JPS6278195A - Method of growing garnet ferrite single crystal - Google Patents

Abstract

PURPOSE:To obtain single crystal having uniform composition and structure free from admixture of impurities, inexpensively by growing garnet ferrite single crystal by the use of a container made of a sintered polycrystal having the same composition as that of the single crystal. CONSTITUTION:In growing garnet ferrite single crystal by flux method or liquid- phase epitaxial method, a growth container consisting of a sintered garnet ferrite polymcrystal having the same composition as that of the garnet ferrite single crystal or a composition of its garnet ferrite single crystal derivative is used. The garnet single crystal derivative means a compound obtained by replacing partially substitution element of the aimed yttrium or rare earth element-substituted iron garnet with another metallic ion. Usually cylindrical or square pillar shape, etc., are preferable as the shape of the growth container.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for growing a garnet ferrite single crystal useful as a magneto-optical material, and more specifically, to a method for growing a garnet ferrite single crystal useful as a magneto-optical material, and more specifically, a method for growing a garnet ferrite single crystal useful as a magneto-optical material. The present invention relates to a method for growing a ferrite single crystal having a Faraday effect suitable for application to optical isolators and the like.

[Technical background of the invention and its problems]

Conventionally, the flux method or liquid phase epitaxy method (abbreviated as LPE method) has been most commonly used to grow garnet ferrite single crystals useful as magneto-optical materials.

When growing garnet ferrite single crystals using the flux method, yttrium (Y) or rare earth iron garnet raw materials, lead oxide (PbO), lead fluoride (PbFz
), boron oxide (B2Oyo), bismuth oxide (Bi2
A garnet single crystal was grown by slow cooling or evaporation of the flux after uniformly melting it by putting it in a crucible and melting it uniformly.

In addition, in growing a garnet ferrite single crystal by the LPE method, the above-mentioned garnet raw material and flux are uniformly decomposed in a crucible, and then a garnet ferrite single crystal is epitaxially grown using a nonmagnetic garnet single crystal as a substrate. was.

However, in these conventional methods for growing ferrite single crystals, a crucible made of platinum or platinum-rhodium is generally used as the growth container. When using such a noble metal crucible, the following The following problems arise.

(1) In order to obtain a large garnet ferrite single crystal, a correspondingly large precious metal crucible is required. Therefore, as a matter of course, this is not desirable in terms of manufacturing cost.

(2) When growing crystals by the flux method, as garnet ferrite crystals crystallize from the melt, the concentration of the garnet component remaining in the melt gradually decreases, especially when the garnet single crystal with the guide rod composition During growth, the composition of crystals to be crystallized varies at each temperature, making it difficult to obtain a uniform crystal composition.

(3) When the constituent components of the crucible are eluted into the melt, for example, when a platinum crucible is used, impurity ions other than trivalent ions such as Pt4+ are mixed into the garnet ferrite crystal, and as a result, the resulting garnet The light absorption properties of the ferrite crystal deteriorate.

(4) For example, in bismuth-substituted iron garnet, the Faraday effect increases as the amount of bismuth substitution increases;
Therefore, for this purpose, Bi203 or Bi203 B203 or the like is used as a flux. However, with such a flux, when the holding temperature is raised to make the melt uniform, the Bi20 of the flux component is reduced and, for example, Pt, Bi, etc.
Intermetallic compounds such as are generated, which embrittles the precious metal crucible and causes cranks and pinholes in the precious metal crucible.

[Purpose of the invention]

The present invention was made to solve the above-mentioned problems, and is inexpensive, free from contamination with impurities from the growth container, and
The purpose of the present invention is to provide a growth method for producing a garnet ferrite single crystal having a uniform composition and structure without fluctuations in the distribution and content of substitutional elements contained in crystals crystallized throughout the crystal growth period. .

[Summary of the invention]

The method for growing a garnet ferrite single crystal of the present invention involves growing a garnet ferrite single crystal using a flux method or a liquid phase epitaxy method, in which a garnet ferrite having the same composition as the garnet ferrite single crystal or a composition as a derivative of the garnet ferrite single crystal is grown. It is characterized by using a growth container made of a polycrystalline sintered body.

Here, the garnet single crystal derivative refers to a target yttrium or rare earth substituted iron garnet in which some of the substituent elements are partially substituted with other metal ions.

The method for growing garnet ferrite single crystals of the present invention not only reduces the elution of constituent components from the growth container, which was one of the problems in conventional single crystal growing methods, but also actively prevents the elution of constituent components. It was intended to be used for this purpose. That is, when a garnet ferrite single crystal crystallizes from a molten state, crystal nuclei are generated, and as the crystal nuclei grow, the concentration of the garnet component in the melt decreases,
If the growth container is configured with the same composition as the single crystal to be grown or its derivative composition, the garnet component will be eluted from the growth container, suppressing compositional fluctuations in the melt during the growth of the garnet ferrite single crystal, and ensuring uniformity. garnet ferrite single crystal can be obtained. In addition, for example, when the replacement element is supplied from a flux such as Bi20B, as in the case of growing i-substituted rare earth iron garnet single crystals with a large Faraday effect, the growth container may contain a rare earth iron garnet that does not contain the replacement element. It can also be composed only of iron garnet.

The growth container used for growing the garnet ferrite single crystal of the present invention is generally manufactured as follows. That is,
Garnet ferrite raw material having the same composition or derivative composition as the target garnet ferrite single crystal, especially Bi
In the case of a substituted rare earth iron garnet single crystal, after mixing the garnet ferrite raw materials other than the substituted elements supplied from the flux, it is heated in a flame at a temperature of 600 to 1200°C for 1 to 12 hours.
Calcination is performed for a period of time to obtain a dry powder having the same composition or derivative composition as the desired garnet ferrite single crystal.

A binder, such as an aqueous solution of polyvinyl alcohol, is added to this powder, and after molding, the molded container is sintered at a temperature of 1000 to 1600°C for 0.5 to 24 hours in an oxygen flow, and is made of garnet ferrite polycrystal. You can get a growing container.

The shape of this growth container is not particularly limited, but it is usually preferable to have a cylindrical shape, a prismatic shape, or the like.

[Embodiments of the invention]

Example 1 (1) Production of growth container YZ 03 , CaC0B , Fe00) 1 ,
ZrJ was weighed, prepared, ground and mixed in a wet ball mill for 24 hours. This mixture is then 'dried and ground into powder, and after mixing the powder, alumina (Ajz
Oa) Calcined in the air at 1100°C for 4 hours using a crucible, then crushed in a wet ball mill, mixed, and dried to obtain a powder having the composition formula Y 2.9 Ca O, IF 64.9012. Ta.

After adding polyvinyl alcohol solution as a binder to the powder of the above composition and rubber pressing, the inner diameter was 50 mm.
Formed into a cylindrical container with a height of 100I and a thickness of 5m111,
This molded container was sintered at 1450° C. for 8 hours in an oxygen flow to produce a growth container.

In addition, Ca, 7. A sintered body with an r-substituted indium iron garnet composition was created in order to maintain electrical neutrality, and also to improve sinterability and create a high-density growth container.
This is to prevent leakage of flux during the growth of garnet ferrite single crystals.

(2) Growth of garnet ferrite single crystal Y2 03
44.5g, Fez Oa 80.2g
, After weighing and mixing Bi203478g, (1
) and kept at 1200°C for 24 hours in an electric furnace.Then, the melt was heated to 1°C while stirring.
The mixture was slowly cooled to 900° C. at a cooling rate of /H to grow a single crystal.

As a result of the analysis, the obtained crystal was YI B11Fe50+□
The pt content is 1100p, which is the measurement limit.
p or less. Furthermore, after cutting the obtained single crystal and mirror polishing, the Faraday rotation angle and light absorption were measured using light with a wavelength of 1.3 μm, and the light absorption coefficient was α-0.05.
cm-'', and the figure of merit θF/α was large.

Comparative Example Same as Example 1, YZ 0B, Fez Oa, B
After weighing and mixing iz O3, put it in a platinum crucible,
Single crystals were grown under the same temperature conditions.

As a result of analysis, the obtained crystal was YZ B11Fe5012
However, the pt content was 500 ppm.

Further, the obtained crystal was cut and mirror-polished, and then its light absorption characteristics were measured, and the light absorption coefficient was α = 1.3 cm-' for light with a wavelength of 1.3 μm.

Example 2 A cylindrical container with the same composition as Example 1 was molded and heated at 1500°C.
A growth container was produced by sintering at a sintering temperature of .

When the structure of this container was observed using an optical microscope, grain growth was observed, and crystal grains with a particle size of about 2 mm were observed.

Next, using this container, a single crystal was grown from the garnet ferrite raw material and flux having the same composition as in Example 1. It was found that the obtained single crystal grew from the wall or bottom of the container, and the polycrystalline crystal in the growth container served as a seed crystal and contributed to the growth of the crystal.

1 Gdz 03, CaCO3, Fe00H,A
After weighing and blending lz 03 and ZrO2, the composition formula Gd
2.9Cao, +Fe+, o A 12 o, 5Zro
, +012 was prepared. Apart from this, Gd2 03 41.5g, CaCO32,O
g+ Fe203 64.2g.

2.5 g of Ajz 0yo was weighed and mixed. This mixture was placed in the above growth container and maintained at a temperature of 1200° C. for 24 hours in an electric furnace. Then, while stirring the melt, the temperature was increased to 1℃/
The mixture was slowly cooled to 850° C. at a cooling rate of H to grow a single crystal.

As a result of analysis, the obtained crystal was Gd2.5Cao, +Fe
+, o A 1°9Zrt3. It has a composition of +0,2,
No other impurities were detected. When the optical absorption coefficient was measured using light with a wavelength of 1.3 μm, α = 0,03 cm.
-', the figure of merit θF/α was also larger than when crystals were grown using a platinum crucible.

In this example, a growth container with a thickness of approximately 4 mm was used, but even after single crystal growth, the growth container maintains a thickness of 3 mm or more, and the elution of the constituent components of the growth container is smaller than that in a platinum crucible. It has been found that for practical purposes, it is sufficient that the thickness of the growth container is 2 mm or more.

In Example 1 and Example 2, yttrium iron garnet and gadolinium iron garnet have been described in detail as examples, but the present invention is not limited thereto (yttrium, rare earth iron garnet other than gadolinium, and yttrium iron garnet). Similar effects can also be achieved in a method for growing a composite iron garnet single crystal containing at least one element of the rare earth element group.

Example 4 Gdg Oa 8.0g, Fe2O] 22.4g
+ Biz 0a391.4g, B 203 5.
Og was weighed and mixed. Next, this mixture was placed in a growth container having the same composition as in Example 3, maintained at a temperature of 1200°C in an electric furnace, and then rapidly cooled and maintained at 900°C. After that,
A substrate made of a nonmagnetic material having the same composition and crystal structure as the crystal to be grown was placed, and a single crystal was grown by the heteroepitaxial method to obtain a bismuth-substituted rare earth iron garnet.

The light absorption of the obtained garnet single crystal is smaller than that of a single crystal grown in a platinum crucible, and the light absorption coefficient is α=
It was 0.05 cm-'.

Example 5 Bi203 483g, Fe20B 18.8g
were weighed and mixed. Next, this mixture was placed in a growth container having the same composition as in Example 1, kept at a temperature of 1200°C in an electric furnace for 96 hours, and then cooled to 900°C at a cooling rate of 1'C/H while stirring to form a single crystal. cultivated.

As a result of the analysis, the obtained crystal has the composition formula Y 2 B o
9Cao, +Fe4. It has a composition shown by qZro, +012, and after cutting and mirror polishing, the Faraday rotation angle and optical absorption were measured using light with a wavelength of 1.3 μm, and the optical absorption coefficient was α = 0.08 cm-'. It was a single crystal with a small absorption coefficient.

Therefore, when growing a garnet ferrite single crystal using a growth container made of a garnet polycrystalline sintered body,
It has been found that even without adding yttrium and/or rare earth elements as raw materials, yttrium and/or rare earth elements are supplied from the growth container and react with the flux component and ferric oxide to produce garnet ferrite single crystals.

〔Effect of the invention〕

As detailed above, the method for growing garnet ferrite single crystals of the present invention is inexpensive and contains less impurities (
, it is possible to provide a method for growing a garnet ferrite single crystal with excellent magneto-optical properties.

Claims (1)

[Claims] When growing a garnet ferrite single crystal by flux method or liquid phase epitaxy method, a sintered body of garnet ferrite polycrystal having the same composition as the garnet ferrite single crystal or a composition as a derivative of the garnet ferrite single crystal is used. A method for growing a garnet ferrite single crystal, characterized by using a growth container.