Reactor and method for producing reduced oxide sample

Abstract

To provide a reaction device which is capable of increasing a purification refinement amount of a reduced substance, facilitates control of a sample temperature and can be easily mass-produced, and provide a method capable of efficiently obtaining the reduced substance of an oxide specimen using the reaction device.SOLUTION: A reaction device 100 comprises at least: a reaction chamber 15 for storing therein a plasma source 13 such as a metal and an oxide specimen 14 of a reduction processing object which is a separate body from the plasma source; an exhaust pump 12 which exhausts an internal gas of the reaction chamber; one or two or more cavity resonators; and a heating mechanism for heating the oxide specimen. At least one of the cavity resonators includes a first cavity resonator 8 for generating plasma from the plasma source by being shaped to form magnetic field intensity distribution on a center of the cavity resonator and irradiating the entire or partial plasma source with microwaves as the cavity resonator.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an apparatus configuration for generating plasma of solid elements and a technology for a reduction reaction using the generated plasma, and further relates to a reaction apparatus for generating plasma of solid elements and causing a reduction reaction, and a method for producing a reduced product of an oxide sample. [Background technology]

[0002] When generating plasma from gas, a high electric field is used to cause dielectric breakdown, and high-frequency power is applied from the outside to maintain the discharge, thereby sustaining the plasma.The ion species activated by the plasma are then used for surface modification, etc.

[0003] There is also a disclosure of a method for using a solid to generate plasma mainly composed of elements that constitute the solid (see, for example, Patent Document 1). The method for generating metal vapor disclosed in Patent Document 1 describes that a mixture of a metal material and a ceramic body is heated by irradiating it with microwaves, and the metal material is evaporated, thereby generating metal vapor.

[0004] Furthermore, there is a technique for utilizing ions activated by the plasma in a reduction reaction (see, for example, Patent Document 2 or Patent Document 3). Patent Document 2 discloses a method for producing an aluminum-scandium alloy, in which a mixture of a metal material and a ceramic body is irradiated with microwaves to heat the mixture, evaporating the metal material to generate metal vapor, and reacting the metal vapor with scandium oxide and aluminum. Patent Document 3 discloses a method for reducing titanium oxide, in which a mixture of a metal material and a ceramic body is irradiated with microwaves to heat the mixture, evaporating the metal material to generate metal vapor, and reacting the metal vapor with titanium oxide.

[0005] Non-Patent Document 1 describes experimental evidence of a new microwave irradiation process for producing Al-Sc alloys using Mg as a reducing agent, which has been difficult to achieve through scandium oxide reduction. Using this method, the intermetallic compound Al3Sc was obtained in high yield (69.8%) through a low-temperature (660°C) reduction reaction under microwave irradiation.

[0006] Non-Patent Document 2 describes a method for reducing V2O5 to vanadium metal using magnesium vapor and microwave irradiation, and states that it is important to form a precursor, a composite oxide of MgV2O4, by calcining a V2O5 / MgO pellet prior to the reduction reaction. Experiments have shown that by subjecting this precursor to magnesium vapor and microwave irradiation, reduction can be completed in a shorter time of one hour at a heating temperature of 1000°C, compared to conventional reduction methods. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-141190 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-178180 [Patent Document 3] Japanese Patent Application Laid-Open No. 2018-178234 [Non-patent literature]

[0008] [Non-Patent Document 1] S. Fujii, E. Suzuki, N. Inazu, S. Tsubaki, J. Fukushima, H. Takizawa, and Y. Wada, “Micro-wave Irradiation Process for Al Sc Alloy Production,” Scientific Reports, Vol. 10, pp. 2689, February 14, 2020 [Non-patent document 2] N. Inazu et-al, "A facile formation of vanadium(0) by the reduction of vanadium pentoxide pelletized with magnesium oxide enabled by microwave irradiation," Chemistry Select, Vol. 5, pp. 2949-2953, Mar. 2020 Summary of the Invention [Problem to be solved by the invention]

[0009] Patent Document 1 describes the conditions for generating metal vapor under microwave irradiation (such as the mixture of ceramic balls and metal, and their size). Patent Document 2 describes a method for producing an Al-Sc alloy using the conditions of Patent Document 1. The examples in Patent Document 2 and Non-Patent Document 1 disclose a specific device configuration for satisfying these conditions, which is a 40 cm cube multi-mode applicator in which a metal vapor source and raw materials serving as reducing agents are installed. However, there is an issue with the amount of Al-Sc alloy refined in the examples in Patent Document 2, which is small, at around several tens of grams or less.

[0010] Microwaves, a type of electromagnetic wave, exist in two modes known as electric field modes and magnetic field modes, each of which produces different physical phenomena. Multimode is a type of microwave irradiation form. Standing waves of electric and magnetic fields are created inside a metal box, and a multimode applicator is one in which there are two or more antinodes or nodes of this standing wave. Multimode applicators typically include a stirrer fan or turntable to equalize the effects of these nodes and antinodes.

[0011] The technique of Patent Document 2 also has the following problems. (1) Because a single microwave source is used to generate metal vapor, generate plasma, and heat the sample to be reduced, it is difficult to maintain a uniform sample temperature while maintaining the plasma, resulting in an extremely narrow process window. (2) Because the entire reaction system was enclosed in a large SUS box (cavity), it was not possible to install equipment that would be affected by microwaves near the reaction system. As a result, even when a non-contact radiation thermometer was used for temperature measurement, precise temperature control was difficult, making the sample temperature control mentioned above even more difficult. (3) Due to the above, it was also difficult to heat only the sample with a separate heat source. (4) Because the cavity is a large box, the microwave energy distribution is poor, and an installation error of a few mm can cause the reduction to fail. (5) When the technology of Patent Document 2 is used to enlarge the equipment for mass production or to design a continuous reactor, it is clear that the deterioration of microwave distribution and the occurrence of uneven heat due to the enlargement are unavoidable. Furthermore, when designing a continuous reactor, it is clear that the inconvenience of the configuration is great, considering that it is not possible to install instruments and sensors inside the cavity.

[0012] The technology of Patent Document 3 also uses a multi-mode device similar to that of Patent Document 2, and has the same problems as the technology of Patent Document 2. That is, the positions and number of standing waves in the metal box are fixed, so only a limited area can be used, and the locations for magnesium vapor generation and reduction reaction are limited, so that with a batch method, only a few grams of refining can be expected, and there are the problems (1) to (5) above.

[0013] An object of the present disclosure is to provide a reactor that can increase the amount of purified reduced product, that allows easy control of sample temperature, and that facilitates mass production, and also to provide a method for efficiently obtaining reduced products of oxide samples using this reactor. [Means for solving the problem]

[0014] As a result of intensive research into solving the above-mentioned problems, the inventors have found that, when irradiating microwaves to a plasma source, a cavity resonator is used, and the internal space of a cylinder is configured so that the entire plasma source is irradiated with microwaves or so that the microwaves are irradiated to a portion of the plasma source, with the remaining portion being a space located outside the internal space of the cylinder, and at least one of the cavity resonators is configured to form a magnetic field intensity distribution at the center of the cavity resonator, thereby making it possible to stably generate plasma from the plasma source and to easily heat an oxide sample to be reduced, thereby completing the present invention. That is, the reaction apparatus according to the present invention is characterized by comprising at least a reaction chamber for accommodating at least one plasma source selected from the group consisting of a metal, an alloy, an intermetallic compound, a mixture of a metal and a ceramic, a mixture of an alloy and a ceramic, a mixture of an intermetallic compound and a ceramic, and carbon, an oxide sample to be reduced, which is separate from the plasma source, an exhaust pump for exhausting the internal gas of the reaction chamber, one or more cavity resonators, and a heating mechanism for heating the oxide sample, wherein at least one of the cavity resonators has a form that forms a magnetic field intensity distribution at the center of the cavity resonator, and the one or more cavity resonators includes a first cavity resonator that irradiates microwaves to all or a part of the plasma source and generates plasma from the plasma source.

[0015] In the reaction apparatus of the present invention, the heating mechanism is preferably a second cavity resonator for irradiating the oxide sample with microwaves to heat the oxide sample. While conventional multi-mode applicators have not been able to separate the plasma generation section and the heating section, the present invention allows for these sections to be separated. Specifically, the oxide sample can be irradiated with microwaves independently of the plasma source, enabling more precise temperature control. Furthermore, conventional multi-mode applicators limit the types of equipment and devices that can be used because microwaves are distributed throughout the applicator. However, the present invention eliminates limitations on the refining equipment, allowing for larger refining equipment and the use of continuous furnaces. By precisely controlling the temperature conditions, the amount of alloys, such as Al-Sc, refined can be dramatically increased.

[0016] In the reactor of the present invention, the first cavity resonator preferably has an electric field intensity distribution formed at its center, the second cavity resonator preferably has a magnetic field intensity distribution formed at its center, the first cavity resonator irradiating a portion of the plasma source with microwaves to generate plasma from the plasma source, and the second cavity resonator preferably irradiating the remainder of the plasma source and the oxide sample with microwaves to heat the plasma source and the oxide sample. While the electric field mode triggers plasma generation, it can be difficult to sustain the plasma because metal vapor generated from the plasma source is deposited in the system, causing the microwaves generated by the electric field to be reflected by the surface of the deposited metal. However, by using the magnetic field mode in combination, it becomes easier to sustain the plasma even when metal vapor is generated from the plasma source and metal is deposited in the system.

[0017] In the reaction apparatus according to the present invention, it is preferable that the first cavity resonator is a cavity resonator in which a magnetic field intensity distribution is formed at the center of the cavity resonator, the second cavity resonator is a cavity resonator in which a magnetic field intensity distribution is formed at the center of the cavity resonator, the first cavity resonator is a cavity resonator for irradiating microwaves to the plasma source and generating plasma from the plasma source, and the second cavity resonator is a cavity resonator for irradiating microwaves to the oxide sample and heating the oxide sample. Plasma can be stably generated from the plasma source using microwaves in a magnetic field mode, and the oxide sample can be stably heated using microwaves in the magnetic field mode.

[0018] In the reaction apparatus according to the present invention, the first cavity resonator may be a cavity resonator in which a magnetic field intensity distribution is formed at the center of the cavity resonator and also serve as the heating mechanism, and the first cavity resonator may irradiate microwaves to the oxide sample to heat the oxide sample. This is an embodiment in which there is only one cavity resonator, and the reaction apparatus can be simplified.

[0019] In the reactor of the present invention, the first cavity resonator is preferably a single-mode type. Here, the single-mode type refers to a type in which there is only one antinode of the standing wave of the electric field mode and the magnetic field mode generated in the reaction area. By using a single-mode microwave irradiation, the plasma source can be easily generated into plasma and further used as a plasma torch.

[0020] In the reaction apparatus according to the present invention, the second cavity resonator is preferably a single-mode type. By using a single-mode microwave irradiation, the oxide sample can be easily heated and can be heated with reduced energy consumption.

[0021] In the reaction apparatus according to the present invention, it is preferable that the plasma source and the oxide sample placed in the reaction chamber are separate entities, the location of the oxide sample is outside the cavity of the first cavity resonator, and the heating mechanism heats the oxide sample placed in the location.

[0022] In the reaction apparatus according to the present invention, the heating mechanism may heat the oxide sample by heating with a heater, induction heating, or resistance heating. These heating mechanisms also make it easy to control the heating of the oxide sample independently of the generation of plasma by the plasma source in the first cavity resonator.

[0023] The reaction device according to the present invention may be configured such that the oxide sample contains scandium oxide.

[0024] In the reactor according to the present invention, it is preferable that the plasma source has a conductivity of 3000 S / m or more. The first cavity resonator allows stable generation of plasma.

[0025] In the reaction apparatus according to the present invention, the metal serving as the plasma source is calcium, magnesium, or aluminum, the alloy serving as the plasma source is a calcium alloy, magnesium alloy, or aluminum alloy, the intermetallic compound serving as the plasma source is a calcium-containing intermetallic compound, a magnesium-containing intermetallic compound, or an aluminum-containing intermetallic compound, and the ceramic in the mixture is preferably at least one selected from the group consisting of zirconia, quartz, alumina, boron nitride, silicon carbide, silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride. These plasma sources are easy to generate plasma and have high reducing power, allowing oxide samples to be efficiently reduced.

[0026] The method for producing a reduced product of an oxide sample according to the present invention comprises a first step of separately arranging in a reaction chamber at least one plasma source selected from the group consisting of metals, alloys, intermetallic compounds, mixtures of metals and ceramics, mixtures of alloys and ceramics, mixtures of intermetallic compounds and ceramics, and carbon, and an oxide sample to be reduced; a second step of evacuating the internal gas of the reaction chamber; and a third step of irradiating all or part of the plasma source with microwaves to generate plasma from the plasma source and heat the oxide sample, thereby obtaining a reduced product of the oxide sample, wherein in the third step, microwaves in a magnetic field mode are irradiated to at least one of the plasma source and the oxide sample.

[0027] In the method for producing a reduced product of an oxide sample according to the present invention, the microwaves irradiated to all or part of the plasma source in the third step are preferably microwaves in a magnetic field mode. At least the microwaves in the magnetic field mode are used to generate plasma of a metal that serves as a reducing agent, and the oxide sample that is firmly bonded to oxygen, which is the target of reduction, is heated, and the oxide sample is reduced by deoxidizing it with the reducing agent plasma, and the metal separated from the oxygen is bonded to another metal to form an alloy, etc.

[0028] In the method for producing a reduced oxide sample according to the present invention, it is preferable that in the third step, a part of the plasma source is irradiated with microwaves in an electric field mode to generate plasma from the plasma source, and the remainder of the plasma source and the oxide sample are irradiated with microwaves in a magnetic field mode to heat the plasma source and the oxide sample. The electric field mode triggers the generation of plasma, but it can be difficult to maintain the plasma because metal vapor generated from the plasma source is deposited in the system, causing the microwaves derived from the electric field to be reflected by the surface of the deposited metal. However, by using the magnetic field mode in combination, it becomes easier to maintain the plasma even when metal vapor is generated from the plasma source and metal is deposited in the system.

[0029] In the method for producing a reduced product of an oxide sample according to the present invention, it is preferable that in the third step, the plasma source is irradiated with microwaves in a magnetic field mode, plasma is generated from the plasma source, and the oxide sample is irradiated with microwaves in a magnetic field mode to heat the oxide sample. Plasma can be stably generated from the plasma source using microwaves in a magnetic field mode, and the oxide sample can be stably heated using microwaves in a magnetic field mode.

[0030] In the method for producing a reduced product of an oxide sample according to the present invention, it is preferable that in the first step, the oxide sample is placed outside the cavity of a first cavity resonator, and in the third step, the first cavity resonator irradiates the plasma source with microwaves in a magnetic field mode, and the oxide sample is heated by a heating mechanism different from that of the first cavity resonator.

[0031] In the method for producing a reduced oxide sample according to the present invention, the oxide sample may be heated by a heater, induction heating, or resistance heating in the third step. These heating mechanisms also make it possible to control the heating of the oxide sample independently of the generation of plasma by the plasma source using the first cavity resonator.

[0032] The method for producing a reduced product of an oxide sample according to the present invention encompasses a mode in which the oxide sample contains scandium oxide. [Effects of the Invention]

[0033] According to the present disclosure, it is possible to provide a reactor that can increase the amount of purified reduced product, that can easily control the sample temperature, and that is easy to mass-produce, and it is also possible to provide a method that can efficiently obtain reduced products of oxide samples using this reactor. [Brief explanation of the drawings]

[0034] [Figure 1] FIG. 1 is a schematic diagram of a first example of a reaction apparatus according to the present embodiment. [Figure 2] AA cross-sectional view. [Figure 3] FIG. 2 is a schematic diagram of a second example of a reaction apparatus according to the present embodiment. [Figure 4] FIG. 10 is a schematic diagram of a third example of a reaction apparatus according to the present embodiment. [Figure 5] FIG. 10 is a schematic diagram of a fourth example of a reaction apparatus according to the present embodiment. [Figure 6]1 is an XRD diffraction chart of the powder pellets obtained in Example 1. [Figure 7] 1 is an XRD diffraction chart of the powder pellets obtained in Example 2. [Figure 8] 1 is an XRD diffraction chart of the powder pellets obtained in Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention will now be described in detail with reference to the following embodiments, but the present invention is not limited to these descriptions. Various modifications may be made to the embodiments as long as the effects of the present invention are achieved.

[0036] The reactor of this embodiment includes at least one plasma source selected from the group consisting of a metal, an alloy, an intermetallic compound, a mixture of a metal and a ceramic, a mixture of an alloy and a ceramic, a mixture of an intermetallic compound and a ceramic, and carbon; a reaction chamber for accommodating an oxide sample to be reduced, which is separate from the plasma source; an exhaust pump for evacuating the internal gas of the reaction chamber; one or more cavity resonators; and a heating mechanism for heating the oxide sample. At least one of the cavity resonators has a configuration that forms a magnetic field intensity distribution at the center of the cavity resonator. The one or more cavity resonators includes a first cavity resonator for irradiating all or part of the plasma source with microwaves to generate plasma from the plasma source. The reactor of this embodiment may be, for example, four forms, first to fourth examples. Each of these will be described in order below.

[0037] (First example of reactor) 1 shows a schematic diagram of a reaction apparatus 100 according to this embodiment. The reaction chamber 15 is, for example, the internal chamber of a first quartz tube 9, one end of which is covered with a lid 10 and the other end of which is connected to an exhaust pump 12. An open valve (not shown) is installed on the lid 10, and the reaction chamber 15, which has been made into a reduced-pressure space by operation of the exhaust pump 12, i.e., the internal space of the first quartz tube 9, is brought to atmospheric pressure by opening the open valve. The open valve may be installed in the exhaust line connecting the first quartz tube 9 and the exhaust pump 12.

[0038] A second quartz tube 11 is further disposed inside the first quartz tube 9. If deposition of a vapor deposit occurs on the inner wall of the second quartz tube 11, the second quartz tube 11 is replaced. If the second quartz tube 11 is not disposed, deposition of a vapor deposit occurs on the inner wall of the first quartz tube 9, so the second quartz tube 11 can reduce the frequency of replacement of the first quartz tube 9.

[0039] As shown in FIGS. 1 and 2 , the first cavity resonator 8 is disposed such that a first quartz tube 9 penetrates the cavity. A first tuner 7 is connected to the first cavity resonator 8, and a first power meter 6 is connected to the first microwave power supply 5. The first cavity resonator 8 is a cylindrical single-mode applicator in which an electric field intensity distribution at, for example, 2.45 GHz is formed at the center of the cylinder. By controlling the output and frequency of the first microwave power supply 5, high-frequency power is applied to the first cavity resonator 8 via the first power meter 6 and the first tuner 7. The first cavity resonator 8 can apply a standing wave of a single-mode electric field to a portion of a plasma source 13 disposed in the internal space of the first quartz tube 9, which serves as a reaction chamber 15. This causes plasma to be generated from the plasma source 13. The frequency of the first cavity resonator 8 is preferably, for example, 915 MHz, 2.45 GHz, or 5.8 GHz, and the high frequency output is preferably 50 to 2000 W.

[0040] The second cavity resonator 4 is arranged so that the first quartz tube 9 penetrates the cavity. Its appearance is similar to that of the first cavity resonator 8 shown in FIG. 2 . A second tuner 3 is connected to the second tuner 3, which is connected to a second power meter 2, which is connected to a second microwave power source 1. The second cavity resonator 4 is, for example, a cylindrical single-mode applicator in which a magnetic field intensity distribution at 2.45 GHz is formed at the center of the cylinder. By controlling the output and frequency of the second microwave power source 1, high-frequency power is applied to the second cavity resonator 4 via the second power meter 2 and the second tuner 3. The second cavity resonator 4 can apply a standing wave of a single-mode magnetic field to the oxide sample 14 and the remaining portion of the plasma source 13, which are located in the internal space of the first quartz tube 9 and serve as the reaction chamber 15. This sustains the plasma generated by the plasma source 13. Furthermore, the second cavity resonator 4 irradiates the remaining portion of the plasma source 13 and the oxide sample 14 with microwaves, thereby heating the plasma source 13 and the oxide sample 14. The frequency of the second cavity resonator 4 is preferably, for example, 915 MHz, 2.45 GHz, or 5.8 GHz, and the radio-frequency output is preferably 50 to 2000 W. The electric field mode triggers plasma generation, but metal vapor generated from the plasma source is deposited in the system, causing the microwaves derived from the electric field to be reflected by the surface of the deposited metal, making it difficult to maintain the plasma. However, by using the magnetic field mode in combination, it becomes easier to maintain the plasma even when metal vapor is generated from the plasma source and metal is deposited in the system.

[0041] The second cavity resonator 4 also serves as a heating mechanism for irradiating the oxide sample 14 with microwaves to heat it. In other words, the oxide sample 14 is heated by a standing wave of a single-mode magnetic field. This allows the metal vapor generation section and the heating section to be separated. The oxide sample 14 can be irradiated with microwaves independently of the plasma source 13, enabling more precise temperature control. Furthermore, while conventional multi-mode applicators restrict the types of equipment and devices that can be used because microwaves are distributed throughout the applicator, the present invention eliminates restrictions on the refining equipment, allowing for larger equipment and continuous furnace configurations. Separating the power sources allows for precise control of temperature conditions, dramatically increasing the yield of refined alloys, such as Al-Sc.

[0042] A portion of the plasma source 13 is heated by a single-mode standing wave of an electric field to generate plasma. The remaining portion is heated by a single-mode standing wave of a magnetic field. That is, depending on the location, the plasma source 13 is heated by either a single-mode standing wave of an electric field or a single-mode standing wave of a magnetic field. In this way, because the plasma source 13 is heated by two types of standing waves, even if metal deposition occurs on the inner wall of the second quartz tube 11 and the electric field standing wave is reflected by the deposited metal surface, microwaves are supplied to the plasma by the magnetic field standing wave, and the deposit is reheated to become metal vapor and plasma, so plasma can be generated stably.

[0043] The plasma source 13 is at least one selected from the group consisting of a metal, an alloy, an intermetallic compound, a mixture of a metal and a ceramic, a mixture of an alloy and a ceramic, a mixture of an intermetallic compound and a ceramic, and carbon. The plasma source 13 preferably has a conductivity of 3000 S / m or more at room temperature and atmospheric pressure. Plasma is easily generated. The metal used for the plasma source 13 is preferably calcium, magnesium, or aluminum. The alloy used for the plasma source 13 is preferably a calcium alloy, a magnesium alloy, or an aluminum alloy. An example of the calcium alloy is a Ca-Al alloy. An example of the magnesium alloy is an Mg-Al alloy. An example of the aluminum alloy is an Al-Sc alloy. The intermetallic compound used for the plasma source 13 is preferably a calcium-containing intermetallic compound, a magnesium-containing intermetallic compound, or an aluminum-containing intermetallic compound. An example of the calcium-containing intermetallic compound is CaMg2. An example of the magnesium-containing intermetallic compound is Mg2Ni. An example of the aluminum-containing intermetallic compound is Al3Sc. The ceramic in the mixture is preferably at least one selected from the group consisting of zirconia, quartz, alumina, boron nitride, silicon carbide, silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride. Mixing ceramic with at least one of a metal, an alloy, and an intermetallic compound makes the plasma source 13 more easily heated, promoting the vaporization of the metal. Graphite is preferred as the carbon. These plasma sources generate plasma easily and have high reducing power, allowing oxide samples to be efficiently reduced. For ease of handling, the plasma source 13 is preferably placed in an alumina board and placed inside the second quartz tube 11. The plasma source 13 is preferably in the form of a powder, granules, plate, or foil.

[0044] The oxide sample 14 is disposed separately from the plasma source 13. The oxide sample 14 is a metal oxide such as scandium oxide, titanium oxide, or vanadium oxide. The oxide sample 14 is reduced by the plasma to become a metal. The oxide sample 14 may also be mixed with a metal other than the metal that constitutes the metal oxide. The other metal may be, for example, aluminum. In this case, the metal oxide is reduced to become a metal, and this metal is then alloyed with the other metal. The oxide sample 14 and the other metal are preferably in the form of powder. It is preferable to mix the powder of the oxide sample 14 with the powder of the other metal to form a mixed powder, and then pelletize the mixed powder to form the oxide sample 14.

[0045] (Second example of reactor) Next, a second example of the reaction apparatus will be described with reference to Fig. 3, focusing on differences from the first example of the reaction apparatus. Fig. 3 shows a schematic diagram of a reaction apparatus 200 according to this embodiment. The reaction chamber 15 is the same as that of the reaction apparatus 100.

[0046] The first cavity resonator 24 is disposed so that the first quartz tube 9 penetrates the cavity. Its appearance is similar to that of the first cavity resonator 8 shown in FIG. 2 . A first tuner 23 is connected to the first cavity resonator 24, and a first power meter 22 is connected to the first microwave power supply 21. The first cavity resonator 24 is a cylindrical single-mode applicator in which a magnetic field intensity distribution at, for example, 2.45 GHz is formed at the center of the cylinder. By controlling the output and frequency of the first microwave power supply 21, high-frequency power is applied to the first cavity resonator 24 via the first power meter 22 and the first tuner 23. The first cavity resonator 24 can apply a standing wave of a single-mode magnetic field to the entire plasma source 13 disposed in the internal space of the first quartz tube 9, which serves as the reaction chamber 15. This generates plasma from the plasma source 13. The frequency of the first cavity resonator 24 is preferably, for example, 915 MHz, 2.45 GHz, or 5.8 GHz, and the high-frequency output is preferably 50 to 2000 W.

[0047] The second cavity resonator 34 is similar to the second cavity resonator 4 of the reaction apparatus 100. That is, by controlling the output and frequency of the second microwave power supply 31, high-frequency power is applied to the second cavity resonator 34 via the second power meter 32 and the second tuner 33, and the second cavity resonator 34 can apply a standing wave of a single-mode magnetic field to the oxide sample 14 placed in the internal space of the first quartz tube 9, which serves as the reaction chamber 15.

[0048] Like the second cavity resonator 4 of the reaction apparatus 100, the second cavity resonator also serves as a heating mechanism for heating the oxide sample by irradiating the oxide sample with microwaves.

[0049] The plasma source 13 is heated entirely by a standing wave of a single-mode magnetic field to generate plasma, and the oxide sample 14 can be stably heated using microwaves in the magnetic field mode.

[0050] The plasma source 13 and oxide sample 14 are similar to those in the reactor 100 .

[0051] (Third example of reactor) Next, a third example of the reaction apparatus will be described with reference to Fig. 4, focusing on differences from the first example of the reaction apparatus. Fig. 4 shows a schematic diagram of a reaction apparatus 300 according to this embodiment. The reaction chamber 15 is the same as that of the reaction apparatus 100.

[0052] The first cavity resonator 44 is disposed such that the first quartz tube 9 penetrates the cavity. Its appearance is similar to that of the first cavity resonator 8 shown in FIG. 2 . A first tuner 43 is connected to the first cavity resonator 44, and a first power meter 42 is connected to the first power meter 42, which is connected to a first microwave power supply 41. The first cavity resonator 44 is a cylindrical single-mode applicator in which a magnetic field intensity distribution is formed at the center of the cylinder at, for example, 2.45 GHz. By controlling the output and frequency of the first microwave power supply 41, high-frequency power is applied to the first cavity resonator 44 via the first power meter 42 and the first tuner 43. The first cavity resonator 44 can apply a standing wave of a single-mode magnetic field to the entire plasma source 13 disposed in the internal space of the first quartz tube 9, which serves as the reaction chamber 15. This generates plasma from the plasma source 13. The frequency of the first cavity resonator 44 is preferably, for example, 915 MHz, 2.45 GHz, or 5.8 GHz, and the high-frequency output is preferably 50 to 2000 W.

[0053] No second cavity resonator is installed in the reaction apparatus 300. The plasma source 13 and the oxide sample 14 are separately placed in the cavity of the first cavity resonator 44, which is the internal space of the second quartz tube 11 disposed inside the first quartz tube 9. The first cavity resonator 44 allows a standing wave of a single-mode magnetic field to act on the entire plasma source 13 and the entire oxide sample 14.

[0054] Like the second cavity resonator 4 of the reaction apparatus 100, the first cavity resonator 44 also serves as a heating mechanism for heating the oxide sample 14 by irradiating the oxide sample 14 with microwaves.

[0055] The plasma source 13 generates plasma by being heated as a whole by the standing wave of the single-mode magnetic field generated by the first cavity resonator 44. Even if metal deposits occur on the inner wall of the second quartz tube 11 due to the generation of metal vapor, the use of microwaves in the magnetic field mode allows stable plasma generation from the plasma source, and also allows stable heating of the oxide sample 14.

[0056] The plasma source 13 and oxide sample 14 are similar to reactor 100 except for their placement.

[0057] (Fourth example of reactor) Next, a fourth example of the reaction apparatus will be described with reference to Fig. 5, focusing on differences from the third example of the reaction apparatus. Fig. 5 shows a schematic diagram of a reaction apparatus 400 according to this embodiment. The reaction chamber 15 is the same as that of the reaction apparatus 300, i.e., the reaction apparatus 100.

[0058] The first cavity resonator 54 is similar to the first cavity resonator 44 of the reaction apparatus 300. A first tuner 53 is connected to the first cavity resonator 54, and a first power meter 52 is connected to the first power meter 52, which is connected to a first microwave power supply 51. The first cavity resonator 54 is a cylindrical single-mode applicator in which a magnetic field intensity distribution is formed at the center of the cylinder at, for example, 2.45 GHz. By controlling the output and frequency of the first microwave power supply 51, high-frequency power is applied to the first cavity resonator 54 via the first power meter 52 and the first tuner 53. The first cavity resonator 54 can apply a standing wave of a single-mode magnetic field to the entire plasma source 13 disposed in the internal space of the first quartz tube 9, which serves as the reaction chamber 15. This generates plasma from the plasma source 13. The frequency of the first cavity resonator 54 is preferably, for example, 915 MHz, 2.45 GHz, or 5.8 GHz, and the high-frequency output is preferably 50 to 2000 W.

[0059] No second cavity resonator is installed in the reactor 400. The plasma source 13 is disposed in the cavity of the first cavity resonator 54, which is the internal space of the second quartz tube 11 disposed inside the first quartz tube 9. The first cavity resonator 54 allows a single-mode magnetic standing wave to act on the entire plasma source 13.

[0060] Unlike the reactor 300, the first cavity resonator 54 is the internal space of the second quartz tube 11 disposed inside the first quartz tube 9, and the oxide sample 14 is not disposed in the cavity of the first cavity resonator 54. Instead, the oxide sample 14 is disposed outside the cavity of the first cavity resonator 54, in the internal space of the second quartz tube 11, as a separate entity from the plasma source 13. A heating mechanism 30 for heating the oxide sample 14 is provided. The heating mechanism 30 heats the oxide sample 14 by heating with a heater, induction heating, or resistance heating.

[0061] The plasma source 13 generates plasma by being heated as a whole by a standing wave of a single-mode magnetic field generated by the first cavity resonator 54. Even if metal deposits form on the inner wall of the second quartz tube 11 due to metal vapor generation, stable plasma generation from the plasma source is possible because microwaves in the magnetic field mode are used. The oxide sample 14 is then heated by a heating mechanism 30, such as a lamp heater.

[0062] The plasma source 13 and oxide sample 14 are similar to reactor 300, ie, reactor 100, except for the arrangement.

[0063] The thermometer installation position and temperature measurement method are, for example, to drill holes of approximately 5 mm diameter in the upper portions of the first cavity resonators 8, 24, 44, and 54 and the second cavity resonators 4 and 34, and install a thermometer 16 such as a two-color radiation thermometer to measure the temperatures of the plasma source 13 and the oxide sample 14. When measuring the temperature of the oxide sample 14 heated by a lamp heater, the thermometer 16 such as a two-color radiation thermometer is pointed toward the oxide sample 14. Because the entire reaction system is not covered by a large SUS box (cavity), sufficient temperature measurement can be performed even using a non-contact radiation thermometer, allowing for precise temperature control and facilitating sample temperature control. If more precise temperature control is required, the temperatures of the plasma source 13 and the oxide sample 14 can also be measured by installing contact-type thermocouples that do not react with the plasma source 13 or the oxide sample 14 near the plasma source 13 and the oxide sample 14. Since the entire reaction system is not covered by a large SUS box (cavity), temperature can be measured using a contact thermocouple, allowing for more precise temperature control and making it easier to control the sample temperature.

[0064] (Method for producing reduced oxide samples) Next, a method for producing a reduced product of an oxide sample according to this embodiment will be described. The method for producing a reduced product of an oxide sample according to this embodiment includes the following steps: a first step of disposing, in a reaction chamber, at least one plasma source selected from the group consisting of metals, alloys, intermetallic compounds, mixtures of metals and ceramics, mixtures of alloys and ceramics, mixtures of intermetallic compounds and ceramics, and carbon, and an oxide sample to be reduced; a second step of evacuating the gas inside the reaction chamber; and a third step of irradiating all or part of the plasma source with microwaves to generate plasma from the plasma source and heat the oxide sample, thereby obtaining a reduced product of the oxide sample.

[0065] (1st step) A plasma source 13 placed on an alumina board and an oxide sample 14 solidified into a pellet are separately placed in the internal space of a second quartz tube 11 in the reaction chamber. In this case, in the reactor 100, a portion of the plasma source 13 is placed in the cavity of the first cavity resonator 8, and the remainder of the plasma source 13 and the entire oxide sample 14 are placed in the cavity of the second cavity resonator 4. In the reactor 200, the entire plasma source 13 is placed in the cavity of the first cavity resonator 24, and the entire oxide sample 14 is placed in the cavity of the second cavity resonator 34. In the reactor 300, the entire plasma source 13 and the entire oxide sample 14 are placed in the cavity of the first cavity resonator 44. In the reactor 400, the entire plasma source 13 is placed in the cavity of the first cavity resonator 54, and the entire oxide sample 14 is placed outside the cavity of the first cavity resonator 54.

[0066] (2nd process) The exhaust pump 12 is operated to exhaust the gas inside the reaction chamber 15. The pressure inside the reaction chamber 15 is set to, for example, 5 Pa or less, preferably 10 -1 Pa or less.

[0067] (3rd step) By operating the first cavity resonator, the second cavity resonator, the heating mechanism, and other devices, microwaves are irradiated onto all or part of the plasma source 13, generating plasma from the plasma source 13 and heating the oxide sample 14 to obtain a reduced oxide sample. More specifically, in the reactor 100, the first cavity resonator 8 and the second cavity resonator 4 are operated, microwaves, preferably a single-mode electric field standing wave, are applied to part of the plasma source 13, generating plasma from the plasma source 13, and microwaves, preferably a single-mode magnetic field standing wave, are applied to the remainder of the plasma source 13 and the oxide sample 14 to heat them, thereby obtaining a reduced oxide sample. The electric field mode triggers plasma generation, but plasma maintenance can be difficult because metal vapor generated from the plasma source is deposited in the system, causing the microwaves generated by the electric field to be reflected by the surface of the deposited metal. However, by using the magnetic field mode in combination, plasma maintenance becomes easier even when metal vapor is generated from the plasma source and metal is deposited in the system.

[0068] In the reaction apparatus 200, the first cavity resonator 24 and the second cavity resonator 34 are operated, microwaves, preferably a standing wave of a single-mode magnetic field, are applied to the entire plasma source 13, plasma is generated from the plasma source 13, and the oxide sample 14 is heated by applying microwaves, preferably a standing wave of a single-mode magnetic field, to the entire oxide sample 14, thereby obtaining a reduced product of the oxide sample. Plasma can be stably generated from the plasma source using the magnetic field mode microwaves, and the oxide sample 14 can be stably heated using the magnetic field mode microwaves.

[0069] In the reaction apparatus 300, the first cavity resonator 44 is operated to apply microwaves, preferably a single-mode magnetic standing wave, to the entire plasma source 13, generating plasma in the plasma source 13, and the oxide sample 14 is heated by applying microwaves, preferably a single-mode magnetic standing wave, to the entire oxide sample 14, thereby obtaining a reduced product of the oxide sample. Plasma can be stably generated from the plasma source 13 using the magnetic field mode microwaves, and the oxide sample 14 can be stably heated using the magnetic field mode microwaves.

[0070] In the reaction apparatus 400, the first cavity resonator 54 is operated to apply microwaves, preferably single-mode magnetic standing waves, to the entire plasma source 13, generating plasma from the plasma source 13. The entire oxide sample 14 is then heated by a heating mechanism 30, such as a lamp heater, to obtain a reduced oxide sample. In the third step, the microwaves irradiated to all or part of the plasma source 13 are preferably magnetic field microwaves. At least the magnetic field microwaves are used to generate plasma of a metal serving as a reducing agent, and the oxide sample 14, which is tightly bound to oxygen, is heated. The reducing agent plasma reduces the oxide sample 14, deoxidizing it, and the metal separated from the oxygen can be bound to another metal to form an alloy or the like. These heating mechanisms 30 also make it easy to control the heating of the oxide sample 14 independently of the plasma generation by the first cavity resonator 54 in the plasma source 13. [Example]

[0071] Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[0072] Example 1 The reactor 100 shown in FIG. 1 was used. A cylindrical single-mode applicator (first cavity resonator 8) in which an electric field intensity distribution at 2.45 GHz is formed at the center of the cylinder and a cylindrical single-mode applicator (second cavity resonator 4) in which a magnetic field intensity distribution at 2.45 GHz is formed at the center of the cylinder were arranged side by side. A first quartz tube 9 was placed at the center of the first cavity resonator 8 and the second cavity resonator 4. Next, a mixture (2.0 g) obtained by mixing magnesium metal powder (1.0 g) and zirconia balls (1.0 g) to serve as the plasma source 13 was placed in an alumina boat. Powder pellets (0.9 g) of Al powder (0.6 g) and scandium oxide powder (0.3 g) (Al-Sc2O3 pellets) were placed in the alumina boat as oxide sample 14, except for the part where the mixture of magnesium metal powder and zirconia balls was placed in the alumina boat. Next, the alumina boats were placed in the second quartz tubes 11, and the second quartz tubes 11 were placed in the first quartz tube 9, so that the mixture of magnesium metal powder and zirconia balls was contained within the first and second cavity resonators 8 and 4, and the powder pellets of Al powder and scandium oxide powder were contained within the second cavity resonator 4. Next, the first quartz tube 9 was evacuated using an exhaust pump 12 (a rotary pump), and while maintaining a vacuum of approximately 0.5 to 1 Pa, high-frequency power of approximately 90 W was applied to each of the first and second cavity resonators 8 and 4. After approximately one minute, the entire mixture of magnesium metal powder and zirconia balls reached a temperature of approximately 300°C or higher, and then stable magnesium plasma generation was observed for approximately 10 to 15 minutes. While plasma generation was being observed, microwaves were irradiated onto the powder pellet of Al powder and scandium oxide powder in the second cavity resonator 4, heating it to above 500°C. After cooling and removing the powder pellet (approximately 1 g), XRD analysis of the Al powder and scandium oxide powder pellet confirmed the formation of Al3Sc, as shown in Figure 6, confirming the reduction reaction. A high electric field was generated between the zirconia balls and magnesium powder in the first cavity resonator 8, causing the magnesium to evaporate and easily turn into plasma. Because energy is supplied by a magnetic field in the second cavity resonator 4, the magnetic field penetrates even if a thin magnesium film adheres to the quartz tube, allowing microwave energy to be supplied to the powder pellet.

[0073] Example 2 A reactor 200 shown in Figure 3 was used. Two cylindrical single-mode applicators, a first cavity resonator 24 and a second cavity resonator 34, were used, each of which had a magnetic field strength distribution at the center of the cylinder at 2.45 GHz. A first quartz tube 9 was placed at the center of the first cavity resonator 24 and the other, the second cavity resonator 34. Next, a mixture (2.0 g) obtained by mixing magnesium metal powder (1.0 g) and zirconia balls (1.0 g) to serve as the plasma source 13 was placed in an alumina boat. Powder pellets (1.5 g) of Al powder (1.0 g) and scandium oxide powder (0.5 g) (Al-Sc2O3 pellets) were placed in the alumina boat as oxide samples 14, except for the location where the mixture of magnesium metal powder and zirconia balls was placed in the alumina boat. Next, the alumina boats were placed in the second quartz tube 11, and the second quartz tube 11 was placed in the first quartz tube 9, so that the entire mixture of magnesium metal powder and zirconia balls was contained within the first cavity resonator 24, and the entire powder pellets of Al powder and scandium oxide powder were contained within the second cavity resonator 34. Next, the first quartz tube 9 was evacuated using an exhaust pump 12 (a rotary pump). While maintaining a vacuum of approximately 0.5 to 1 Pa, high-frequency power of approximately 90 W was applied to the first cavity resonator 24. After approximately 1 to 2 minutes, the entire mixture of magnesium metal powder and zirconia balls reached a temperature of approximately 300°C or higher, and stable magnesium plasma generation was observed for approximately 10 to 15 minutes thereafter. While plasma generation was being observed, the powder pellets of Al powder and scandium oxide powder in the second cavity resonator 34 were irradiated with microwaves and heated to 500°C or higher. After cooling, the apparatus was removed and a powder pellet (approximately 1 g) of Al powder and scandium oxide powder was subjected to XRD analysis. As shown in Figure 7, the formation of Al3Sc was confirmed, confirming the reduction reaction. Within the first cavity resonator 24, an induced current is generated between the magnesium powder particles due to the magnetic field, causing the magnesium to rise in temperature and evaporate. At this time, thermions are released simultaneously with the magnesium ions, and thermions easily convert the magnesium into plasma.Furthermore, since energy is supplied by the magnetic field in the first cavity resonator 24, even if a thin magnesium film adheres to the quartz tube, the magnetic field penetrates the metal, so microwave energy is supplied to the powder pellets and the reduction reaction continues.

[0074] Example 3 The reactor 300 shown in Figure 4 was used. A first quartz tube 9 was placed in a cylindrical single-mode applicator (first cavity resonator 44) in which a magnetic field intensity distribution at 2.45 GHz was formed at the center of the cylinder. Next, a mixture (2.0 g) obtained by mixing magnesium metal powder (1.0 g) and zirconia balls (1.0 g) to serve as the plasma source 13 was placed in an alumina boat. Powder pellets (1.5 g) of Al powder (1.0 g) and scandium oxide powder (0.5 g) (Al-Sc2O3 pellets) were placed in the alumina boat as oxide samples 14, in a location other than the location where the mixture of magnesium metal powder and zirconia balls was placed in the alumina boat. Next, the alumina boat was placed in the second quartz tube 11, and the second quartz tube 11 was placed in the first quartz tube 9, so that the mixture of magnesium metal powder and zirconia balls and the powder pellets of Al powder and scandium oxide powder were contained within the first cavity resonator 44. Next, the first quartz tube 9 was evacuated using an exhaust pump 12 (a rotary pump). While maintaining a vacuum of approximately 0.5 to 1 Pa, high-frequency power of approximately 90 W was applied to the first cavity resonator 44. After approximately 1 to 2 minutes, the entire mixture of magnesium metal powder and zirconia balls reached a temperature of approximately 300°C or higher, and stable magnesium plasma was observed for approximately 10 to 15 minutes. It was confirmed that the first cavity resonator 44 alone was sufficient to generate plasma from the plasma source.

[0075] Example 4 The reactor 400 shown in Figure 5 was used. A first quartz tube 9 was placed in a cylindrical single-mode applicator (first cavity resonator 54) in which a magnetic field intensity distribution at 2.45 GHz was formed at the center of the cylinder. Next, a mixture (2.0 g) obtained by mixing magnesium metal powder (1.0 g) and zirconia balls (1.0 g) to serve as the plasma source 13 was placed in an alumina boat. Next, powder pellets (1.5 g) of Al powder (1.0 g) and scandium oxide powder (0.5 g) (Al-Sc2O3 pellets) were placed in the alumina boat at a location other than the location where the mixture of magnesium metal powder and zirconia balls was placed in the alumina boat, forming the oxide sample 14. Next, the alumina boat was placed inside the second quartz tube 11, and the second quartz tube 11 was placed inside the first quartz tube 9, so that the mixture of magnesium metal powder and zirconia balls was contained within the first cavity resonator 54, and the powder pellets of Al powder and scandium oxide powder were contained within the installation location of the lamp heater for sample heating, which is the heating mechanism 30. Next, the first quartz tube 9 was evacuated using the exhaust pump 12 (rotary pump). While the vacuum was maintained at approximately 0.5 to 1 Pa, high-frequency power of approximately 90 W was applied to the first cavity resonator 54. After approximately 1 to 2 minutes, the entire mixture of magnesium metal powder and zirconia balls reached a temperature of approximately 300°C or higher, and then stable magnesium plasma generation was observed for approximately 10 to 15 minutes. While plasma generation was observed, the powder pellets of Al powder and scandium oxide powder were heated to 500°C or higher using the lamp heater for sample heating, which is the heating mechanism 30. After that, the powder pellets (approximately 1 g) were cooled and removed from the device, and XRD analysis was performed. As a result, the formation of Al3Sc was confirmed as shown in Figure 8, confirming the reduction reaction and that the lamp heater alone was a sufficient heat source.

[0076] (Comparative Example 1) The same experiment as in Example 3 was performed using the apparatus shown in Figure 4, except that the first cavity resonator 44 was replaced with a cylindrical single-mode applicator in which the electric field intensity distribution at 2.45 GHz was formed at the center of the cylinder. The first quartz tube 9 was evacuated using an exhaust pump 12 (a rotary pump). While maintaining a vacuum of approximately 0.5 to 1 Pa, high-frequency power of approximately 90 W was applied to the first cavity resonator. After approximately 1 to 2 minutes, the entire mixture of magnesium metal powder and zirconia balls reached approximately 300°C or higher. Magnesium plasma was then observed, but the plasma disappeared after only about 14 seconds. This was because magnesium metal adhered to the second quartz tube 11, and the microwaves derived from the electric field were reflected by the metal surface adhered to the inside of the second quartz tube 11, preventing energy from being supplied to the plasma.

[0077] According to this embodiment, a plasma is generated from the reducing agent plasma source 13 using at least microwaves in magnetic field mode. The oxide sample 14, which is tightly bound to oxygen and is the target of reduction, is heated. The oxide sample 14 is reduced by deoxidizing it with the reducing agent plasma, and the metal separated from the oxygen is bonded to another metal to form an alloy. Furthermore, while the electric field mode triggers plasma generation, the magnetic field mode alone can generate and sustain plasma. While the conventional multi-mode applicator was unable to separate the metal vapor generation and heating points, this now allows them to be separated. This eliminates limitations on the refining equipment, allowing for larger scale and continuous furnace configurations, dramatically increasing the amount of alloys, such as Al-Sc, refined. [Explanation of symbols]

[0078] 1,31 Second microwave power source 2,32 Second Power Meter 3,33 Second Tuner 4,34 Second cavity resonator 5, 21, 41, 51 First microwave power source 6,22,42,52 First power meter 7,23,43,53 First Tuner 8,24,44,54 1st cavity resonator 9. First Quartz Tube 10 Lid 11 Second quartz tube 12 Exhaust pump 13 Plasma Source 14 Oxide samples 15 Reaction chamber 16 Thermometer 100,200,300,400 reactors

Claims

1. a reaction chamber for accommodating at least one plasma source selected from the group consisting of a metal, an alloy, an intermetallic compound, a mixture of a metal and a ceramic, a mixture of an alloy and a ceramic, a mixture of an intermetallic compound and a ceramic, and carbon, and an oxide sample to be reduced, which is separate from the plasma source; an exhaust pump that exhausts the internal gas of the reaction chamber; one or more cavity resonators; a heating mechanism for heating the oxide sample, At least one of the cavity resonators has a shape that forms a magnetic field strength distribution at the center of the cavity resonator, A reactor characterized in that the one or more cavity resonators include a first cavity resonator for irradiating microwaves to all or a part of the plasma source and generating plasma from the plasma source.

2. 2. The reaction apparatus according to claim 1, wherein the heating mechanism is a second cavity resonator for irradiating the oxide sample with microwaves to heat the oxide sample.

3. the first cavity resonator is a cavity resonator in which an electric field intensity distribution is formed at the center of the cavity resonator, the second cavity resonator is a cavity resonator in which a magnetic field intensity distribution is formed at the center of the cavity resonator, the first cavity resonator is a cavity resonator for irradiating a part of the plasma source with microwaves to generate plasma from the plasma source; and 3. The reactor according to claim 2, wherein the second cavity is a cavity for irradiating the remainder of the plasma source and the oxide sample with microwaves to heat the plasma source and the oxide sample.

4. the first cavity resonator is a cavity resonator in which a magnetic field intensity distribution is formed at the center of the cavity resonator, the second cavity resonator is a cavity resonator in which a magnetic field intensity distribution is formed at the center of the cavity resonator, the first cavity resonator is a cavity resonator for irradiating microwaves to the plasma source to generate plasma from the plasma source, and 3. The reaction apparatus according to claim 2, wherein the second cavity resonator is a cavity resonator for irradiating the oxide sample with microwaves to heat the oxide sample.

5. 2. The reaction apparatus according to claim 1, wherein the first cavity resonator is a cavity resonator in which a magnetic field intensity distribution is formed at the center of the cavity resonator and also serves as the heating mechanism, and the first cavity resonator irradiates microwaves onto the oxide sample to heat the oxide sample.

6. 6. The reaction apparatus according to claim 1, wherein the first cavity resonator is of a single mode type.

7. 5. The reaction device according to claim 2, wherein the second cavity resonator is of a single mode type.

8. The plasma source and the oxide sample disposed in the reaction chamber are separate entities, the oxide sample is disposed outside the cavity of the first cavity resonator; 2. The reaction device according to claim 1, wherein the heating mechanism heats the oxide sample placed in the placement location.

9. 9. The reaction apparatus according to claim 1, wherein the heating mechanism heats the oxide sample by heating with a heater, induction heating, or resistance heating.

10. A reaction apparatus according to claim 1, wherein the oxide sample contains scandium oxide.

11. 11. The reactor according to claim 1, wherein the plasma source has a conductivity of 3000 S / m or more.

12. the metal serving as the plasma source is calcium, magnesium, or aluminum; the alloy serving as the plasma source is any one of a calcium alloy, a magnesium alloy, and an aluminum alloy; the intermetallic compound serving as the plasma source is any one of a calcium-containing intermetallic compound, a magnesium-containing intermetallic compound, and an aluminum intermetallic compound; The reaction device according to any one of claims 1 to 11, wherein the ceramic in the mixture is at least one selected from the group consisting of zirconia, quartz, alumina, boron nitride, silicon carbide, silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride.

13. a first step of disposing, in a reaction chamber, at least one plasma source selected from the group consisting of a metal, an alloy, an intermetallic compound, a mixture of a metal and a ceramic, a mixture of an alloy and a ceramic, a mixture of an intermetallic compound and a ceramic, and carbon, and an oxide sample to be reduced; a second step of exhausting the internal gas of the reaction chamber; a third step of irradiating microwaves to all or a part of the plasma source to generate plasma from the plasma source and heating the oxide sample to obtain a reduced product of the oxide sample; In the third step, at least one of the plasma source and the oxide sample is irradiated with microwaves in a magnetic field mode.

14. In the third step, 14. The method for producing a reduced product of an oxide sample according to claim 13, wherein the microwaves irradiated to the whole or part of the plasma source are microwaves in a magnetic field mode.

15. In the third step, irradiating a part of the plasma source with microwaves in an electric field mode to generate plasma from the plasma source; 14. The method for producing a reduced product of an oxide sample according to claim 13, wherein the remaining portion of the plasma source and the oxide sample are irradiated with microwaves in a magnetic field mode to heat the plasma source and the oxide sample.

16. In the third step, irradiating the plasma source with microwaves in a magnetic field mode to generate plasma from the plasma source; 15. The method for producing a reduced product of an oxide sample according to claim 13, wherein the oxide sample is heated by irradiating the oxide sample with microwaves in a magnetic field mode.

17. In the first step, the oxide sample is placed outside the cavity of a first cavity resonator; 14. The method for producing a reduced product of an oxide sample according to claim 13, wherein in the third step, the first cavity resonator irradiates the plasma source with microwaves in a magnetic field mode, and the oxide sample is heated by a heating mechanism different from the first cavity resonator.

18. In the third step, 18. The method for producing a reduced product of an oxide sample according to claim 13, 14 or 17, wherein the oxide sample is heated by heating with a heater, induction heating or resistance heating.

19. A method for producing a reduced product of an oxide sample according to any one of claims 13 to 18, characterized in that the oxide sample contains scandium oxide.

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