

Example 4 A solid solution single crystal having the composition (Gd _0.5 Y _0.5 ) ₃ (Fe _0.8 Co _0.1 Al _0.1 ) ₅ O ₁₂ was produced by the floating zone method.

Mix Gd ₂ O ₃ and Y ₂ O ₃ in a molar ratio of 50:50,
The molar ratio of Fe ₂ O ₃ , Co ₂ O ₃ and Al ₂ O ₃ is 80:10:
10 and make their mixture a molar ratio of 3.0
The mixture of 5.0% and
Mix Gd ₂ O ₃ and Y ₂ O ₃ in a molar ratio of 55:45,
The mixture is 20 mol% Fe ₂ O ₃ and Co ₂ O ₃ and Al ₂ O ₃
A mixture of 80:10:10 in a molar ratio of 80
Using the powder mixed in mol% as a solvent, the same procedure as in Example 1 was carried out and the same process was carried out.
A round bar with a diameter of 7 mm and a length of 20 mm (Gd _0.5 Y _0.5 ) ₃ (Fe _0.8
A Co _0.1 Al _0.1 ) ₅ O ₁₂ solid solution single crystal was obtained.

In Example 4, the iron atom position was replaced with a small amount of a different element, but this is because the phase equilibrium diagram qualitatively corresponds to the phase of the (Gd ₂ O ₃ + Y ₂ O ₃ )-Fe ₂ O ₃ system in Figure 1. This shows that it is possible to produce a gadolinium yttrium iron garnet solid solution single crystal mixed with a different element by mixing a small amount of the different element into the raw material rod if it is essentially the same as the equilibrium diagram. .

Similarly, if a small amount of a different element is mixed in the position of gadolinium and yttrium, but the above phase equilibrium diagram does not essentially change qualitatively, gadolinium yttrium iron garnet mixed with a different element in the same manner can be used. A solid solution single crystal can be obtained.

(Effects of the Invention) In summary, according to the present invention, a high-quality (GdY) ₃ Fe ₅ O ₁₂ single crystal with a high Gd content can be produced in a short time, and it can be produced long ( GdY) ₃ Fe ₅ O ₁₂ single crystal can be produced.

[Brief explanation of the drawing]

Figure 1 was created by the inventor of the present application (50 mol%
Phase equilibrium diagram of Gd ₂ O ₃ + 50 mol% Y ₂ O ₃ )-Fe ₂ O ₃ system,
Figure 2 shows Gd ₂ O ₃ for explaining the history of the invention of the present application.
- Phase equilibrium diagram of the Fe ₂ O ₃ system, Figure 3 is a phase equilibrium diagram of the Y ₂ O ₃ -Fe ₂ O ₃ system for explaining the background of the present invention,
Figure 4 shows the composition ratio of the solvent (Y ₂ O ₃ /Gd ₂ O ₃ +
FIG. 2 is a diagram showing the relationship between Y ₂ O ₃ ) and the composition ratio (Y/Gd+Y) of a grown crystal.

Claims (1)

[Claims] 1. A solvent is provided between the raw material rod and the seed crystal, and the solvent is heated, melted, and moved toward the raw material rod to precipitate a single crystal on the seed crystal to produce gadolinium yttrium iron garnet. In the method for producing a solid solution single crystal, the solvent provided between the raw material rod and the seed crystal is an oxide having a predetermined composition ratio within the range of 99.9 to 20.0 mol% of gadolinium oxide and 0.1 to 80.0 mol% of yttrium oxide. Mixture of gadolinium and yttrium oxide from 14.1 to 21.9 mol%, ferric oxide from 85.9 to 21.9 mol%
The composition is 78.1 mol%, and the above solvent is heated to 1450 to 1550°C to form a floating molten zone,
A method for producing a gadolinium yttrium iron garnet solid solution single crystal, characterized in that the solid solution single crystal is precipitated in a seed crystal by moving the floating molten zone in the direction of the raw material rod. 2. The method according to claim 1, wherein a raw material rod of (GdY) ₃ Fe ₅ O ₁₂ mixed with a small amount of a different element is used as the raw material rod.