JP2013060352A - Crucible furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crucible furnace for using a metal crucible at high temperatures not lower than 1,000°C, in which atmosphere in the vicinity of the crucible during the time of the high temperature is controlled, the temperature control in the crucible can be made precise, and the life of the crucible is made long.SOLUTION: The crucible furnace for processing a compound in the metal crucible 4 at the high temperatures not lower than 1,000°C is characterized in that the first sleeve 1 comprising a detachable heat resistant thin dense ceramics is placed around the metal crucible 4, and the second sleeve 2 comprising an insulation material and a heating device 3 is placed outside of the first sleeve 1.

Description

The present invention relates to a structure of a crucible furnace for performing crystal melting using a metal crucible such as a platinum group metal mainly used for crystal pulling.

With the development of electronic devices, the opportunity to use single crystals, particularly compound single crystals, as semiconductor members and electronic circuit members is increasing. In particular, there has recently been an increasing demand for compound single crystals having a very high melting point, such as lithium tantalate and sapphire single crystals used as the base of LEDs, which are used in surface wave filters for mobile phones. In the production of these single crystals, ceramic crucibles cannot be used in many cases because of their reaction potential, and heat-resistant metals, particularly stable platinum group metals such as platinum and iridium, have been widely used.

The platinum group metals such as platinum and iridium used in these materials have high heat resistance, and are characterized by being able to be used effectively over a long period of time because they hardly react with the compound, and are relatively easy to handle. It has been widely used because it is.
However, it is known that even if the platinum group metal itself is stable, the life may be shortened depending on the atmosphere. For example, platinum placed in a reducing atmosphere has significant grain growth and cracks from grain boundaries are very likely to occur. In the case of iridium, partial oxidation occurs in the oxidizing atmosphere at around 1000 ° C. There was a problem of becoming easy to volatilize. In order to avoid these, it is necessary to control the atmosphere around the crucible. For example, for platinum, the atmosphere may be oxidizing, and for iridium, the oxygen in the atmosphere is reduced or weakly reduced, and its volatile oxidation can be prevented by slightly raising the pressure.

However, in a crucible furnace used at 1000 ° C. or higher, the heating method varies depending on the heating method. In the case of resistance heating, the crucible is not directly subjected to heat radiation from the heater itself, and a certain amount of heat capacity is given to maintain the temperature. Stabilization is necessary. For this purpose, a refractory called a sleeve is usually installed around the crucible. This sleeve uses porous ceramics to make it less likely to break itself and to improve heat retention performance. In addition, when a crucible such as a high-frequency furnace itself is heated, a porous heat-resistant ceramic sleeve (heat insulating material / heat insulating material) is also inserted in order to prevent escape of heated heat. Such heat-resistant heat insulating materials (usually porous) have a thickness of several centimeters or more for these purposes, and the thickness usually increases as the temperature increases. Furthermore, in the case of resistance heating, the outside of the heater is also surrounded by such a heat insulating material, and the volume of the porous portion becomes extremely large. Atmosphere control in such a state must be performed including this sleeve, and it takes a large volume, and it is difficult to control the atmosphere only in the crucible portion intensively. Especially in the case of resistance heating, when the required atmosphere of the heater and the crucible part is different because the crucible part and the heater part are connected via a porous heat insulating material / heat insulation material, special measures are required. was there. In addition, there is a possibility that the amount of atmospheric gas or the like increases. Furthermore, adverse effects on the surrounding atmosphere were also considered.

Although little is known about the direct response techniques for such problems, several relevant techniques are found for the structure of the furnace section.

For example, as a method of cutting the edge between the heater side and the crucible, although the use is different, Japanese Patent Application Laid-Open No. 8-303965 discloses a technique for handling molten zinc, in which molten zinc is used to cut the furnace wall. It is said that there is a possibility of trouble because it diffuses through and passes through the stamp material inside and reaches the induction coil. For this purpose, a technique of providing a metal partition wall in the intermediate stamp material between the molten zinc and the high frequency coil is shown. Although this does not meet the purpose of the present application of blocking the atmosphere, it is one reference in terms of blocking technology. However, it is different whether such a structure is practically possible, and there are problems in handling because the use is different.

Considering only the separation of the heater portion and the crucible, several techniques for making the crucible substantially a double crucible have been shown. That is, in Japanese Patent Application Laid-Open No. 2011-32125, as a crucible for producing a silicon single crystal, a quartz crucible and a graphite crucible have a double structure, and a silicon carbide layer is provided on one side between the quartz crucible and a black smoke crucible. It has been shown to contain graphite sheets. This technology is a special case to partition silicon and carbon, and to suppress mutual reaction. No effect is considered from the viewpoint of heat insulation or soaking, and from now on. Of course, such an effect is not recognized.

Japanese Patent Application Laid-Open No. 2008-222455 also discloses a crucible for pulling a silicon single crystal, but shows a structure that is completely surrounded by a split graphite crucible outside a quartz glass crucible. For these two technologies, it is possible to use a graphite sheet that is heat resistant and easily deformable, or a structure that is only possible with a graphite material that has good workability. There is a problem that it may be reduced, and sometimes metal carbide may be generated. Furthermore, there was a problem that the atmosphere could not be adjusted.

JP-A-8-303965 JP 2011-33215 A JP 2008-222455 A

In the present invention, in a crucible furnace for using a metal crucible at a high temperature of 1000 ° C. or higher, the atmosphere in the vicinity of the crucible at a high temperature can be controlled, the temperature control in the crucible can be made precise, and the crucible life can be extended. An object was to provide a crucible furnace.

The present invention is a crucible furnace for processing a compound in a metal crucible at a high temperature of 1000 ° C. or higher, and a first sleeve made of a thin dense ceramic that is heat-resistant and detachable around the crucible. A crucible furnace characterized in that a second sleeve made of a heat insulating material and a heating device are placed outside the first sleeve, and the dense first sleeve is an outer second sleeve Since it is integrated with the external temperature by contacting with the heat insulating material and the heat insulating material, it is dense and, naturally, the thermal conductivity is better than that of the porous material, so that the temperature around the crucible becomes a more constant temperature. The temperature distribution becomes more constant accordingly. This also prevents heat radiation.

The crucible furnace of the present invention is for use at a high temperature of 1000 ° C. or higher, where there is a space, where there is a tendency for heating to proceed by heat conduction or heat radiation.
By inserting the first sleeve, when the heater is outside, the influence of the heat radiation from the outside can be completely blocked, and furthermore, the same temperature as that of the second sleeve is maintained. Moreover, since it is dense, the temperature distribution is uniform throughout, and the crucible can be heated at a more uniform temperature. Furthermore, only the periphery of the crucible can be made a necessary atmosphere without being influenced by the outside, and the influence on the outer periphery can be minimized.

In addition, even when the crucible is directly heated by induction heating or the like, the temperature non-uniformity that appears due to the induction field can be prevented by reciprocating the heat between the crucible itself, which is a heating element, and the dense first sleeve. Can be obtained. Of course, the atmosphere can be adjusted only around the crucible. Further, it is desirable to make the atmosphere in the crucible portion more complete by making the height of the first sleeve higher than the height of the crucible.

Furthermore, since the first sleeve is made of a dense material, the volatilized matter that comes from the volatilization of the crucible metal itself and the volatilization of the dissolved substance that normally occur in high-temperature processing stops at the surface of the first sleeve. Utilizing this, it is possible to collect the volatile matter and suppress diffusion into the sleeve and prevent problems such as poor insulation due to the volatile matter. This also has the advantage that the crucible furnace, which has conventionally had to be replaced periodically, has a relatively short life and can be used semi-permanently except for the first sleeve.

Furthermore, when volatilized material accumulates to some extent, it is necessary to replace the first sleeve, but it can be used continuously, and it is not necessary to break the entire refractory, which is a sleeve as in the past. This makes it possible to minimize the downtime of the device. In addition, the maintenance is extremely easy. The inner surface of the first sleeve can be coated with an alkaline earth metal oxide such as magnesia which is dissolved by acid and has heat resistance. Alternatively, when the first sleeve itself is made of an alkaline earth metal such as magnesia, the first sleeve itself can be used repeatedly by acid cleaning as appropriate.

Further, the sleeve and the crucible are not in contact with each other except the bottom, and a slight gap is left therebetween. Of course, partial contact may be possible, but by providing a space here, the atmosphere around the crucible can be maintained with minimal adjustment. Further, the gas in the gap has a larger heat capacity than the refractory, and the temperature distribution is improved because it moves in the gap. This is particularly effective when the crucible itself is heated by an induced current, but can also be used effectively depending on conditions when heating by heat conduction from a refractory by an external heater. In either case, heating by heat radiation from the entire dense sleeve is possible, and more stable heating can be achieved in combination with the heat conduction of the dense refractory.

The dense refractory material is not particularly specified as long as it is resistant to the target temperature and atmosphere. For example, in an oxidizing atmosphere, an oxide-based ceramic is desirable, and a neutral melt such as sapphire (α alumina) and In addition, when there are volatilized substances, it is desirable to use so-called neutral refractories such as alkaline earth metal oxides such as stabilized zirconia, magnesia, and calcia. When using in a reducing atmosphere, especially when soaking is important, it is desirable to use non-oxide ceramics such as silicon nitride and silicon carbide. Of course, it is natural that oxides such as stabilized zirconia and magnesia can be used even in a reducing atmosphere.

In addition, when considering the recovery of volatilized materials, the first sleeve made of stabilized zirconia or non-oxide, in order to protect itself, the surface facing the crucible and volatilized material in advance of magnesia and calcia. It is desirable to have a coating. In other words, if volatiles accumulate on the surface to some extent, the surface coating can be dissolved by immersing it in acid, and the volatiles can be recovered in the acid and the sleeve can be reused. .

Of course, the first sleeve of alkaline earth metal oxide made of magnesia or calcia can be subjected to acid treatment as it is to corrode the surface layer and peel only that portion. As a result, the first sleeve can be used repeatedly while the surface deposits are removed or collected by acid treatment, although the thickness is reduced each time.

The first sleeve and the second sleeve may be in close contact with each other, or may be slightly separated so as not to cause gas convection, but these can be selected depending on the heating method or conditions. . In other words, in the case of induction heating, it is necessary to prevent diffusion of heat to the outside, and for this purpose, there is a gap that does not cause gas convection between the first sleeve and the second sleeve, that is, the outer sleeve. It is desirable to prevent heat conduction and diffusion.

In addition, when the heating element is placed outside and heated through the second sleeve, it is desirable that the first sleeve and the second sleeve are in contact with each other, thereby enabling more efficient heat conduction. Can be given. However, when temperature control is performed very precisely, it is desirable that a slight gap is provided so that thermal convection does not occur, or that a slight gap is provided while making point contact. In other words, if they are in contact, heat conduction can transfer heat more efficiently, but if you want better soaking, you can combine radiation and heat conduction by leaving a small gap. It is possible to obtain better thermal uniformity.

As for the material of the second sleeve, it is natural to withstand high temperatures, but it is important to maintain soaking, and it is based on heat conduction as much as possible without depending on heat radiation from the heating element. The material is not particularly specified. For example, when an iridium crucible is used to produce a sapphire single crystal, the melting point of sapphire is 2050 ° C., and therefore a higher heat resistance temperature is required. A refractory material such as stabilized zirconia, magnesia, and calcia having slight porosity and heat insulation is desirable. However, since it is away from the crucible atmosphere here, there is no particular limitation on the material as long as it is heat-resistant and heat-insulating, that is, alkaline or acidic.

In the technique of the present invention, for example, even when dealing with a silica melt that is acidic, or when dealing with a nearly neutral melt such as sapphire, it is necessary to replace the second sleeve by simply replacing the first sleeve. It also has the feature of disappearing. In other words, without changing the main body including the second sleeve, the first sleeve and the crucible can be replaced, and the conditions can be changed as necessary to achieve other conditions, such as ferrite growth using a platinum crucible. It can be used. Of course, in this case, when a platinum crucible is used, the crucible atmosphere needs to be an oxidizing atmosphere. However, since it is only necessary to control the inside of the first sleeve, the control becomes easy.

The wall thickness of the first sleeve is not particularly specified, but it is preferably thin from the viewpoint of heat conduction and heat loss, preferably 3 mm to 10 mm, and more preferably about 4 to 7 mm. Although there is no special definition for the wall thickness limitation here, for example, if it is thinner than 3 mm, there is a problem that a large object has insufficient physical strength or is difficult to make. A large temperature distribution is generated, and there is a possibility that heat is wasted, and some materials are easily broken. Therefore, in the case of using a standard type crucible having a diameter of 100 mm and a height of about 100 mm to 200 mm, about 3 to 6 mm is empirically appropriate.

In this way, by combining the sleeve part for heat insulation / soaking in the crucible furnace with the dense and thin sleeve which is the first sleeve and the second sleeve outside it, the soaking of the crucible body is greatly increased. In addition, the atmosphere of the crucible portion can be easily adjusted, and the crucible furnace can be used for a long period of time only by exchanging the first sleeve, or by cleaning and washing, and further maintenance is facilitated. In addition, since the contamination by the volatilized material from the object to be processed such as melt growth by the crucible itself or the crucible is almost eliminated, the life of the furnace body can be greatly extended, and the maintenance period is further extended. This will lead to significant cost reductions directly and indirectly, such as a reduction in maintenance. In addition, when the crucible to be used is iridium or platinum, it becomes easy to recover the noble metal which is a material of these expensive crucibles which are volatilized by long-term use.

The drawings are described for the sake of clarity. FIG. 1 shows an example of a crucible furnace having a high-frequency coil 3 on the outside and directly heating a metal crucible. 1 is a first sleeve, and a crucible-type sleeve is placed between the second sleeve 2 and the crucible. ing. Here, the crucible and the first sleeve are slightly separated. Normally, an atmosphere gas is put in this portion to prevent the volatilization of the melt in the crucible, and to prevent the volatilization of the crucible metal itself as an optimum atmosphere and to prevent the crucible metal from deteriorating. For example, if the crucible is iridium and α-alumina is grown, it is slightly reduced. At this time, since the first sleeve itself surrounds the crucible and is isolated from the others, the atmosphere can be easily controlled. In addition, since there is a gap between the crucible and the first sleeve, it is possible to prevent escape of heat due to heat transfer. Further, in this figure, a slight gap is provided at the bottom of the first sleeve by the pan-plate 6 made of saw-like material, but this need not necessarily be provided. However, this makes it possible to further reduce heat escape and reduce energy consumption.

The material of the first sleeve may be determined according to the operating conditions, the atmosphere and temperature associated therewith, and the crucible material.For example, when producing an α-alumina crystal using an iridium crucible, Dense stabilized zirconia with a thin layer of magnesia is optimal. Of course, a dense stabilized zirconia itself and having no surface magnesia surface layer can also be used. The magnesia layer provided on the inner side of the first sleeve is contaminated on the surface by utilizing for a long time, but it is possible to dissolve and remove the magnesia part by acid treatment by pickling, and it is possible to remove or collect surface deposits. It becomes easy. Further, the first sleeve can be reused by applying the magnesia coating. Of course, other materials can be used, but it is necessary to make the material compatible with the external second sleeve material. Here, the magnesia dissolution conditions are not particularly specified, but an active mineral acid such as hydrochloric acid, sulfuric acid, nitric acid or a mixed acid thereof is optimal.

The second sleeve 2 serves as a heat insulating agent, and a sleeve made of a porous agent is inserted with a slight gap between the second sleeve 2 and the first sleeve. The material of the sleeve is not particularly specified, but it goes without saying that it needs to be non-reactive with the first sleeve as seen above. When the first sleeve is neutral, a neutral heat insulating material and a heat resistant material are required. Also, a porous material is required to keep the heat retaining function sufficiently, and it is usually filled with castable refractory material, or depending on heat resistance, the outer side should use alumina, magnesia or zirconia fiber, wool or filler. You can also. Since the purpose is heat insulation, it is necessary to have a porous material with excellent heat insulation properties, and a material having a degree of porosity as high as possible is desirable.

FIG. 2 shows a crucible furnace that heats the crucible by high-frequency induction as in FIG. 1, and is a type in which the first sleeve 1 is cylindrical with no bottom and the cylinder is inserted. Although there is a problem that the heat escape from the bottom is slightly increased, there are also advantages such as easy handling. However, in this case, the contact portion with the second sleeve crucible, which is in direct contact with the crucible, must have sufficient heat resistance and must not react with the crucible. Only the crucible contact portion of the second sleeve can be changed to another corrosion-resistant material.

The thickness of the sleeve used here is about 3-10 mm. If the thickness is less than 3 mm, the strength of the sleeve tends to be insufficient. If the thickness is more than 10 mm, the sleeve becomes physically heavy, and the response to temperature fluctuation is slightly but insufficient. The sleeve and the crucible here naturally come into contact at the bottom, but a slight gap is provided on the wall side from the crucible. Although the width of the gap is not particularly specified, it is desirably about 3 to 10 mm, which makes it easy to control the atmosphere and stabilizes it. Moreover, the temperature distribution of the crucible becomes better due to this gap.

FIG. 3 shows an example of external heating. In this case, heat from the heating element is transmitted to the first sleeve not by heat radiation but by heat conduction. In the case of an external heater, the temperature of the heater itself may be considerably higher than the desired temperature, and if there is a gap, partial high temperatures due to heat radiation may make temperature control difficult, and sometimes Some parts of the crucible have a temperature distribution.

Therefore, it is desirable that the second sleeve 2 is a porous structure but has no gap. Here, even if this is the case, the radiation of heat is cut by the first sleeve 1, so that the problems of temperature distribution and temperature control due to such causes are completely eliminated. However, in the case of such an external heater, it is desirable that the first sleeve and the second sleeve are in contact with each other in order to improve heat conduction. Of course, there is no problem even if there is a gap without contact, but in that case, it may take a little extra time to raise the temperature. Instead, depending on the temperature, it becomes easy to achieve a uniform temperature distribution. Therefore, it can be appropriately determined depending on the purpose and temperature and other conditions.

FIG. 4 shows an example of external heating, and shows a case where the first sleeve is not crucible but cylindrical.
Although an Example is shown below, it is not restrict | limited to this, The one part was performed in order to emphasize the effect of this application.

The small apparatus shown in FIG. 1 was assembled in a barraque manner, and the presence or absence of the first sleeve was examined. In other words, the corundum powder was put into a molybdenum crucible having an outer diameter of 50 mm and a height of 100 mm, and a dissolution test was performed. Here, thermocouples were placed at 30 mm and 70 mm portions from the bottom of the crucible, and the temperature was measured there. The heating is due to the heat generated by the crucible itself by high frequency induction.

This molybdenum crucible is used as a first sleeve in a dense stabilized zirconia crucible having an inner diameter of 60 mm, an outer diameter of 70 mm, a wall thickness of 5 mm, and a height of 150 mm, and this has a depth of 145 mm in the center of the second sleeve. Centered around a 77 mm hole. The second sleeve having such a hole in the center is a combination of porous zirconia bricks having an outer diameter of 250 mm and a diameter of 400 mm, and a high frequency coil having an inner diameter of 300 mm and a coil part height of 120 mm is placed on the outer side to melt. A test was conducted. A 5 mm-thick eye plate made of stabilized zirconia was placed at the bottom of the hole portion of the second sleeve. For comparison, prepare a crucible directly in the center of a sleeve (second sleeve) where the diameter of the central hole is 144mm and the diameter is 77mm without placing the first sleeve. Experiments were conducted on these differences.

As a result, both of the crucible temperatures first increased to 2150 ° C., then gradually decreased and melted, and stabilized at about 2050 ° C. on the temperature display. That is, in the case having the first sleeve, the lower thermocouple temperature was 2050 ° C., and the upper thermocouple was 2056 ° C. In addition, argon gas was made to flow continuously in the gas atmosphere in this.

In the case where the first sleeve for comparison was removed, the temperature outside the crucible at the stable temperature at which the alumina melted was 2065 ° C. at the lower part and 2058 ° C. at the upper part, which is almost the same as the melting point, It was necessary to pass an excess current through the crucible body by a large amount of heat escape as compared to the case with the sleeve. Naturally, this extra current has a problem that the power consumption becomes too large, and the power consumption of the present invention is reduced. (Appearance was about 5% reduction in power consumption.)

The same crucible furnace as in Example 1 was used, except that a densely stabilized zirconia cylinder having a wall thickness of 3 mm was used as the first sleeve instead of the crucible type densely stabilized zirconia (corresponding to FIG. 2). Alumina was dissolved under the same conditions as in Example 1. As a result, the temperature of the upper thermocouple was 2060 ° C, the stock thermocouple temperature was 2051 ° C, and it was confirmed that the heat escape from the lower part was slightly larger, but the temperature difference was much smaller than the proportionality. It was found that power consumption was also reduced.

A paste obtained by dissolving magnesium butoxide in butyl alcohol was applied to the inner surface of the first sleeve used in Example 1, and fired at 800 ° C. to provide a magnesium oxide coating with an apparent thickness of 10 μm. did. This was subjected to corundum dissolution under the same conditions as in the first aspect. After this operation was performed 10 times, the inner surface of the first sleeve was observed, and black deposits considered to be alumina and molybdenum were partially attached. When this first sleeve was removed and immersed in 15% sulfuric acid at 70 ° C., the alumina and black deposits dropped into the acid, and the deposit on the first sleeve disappeared together with magnesia. By doing it again, it was possible to continue reuse without contamination.

A crucible furnace with an external heater was assembled. That is, using a platinum crucible having a diameter of 50 mm and a height of 100 mm, a furnace body (second sleeve) made of alumina wool having an inner hole diameter of 80 mm, a depth of 150 mm, an outer diameter of 300 mm and a height of 300 mm is prepared, and graphite is formed on the outside thereof. A heater was placed, and a crucible furnace was formed by enclosing the heater with a porous body made of alumina wool having a thickness of 100 mm. In addition, a crucible made of dense magnesium oxide having an outer diameter of 78 mm (apparent), a wall thickness of 4 mm, and a height of 160 mm as a first sleeve is provided inside the hole in the center of the crucible furnace. It installed so that it might contact the 2nd sleeve made from an alumina wool.

Put a mixture of lithium carbonate and quartz glass powder so that the ratio of Li: Si = 1: 2 (mol), and dissolve and synthesize while flowing a small amount of air inside the first sleeve. Went. First, lithium carbonate was decomposed, further heated up to 1100 ° C. and melted, held for about 2 hours, gradually decreased in temperature, and held at about 1030 ° C. for 1 hour to grow crystals. This test was repeated 5 times, but almost no grain growth of the platinum crucible was observed, and no change was observed in the state.

For the comparison, the same crucible furnace as in Example 4 was assembled, except that the first sleeve was removed, and alumina wool was wound up to that part to make an integral sleeve with the same crucible installation part size. The synthesis of Li ₂ O.2SiO ₂ was tested under the same conditions while flowing the same amount of air inside the sleeve as in Example 4. When the synthesis and crystal growth tests were performed about three times, grain growth was observed particularly in the outer portion of the platinum crucible, and considerable hardening and large grain growth were observed at the fifth time. Deterioration of was observed. This is due to the fact that a reducing substance such as CO (carbon monoxide) from the carbon heater has penetrated into the crucible portion through the porous sleeve portion, resulting in a substantially reducing atmosphere. It was thought that it became.

For electronic devices, single crystals are often grown, and heat-resistant tungsten and molybdenum are sometimes used as crucibles. Recently, however, expensive platinum group metals such as platinum and iridium, The number of cases using the alloy is increasing. As explained here, the life of these platinum group metals varies greatly depending on the atmosphere in which they are used. Therefore, it is necessary to adjust the atmosphere around the crucible depending on the metal and platinum group metal to be used. In this application, the portion to be adjusted is specified, and adjustment with a small amount of atmospheric gas is possible. Platinum, iridium, and their alloys used in the process are partially volatilized as they are used, but they remain almost as metals in the furnace, but most of them deposit on the first sleeve, Recovery is extremely easy. From these, we think that the use will be greatly expanded especially in the crystal growth field using platinum group metal crucibles in the future.

It is a conceptual sectional view of the crucible furnace of the present invention, and is a case of a crucible type having an induction heating mechanism by high frequency and having a first sleeve at the bottom. It is a conceptual sectional view of the processing device of the present invention, and has a high frequency induction heating mechanism, and the first sleeve is a cylinder. It is a conceptual sectional view of the crucible furnace of the present invention, and is a case of a crucible type having a resistance heater in the second sleeve and the first sleeve having a bottom. It is a conceptual sectional view of the crucible furnace of the present invention, and has a resistance heater in the second sleeve, and the first sleeve is a cylinder.

DESCRIPTION OF SYMBOLS 1 1st sleeve 2 2nd sleeve 3 High frequency induction heating coil 4 Crucible 5 Resistance heater 6 Bottom heat insulation pan

Claims (10)

A crucible furnace for treating a compound in a metal crucible at a high temperature of 1000 ° C. or higher, wherein a first sleeve made of heat-resistant and removable thin dense ceramic is placed around the crucible, A crucible furnace, wherein a second sleeve made of a heat insulating material and a heating device are placed outside the one sleeve. The heating device is an induction heating device, the induction heating coil device is placed outside the second sleeve, and a gap is provided between the wall portion excluding at least the bottom of the first sleeve and the second sleeve. The crucible furnace according to claim 1. The crucible furnace according to claim 1, wherein the heating device is an electric resistance heating device, the resistance heating portion is placed in the second sleeve, and the first sleeve and the second sleeve are in contact with each other. . The crucible furnace according to claim 1, wherein the wall thickness of the first sleeve is 10 mm or less. The crucible furnace according to claim 1, wherein the gas atmosphere in the first sleeve is controlled. The crucible furnace according to claim 1, wherein the wall height of the first sleeve is higher than the height of the crucible. The crucible furnace according to claim 1, wherein the first sleeve is a dense magnesia-based ceramic. The crucible furnace according to claim 1, wherein the first sleeve is a dense stabilized zirconia ceramic. The crucible furnace according to claim 1, wherein the crucible furnace is a stabilized zirconia ceramic having a dense alkaline earth metal oxide coating on the inner surface of the first sleeve on the crucible side. The crucible furnace according to claim 1 or 9, wherein the alkaline earth metal oxide is magnesia.

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