JP4667011B2 - Thermocouple and reaction system and crystal production equipment - Google Patents

Description

The present invention, a thermocouple and a reaction system and a crystal manufacturing apparatus.

  The inventors of the present application have heretofore reacted a mixed melt composed of an alkali metal and a group III metal with a group V raw material containing nitrogen, as shown, for example, in Patent Document 1 and the like. A so-called flux method for producing a group III nitride crystal (for example, GaN) has been adopted.

  In the production of the group III nitride crystal by the flux method, it is necessary to control the temperature, and a thermocouple is generally used to control the temperature. Since the thermocouple deteriorates due to contact with the alkali metal vapor, it may be installed outside the reaction vessel so as not to contact the alkali metal vapor. However, in order to precisely control the temperature, it is necessary to install a thermocouple in the reaction vessel. In this case, a sheath thermocouple having a core wire covered with a protective tube (sheath) is used. In general, stainless steel or Inconel steel is used for the protective tube (sheath).

  In the flux method, as general growth conditions for the group III nitride crystal, a temperature of 700 to 900 ° C., a nitrogen pressure of 20 to 100 atmospheres, Na as an alkali metal, and Ga as a group III material are used. Under such conditions, deterioration of the thermocouple occurs even when a sheath thermocouple is used. For example, in the case of a K (chromel-alumel) thermocouple with a stainless steel or Inconel sheath, an electromotive force drop corresponding to about 20 ° C. occurred at 900 ° C. for 200 hours.

  On the other hand, as a general deterioration in the case of the K thermocouple, there is a reduction in electromotive force due to selective oxidation of the core wire, which is called a green rod phenomenon. In this case, the electromotive force is reduced by about 1 ° C. in 1000 hours at 900 ° C. in an air atmosphere. Even in a reducing atmosphere in which a more prominent green rod phenomenon occurs, the electromotive force decreases corresponding to about 10 ° C. in 1000 hours.

Therefore, the deterioration of the K thermocouple caused by the flux method is clearly different from the general deterioration of the K thermocouple that has been known so far, and the degree of deterioration is large.
JP 2001-58900 A

An object of the present invention is to provide a thermocouple, a reaction system, and a crystal manufacturing apparatus with little deterioration even when used in an environment in which a substance containing an alkali metal and at least nitrogen exists, such as a flux method. It is said.

In order to achieve the above object, according to the first aspect of the present invention, there is provided a sheath that suppresses nitriding of a thermocouple core wire even when used in an environment where a substance containing an alkali metal and at least nitrogen is present. The sheath provided on the outside of the core wire, the sheath provided on the outside of the thermocouple core wire is composed of a plurality of layers of sheaths, and there is a space between at least one adjacent sheath of the plurality of layers of sheaths, The space between the sheaths is filled with a gas that forms a compound with an alkali metal .

Further, an invention according to claim 2, wherein, in the thermocouple of Claim 1, the sheath material is characterized in that a Ni.

The invention according to claim 3 is a reaction system using a substance containing an alkali metal and at least nitrogen, wherein the thermocouple according to claim 1 or 2 is used in the reaction system. .

According to a fourth aspect of the present invention, in the reaction vessel, an alkali metal and a substance containing at least a group III metal form a mixed melt, and from the mixed melt and a substance containing at least nitrogen, a group III metal In a crystal manufacturing apparatus for growing a group III nitride composed of nitrogen and nitrogen, the thermocouple according to claim 1 or 2 is used in the crystal manufacturing apparatus.

According to the first and second aspects of the invention, the sheath that suppresses nitriding of the thermocouple core wire even when used in an environment where a substance containing an alkali metal and at least nitrogen is present is provided outside the thermocouple core wire. Since it is provided, nitriding of the core wire of the thermocouple can be suppressed.

  That is, as described above, when there is a substance containing alkali metal and at least nitrogen, for example, nitriding of a sheath made of stainless steel or Inconel and a core wire of a thermocouple (for example, K (chromel-alumel)) is accelerated. The inventor of the present application has found. In the present invention, by using a sheath that suppresses nitriding of a thermocouple core wire even when used in an environment where a substance containing an alkali metal and at least nitrogen is present (specifically, for example, a ninth embodiment described later) (For example, by using Ni (nickel) for the sheath), diffusion of nitrogen and alkali metal to the inside can be prevented, and thus, nitriding of the core wire of the thermocouple can be prevented. As a result, a decrease in thermoelectromotive force can be prevented, and environmental temperature measurement and temperature control can be performed stably for a long time.

In particular, in the first aspect of the present invention, the sheath is provided on the outside of the thermocouple wire, which is configured with a sheath of a plurality of layers (multi-structure), more suppress the nitriding of the core wire of the thermocouple be able to.

  That is, since the sheath has a plurality of layers (that is, has a multiple structure), nitriding can be suppressed as compared with a sheath having a single layer structure (single structure). That is, in the case of one layer (single layer), nitriding proceeds continuously from the outside of the sheath toward the inside (ie, the core line direction of the thermocouple). However, in the case of a multi-layer structure (multiple structure), nitriding once terminates between the layers of the sheath. After that, when the alkali metal and nitrogen diffuse between the layers and reach the next sheath layer, nitriding of the sheath proceeds from there, but nitriding more than the single layer structure (single structure). It can be effectively suppressed.

Further, in the first aspect of the present invention, among the sheath before Symbol multilayer (multiple structure), there is a space between at least one adjacent sheath, even more even more effectively, the nitride of the core wire of the thermocouple Can be suppressed.

  That is, since there is a space between the sheaths of a multi-layer structure (multiple structure), diffusion of alkali metal and nitrogen supplied from the outside of the outermost sheath is suppressed by this space, and the alkali metal to the inner sheath is suppressed. And nitrogen diffusion is further suppressed. For this reason, compared with the case where there is no space, nitriding of the sheath and the innermost core wire can be more effectively suppressed.

Further, in the first aspect of the present invention, the space between the front Symbol sheath, since the gas to form the alkali metal and the compound is filled, even more even more effectively suppress the nitriding of the core wire of the thermocouple be able to.

  That is, the gas in the space between the sheaths can form a compound with the alkali metal, thereby suppressing the diffusion of the alkali metal to the inner sheath. As a result, the nitridation of the inner sheath (by the alkali metal) (Promoting nitriding) can be suppressed, and nitriding of the core wire of the thermocouple can be suppressed.

  At this time, it is desirable that there is no gas containing nitrogen as a constituent element in the space between the sheaths, but even if there is, the alkali metal forms a compound so that the inner sheath and the core wire of the thermocouple are formed. The nitridation of can be greatly suppressed.

In the invention according to claim 2 , in the thermocouple according to claim 1 , since the sheath material is Ni, nitriding of the core wire of the thermocouple can be suppressed.

  That is, even if an alkali metal is present, Ni does not form a nitride under the condition that the group III nitride grows. For this reason, it is possible to prevent diffusion of nitrogen and alkali metal to the inside of the sheath formed of Ni. As a result, deterioration of the core wire of the thermocouple can be significantly suppressed.

According to the invention of claim 3 , in the reaction system using a substance containing an alkali metal and at least nitrogen, the thermocouple according to claim 1 or 2 is used in the reaction system. In a reaction system using a substance containing metal and at least nitrogen, high-precision temperature measurement and temperature control of the reaction system can be performed stably for a long time.

According to the invention described in claim 4 , in the reaction vessel, the alkali metal and the substance containing at least a group III metal form a mixed melt, and the mixed melt and the substance containing at least nitrogen are used to form III. In a crystal manufacturing apparatus for growing a group III nitride composed of a group metal and nitrogen, the thermocouple according to claim 1 or 2 is used in the crystal manufacturing apparatus. It is possible to grow a group III nitride crystal.

That is, even if a substance containing an alkali metal and at least nitrogen is present, the core wire of the thermocouple can be suppressed from nitriding, leading to prevention of a decrease in thermoelectromotive force, and a group III nitride crystal growth apparatus stably for a long time. High-accuracy temperature measurement and temperature control of the reaction system is possible. As a result, it is possible to grow a large group III nitride crystal with high quality.

  Hereinafter, the best mode for carrying out the present invention will be described.

  The inventor of the present application, when used in an environment where a substance containing an alkali metal and at least nitrogen exists, as in the flux method, the main cause of deterioration of the thermocouple is that the core wire of the thermocouple is nitrided. I found out that it is due to. In other words, when used in an environment where a substance containing an alkali metal and at least nitrogen is present, such as the flux method, the nitrogen and the alkali metal (the alkali metal becomes a kind of catalyst) The nitridation of the sheath of the material is promoted, which promotes the diffusion of nitrogen and alkali metal to the inside, and ultimately the nitriding of the core wire of the thermocouple is promoted. The present inventors completed the present invention by finding that the electric power decreased and the thermocouple deteriorated.

  That is, the present invention is basically intended to prevent nitriding of the core wire of a thermocouple when used in an environment containing a substance containing an alkali metal and at least nitrogen.

(First form)
In the first aspect of the present invention, a sheath for suppressing nitriding of a thermocouple core wire is provided outside the thermocouple core wire even when used in an environment where a substance containing an alkali metal and at least nitrogen is present. It is characterized by being.

  Here, Li, Na, K, etc. can be used for the alkali metal. The substance containing nitrogen is a compound containing nitrogen gas, nitrogen such as sodium azide or ammonia as a constituent element.

  In the first embodiment of the present invention, the thermocouple includes a core wire that generates a thermoelectromotive force and a sheath that protects the core wire. In the thermocouple having such a configuration, the temperature of the environment in which the thermocouple is placed is transmitted to the core wire of the thermocouple through the sheath, and a thermoelectromotive force corresponding to the above temperature is generated in the core wire of the thermocouple. By taking out the electromotive force and measuring it, the temperature of the environment where the thermocouple is placed can be measured. At this time, the thermocouple sheath of the present invention suppresses nitriding of the thermocouple core wire even when used in an environment where a substance containing an alkali metal and at least nitrogen is present.

  As described above, in the first embodiment of the present invention, the sheath that suppresses nitriding of the thermocouple core wire even when used in an environment where a substance containing an alkali metal and at least nitrogen is present is provided on the outer side of the thermocouple core wire. Therefore, nitriding of the core wire of the thermocouple can be suppressed.

  That is, as described above, when there is a substance containing alkali metal and at least nitrogen, for example, nitriding of a sheath made of stainless steel or Inconel and a core wire of a thermocouple (for example, K (chromel-alumel)) is accelerated. The inventor of the present application has found. In the present invention, by using a sheath that suppresses nitriding of the thermocouple core wire even when used in an environment in which a substance containing an alkali metal and at least nitrogen is present (specifically, as in a ninth embodiment described later) In addition, for example, by using Ni (nickel) for the sheath), it is possible to prevent diffusion of nitrogen and alkali metal into the inside, thereby preventing nitriding of the core wire of the thermocouple. As a result, a decrease in thermoelectromotive force can be prevented, and environmental temperature measurement and temperature control can be performed stably for a long time.

(Second form)
The second aspect of the present invention is characterized in that, in the thermocouple of the first aspect, the sheath provided outside the thermocouple core wire is formed of a sheath having a plurality of layers (multiple structure).

  Here, the sheaths of each layer may be in contact with each other, and as described later, there may be a space between adjacent sheaths, or other substances are clogged between adjacent sheaths. May be. Moreover, the material which comprises the sheath of each layer may be the same, and may differ.

  Thus, in the second mode, in the thermocouple of the first mode, the sheath provided outside the thermocouple core wire is composed of a sheath having a plurality of layers (multiple structure). The nitriding of the core wire can be further suppressed.

  That is, since the sheath has a plurality of layers (that is, has a multiple structure), nitriding can be suppressed as compared with a sheath having a single layer structure (single structure). That is, in the case of one layer (single layer), nitriding proceeds continuously from the outside of the sheath toward the inside (ie, the core line direction of the thermocouple). However, in the case of a multi-layer structure (multiple structure), nitriding once terminates between the layers of the sheath. After that, when the alkali metal and nitrogen diffuse between the layers and reach the next sheath layer, nitriding of the sheath proceeds from there, but nitriding more than the single layer structure (single structure). It can be effectively suppressed.

(Third form)
A third aspect of the present invention is characterized in that in the thermocouple of the second aspect, a space is provided between at least one adjacent sheath among the multiple layer (multiple structure) sheaths.

  Here, “there is a space” means any of the above-mentioned cases where “a space may be vacant between adjacent sheaths, or other substances may be clogged between adjacent sheaths”. Is included.

  As described above, in the third embodiment, in the thermocouple of the second embodiment, since there is a space between at least one adjacent sheath among the multiple layer (multiple structure) sheaths, it is even more effective. The nitriding of the core wire of the thermocouple can be suppressed.

  That is, since there is a space between the sheaths of a multi-layer structure (multiple structure), diffusion of alkali metal and nitrogen supplied from the outside of the outermost sheath is suppressed by this space, and the alkali metal to the inner sheath is suppressed. And nitrogen diffusion is further suppressed. For this reason, compared with the case where there is no space, nitriding of the sheath and the innermost core wire can be more effectively suppressed.

(4th form)
According to a fourth aspect of the present invention, in the thermocouple of the third aspect, the space between the sheaths is filled with a gas not containing nitrogen as a constituent element.

  In the fourth embodiment, in the thermocouple of the third embodiment, the space between the sheaths is filled with a gas that does not contain nitrogen as a constituent element, so that the nitriding of the core wire of the thermocouple is more effectively performed. Can be suppressed.

  That is, when the space between the sheaths is filled with a gas containing nitrogen as a constituent element, the nitrogen concentration is higher than the nitrogen concentration in this region due to nitrogen diffusing from the outside of the outermost sheath. Get higher. Therefore, nitriding from the space toward the inside (core side) tends to proceed.

  On the other hand, when there is no gas containing nitrogen as a constituent element in the space between the sheaths as in the fourth embodiment, nitriding in the inner direction from this space can be suppressed, and as a result, the thermocouple It becomes possible to more effectively suppress nitriding of the core wire.

(5th form)
According to a fifth aspect of the present invention, in the thermocouple of the third aspect, the space between the sheaths is filled with a gas that forms a compound with an alkali metal.

  Here, the alkali metal is the same element as the alkali metal described in the first embodiment.

  In the fifth embodiment, in the thermocouple of the third embodiment, the space between the sheaths is filled with a gas that forms a compound with an alkali metal, so that the core wire of the thermocouple is even more effective. Can be suppressed.

  That is, the gas in the space between the sheaths can form a compound with the alkali metal, thereby suppressing the diffusion of the alkali metal to the inner sheath. As a result, the nitridation of the inner sheath (by the alkali metal) (Promoting nitriding) can be suppressed, and nitriding of the core wire of the thermocouple can be suppressed.

  At this time, it is desirable that there is no gas containing nitrogen as a constituent element in the space between the sheaths, but even if there is, the alkali metal forms a compound so that the inner sheath and the core wire of the thermocouple are formed. The nitridation of can be greatly suppressed.

(Sixth form)
According to a sixth aspect of the present invention, in the thermocouple of the third aspect, the space between the sheaths is filled with a solid material different from the material constituting the sheath.

  In the sixth embodiment, in the thermocouple of the third embodiment, the space between the sheaths is filled with a solid material different from the material constituting the sheath, so that the thermocouple can be made even more effective. Nitriding of the pair of core wires can be suppressed.

  That is, in the sixth embodiment, since diffusion of alkali metal and nitrogen once terminates at the interface between the outer sheath of the space and a solid material different from the sheath, the inner sheath is nitrided ( (Promotion of nitriding by alkali metal) can be suppressed. As a result, nitriding of the core wire of the thermocouple can be suppressed.

(7th form)
According to a seventh aspect of the present invention, in the thermocouple of the sixth aspect, the solid filled in the space between the sheaths has an alkali metal diffusion rate higher than the alkali metal diffusion rate in the material constituting the sheath. Is made of a small material.

  In the seventh embodiment, in the thermocouple of the sixth embodiment, the solid filled in the space between the sheaths has an alkali metal diffusion rate lower than the alkali metal diffusion rate in the material constituting the sheath. Since it is made of a material, nitriding of the core wire of the thermocouple can be more effectively suppressed.

  That is, as described above, suppressing the diffusion of alkali metal to the inner side ultimately leads to suppression of deterioration of the thermocouple. In the seventh embodiment, the material that is slower than the diffusion rate of the alkali metal in the material constituting the sheath fills the space between the sheaths, so that the diffusion of the alkali metal to the inside can be suppressed. As a result, nitriding of the inner sheath can be suppressed, and nitriding of the core wire of the thermocouple can be suppressed.

(8th form)
According to an eighth aspect of the present invention, in the thermocouple of the sixth aspect, the solid filled in the space between the sheaths is made of a material that reacts with an alkali metal.

  In the eighth embodiment, in the thermocouple of the sixth embodiment, since the solid filled in the space between the sheaths is made of a material that reacts with an alkali metal, the core wire of the thermocouple is more effectively obtained. Can be suppressed.

  That is, the solid filled in the space between the sheaths forms a compound with the alkali metal, so that the diffusion of the alkali metal to the inner sheath can be suppressed. As a result, nitriding of the inner sheath (promoting nitriding with an alkali metal) can be suppressed, and nitriding of the core wire of the thermocouple can be suppressed.

  At this time, it is desirable that the solid between the sheaths does not have a substance containing nitrogen as a constituent element, but even if there is, the alkali metal forms a compound, so that the nitriding of the inner sheath is greatly reduced. Can be suppressed.

(9th form)
According to a ninth aspect of the present invention, in the thermocouple according to any one of the first to eighth aspects, the sheath material is Ni.

  In the ninth embodiment, in the thermocouple of any one of the first to eighth embodiments, since the sheath material is Ni, nitriding of the core wire of the thermocouple can be suppressed.

  That is, even if an alkali metal is present, Ni does not form a nitride under the condition that the group III nitride grows. For this reason, it is possible to prevent diffusion of nitrogen and alkali metal to the inside of the sheath formed of Ni. As a result, deterioration of the core wire of the thermocouple can be significantly suppressed.

(10th form)
According to a tenth aspect of the present invention, in the reaction system using a substance containing an alkali metal and at least nitrogen, the thermocouple of any one of the first to ninth aspects is used for the reaction system. It is said.

  In the tenth embodiment, in the reaction system using a substance containing an alkali metal and at least nitrogen, the thermocouple of any one of the first to ninth forms is used in the reaction system. In a reaction system using a substance containing at least nitrogen, highly accurate temperature measurement and temperature control of the reaction system can be stably performed for a long time.

  The tenth embodiment is not only a system that performs group III nitride crystal growth, but also a system that performs a reaction using a substance containing an alkali metal and at least nitrogen, in addition to a system that performs group III nitride crystal growth. If so, it can be applied to all.

(Eleventh form)
In an eleventh aspect of the present invention, in a reaction vessel, an alkali metal and a substance containing at least a group III metal form a mixed melt, and from the mixed melt and a substance containing at least nitrogen, a group III metal and In a crystal growth apparatus for crystal growth of a group III nitride composed of nitrogen, the crystal growth apparatus uses a thermocouple of any one of the first to ninth forms.

  Here, in the crystal growth apparatus, for example, in a reaction vessel, an alkali metal and a substance containing at least a group III metal form a mixed melt, and from the mixed melt and a substance containing at least nitrogen, a group III metal Group III nitride crystal growth apparatus for growing a group III nitride composed of nitrogen and nitrogen.

  The group III metal is Ga, Al, In or the like.

  As described above, when the thermocouple of the present invention is used in a group III nitride crystal growth apparatus, the temperature in the reaction container is set in the reaction container of the group III nitride crystal growth apparatus via the sheath. The core wire is generated as a thermoelectromotive force, and the thermoelectromotive force is taken out and measured, whereby the temperature in the reaction vessel can be measured with high accuracy.

  In the eleventh embodiment, the alkali metal and the substance containing at least a group III metal form a mixed melt in the reaction vessel, and the group III metal and nitrogen are separated from the mixed melt and the substance containing at least nitrogen. In the crystal growth apparatus for growing a group III nitride composed of the above-described crystal growth apparatus, since the thermocouple of any one of the first to ninth forms is used, a high-quality and large-sized III It becomes possible to grow a group nitride crystal.

  That is, even if a substance containing an alkali metal and at least nitrogen is present, the core wire of the thermocouple can be suppressed from nitriding, leading to prevention of a decrease in thermoelectromotive force, and a group III nitride crystal growth apparatus stably for a long time. High-accuracy temperature measurement and temperature control of the reaction system is possible. As a result, it is possible to grow a large group III nitride crystal with high quality.

  Next, examples of the present invention will be described.

  Example 1 corresponds to the first and ninth embodiments. 1 is a diagram illustrating a thermocouple of Example 1. FIG. In FIG. 1, only a region of the thermocouple that is in contact with a reaction system using a substance containing an alkali metal and at least nitrogen is shown in cross section. An area not shown in the lower part of FIG. 1 is not directly related to the present invention, and is not shown. The illustration of the lower region is the same in the following embodiments.

  Referring to FIG. 1, there is an insulating material 103 between the core wire 101 and the sheath 102 of the thermocouple. In the first embodiment, the core wire 101 is made of K (chromel-alumel) (that is, a K thermocouple), the sheath 102 is made of Ni (nickel), and the insulating material 103 is made of MgO. is there. Here, the sheath 102 is a protective tube and has a cylindrical shape. The distal end portion (uppermost portion) of the sheath 102 is rectangular, but this shape is not particularly limited. Regarding the shape of the sheath, the following examples are the same as those of the example 1.

In the first embodiment, since the material of the sheath 102 is Ni, the sheath 102 is nitrided even if there is Na as an alkali metal and nitrogen gas (N ₂ ) as a substance containing at least nitrogen outside the sheath 102. Is suppressed, and a decrease in thermocouple electromotive force can be prevented.

  Even when the sheath is SUS (stainless steel), if the sheath surface is Ni-plated, the same effect as that obtained when the sheath material is Ni can be obtained.

  Example 2 corresponds to the first and second embodiments. FIG. 2 is a diagram showing a thermocouple of the second embodiment. In FIG. 2, the same parts as those in FIG.

  Referring to FIG. 2, a first sheath 202 is provided outside the core wire 101 and the insulating material 103 of the thermocouple, and a second sheath 204 is provided outside the first sheath 202. There is a sheath interface 205 between the first sheath 202 and the second sheath 204, which forms a double sheath structure. Both the material of the first sheath 202 and the second sheath 204 is SUS (stainless steel).

  In the case of a general single SUS sheath K thermocouple, if Na and nitrogen gas as alkali metals are present outside the sheath, as described in the background art at a temperature of about 800 ° C. Reduced electromotive force. On the other hand, in this Example 2, since the sheath has a double sheath structure, SUS nitridation once terminates at the interface 205, so that deterioration of the thermocouple can be suppressed.

  If the material of the second sheath 204 is Ni as described in the first embodiment (or if the surface of the second sheath 204 is Ni-plated), the deterioration is further improved compared to SUS. Can be suppressed.

FIG. 3 shows a comparison result of deterioration of thermocouple between the case where the Ni tube is used as the second sheath 204 outside the first sheath 202 made of SUS and the case where only the first sheath 202 is used. ing. In addition, the vertical axis | shaft L of FIG. 3 is time (namely, time when the fall of an electromotive force starts from a use start) when deterioration of a thermocouple starts. The horizontal axis represents a value obtained by multiplying the inverse of absolute temperature by 10 ⁴ (10 4).

  From FIG. 3, it can be seen that the use of a Ni tube as the second sheath 204 makes it possible to increase the life of the thermocouple by an order of magnitude as compared to the case where it is not used.

  As a result, by using a Ni tube as the second sheath 204, it is possible to provide a thermocouple capable of temperature measurement and temperature control stably for a long time.

  In Example 2, the sheath has a double structure. However, the sheath may have a double or more multiple structure. The third sheath is outside the second sheath, and the fourth sheath is outside. The more the sheath and the multiple structure, the more the deterioration of the thermocouple can be suppressed.

  The third embodiment corresponds to the first, second, third, fourth, and fifth embodiments. FIG. 4 is a diagram illustrating a thermocouple of Example 3. In FIG. 4, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof is omitted.

  Referring to FIG. 4, there is a second sheath 204 outside the first sheath 202, and there is a space 305 between these sheaths 202, 204. This space 305 is filled with, for example, air. The material of these sheaths 202 and 204 is SUS as in the second embodiment.

  In Example 3, there are Na and nitrogen gas as alkali metals outside the second sheath 204, and the sheath has a double sheath structure even at a temperature of about 800 ° C. The presence of the space 305 between the sheaths can more effectively suppress deterioration of the thermocouple. That is, in Example 3, the time until Na diffused from the outside of the second sheath 204 adheres to the surface of the first sheath 202 due to the presence of the space 305 does not exist in the space 305 (the first More than the case where the sheath 202 and the second sheath 204 are in contact with each other. As a result, it is possible to more effectively suppress deterioration of the thermocouple.

  In the above-described example, the space 305 between the sheaths is filled with air. However, for example, when Ar (argon) is filled in the space 305 as a gas that does not contain nitrogen, the space 305 starts from the surface of the first sheath 202. This nitriding can be further suppressed as compared with the case of filling with air. In this case, nitriding proceeds from the outside of the second sheath 204, and nitrogen diffuses into the space 305. However, since the nitrogen concentration in the space 305 is less in the case of Ar than in air, the first The nitriding rate of one sheath can be suppressed.

  Furthermore, even when this space 305 is filled with moisture (water vapor), deterioration of the thermocouple can be suppressed. This is because Na diffused through the second sheath 204 can be prevented from diffusing through the first sheath 202 by reacting with moisture in the space 305.

  In this case, since there is no introduction of gas (that is, heat does not move due to gas movement), more accurate temperature measurement is possible.

  In Example 3, the sheath has a double structure. However, the sheath can have a double or more multiple structure. The third sheath is outside the second sheath, and the sheath is outside the second sheath. As the number of spaces between the four sheaths and the multiple structure increases, deterioration of the thermocouple can be further suppressed.

  Example 4 corresponds to the sixth, seventh, and eighth embodiments. FIG. 5 is a diagram illustrating a thermocouple of Example 4. In FIG. 5, the same parts as those in FIGS. 1, 2, and 4 are denoted by the same reference numerals, and description thereof is omitted.

Referring to FIG. 5, there is an inter-sheath filler 405 between the first sheath 202 and the second sheath 204. The material of the sheaths 202 and 204 is SUS as in the second and third embodiments, but the inter-sheath filler 405 is SiO _{2 made} of a material different from that of the sheaths 202 and 204. This SiO ₂ may be a powder or a dense solid such as a quartz tube.

  In Example 4, there are Na and nitrogen gas as alkali metals outside the second sheath 204, and the sheath has a double sheath structure even at a temperature of about 800 ° C. By having the filler 405 between the sheaths, it is possible to more effectively suppress deterioration of the thermocouple. That is, in Example 4, the time until Na diffused from the outside of the second sheath 204 adheres to the surface of the first sheath 202 is such that the inter-sheath filler 405 Compared to the case where the first sheath 202 and the second sheath 204 are in contact with each other, the length becomes longer. As a result, it is possible to more effectively suppress deterioration of the thermocouple.

In the above example, SiO ₂ is filled as the filler 405 between the sheaths, but when silicon nitride (Si ₃ N ₄ ), whose diffusion rate of alkali metal Na is slower than SiO ₂ , is filled as the inter-sheath filler 405. Is more effective in suppressing deterioration of the thermocouple than when the above-mentioned SiO ₂ is used as the inter-sheath filler 405.

Further, when alumina (Al ₂ O ₃ ) is used as the inter-sheath filler 405, the alumina and Na diffused through the second sheath 204 react to form β-alumina (Na ₂ O · 11Al ₂ O ₃ ) As a result, deterioration of the thermocouple can be suppressed.

  Example 5 corresponds to the eleventh mode. FIG. 6 is a view showing a group III nitride crystal growth apparatus of Example 5.

  Referring to FIG. 6, there is a second reaction vessel 513 inside the first reaction vessel 501, and a group III nitride in between (inside the first reaction vessel 501 and outside the second reaction vessel 513). Is provided with a heating device 506 so that the temperature can be controlled so that the crystal can grow. A mixed melt holding vessel 502 is installed inside the second reaction vessel 513. In the mixed melt holding container 502, there is a mixed melt 503 composed of Ga as a substance containing at least a group III metal and Na as an alkali metal. A lid 509 is provided on the mixed melt holding container 502. There is a slight gap between the mixed melt holding container 502 and the lid 509 so that gas can enter and exit.

  In the apparatus of FIG. 6, a thermocouple 512 for detecting the temperature of the mixed melt holding container 502 is installed in the second reaction container 513. As the thermocouple 512, the sheathed thermocouple of the present invention as described in the above embodiments is used. The thermocouple 512 is connected to the heating device 506 so that temperature feedback control is possible.

  In the apparatus of FIG. 6, nitrogen gas is used as a substance containing at least nitrogen. Nitrogen gas is supplied from the nitrogen gas container 507 installed outside the first reaction container 501 to the space 508 in the first reaction container 501 and the second reaction container 513 through the gas supply pipe 504. be able to. In order to adjust the pressure of the nitrogen gas, a pressure adjustment valve 505 is provided. Further, a pressure sensor 511 for detecting the pressure of nitrogen gas in the reaction vessel is installed. At this time, the pressure sensor 111 feeds back the pressure regulating valve 105 so that the pressures in the first reaction vessel 501 and the second reaction vessel 513 are substantially the same pressure and become a predetermined pressure. It has become.

  Using the apparatus of FIG. 6, the nitrogen pressure in the reaction vessel 101 is set to 3 MPa and the temperature of the mixed melt holding vessel 102 is set to 850 ° C. In this state, these temperatures and pressures are maintained, whereby the GaN crystal 510 Can grow.

  At this time, since the thermocouple of the present invention is used for the thermocouple 512, even when Na and nitrogen are present, the thermocouple can be prevented from deteriorating, so that stable crystal growth of several hundred hours is possible. . As a result, it is possible to grow a large GaN crystal with high quality.

Thus, the thermocouple of the present invention is particularly used in a reaction system using an alkali metal and nitrogen. More specifically, as described above, for example, it is used in a group III nitride crystal growth apparatus.

1 is a diagram illustrating a thermocouple of Example 1. FIG. 6 is a diagram showing a thermocouple of Example 2. FIG. It is a figure which shows the comparison result of the thermocouple deterioration when the Ni tube is used as the second sheath 204 outside the first sheath 202 made of SUS and when only the first sheath 202 is used. 6 is a diagram showing a thermocouple of Example 3. FIG. 6 is a diagram showing a thermocouple of Example 4. FIG. FIG. 10 is a view showing a group III nitride crystal growth apparatus of Example 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Thermocouple core wire 102 Thermocouple sheath 103 Insulating material 202 First sheath 204 Second sheath 205 Sheath interface 305 Space between sheaths 405 Filler between sheaths 501 First reaction vessel 502 Mixed melt holding vessel 503 Mixing Melt 504 Gas supply pipe 505 Nitrogen pressure regulating valve 506 Heating device 507 Nitrogen gas container 508 Space in reaction container 509 Lid of mixed melt holding container 510 GaN crystal 511 Pressure sensor 512 Thermocouple 513 Second reaction container

Claims (4)

A sheath that suppresses nitriding of the thermocouple core wire even when used in an environment in which a substance containing alkali metal and at least nitrogen exists is provided outside the thermocouple core wire ,
The sheath provided outside the thermocouple core wire is composed of a plurality of layers of sheaths,
There is a space between at least one adjacent sheath of the multiple layers of sheaths;
A thermocouple characterized in that the space between the sheaths is filled with a gas that forms a compound with an alkali metal . The thermocouple according to claim 1, wherein the sheath material is Ni. The reaction system using the substance containing an alkali metal and at least nitrogen, The thermocouple of Claim 1 or 2 is used for this reaction system, The reaction system characterized by the above-mentioned. In the reaction vessel, an alkali metal and a substance containing at least a group III metal form a mixed melt, and a group III nitridation composed of a group III metal and nitrogen is formed from the mixed melt and a substance containing at least nitrogen. in things a crystal manufacturing apparatus for crystal growth, the crystal production apparatus, the crystal production apparatus characterized in that it thermocouple is used according to claim 1 or 2.

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