JPH0459687A - Mn-Zn ferrite single crystal growth crucible - Google Patents

Abstract

PURPOSE:To reduce the contamination of a Mn-Zn ferrite single crystal with platinum or rhodium particles by coating the inner wall of a platinum crucible or platinum-rhodium alloy crucible for growing the single crystal with iron metal or an iron oxide. CONSTITUTION:The inner wall of a platinum crucible or platinum-rhodium alloy crucible employed on the growth of a Mn-Zn ferrite single crystal by a Bridgeman method is preliminarily coated with iron metal or an iron oxide by a vacuum deposition method, etc., suitably in a thickness of approximately 3-500mum, thereby permitting to prevent a phenomenon where the platinum or rhodium is diffused into the melted material from the interface between the melted material and the crucible on the growth of the Mn-Zn ferrite single crystal, i.e. preventing the single crystal from absorbing the vapor of the platinum or rhodium from the surface of the melted material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a Mn--Zn ferrite single crystal growth crucible that makes it possible to significantly reduce the amount of platinum or rhodium alloy mixed into the single crystal.

(Prior art) In order to grow Mn-Zn ferrite single crystals by the Bridgman method, the common growth method is to melt and solidify them in an oxidizing atmosphere at a high temperature of 640 to 1,700°C. The material used was platinum or a platinum-rhodium alloy.

(Problems to be Solved by the Invention) When these crucibles are used, platinum or rhodium diffuses into the melt from the interface between the melt and the crucible, and vapors of platinum and rhodium are absorbed from the surface of the melt. These particles are several μ in size in the grown single crystal.
There is a phenomenon in which particles are precipitated with a particle size of about 100 μm to 100 μm, which poses a quality problem.

The purpose of the present invention is to provide high-purity Mn that solves these drawbacks.
- It is an object of the present invention to provide a method for growing Zn ferrite single crystals.

(Means for Solving the Problems) In order to solve the above problems, the present inventor has actively elucidated the contamination route of platinum-rhodium, and as a result, it is possible to suppress the diffusion and contamination from the melt contact area. Although this is extremely difficult, we came to the conclusion that it is more reliable and practical to prevent vapor absorption from the surface of the melt. It was found that the generation of steam from the crucible could be suppressed by narrowing the crucible space and by coating the inner wall of the crucible in this space, and after studying various conditions, the present invention was arrived at.

The gist of the present invention is to provide an Mn-Zn ferrite single crystal growth crucible made of platinum or platinum-rhodium alloy whose inner wall is coated with a coating of metallic iron or iron oxide. 3 to 500 μm thick.

The present invention will be explained in detail below.

The coating material for platinum or platinum-rhodium crucibles must have the same composition as the main component of the melt and have a melting point of 1.5.
It is necessary that the temperature be 00°C or higher.

In the case of Mn-Zn ferrite, the constituent elements are Fe, M
In particular, if Fe is used, it becomes iron oxide Fear4 in a high-temperature oxidizing atmosphere, forming a stable oxide film, which is highly effective in suppressing the generation of platinum and rhodium vapors.

In order to coat the inner wall of the crucible with these coating materials, it is recommended to use a vacuum evaporation method (the thickness thereof is preferably 1 to 500 μm, preferably 3 to 300 μm. If the thickness is less than 1 μm, it is effective in suppressing the generation of platinum and rhodium vapors. If the thickness exceeds 500 μm, the Fe20s component will increase by 2 mol% or more from the target ferrite composition, making composition control difficult.

The conditions for the vacuum evaporation method are that in the case of Fe, the crucible is installed horizontally in the chamber of the vacuum evaporation device so that it can rotate on a horizontal axis, and the tungsten boat is inserted horizontally into the crucible from the crucible opening. do. While rotating the crucible, the metal Fe placed on the port is evaporated by resistance heating to deposit Fe on the inner wall of the crucible. The thickness of the film is controlled by the amount of Fe to be evaporated. The area to be coated is preferably from the line of the inner wall of the crucible that contacts the melt, which is located somewhat below the boundary line with the surface of the melt, to the edge of the opening of the crucible.

Hereinafter, specific embodiments of the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Examples 1 to 6) Pt with an outer diameter of 70 mm, a total length of 200 mm, and a thickness of 0.4 mm.
- A metallic iron coating was formed on the inner wall of the 100% crucible by vacuum evaporation. The thickness is from 5 μm as shown in Table 1.
Various types were manufactured within the range of 500 μm. Using this crucible, Mn-Zn ferrite single crystals (Mn029, ZnO1
8. As a result of growing Fe2e353 (each mol%),
As shown in Table 1, a high-purity Mn--Zn ferrite single crystal with extremely low platinum content was obtained.

However, in Example 6, the amount of platinum mixed achieved the objective, but M
The composition of the n-Zn ferrite single crystal increased by 2 mol% in FeJ3 compared to the raw material blending ratio.

(Example 7) The process was carried out in the same manner as in Example 3 except that the crucible material was Pt-10%Rh, and the amount of platinum mixed was determined. The results are shown in Table 1.

(Example 8) The 100 μm Fe-coated crucible of Example 4 was exposed to air at 1.4 μm.
A heat treatment was performed at 00° C. for 1 hour to grow a single crystal as a film of iron oxide Fe5r.

(Comparative Example 1.2) The crucible material was platinum (Comparative Example 1) and platinum-rhodium (Comparative Example 2), and the process was carried out in the same manner as in Example 1 except that no film treatment was performed, and the amount of platinum mixed was determined. It is also listed in Table 1.

(Comparative Example 3) The process was carried out in the same manner as in Example 1 except that the thickness of the metal Fe film was 1 μm, and the amount of platinum mixed was determined and is also listed in Table 1.

1st class l alternating 11 (common to each example) Melting growth temperature: 1,650'C Crucible movement speed: 5 mm/h Atmosphere: l atm 02 during growth, 1 atm during temperature cooling
mN2.

(Effect of the invention) If a Mn-Zn ferrite single crystal is grown using a platinum or platinum-rhodium crucible whose inner wall is coated with metallic iron or iron oxide film, the contamination of platinum and rhodium particles can be significantly reduced. The quality improvement effect is significant (and its practical value is extremely high.

Patent applicant Shin-Etsu Chemical Co., Ltd. - Agent/patent attorney Ryo Yamamoto -

Claims (2)

[Claims] 1. A Mn--Zn ferrite single crystal growth crucible made of platinum or platinum-rhodium alloy whose inner wall is coated with a film of metallic iron or iron oxide. 2. The thickness of the metallic iron or iron oxide film is 3 to 500μ
The Mn-Zn ferrite single crystal growth crucible according to claim 1, wherein the Mn-Zn ferrite single crystal growth crucible is m.