Gallium nitride powder and method for producing same

Abstract

The invention provides gallium nitride powder and a manufacturing method thereof. [Problem] To provide at least one of a gallium nitride powder with which it is possible to obtain a molded body having a higher molding density than conventional gallium nitride powder, a method for producing the same, and a method for producing a sintered body using the same. [Solution] The gallium nitride powder has an oxygen content of 0.5 at% or less, and has a resistivity of 1.0 * 107 [Omega] cm or less when 8 g of the powder is filled into a rectangular parallelepiped-shaped mold having a size of 10 mm * 40 mm and subjected to one-way press molding at a pressure of 100 MPa.

Description

Technical Field

[0001] The present invention relates to a gallium nitride powder, in particular to a gallium nitride powder suitable as a precursor of a sputtering target. Background Art

[0002] In the past, sintered bodies of gallium nitride (GaN) were produced by pressure firing such as hot pressing treatment that simultaneously molds and fires (sinters) gallium nitride powder. Pressure firing requires large-scale equipment, and the shape of the resulting gallium nitride sintered body is limited. Therefore, a method for producing a sintered body of gallium nitride without pressure firing is needed. However, gallium nitride has low moldability, and molding (forming into a powder compact) before firing is difficult. Therefore, research is being conducted on gallium nitride powder that can provide a molded body before firing. For example, in non-patent document 1, it is reported that a gallium nitride molded body is obtained by controlling the particle size of the powder by pulverizing with a jet mill.

[0003] Prior art literature

[0004] Non-patent literature

[0005] Non-patent document 1: Journal of Crystal Growth 208 (2000) 100-106 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] The gallium nitride powder disclosed in Non-Patent Document 1 can be molded, but the relative density of the obtained molded body is as low as 60%, and since the molded body is cracked, it is difficult to maintain a stable shape as the molded body.

[0008] An object of the present invention is to provide at least any one of a gallium nitride powder capable of obtaining a molded body having a higher molding density than conventional gallium nitride powders, a method for producing the same, and a method for producing a sintered body using the same.

[0009] Solutions for solving problems

[0010] In the present invention, in order to obtain a sintered body of gallium nitride suitable for a sputtering target without pressure sintering, a molded body of gallium nitride was prepared before sintering. As a result, focusing on the electrical properties of the powder, it was found that a molded body with a high molding density could be obtained by controlling the electrical properties within a specific range.

[0011] That is, the present invention is as described in the claims, and the gist of the present invention is as follows.

[0012] [1] A gallium nitride powder having an oxygen content of 0.5 at % or less, wherein when 8 g of the powder is filled into a 10 mm × 40 mm rectangular parallelepiped mold and subjected to uniaxial press molding at a pressure of 100 MPa, the resistivity is 1.0 × 10 7 Ω·cm or less.

[0013] [2] The powder according to [1] above, wherein the gallium nitride is gallium nitride having nitrogen defects.

[0014] [3] The powder according to [1] or [2] above, wherein the powder has a bulk density of 1.00 g / mL to 1.85 g / mL.

[0015] [4] The powder according to any one of [1] to [3] above, wherein the average particle size is 1 μm or more and 150 μm or less.

[0016] [5] The powder according to any one of [1] to [4] above, wherein the 10% area diameter relative to the 90% area diameter is 0.01 to 0.45.

[0017] [6] A method for producing a powder according to any one of [1] to [5] above, comprising a heat treatment step of heat treating the gallium nitride powder at 900° C. to 1300° C. in an inert gas circulation atmosphere.

[0018] [7] The production method according to [6] above, wherein the gallium nitride powder is a gallium nitride powder obtained by nitriding metal gallium.

[0019] [8] The manufacturing method according to [6] or [7] above, wherein the inert gas circulation atmosphere is an atmosphere in which a gas containing at least one of argon and nitrogen is circulated.

[0020] [9] The production method according to any one of [6] to [8] above, wherein the flow rate of the inert gas is 500 mL / min to 5000 mL / min.

[0021]

[10] A method for producing a sintered body of gallium nitride, comprising: a step of compacting the powder according to any one of [1] to [5] to obtain a compact; and a firing step of firing the compact.

[0022] Effects of the Invention

[0023] According to the present invention, at least any one of a gallium nitride powder capable of obtaining a molded body having a higher molding density than conventional gallium nitride powders, a method for producing the same, and a method for producing a sintered body using the same can be provided. DETAILED DESCRIPTION

[0024] The powder of the present invention is described below by showing an example of an embodiment. It should be noted that, in the present invention, "at%" and "atm%" have the same meaning and are units representing the ratio of the atomic number basis. In addition, the present invention includes any combination of the various configurations and parameters disclosed in this specification, and the range of any combination of the upper and lower limits of the values ​​disclosed in this specification is also included in the present invention.

[0025] The powder of this embodiment is a gallium nitride powder having an oxygen content of 0.5 at% or less. When 8 g of the powder is filled into a 10 mm×40 mm rectangular parallelepiped mold and subjected to unidirectional press molding at a pressure of 100 MPa, the resistivity is 1.0×10 7 Ω·cm or less.

[0026] The powder of the present embodiment may be a powder having gallium nitride (GaN) as a main component (matrix), that is, a powder essentially composed of gallium nitride, and may contain inevitable impurities.

[0027] The oxygen content of the powder of this embodiment is 0.5 at% or less, preferably 0.4 at% or less or 0.3 at% or less. If the oxygen content exceeds 0.5 at%, a gallium oxide layer is formed, so the resistivity becomes high. The oxygen content is preferably small, for example, 0.02 at% or more or 0.05 at% or more. As preferred oxygen contents, 0.02 at% or more and 0.5 at% or 0.05 at% or less can be cited.

[0028] In the present embodiment, the oxygen content is the atomic ratio [at %] of oxygen in the powder relative to the gallium nitride powder, and is a value obtained by the following formula (1) based on the value [mass %] measured by an inert gas fusion-infrared absorption method using an oxygen / nitrogen analyzer (e.g., LECO ON736, manufactured by Leco).

[0029] Oxygen content [at%] = (W O / M O ) / {(W Ga / M Ga )+(W N / M N )+(W O / M O )}(1)

[0030] (1) In the formula, M O is the atomic weight of oxygen (16.00 [g / mol]), M Ga is the atomic weight of gallium (69.72 [g / mol]), and M Nis the atomic weight of nitrogen (14.01 [g / mol]). O and W N W is a value [mass %] measured by an inert gas fusion-infrared absorption method using an oxygen / nitrogen analyzer (e.g., LECO ON736, manufactured by Leco Corporation). Ga Because W O and W N The measured value of is obtained by formula (2).

[0031] 100 = W Ga [Mass %] + W O [Mass %] + W N [Mass %] (2)

[0032] The resistivity of the powder of this embodiment when 8 g of the powder was filled into a 10 mm × 40 mm rectangular parallelepiped mold and subjected to uniaxial press molding at a pressure of 100 MPa (hereinafter referred to as “resistivity”) was 1.0 × 10 7 Ω·cm or less. By making the powder of the present embodiment have both the resistivity and the above-mentioned oxygen content, it becomes a powder with high moldability, and a molded body can be obtained without sintering. As one of the reasons why the powder of the present embodiment shows excellent moldability, the following reason can be considered. That is, by having both the oxygen content and resistivity of the powder of the present embodiment, the powder particles repel each other moderately, and it is difficult to produce local aggregation. On the other hand, when an external force is applied, the powder particles tend to become dense with each other, and as a result, it is considered that excellent moldability is shown.

[0033] Since there is a tendency that the moldability is improved as the resistivity is lower, the resistivity is preferably 1×10 5 Ω·cm or less, 1Ω·cm or less or 1×10 -1 Ω·cm or less. The lower the resistivity, the better. For example, 1×10 -4 Ω·cm or more or 1×10 -3 Ω·cm or more. As a preferred resistivity, 1×10 -4 Ω·cm or more and 1×10 7 Ω·cm or less, 1×10 -3 Ω·cm or more and 1×10 5 Ω·cm or less, or 1×10 -4 Ω·cm or more and 1×10 -1 Ω·cm or less.

[0034] In this embodiment, the resistivity of the powder is a value measured by the following method. That is, 8 g of the powder is filled into a 10×40 mm rectangular parallelepiped mold and molded by unidirectional press molding at a pressure of 100 MPa to form an evaluation molded body. The resistivity of the evaluation molded body can be measured using a general resistivity meter (e.g., Loresta GX MCP-T700, manufactured by Nittoseiko Analytech Co., Ltd.) and a TFP probe as a measurement probe.

[0035] Since it is easy to have such a resistivity, the gallium nitride in the powder of the present embodiment is preferably a powder composed of gallium nitride having nitrogen defects, so-called nitrogen-deficient gallium nitride.

[0036] The powder of the present embodiment is high in formability, and preferably has high filling properties during operations such as conveying. In order to easily demonstrate such filling properties, the bulk density of the powder of the present embodiment is more than 1.00g / mL, more than 1.30g / mL or more than 1.50g / mL. In addition, the bulk density is preferably high, and can exemplify less than 1.85g / mL, less than 1.80g / mL or less than 1.70g / mL, preferably more than 1.00g / mL and less than 1.85g / mL, more than 1.30g / mL and less than 1.85g / mL or more than 1.50g / mL and less than 1.70g / mL.

[0037] The bulk density can be measured by a method in accordance with JIS Z 2504. That is, in this embodiment, the bulk density can be measured by the following method. That is, a funnel with a hole diameter of 2.5 mm and a funnel angle of 60° is used to inject the powder into a funnel with an inner diameter of 28 mm and a volume of 25 cm. 3 The cylindrical container is filled with powder and the powder injection is stopped when the cylindrical container is filled with powder. After injection, the surface of the cylindrical container is scraped flat without applying compression and vibration. 3 ]The mass [g] of the powder after scraping and leveling can be taken as the loose density.

[0038] The average particle size of the powder of this embodiment is 1 μm or more or 2 μm or more, and can be 150 μm or less, 50 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less. Preferred average particle sizes include 1 μm or more and 150 μm or less, 2 μm or more and 50 μm or less, 2 μm or more and 20 μm or less, or 2 μm or more and 10 μm or less. By having such an average particle size, the oxygen content does not become too much, and the moldability is easily improved.

[0039] In the present embodiment, the average particle size is a value obtained from the area of ​​primary particles observed in a SEM observation image obtained under the following conditions using a general scanning electron microscope (eg, VE-9800, manufactured by KEYENCE; hereinafter also referred to as “SEM”).

[0040] Accelerating voltage: 10 kV

[0041] Observation magnification: 50 to 5000 times

[0042] The obtained SEM observation image is binarized and analyzed using general image analysis software (e.g. Image-Pro10), 1200±400 primary particles whose contours are observed uninterruptedly in the SEM observation image are extracted, and the longest diameter of each primary particle is measured, which is used as the particle size of each primary particle. The average value of the particle sizes of each primary particle can be used as the average particle size.

[0043] Since the moldability is easily improved, the primary particles of the powder of this embodiment preferably have a moderate particle size distribution. For example, the 10% area diameter (D10) [μm] relative to the 90% area diameter (D90) [μm] is preferably greater than 0.01 and less than 0.45, and more preferably greater than 0.04 and less than 0.20.

[0044] Regarding D10 and D90 in this embodiment, the equivalent area of ​​a circle with the longest diameter as the diameter is calculated based on the longest diameter (particle size) of each primary particle obtained by the same method as the measurement of the average particle size, and the longest diameter corresponding to the equivalent area of ​​the circle equivalent to 10% and 90% of the cumulative area is used as D10 and D90, respectively.

[0045] The powder of the present embodiment may be molded without molding involving sintering such as pressure sintering.

[0046] The powder of this embodiment has high moldability. For example, when 8 g of the powder is filled into a 10 mm × 40 mm rectangular parallelepiped mold and subjected to unidirectional pressure molding at a pressure of 100 MPa, the measured density (hereinafter also referred to as "molding density") at this time can be 2.0 g / cm 3 Above, 3.0g / cm 3 Above, 3.5g / cm 3 Above, 3.8g / cm 3 Above or 4.0g / cm 3 The higher the molding density, the better. For example, 5.0g / cm 3 Below, 4.5g / cm 3 Below, 4.2g / cm 3 Below, or 4.1g / cm 3The following examples include 2.0 g / cm 3 Above and 5.0g / cm 3 Below, 3.0g / cm 3 Above and 4.5g / cm 3 Below, 3.5g / cm 3 Above and 4.5g / cm 3 Below, 3.8g / cm 3 Above and 4.5g / cm 3 Below, 3.5g / cm 3 Above and 4.2g / cm 3 Below, or 4.0g / cm 3 Above and 4.1g / cm 3 the following.

[0047] In addition, regarding the powder of the present embodiment, when 8 g of the powder is filled into a 10 mm × 40 mm rectangular parallelepiped mold and subjected to unidirectional press molding at a pressure of 100 MPa, the flexural strength (hereinafter also referred to as "flexural strength of the molded body") can be 2.1 MPa or more, 2.3 MPa or more, or 2.5 MPa or more. The higher the flexural strength of the molded body, the better, and can be 10 MPa or less, 8 MPa or less, 7.0 MPa or less, 5.0 MPa or less, 4.5 MPa or less, or 4.0 MPa or less, and can be 2.1 MPa or more and 10 MPa or less, 2.3 MPa or more and 7 MPa or less, 2.5 MPa or more and 5.0 MPa or less, or 2.5 MPa or more and 4.0 MPa or less.

[0048] The powder of this embodiment can be used for known applications of gallium nitride powder, and is particularly preferably used as a precursor of a sintered body, a precursor of a sintered body for a sputtering target, and a precursor of a polycrystalline gallium nitride substrate.

[0049] Next, a method for producing the powder according to the present embodiment will be described.

[0050] The powder of this embodiment can be produced by any method as long as the gallium nitride powder having the above-mentioned structure can be obtained. As a preferred production method, a method for producing the powder includes a heat treatment step of heat-treating the gallium nitride powder at 900°C to 1300°C in an inert gas circulation atmosphere.

[0051] The gallium nitride powder (hereinafter also referred to as “raw material powder”) to be subjected to the heat treatment step is preferably a gallium nitride powder in a state obtained by nitriding metal gallium.

[0052] The metal gallium used for the nitridation treatment may be commercially available metal gallium, and examples thereof include metal gallium having a purity of 3N or more and 7N or less.

[0053] The nitridation treatment may be carried out under any conditions under which nitridation of metal gallium proceeds, and for example, the following conditions may be mentioned.

[0054] Nitriding treatment atmosphere: nitrogen-containing gas circulation atmosphere,

[0055] Preferably, the atmosphere is nitrogen or ammonia.

[0056] More preferably, an ammonia circulating atmosphere

[0057] Nitriding treatment temperature: 900°C or higher and 1100°C or lower.

[0058] Preferably 950°C or higher and 1050°C or lower

[0059] Heating rate: 5℃ / min or more and 50℃ / min or less

[0060] Preferably, the temperature is 8°C / min or more and 20°C / min or less.

[0061] The nitridation treatment time may be appropriately adjusted depending on the metal gallium to be subjected to the nitridation treatment and the nitridation treatment method, and for example, it may be 30 minutes to 15 hours, or 1 hour to 10 hours.

[0062] In the heat treatment step, the raw material powder is heat treated at 900° C. to 1300° C. in an inert gas flow atmosphere. It is believed that gallium nitride is appropriately thermally decomposed, and part of nitrogen is released to form nitrogen-deficient gallium nitride, which forms a conductive carrier. In this way, the powder of this embodiment having a resistivity that helps improve moldability is obtained.

[0063] In the heat treatment step, the heat treatment atmosphere is an inert gas circulation atmosphere. Thus, the oxygen content of the obtained powder does not increase excessively. The inert gas circulation atmosphere can be an atmosphere in which oxidation of the raw material powder does not proceed, and is preferably an atmosphere in which at least one of argon and nitrogen is circulated, and more preferably a nitrogen circulation atmosphere.

[0064] The flow rate of the inert gas can be any rate that can suppress the scattering of the raw material powder to be processed and replace the amount of gas generated by the heat treatment. For example, it can be 500 mL / minute to 5000 mL / minute, 800 mL / minute to 4000 mL / minute, or 1000 mL / minute to 2500 mL / minute.

[0065] The heat treatment is performed under an inert gas circulation atmosphere at a temperature of 900°C to 1300°C. If the heat treatment temperature is less than 900°C, the thermal decomposition of gallium nitride takes a very long time, and it is difficult to perform the heat treatment in a practical time. On the other hand, if the heat treatment temperature exceeds 1300°C, the thermal decomposition of gallium nitride proceeds excessively, and the powder itself collapses. The preferred heat treatment temperature is 950°C to 1000°C, and can be 1200°C to 1100°C or less, 950°C to 1200°C, or 1000°C to 1100°C.

[0066] The heat treatment time may be appropriately adjusted depending on the characteristics of the heat treatment furnace, and examples thereof include 15 minutes to 15 hours, 30 minutes to 10 hours, or 1 hour to 3 hours.

[0067] The heat treatment may be carried out in any heat treatment furnace capable of performing heat treatment in an inert gas circulation atmosphere, and may be one or more selected from the group consisting of a tubular furnace, an atmosphere box-type electric furnace, and an atmosphere muffle furnace, and may be a tubular furnace.

[0068] Next, a method for producing a sintered body using the powder of the present embodiment will be described.

[0069] The powder of this embodiment can be made into a sintered body by the same method as the existing method for producing a sintered body of gallium nitride, and can be used as a precursor of a sintered body of gallium nitride. As an existing production method, a method for producing a sintered body of gallium nitride having a step of pressurizing and sintering the powder of this embodiment can be cited. The pressurized sintering can be at least one of hot pressing and hot hydrostatic pressing, preferably hot pressing. In this way, the powder can be formed and sintered at the same time.

[0070] In addition, the powder of the present embodiment has high moldability and can be molded without heating. Therefore, the powder of the present embodiment is preferably used in a method for producing a sintered body of gallium nitride having the following steps: a step of molding the powder of the present embodiment to obtain a molded body; and a sintering step of sintering the molded body.

[0071] The molding method in the molding process can be any method that can obtain a molded body (powder compact) of the desired shape, and can include one or more selected from the group consisting of unidirectional pressure molding, cold water pressure pressing, mud casting molding and injection molding. Unidirectional pressure molding is preferred, and a molding method in which unidirectional pressure molding is performed at a molding pressure of more than 50 MPa and less than 150 MPa is more preferred.

[0072] The firing method in the firing step can be at least one of normal pressure firing and pressure firing, and normal pressure firing is preferred. It should be noted that "normal pressure firing" in this embodiment refers to a method of heating the fired object such as a molded body at a temperature above the firing temperature without applying external force.

[0073] The sintered body obtained by the production method of this embodiment can be applied to known uses of gallium nitride, and can be used for one or more selected from the group consisting of sputtering targets, gallium nitride polycrystalline substrates, and single crystal gallium nitride growth raw materials, and is particularly suitable as a sputtering target.

[0074] Example

[0075] Hereinafter, the present invention will be described using examples, but the present invention is not limited thereto.

[0076] (Resistivity)

[0077] The resistivity of the powder was measured using Loresta GX MCP-T700 (Nittoseiko Analytech). That is, 8 g of the powder sample was filled into a 10×40 mm rectangular parallelepiped mold and molded by uniaxial press molding at a pressure of 100 MPa to form an evaluation molded body. The resistivity of the evaluation molded body was measured using a TFP probe as a measurement probe.

[0078] (Flexural Strength)

[0079] The flexural strength of the molded article was measured in accordance with JIS R 1601 by the method under the following conditions.

[0080] Test method: 3-point bending test

[0081] Distance between pivot points: 30mm

[0082] Sample size: 5×10×40mm

[0083] Head speed: 0.5mm / min

[0084] (oxygen content)

[0085] The oxygen content [mass %] was measured by an inert gas melting-infrared absorption method using an oxygen and nitrogen analyzer (device name: LECO ON736, manufactured by Leco). The oxygen content [at %] was calculated using equations (1) and (2) from the obtained oxygen content [mass %] and nitrogen content [mass %].

[0086] (Powder X-ray Diffraction)

[0087] The crystal phase was determined by XRD measurement under the following conditions using a general powder X-ray diffractometer (apparatus name: Ultima III, manufactured by Rigaku Corporation).

[0088] Radiation source: CuKα radiation (λ = 0.15418nm)

[0089] Measurement mode: 2θ / θ scanning

[0090] Measuring interval: 0.01°

[0091] Divergence slit: 0.5deg

[0092] Light receiving slit: 0.3mm

[0093] Measuring time: 1.0 seconds

[0094] Measuring range: 2θ = 20° to 80°

[0095] The obtained XRD pattern was compared with JCPDS No. 00-050-0792 to identify the crystal phase.

[0096] (Average particle size)

[0097] The average particle size of the raw material powder was measured by using a SEM (device name: VE-9800, manufactured by KEYENCE Corporation) and obtaining a SEM observation graph under the following conditions.

[0098] Accelerating voltage: 10 kV

[0099] Observation magnification: 50 to 5000 times

[0100] The obtained SEM observation image was analyzed using image analysis software (Image-Pro10), and 1200±400 primary particles whose contours were observed uninterruptedly in the SEM observation image were extracted to determine the area of ​​each primary particle. The circle equivalent diameter was determined from the obtained area, and the average value was calculated as the average particle size.

[0101] (Loose density)

[0102] The bulk density of the powder was measured by the following method. That is, using a funnel with a hole diameter of 2.5 mm and a funnel angle of 60°, the powder was poured into a funnel with an inner diameter of 28 mm and a volume of 25 cm. 3 When the cylindrical container is filled with powder, the powder injection is stopped. After injection, the surface of the powder filled in the cylindrical container is scraped flat with a scraper without applying compression and vibration. 3 The mass [g] of the powder was taken as the bulk density. It should be noted that the mass of the powder was obtained by subtracting the mass of the cylindrical container from the mass of the cylindrical container after being scraped flat.

[0103] (Measured density)

[0104] The measured density of the molded body was obtained from the mass [g] measured by an electronic balance relative to the volume [volume %] obtained by the dimension measurement using a vernier caliper. The dimension measurement measured the length, width and thickness of the rectangular parallelepiped molded body.

[0105] Example 1

[0106] 30 g of metal gallium (purity: 6N) was placed in an alumina container, and the metal gallium and the alumina container were placed in a tubular furnace, and then nitridation was performed under the following conditions while vacuum replacement and ammonia gas was flowed to obtain a raw material powder.

[0107] Heating rate: 10℃ / min

[0108] Processing temperature: 1050℃

[0109] Processing time: 2 hours

[0110] After the holding, the mixture was naturally cooled in a tubular furnace, and after cooling to room temperature, the alumina container was recovered to obtain a raw material powder.

[0111] 30 g of the obtained raw material powder was put into an alumina container, and the raw material powder and the alumina container were placed in a tubular furnace, vacuum replaced, and then the raw material powder was sintered under the following conditions while nitrogen gas was flowing.

[0112] Heating rate: 10℃ / min

[0113] Firing temperature: 1000℃

[0114] Firing time: 3 hours

[0115] After sintering, the mixture was naturally cooled in a tubular furnace to obtain the gallium nitride powder of this example.

[0116] The oxygen content of the gallium nitride powder of this embodiment is 0.21 at%, the bulk density is 1.35 g / mL, and the resistivity is 8.45×10 -2 Ω·cm.

[0117] Example 2

[0118] Gallium nitride powder of this example was obtained by the same method as in Example 1 except that the raw material powder was sintered under the following conditions.

[0119] Heating rate: 10℃ / min

[0120] Firing temperature: 1050℃

[0121] Firing time: 1 hour

[0122] The oxygen content of the gallium nitride powder of this embodiment is 0.20 at%, the bulk density is 1.35 g / mL, and the resistivity is 2.21×10 -4 Ω·cm.

[0123] Example 3

[0124] Gallium nitride powder of this example was obtained by the same method as in Example 1 except that the raw material powder was sintered under the following conditions.

[0125] Heating rate: 10℃ / min

[0126] Firing temperature: 1000℃

[0127] Firing time: 0.5 hours

[0128] The oxygen content of the gallium nitride powder of this embodiment is 0.20 at%, the bulk density is 1.42 g / mL, and the resistivity is 7.60×10 -1 Ω·cm.

[0129] Example 4

[0130] 300 g of metal gallium (purity: 6N) was placed in an alumina container, the metal gallium and the alumina container were placed in a tubular furnace, the tubular furnace was evacuated, and then nitridation was performed under the following conditions while ammonia gas was passed, to obtain a raw material powder.

[0131] Heating rate: 10℃ / min

[0132] Processing temperature: 1140℃

[0133] Processing time: 2 hours

[0134] After the nitridation treatment, the temperature was lowered to 1000°C at a cooling rate of 10°C / min, and then the ammonia gas was switched to nitrogen gas. The mixture was sintered at 1000°C for 30 minutes while flowing nitrogen gas, and then naturally cooled to room temperature to obtain the gallium nitride powder of this example.

[0135] The oxygen content of the gallium nitride powder of this embodiment is 0.04 at%, the bulk density is 1.71 g / mL, and the resistivity is 4.24×10 -2 Ω·cm.

[0136] Example 5

[0137] 30 g of metal gallium (purity: 6N) was placed in an alumina container, the metal gallium and the alumina container were placed in a tubular furnace, the tubular furnace was evacuated, and then nitridation was performed under the following conditions while ammonia gas was passed, to obtain a raw material powder.

[0138] Heating rate: 10℃ / min

[0139] Processing temperature: 1125℃

[0140] Retention time: 2 hours

[0141] After the nitriding treatment, the product was cooled to room temperature by natural cooling in a tubular furnace to obtain a raw material powder.

[0142] 30 g of the obtained raw material powder was put into an alumina container. After placing the metal gallium and the alumina container in a tubular furnace, the tubular furnace was evacuated and calcined under the following conditions while nitrogen gas was flowed.

[0143] Heating rate: 10℃ / min

[0144] Firing temperature: 1000℃

[0145] Firing time: 3 hours

[0146] After sintering, the mixture was cooled to room temperature by natural cooling to obtain the gallium nitride powder of this example.

[0147] The oxygen content of the gallium nitride powder of this embodiment is 0.07 at%, the bulk density is 1.81 g / mL, and the resistivity is 3.82×10 -2 Ω·cm.

[0148] Comparative Example 1

[0149] The heat-treated powder was used as the gallium nitride powder of this comparative example. That is, 30 g of metal gallium (purity: 6N) was put into an alumina container. The metal gallium and the alumina container were placed in a tubular furnace, and then the tubular furnace was evacuated. Then, while ammonia gas was circulated, nitridation treatment was performed under the following conditions to obtain the gallium nitride powder of this comparative example.

[0150] Heating rate: 10℃ / min

[0151] Processing temperature: 1125℃

[0152] Keep temperature: 2 hours

[0153] The gallium nitride powder of this comparative example has an oxygen content of 0.19 at%, a bulk density of 1.89 g / mL, and a resistivity of more than 1×10 7 Ω·cm.

[0154] Comparative Example 2

[0155] Commercially available gallium nitride powder (manufactured by High Purity Chemical, 4N, Lot. 302577) was used as the gallium nitride powder of this comparative example.

[0156] The oxygen content of the gallium nitride powder of this comparative example is 15.50 at%, the bulk density is 0.28 g / mL, and the resistivity is 8.91×10 6 Ω·cm.

[0157] Measurement example

[0158] 8 g of the gallium nitride powder obtained in Examples 4 and 5 and Comparative Examples 1 and 2 were weighed respectively, filled into a 10×40 mm rectangular parallelepiped mold and molded by uniaxial press molding at a pressure of 100 MPa to produce a molded body, and its measured density and flexural strength were measured. The results are shown in the table below.

[0159] [Table 1]

[0160]

[0161] It was confirmed that a particle having a particle size of 4.0 g / cm can be produced from the powder of the example. 3 A molded body with a high measured density of more than 2.1 MPa. In addition, it can be confirmed that such a molded body has a high flexural strength of more than 2.1 MPa. It should be noted that the gallium nitride powder of Comparative Example 1, compared with the powder of the embodiment, has a high loose density and high filling capacity, but it disintegrates when taken out of the molding mold after molding, and it is essentially impossible to mold. Therefore, in Comparative Example 1, neither the measured density nor the flexural strength can be measured. From this, it can be confirmed that the strength of the molded body obtained from the powder with a high oxygen content is significantly low. It can be confirmed that although the gallium nitride powder of Comparative Example 2 with a high resistivity can be used to make a molded body, the measured density and flexural strength of the obtained molded body are low.

[0162] It should be noted that this application is based on Japanese Patent Application (Japanese Patent Application No. 2023-095501) filed on June 9, 2023, the entirety of which is incorporated herein by reference. In addition, all references cited herein are incorporated as a whole.

Claims

1. A gallium nitride powder having an oxygen content of 0.5 at% or less, wherein 8 g of the powder is filled into a 10 mm×40 mm rectangular parallelepiped mold and subjected to uniaxial press molding at a pressure of 100 MPa, and has a resistivity of 1.0×10 7 Ω·cm or less.

2. The powder according to claim 1, wherein The gallium nitride is gallium nitride having nitrogen defects. The powder according to claim 1 or 2, which has a bulk density of 1.00 g / mL or more and 1.85 g / mL or less. The powder according to claim 1 or 2, which has an average particle size of 1 μm or more and 150 μm or less. The powder according to claim 1 or 2, wherein a 10% area diameter relative to a 90% area diameter is 0.01 to 0.

45. 6 . A method for producing the powder according to claim 1 , comprising a heat treatment step of heat-treating the gallium nitride powder at 900° C. to 1300° C. in an inert gas circulation atmosphere.

7. The manufacturing method according to claim 6, wherein: The gallium nitride powder is a gallium nitride powder obtained by nitriding metal gallium.

8. The manufacturing method according to claim 6 or 7, wherein: The inert gas flowing atmosphere is an atmosphere in which a gas containing at least one of argon and nitrogen is flowing.

9. The manufacturing method according to claim 6 or 7, wherein: The flow rate of the inert gas is 500 mL / min or more and 5000 mL / min or less. 10 . A method for producing a sintered body of gallium nitride, comprising: a step of compacting the powder according to claim 1 or 2 to obtain a compact; and a sintering step of sintering the compact.

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