JP2009096646A - Manufacturing method of oxide powder, manufacturing method of iridium oxide powder, and roasting furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roasting furnace which has a simple structure and can efficiently roast a fine powder, and an efficient manufacturing method of an iridium oxide powder preferable for forming a thick film resistor using the furnace. <P>SOLUTION: The roasting furnace to be used has an inside of the roasting furnace divided into a plurality of heating areas and can control the temperature of the each heating area separately. The inside of the roasting furnace is generally rectangular in cross section, and the atmosphere gas generally flows as a layer only in the same direction as the blow-in direction of the atmosphere gas. A plurality of blow-in nozzles of the atmosphere gas is arranged in parallel. Using this roasting furnace, an iridium oxide powder having stable qualities is obtained by oxidatively roasting ammonium hexachloroiridate (IV) or potassium hexachloroiridate (IV) at 600-1,050°C while controlling the temperature of the each heating area separately when raising the temperature. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing oxide powder, a method for producing iridium oxide powder, and a roasting furnace suitable for oxidative roasting of fine powder.

  2. Description of the Related Art In recent years, circuit wiring boards on which electronic parts such as resistors and capacitors that are produced by printing a paste on an insulating substrate are mounted on electronic devices. Thick film resistors are widely used in chip resistors, thick film hybrid ICs, resistor networks, and the like. As a method of manufacturing a thick film resistor, usually, a resistor paste in which conductive powder and glass powder are uniformly dispersed is printed on a conductor circuit pattern or electrode formed on the surface of an insulating substrate, and this is fired. It is manufactured using the process to do.

A paste used for manufacturing a thick film resistor is prepared by uniformly dispersing conductive powder and a glass binder in an organic medium called a vehicle. Of these, conductive powder plays the most important role in determining the electrical characteristics of thick film resistors, and fine powders of ruthenium oxide (RuO ₂ ) and lead ruthenate (Pb ₂ Ru ₂ O ₇ ) are widely used. Yes.
In general, ruthenium oxide is used as a conductor in a wide range from a low resistance value to a high resistance value, and in the high resistance region, lead ruthenate having a smaller variation in the resistance value with respect to the conductor concentration is often used.
However, in recent years, for the purpose of eliminating the use of toxic lead from electronic devices, as a conductive powder for thick film resistors in the high resistance region, a conductive powder containing no lead instead of lead ruthenate powder is desired. Yes. As a solution to this, ruthenium composite oxides such as Bi ₂ Ru ₂ O ₇ , CaRuO ₃ , SrRuO ₃ , BaRuO ₃ , LaRuO ₃ have been proposed, but have not yet been put into practical use.

Iridium oxide (IrO ₂ ) is generally known as a conductive powder that has a higher resistance than a ruthenium oxide powder when a resistor is formed from a paste containing the powder. Therefore, iridium oxide powder is promising as a conductive powder containing no lead in place of lead ruthenate powder.
As an efficient method for producing such iridium oxide powder, chlorinated iridium salts such as ammonium hexachloroiridium (IV) or potassium hexachloroiridium (IV) can be roasted at a high temperature in an oxidizing atmosphere. .

However, in such oxidative roasting of iridium chloride, the thickness of the raw material layer should be about 1 to 2 mm in order to make the properties of the obtained iridium oxide powder uniform, and it must react uniformly with the atmospheric gas. In other words, productivity is low with respect to the hearth area. The low productivity with respect to the hearth area can be improved by spreading the raw material on a tray and stacking it in multiple stages in the vertical direction to increase the effective area of the furnace. However, when the trays are stacked in a plurality of stages in the vertical direction, if the number of stages increases, a large difference occurs in how heat is transferred from each stage, and uniform roasting becomes difficult. Therefore, the number of stages is limited, and in order to secure the production amount, it is necessary to make the area per tray as wide as possible. As such a baking furnace, what is to be fired is accommodated in a plurality of stages in a roasting chamber and the atmosphere is circulated with hot air so that it can be uniformly fired in each part of the roasting chamber (for example, Patent Documents). 1).
When trying to make the atmosphere in the roasting chamber uniform in a hot air circulation furnace, it is necessary to make the air volume extremely large, which is not suitable for roasting fine powder. This is because the circulating hot air becomes turbulent and the powder is scattered. Further, when the air volume is reduced, stagnation of the atmosphere occurs and uniform roasting cannot be performed.

As an improvement measure for the homogenization of the atmosphere in the roasting chamber, the flow rate of the atmospheric gas supplied to each of the mounting surfaces of the heat treatment objects installed in multiple stages in the roasting chamber is set to a specific value, and the mounting surface is An atmosphere gas supply method of a heat treatment apparatus that can perform uniform firing by moving in the horizontal direction is disclosed (for example, see Patent Document 2).
However, continuous furnaces that move heat by moving the loading surface are expensive and unsuitable for production of products with a relatively small production volume. It is complicated to move the loading surface even in a batch furnace. It becomes a structure. Further, the atmospheric gas flow rate required for the homogenization of the disclosed atmosphere is too large for fine powder roasting, and is not suitable for fine powder roasting.

In addition, as a furnace that can homogenize the atmosphere in the roasting chamber, it has a structure in which soot is stacked in multiple stages in the roasting chamber, and the atmosphere gas flow is switched by switching the atmosphere gas supply pipe and exhaust pipe. A firing furnace that can supply gas uniformly to the raw material in the roasting chamber has been proposed (see, for example, Patent Document 3).
In addition, heat treatment that makes it possible to keep the atmosphere in the roasting chamber uniform by changing the shape of the outlet of the atmosphere gas supply pipe and rotating or moving at least one of the object to be heat-treated and the atmosphere gas supply pipe A furnace has also been proposed (see, for example, Patent Document 4).
All of the above roasting furnaces have movable parts, and the apparatus has a complicated structure. In addition, there is no description about the atmospheric gas flow rate that needs to be fully considered for the roasting of fine powders, and there is a problem that the atmospheric gas flow rate must be increased in order to forcibly circulate the atmospheric gas. is there.
Under such circumstances, an efficient industrial production method of iridium oxide powder having good powder characteristics as a conductive powder containing no lead as a substitute for ruthenate lead powder as a thick film resistor forming paste is desired. Therefore, it is desired to provide a furnace suitable for roasting fine powders necessary for the production thereof.
JP 05-172464 A JP-A-2005-50849 Japanese Patent Laid-Open No. 04-273388 JP 2002-39691 A

  In view of such a situation, the present invention provides an oxide powder manufacturing method capable of efficiently roasting fine powder with a simple structure, and a roasting furnace suitable for manufacturing oxide powder and the use thereof. An object of the present invention is to provide an industrially efficient method for producing iridium oxide powder as a conductive powder suitable for the thick film resistor forming paste.

  In the method for producing oxide powder of the present invention, a plurality of heating regions are provided in the roasting furnace along the flow direction of the atmosphere gas, and the atmosphere gas is flowed in a laminar flow on the surface of the raw material placed in the heating region. The temperature difference between the plurality of heating regions and the direction orthogonal to the flow of the atmospheric gas are increased at the same temperature, and after the heating of each heating region is completed, all the raw materials are heated at the same temperature. The raw material is roasted.

In the method for producing oxide powder of the present invention, an oxidizing atmosphere gas can be used as the atmosphere gas.
The temperature difference between the plurality of heating regions is preferably 80 ° C to 100 ° C.

  The method for producing iridium oxide powder according to the present invention includes a plurality of heating regions along the flow direction of the oxidizing atmosphere gas in the roasting furnace, and ammonium hexachloroiridium (IV) placed in the heating region or An oxidizing atmosphere gas is made to flow in a laminar flow on the raw material surface made of potassium hexachloroiridium (IV), a temperature difference of 80 ° C. to 100 ° C. is provided in the plurality of heating regions, and the direction orthogonal to the flow of the atmosphere gas is the same. The temperature is raised at 600 ° C., and after the heating of each heating region is completed up to 600 ° C., all the raw materials are heated at a temperature of 600 to 1050 ° C. and roasted.

  The roasting furnace for producing the oxide powder of the present invention is provided with a plurality of heating regions in the furnace, and is provided with an atmosphere gas supply / discharge mechanism that generates a laminar flow in the furnace at both ends of the furnace. A roasting furnace provided with a temperature control mechanism for independently and arbitrarily controlling the heating rate of the region.

  In the roasting furnace for producing oxide powder according to the present invention, the atmosphere gas supply / discharge mechanism is provided with an atmosphere gas supply nozzle on one surface of the inner wall of the roasting furnace, and the atmosphere gas discharge port is provided with the atmosphere gas supply nozzle. It is preferable to provide a roasting furnace provided on a plane symmetrical to the formed plane.

  In the roasting furnace for producing oxide powder of the present invention, the roasting furnace may be a tubular furnace, or the tubular furnace may have a substantially square cross section.

  According to the present invention, since fine powder raw material can be efficiently roasted, a roasting furnace suitable for the production of oxide powder with little particle size variation can be obtained, and thick film resistance can be obtained using it. An iridium oxide powder as a conductive powder suitable for a body forming paste can be produced industrially and efficiently, and the effect of contributing to the industry is very large.

In the production method of the oxide powder of the present invention, a laminar flow in only the same direction of the atmospheric gas is caused to flow on the surface of the placed raw material. The temperature is raised and the temperature is raised at the same temperature in the direction perpendicular to the laminar flow of the atmospheric gas. After the temperature rise is completed, all the raw materials are heated at the same temperature to roast the raw materials. is there.
The structure of the roasting furnace will be specifically described.
FIG. 1 is a schematic view of a roasting furnace of the present invention. It is a figure explaining an atmospheric gas supply mechanism and a temperature control mechanism, and is a case where the main body 1 is comprised with the tubular furnace. The atmospheric gas supply mechanism includes an atmospheric gas blowing nozzle 4 for supplying atmospheric gas to one side of the long axis direction of the furnace core tube 2 and an atmospheric gas discharge port 10 on the other side. The atmospheric gas blown from the atmospheric gas blowing nozzle 4 flows gently so as to form a laminar flow in the blowing direction. The reason why the atmospheric gas is laminar is to prevent the atmospheric gas from flowing backward and to make the reaction between the atmospheric gas and the raw material uniform.
A plurality of heating regions are provided in the roasting furnace main body 1 along the flow direction of the atmospheric gas (FIG. 1 shows an example in which three heating regions A, B, and C are provided).
The temperature control mechanism is composed of a plurality of heating elements, with heating elements 3 for heating the core tube 2 above and below each heating region. One set of upper and lower heating elements is set as one heating region, and the temperature of each heating region can be controlled separately. A plurality of heating regions are arranged in the direction in which the laminar flow of the atmospheric gas flows, and instead of heating all trays 7 in the core tube 2 on which the raw material is placed at the time of temperature rise, By making a temperature difference between the trays 7 positively, it is possible to provide a time difference in the roasting reaction to maintain good contact between the raw material and the atmospheric gas, and to control the cracked gas generated by the decomposition of the raw material. As a result, the atmosphere gas and the raw material can be contacted uniformly.

It is important for the atmospheric gas to flow into the roasting chamber in a laminar flow. In order to make the atmospheric gas laminar, the atmospheric gas flow rate in the furnace needs to be 100 cm / second or less.
The atmosphere gas supply mechanism of the roasting furnace according to the present invention has the atmosphere gas supply nozzle 4 provided on one side surface of the inner wall of the roasting furnace and the atmosphere gas discharge port 10 relative to the surface on which the atmosphere gas supply nozzle 4 is provided. Prepare for the side to do. In the tubular roasting furnace of FIG. 1, a plurality of atmospheric gas blowing nozzles 4 are attached to the side wall of one end of the roasting chamber 6, and the other end is completely open. The atmospheric gas introduced into the roasting chamber 6 by each atmospheric gas blowing nozzle 4 flows along the major axis direction of the furnace core tube 2 and is directly discharged out of the system.

2A and 2B are diagrams for explaining the internal structure of the roasting furnace according to the present invention. FIG. 2A is a perspective view, and FIG. 2B is a cross-sectional view taken along line AA ′ in FIG. . It is preferable that the four atmosphere gas supply nozzles 4 are installed horizontally and have a diameter as large as possible. Furthermore, it is preferable that the flow rate be uniform between the atmospheric gas supply nozzles 4. The atmosphere gas can be made into a laminar flow from the position, size, and gas flow rate of the atmosphere gas supply nozzle 4.
The flow rate of the atmospheric gas can be adjusted easily even if a simple flow rate adjusting device (not shown) is attached to each atmospheric gas blowing nozzle 4.
The flow rate of the atmospheric gas forming the laminar flow can be adjusted by the arrangement and the diameter of the atmospheric gas blowing nozzle 4. The arrangement of the atmospheric gas blowing nozzle for flowing the atmospheric gas in only one direction can be easily obtained by performing numerical calculation using commercially available software (for example, general-purpose fluid analysis software CFX). What is necessary is just to input and calculate the conditions changed by the roasting scale, that is, the number and interval of nozzles for blowing atmospheric gas, the roasting temperature condition, and the like.

A plurality of heating areas A, B, and C provided in the roasting furnace are divided into a plurality of areas in the roasting furnace along the flow of the atmospheric gas, and the heating rate of each heating area is controlled independently to thereby provide a time difference. Provide and heat up. In the process of raising the temperature, the raw material roasting reaction is almost completed. Since the roasting reaction proceeds sequentially with a time difference for each heating region, the contact between the raw material and the atmospheric gas is sufficiently performed, and the reaction product gas can be quickly carried out of the system, so that the roasting reaction Can proceed efficiently and uniformly.
In the present invention, since the operation is a badge operation, it is important to react the raw materials little by little. If all the raw materials are reacted at the same time, a uniform roasting reaction cannot be expected. In this regard, according to the roasting method of the present invention, since the raw materials in the furnace are reacted in small amounts, a uniform roasted product can be obtained efficiently.

The heating of each heating area continues until the temperature of each heating area reaches a predetermined temperature. The temperature difference between the heating regions is kept at about 80 ° C. to 100 ° C. to raise the temperature. When each heating region reaches a predetermined roasting temperature, the temperature rise is stopped, and the whole is heated at a constant temperature to complete the roasting reaction. At this stage, the roasting is almost finished, so there is no shortage of atmospheric gas. The temperature difference may be a temperature gradient or a stepped temperature difference. Further, the length of each heating region in the laminar flow direction of the atmospheric gas may be any length as long as the raw material in the furnace can react little by little, and can be appropriately determined depending on the input amount of the raw material, the flow rate of the atmospheric gas, and the like.
Furthermore, it is also necessary to raise the temperature at the same temperature in the direction orthogonal to the laminar flow direction of the atmospheric gas. The temperature difference in the furnace of the present invention is that a temperature difference occurs in the laminar flow direction of the atmospheric gas, and a band of the same temperature is formed in the direction orthogonal to the laminar flow. The reason for providing the temperature difference band is to avoid the complexity of temperature management and to facilitate the reaction of the raw materials.
Here, the same temperature is substantially the same temperature, and is preferably substantially the same if the temperature difference is in the range of ± 10 ° C., more preferably in the range of ± 5 ° C. Further, the term “orthogonal” means substantially orthogonal, and desirably ranges from 80 ° to 100 °.
In the production method of the present invention, the temperature rises with a temperature difference, so there are oxide powders having different roasting times. However, even if the baking time is different, the particle size of the oxide powder is not affected.

By making the atmospheric gas into a laminar flow that flows in one direction and creating a temperature difference, the contact between the atmospheric gas and the raw material can be performed uniformly, and the roasting reaction can be performed completely. Among the raw materials in the furnace, the decomposition gas is generated from the raw material that has reached the decomposition temperature, and contact with the atmospheric gas starts. Even if the cracked gas comes into contact with a raw material having a temperature equal to or lower than the cracking temperature, no adverse effect is caused. Further, even if the cracked gas comes into contact with the raw material that has been decomposed, the reaction is completed, so there is no adverse effect.
The adverse effect of the cracked gas is to inhibit the raw material from coming into contact with the atmospheric gas. If the raw material that has reached the decomposition temperature or more cannot be in contact with the atmospheric gas, sintering of the raw material or the intermediate substance generated from the raw material occurs, and the particle size of the resulting oxide powder becomes large. Increase the variation.

For example, when ammonium hexachloroiridium (IV) is heated, iridium and decomposition gas are generated at about 400 to 600 ° C. On the other hand, since the reaction between oxygen and iridium in the atmospheric gas occurs at about 500 ° C., the temperature regions of both overlap.
When the whole raw material is heated uniformly and heated to be roasted, the decomposition gas is uniformly generated from the surface of the whole raw material after 400 ° C, and when it reaches about 500 ° C, oxygen and iridium in the atmosphere gas Reacts. However, since the gas phase flow in the roasting chamber is designed to flow only in substantially the same direction as the blowing direction, oxygen and iridium are likely to react with the raw material placed near the blowing nozzle, In the raw material placed near the discharge port, the cracked gas generated from the raw material placed near the blowing nozzle flows, so the reaction between oxygen and iridium tends to be hindered by the cracked gas. The unreacted iridium thus produced causes the particles to sinter and aggregate as the temperature in the roasting chamber rises, and the iridium oxide after roasting becomes coarse.
As a result, when the whole raw material is uniformly heated and heated to be baked, the difference in particle size between iridium oxide near the blow inlet and the outlet becomes large.

On the other hand, when heating is started sequentially from the raw material on the blowing nozzle side, a temperature gradient is formed at which the temperature of the raw material on the blowing nozzle side becomes high, and the temperature is raised to the roasting temperature.
Since the temperature on the side of the blowing nozzle is high, cracked gas is first generated from the raw material placed near the blowing nozzle. The cracked gas flows toward the discharge port, but the raw material placed near the discharge port does not reach the temperature at which oxygen and iridium react with each other, so there is no influence of the cracked gas that has flowed. After there is no cracked gas flowing from the blow nozzle side, the raw material placed near the discharge port is brought to a temperature at which oxygen and iridium will react. Can be made.
In addition, when heating is performed from the raw material on the outlet side, oxygen and iridium first react from the raw material placed near the outlet. At this time, since the raw material placed near the blowing nozzle has not reached the temperature at which the cracked gas is generated, the cracked gas does not flow toward the discharge port. Therefore, oxygen and iridium can be reacted without being inhibited by the cracked gas. After completion of the reaction at the discharge port side, the temperature of the raw material placed near the blowing nozzle may be raised to generate cracked gas.
As a result, when a temperature difference is provided at the time of temperature increase and roasting is performed, the difference in particle size between the iridium oxide near the inlet and the outlet becomes small.

The roasting furnace of the present invention can be a tubular furnace having a substantially square cross section. By making the cross-sectional shape substantially square, the raw material can be installed without creating a useless space in the furnace.
The core tube in the case of a tubular furnace can be a known heat resistant material such as quartz glass or alumina. It is appropriately selected in consideration of chemical corrosion resistance by the atmospheric gas or the decomposition gas.

  Furthermore, in the roasting furnace of the present invention, a plurality of shelves can be installed in the vertical direction to greatly increase the amount of raw material that can be placed in the furnace. FIG. 3 is a view for explaining the in-furnace structure when the shelf board 8 is installed in one stage. By installing the shelf plate 8 up to the side wall at one end of the roasting chamber, two upper and lower roasting chambers 6 and 6 ′ are formed in the furnace. It is. In addition, an atmospheric gas blowing nozzle 4 is installed on the side wall 5 in accordance with the positions of the roasting chambers 6, 6 '. The top plate of the shelf plate 8 is flat, and the tray 7 on which the raw material is placed is placed thereon. The shelf board 8 is made of a known heat-resistant material such as ceramics such as alumina, quartz glass or stainless steel. Thereby, even if it reduces the thickness of the raw material mounted in each shelf board 8, the quantity of a raw material can be increased significantly.

The roasting furnace of the present invention can also be used for the production of other fine metal oxide powders, and can be suitably used for the production of conductive powders for pastes for thick film resistors such as ruthenium oxide powders.
In the case of producing iridium oxide powder using the roasting furnace of the present invention, ammonium hexachloroiridium (IV) or potassium hexachloroiridium (IV) is used as a raw material, and the atmospheric gas used for roasting is oxygen. Contained gas. A roasting temperature shall be 600-1050 degreeC.
When ammonium hexachloroiridium (IV) is used as a raw material, the potassium component is preferably contained in an amount of 0.02 to 0.3% by weight based on the total amount. The potassium component is not particularly limited, and is at least selected from potassium hexachloroiridium (IV), potassium chloride, potassium hydroxide, or potassium carbonate such as potassium carbonate, potassium bicarbonate, basic potassium carbonate and the like. One type is preferably used, and potassium hexachloroiridium (IV) or potassium chloride is more preferable. By including potassium, potassium chloride is generated during roasting and abnormal grain growth of iridium oxide can be suppressed. When the roasting temperature is less than 600 ° C., unoxidized iridium metal remains, and when it exceeds 1050 ° C., volatilization of iridium oxide increases and the yield decreases.

When the roasting temperature is 760 ° C. or higher, the amount of evaporation of potassium chloride increases. However, potassium chloride may remain depending on roasting conditions. In this case, single-phase iridium oxide powder can be easily obtained by washing with water.
The roasting temperature may be adjusted by the desired primary particle diameter of the iridium oxide powder. A preferable primary particle diameter is 30 to 100 nm, and by setting the particle diameter within this range, an iridium oxide powder having preferable characteristics as a conductive powder of the thick film resistor paste can be obtained.
Unless otherwise specified, the average particle size of the powder is a value obtained by calculating the specific surface area by the BET method.
At the time of roasting, the raw material of each stage is preferably placed with a layer thickness of 3 mm or less. When the layer thickness is greater than 3 mm, the difference in particle diameter increases in the layer thickness direction. Although there is no problem even if the layer thickness is reduced, the raw materials that can be placed in the roasting chamber are reduced, and the productivity is lowered. Even when it is desired to shorten the roasting time, it is sufficient to make the layer thickness about 1 mm.

So far, the roasting furnace used for the production of the oxide powder used for the resistance paste and the method for producing the oxide powder have been described. However, the use of the oxide powder is not limited to the resistance paste, and a catalyst of nm order such as a catalyst is used. It can be used for required applications.
[Examples and Comparative Examples]

Hereinafter, the present invention will be described in more detail with reference to comparative examples and examples of the present invention, but the present invention is not limited to these examples.
(Comparative Example 1)

As a starting material, ammonium hexachloroiridium (IV) acid ((NH ₄ ) ₂ IrCl ₆ manufactured by Furuya Metal Co., Ltd.) having an iridium concentration of 43.6% by weight was used. 140 g of this ammonium hexachloroiridium (IV) is equally divided and placed on the 150 mm square alumina plates 9 and 6 of the square annular furnace shown in FIG. 4 with a layer thickness of 2 mm. It was set | placed on the bottom face in the roasting chamber (inside dimension: 40mmHx350mmWx900mmL) of a square tube furnace. Each alumina plate was arranged in two rows along the major axis direction of the roasting furnace, and was placed at the position indicated by the number in the figure. Four atmosphere gas introduction nozzles were evenly mounted on the surface perpendicular to the gas traveling direction at the end of the roasting chamber, symmetrically about the center line of the furnace. A cylindrical quartz tube having an inner diameter of 35 mm was used as the nozzle, and air was blown from each atmosphere gas blowing nozzle at a rate of 6 liters / minute, for a total of 24 liters / minute.

  In the tubular furnace shown in FIG. 1, the temperature profile of each heating region of the heating element was made the same, and the roasting temperature was kept at 850 ° C. at a heating rate of 15 ° C./min for 4 hours. Thereafter, the BET diameter of the obtained iridium oxide was evaluated. Table 1 shows the BET diameter of the roasted product obtained. The average primary particle diameter was 71 nm, the particle diameter depending on the raw material placement position was 43 nm at the minimum, 181 nm at the maximum, and the difference in BET diameter was as large as 138 nm. The difference between the maximum particle size and the minimum particle size of iridium oxide is preferably 15 μm or less.

  The temperature profile of each heating region of the heating element is heated in the order of the heating region A to the heating region C, and the temperature is increased while maintaining the temperature difference between the heating regions at 100 ° C. went. The roasting time of the heating area B was set to 4 hours. Thereafter, the BET diameter of the obtained iridium oxide was evaluated. Table 1 shows the roasted BET diameter obtained. The average primary particle diameter was 39 nm, the particle diameter depending on the raw material placement position was 38 nm minimum and 41 nm maximum, and the difference in BET diameter was as small as 3 nm.

  The temperature profile of each heating region of the heating element was heated in the order of the heating region C to the heating region A, and the temperature was increased while maintaining the temperature difference between the heating regions at 100 ° C., as in Example 1. After that, the BET diameter of the obtained iridium oxide was evaluated. Table 1 shows the BET diameter of the roasted product obtained. Table 1 shows the roasted BET diameter obtained. The average primary particle diameter was 39 nm, the particle diameter depending on the raw material placement position was 37 nm minimum and 42 nm maximum, and the difference in BET diameter was as small as 5 nm.

As a starting material, an iridium concentration of 39.5 wt% of potassium hexachloroiridate (IV) _(K 2 IrCl _{6 (KK)} Furuya metal) was used to roast 4 hours holding the roasting temperature to 920 ° C. Was performed in the same manner as in Example 1, and then the BET diameter of the obtained iridium oxide was evaluated. Table 1 shows the BET diameter of the roasted product obtained. Table 1 shows the roasted BET diameter obtained. The average primary particle diameter was 62 nm, the particle diameter depending on the raw material placement position was 57 nm minimum and 65 nm maximum, and the difference in BET diameter was as small as 8 nm.

  As described above, in Examples 1 to 3 as compared with Comparative Example 1, the dispersion of the obtained iridium oxide powder depending on the raw material placement position is small, and the present invention can efficiently produce iridium oxide powder with stable quality. I understand.

It is a figure explaining the heater structure of the roasting furnace of this invention. It is a figure explaining the internal structure of the roasting furnace of this invention, Comprising: (a) is a perspective view, (b) is sectional drawing along line A-A '. It is a figure explaining the internal structure at the time of installing a shelf board in the roasting furnace of this invention. It is a figure which shows the raw material loading method of the comparative example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Roasting furnace main body 2 Furnace core tube 3 Heating body 4 Nozzle for atmospheric gas blowing 5 Side wall 6 Roasting chamber 7 Tray 8 Shelf board 9 Alumina plate 10 Atmospheric gas discharge port

Claims (9)

  A plurality of heating regions are provided in the roasting furnace along the flow direction of the atmosphere gas, the atmosphere gas is flowed in a laminar flow on the surface of the raw material placed in the heating region, and a temperature difference is provided in the plurality of heating regions. The oxidation is characterized in that the directions orthogonal to the flow of the atmospheric gas are heated at the same temperature, and after the heating of each heating region is completed, all the raw materials are heated at the same temperature to roast the raw materials. A method for producing powder.   The method for producing an oxide powder according to claim 1, wherein the atmospheric gas is an oxidizing atmospheric gas.   The method for producing an oxide powder according to claim 1 or 2, wherein a temperature difference between the plurality of heating regions is 80 ° C to 100 ° C.   A raw material surface made of ammonium hexachloroiridium (IV) or potassium hexachloroiridium (IV) placed in the heating area, provided with a plurality of heating areas along the flow direction of the oxidizing atmosphere gas in the roasting furnace An oxidizing atmosphere gas is caused to flow in a laminar flow, a temperature difference of 80 ° C. to 100 ° C. is provided in the plurality of heating regions, and the direction perpendicular to the flow of the atmosphere gas is increased at the same temperature, A method for producing iridium oxide powder, characterized in that after the temperature rise is completed to 600 ° C, all raw materials are heated and roasted at a temperature of 600 to 1050 ° C.   The method for producing iridium oxide powder according to claim 4, wherein potassium is added to the ammonium hexachloroiridium (IV) and baked.   Temperature control in which a plurality of heating regions are provided in the furnace, and an atmosphere gas supply / discharge mechanism for generating a laminar flow in the furnace is provided at both ends of the furnace, and the heating rate of the plurality of heating regions is arbitrarily controlled independently. A roasting furnace for producing oxide powder, characterized by comprising a mechanism.   The atmosphere gas supply / discharge mechanism is provided with an atmosphere gas supply nozzle provided on one surface of the inner wall of the roasting furnace and an atmosphere gas discharge port provided on a surface opposite to the surface provided with the atmosphere gas supply nozzle. The roasting furnace according to claim 6, characterized in that   The roasting furnace according to claim 6 or 7, wherein the roasting furnace is a tubular furnace.   The cross-sectional shape of the said roasting furnace is a substantially square shape, The roasting furnace of any one of Claim 6 to 8 characterized by the above-mentioned.