JPH0450162A - Production of calcium-doped lanthanum chromite film, burning thereof, calcium-doped lanthanum chromite-based electrocondutive ceramic produced by said method and solid electrolyte fuel cell utilizing said ceramic - Google Patents

Abstract

PURPOSE:To obtain a flat lanthanum chromite film without warpage by adding specific amounts of solvent, binder, plasticizer, dispersant and anti-foaming agent to calcium-doped lanthanum chromite powder. CONSTITUTION:Calcium-dope lanthanum chromite expressed by the formula is prepared (0<x<=0.4; 0<y<=0.05; y<=x). Next, 280-460ml solvent (e.g. mixed solution of isopropanol and toluene), 45-53g binder (e.g. polyvinyl butyral), 45-55ml plasticizer (e.g. dibutyl phthalate), 13-18ml dispersant (e.g. nonionic surfactant) and 13-18ml anti-foaming agent are added to 500g said powder and adjusted to 500-700g/cm.sec viscosity. Then, resultant slurry is subjected to film formation by a doctor blade method to afford the aimed calcium-doped lanthanum chromite film suitable as a raw material of a separator in a solid electrolyte fuel cell or an interconnector, etc.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing a film of calcium-doped lanthanum chromite (hereinafter sometimes abbreviated as lanthanum chromite), and The present invention relates to a method for firing a lanthanum chromite membrane, a calcium-doped lanthanum chromite conductive ceramic obtained by the method, and a solid electrolyte fuel cell using the same.

(Prior art) Lanthanum chromite-based oxides have excellent chemical stability at high temperatures, low ionic conductivity, and high electronic conductivity. , seems to be suitable for use in electric furnaces for MHD power generation, etc.

For example, in a cylindrical solid electrolyte fuel cell, it is used as an interconnector to lead the fuel electrode inside the electrolyte to the outside. Conventionally, this interconnector was made using 1300°C or higher because lanthanum manganite, the air electrode material, would be deactivated at high temperatures of 1400°C or higher.
The film is formed into a cylindrical shape by electrochemical vapor deposition (EVD), which allows airtight sintering at a low temperature of 0.degree. C. or lower.

On the other hand, in recent years research has been conducted to develop a flat plate fuel cell, which is expected to have a higher output density than the cylindrical type mentioned above, and the use of chromium-deficient lanthanum chromite as a separator for this flat plate fuel cell is being considered. This separator is
It needs to be airtight, have high electronic conductivity, and be easy to manufacture.

In addition, taking into account our experience in the development of cylindrical fuel cells, we are able to manufacture lanthanum chromite membranes using low-cost manufacturing methods with fewer manufacturing steps, manufacturing methods that can use inexpensive raw materials, and manufacturing methods that do not require special equipment. It is hoped that

Conventionally, the doctor blade film formation method has been a common method for producing a separator-sized film at low cost without the need for special equipment. , the lanthanum chromite membrane was warped, and the electrolyte surface was uneven.

In addition, when this lanthanum chromite-based oxide is fired in the air, the chromium oxide evaporates and is sintered by a mechanism in which it recondenses, which inhibits the process of densification due to diffusion within the bulk, resulting in airtight sintering. Therefore, conventionally, in reducing atmosphere,
High temperature firing at 1720℃, AI, Cu,
Adding Zn, etc. to the B site in the lanthanum chromite crystal, adding alkaline earth metal elements to the A site or B site, and adding sintering aids such as fluoride have been considered. Ta.

(Problems to be Solved by the Invention) However, the EVD film formation method is expensive because it has a slow film formation rate and requires the use of expensive metal chloride gas as a starting material. This makes it even more difficult to put solid electrolyte fuel cells into practical use.

Furthermore, in the conventional doctor blade film formation method, the lanthanum chromite film was warped and the film was uneven. To make matters worse, once this lanthanum chromite has been airtightly sintered, it does not have plasticity even at high temperatures, so it cannot be straightened into a flat lanthanum chromite, making it difficult to develop flat solid electrolyte fuel cells. making it difficult.

In addition, with conventional firing methods, when firing at a relatively low temperature of around 1300°C, where lanthanum manganite is not deactivated, an airtight sintered body cannot be obtained, or even if an airtight sintered body is obtained. A firing temperature as high as 1720° C. is required, making it difficult to manufacture separators, interconnectors, etc., and in some cases, the high conductivity inherent to lanthanum chromite may not be obtained. Furthermore, when a sintering aid is used, there are problems such as the sintering aid evaporating from the separator and impairing the properties of lanthanum chromite.

Therefore, in a solid electrolyte fuel cell using such a separator, the fuel gas and oxidant gas sent to the anode and cathode, respectively, cross leak through the separator, reducing the output voltage of the cell and reducing the electronic conductivity of the separator. Due to the low separator, the internal resistance of the battery increases, and the sintering aid that evaporates from the separator corrodes other battery materials.

The present invention provides a manufacturing method for producing lanthanum chromite by a doctor blade method so that an airtight and flat film can be obtained in one firing without impairing the s-electrity, and a method for firing the doctor blade film. The purpose is to Another object of the present invention is to provide a firing method capable of obtaining an airtight lanthanum chromite ceramic film by firing at a relatively low temperature.

Another object of the present invention is to provide a lanthanum chromite-based conductive ceramic that is low in cost and has a high yield, and a solid electrolyte fuel cell using the same.

(Means for Solving the Problems) In order to achieve the above object, the method for producing a lanthanum chromite membrane of the present invention includes: L all-ml Ca +x+y+ Cr tl-
FI OsHowever, per 500 g of lanthanum chromite powder expressed as O<x≦0.4 0<y≦0.05 y≦x,
280-460 ml of solvent, 45-53 g of binder, 45-55 ml of plasticizer, 13-18 ml of dispersant, and 13 antifoaming agents.
~181 was added and the slurry was adjusted to a viscosity of 500 to 700 Q/■·sec to form a film by a doctor blade method.

In addition, in the present invention, a mixed solution of toluene and isopropanol having a mixing ratio of 1:2 to 2:1 by volume is used as the above-mentioned solvent, polyvinyl butyral is used as a binder, and di-n-butyl phthalate is used as a plasticizer. A nonionic surfactant is used as the agent, and mono-p-isooctylphenyl ether is used as the antifoaming agent.

Further, in the present invention, the unfired calcium-doped lanthanum chromite film formed into a desired shape is maintained in a temperature range of 1100 to 1300° C. for 4 hours or more during the firing process.

Furthermore, the present invention provides a method for heating the doctor blade film obtained by the above-mentioned manufacturing method to a temperature range from room temperature to 120°C.
The temperature is raised at a temperature increase rate of 0°C/h or less, preferably 10°C/h or less, and held in a temperature range of 110 to 130°C for 2 hours or more, preferably 4 hours or more, and the temperature range is from 120°C to 360°C. 20°C/h or less, preferably 10°C/h until
The temperature is raised at a temperature increase rate of 350 to 370 °C for 2 hours or more, preferably 4 hours or more, and then 1100 to 370 °C.
In the temperature range of 1300°C, for 4 hours or more, preferably 1
The firing is carried out under heating conditions in which the temperature is maintained for 0 hours or more, and further held in a temperature range of 1300° C. or more for 4 hours or more, preferably 10 hours or more.

Furthermore, in the production of the lanthanum chromite film of the present invention, the unfired lanthanum chromite film is surrounded by ceramics in the above-mentioned firing process to prevent direct heat application.

Furthermore, the lanthanum chromite-based conductive ceramic of the present invention is characterized in that it was manufactured using the above-described manufacturing method and firing method.

Furthermore, the solid electrolyte fuel cell of the present invention is characterized in that the above-described lanthanum chromite membrane is used as an interconnector, gas diffuser, or separator.

In addition, the "viscosity" mentioned in this specification is a value measured at room temperature using a stirring method.

Here, as the calcium-doped lanthanum chromite powder, L a 1l-xl Cal+yl Cr tl-y
l Os, 0<x≦0.4. O<y≦0.05
．． y≦x, preferably 0.1≦x≦O, O<y≦0.0
The composition range of 3y≦x is adopted.

As the solvent, it is preferable to use a non-aqueous solvent, such as an alcohol-based organic solvent, especially at a mixing ratio of 1 by volume.
: A mixed solvent solution of about 2 to 2.1 isopropanol and toluene is preferable, and the amount added is 280 to 460 ml per OOg of lanthanum chromide, preferably 3
00-400nl, more preferably 320-3801
is within the range of This non-aqueous solvent poses problems in ventilation and treatment of exhaust gas, but since the green sheet dries out easily, the doctor blade device can be simplified and the viscosity of the slurry can be easily adjusted.

The addition of a binder also increases the strength of the green sheet.

This binder can be used as long as it has excellent workability and dimensional stability of the green sheet and is soluble in dispersants and solvents, but organic binder-based polyvinyl butyral is preferable. , Manaso is added in an amount of 45 to 53 g, preferably 48 to 53 g, and more preferably 49 to 52 g per 500 g of lanthanum chromite powder. If the amount of binder in the slurry is less than each lower limit, the viscosity of the formed green sheet will increase, making it difficult to handle the green sheet, such as making it impossible to peel it off from the carrier film.

In addition, phthalate esters are used as plasticizers to provide the wetting effect of the lanthanum chromite powder (contributing to the dispersibility and lubricity of raw material particles), the substitute effect of the binder, and the plasticizing effect of the dry sheet. Among these, di-n-butyl phthalate is particularly preferred, and the amount added is 45 to 55 ml per 500 g of lanthanum chromite powder.
, preferably 50-55 ml, more preferably 51-5 ml
The range is 41.

As a dispersant, a nonionic surfactant is used, and the amount used is 13 to 1 per 500 g of lanthanum chromite.
8 ml, preferably 13-17 ml, more preferably 1
It is about 3 to 151. This dispersant prevents van der Waalska agglomeration of primary particles of lanthanum chromite powder, improves dispersibility, and increases the packing density of lanthanum chromite particles in the green sheet.

The antifoaming agent is also not particularly limited, but is preferably mono-p-isooctylphenyl ether,
The amount used is 13-18ml, preferably 13-17ml
l, more preferably in the range of 13-151. When the slurry is mixed using a ball mill, for example, the antifoaming agent has the role of preventing air bubbles from being generated and making it impossible to mix the slurry sufficiently.

It is preferable to use the above-mentioned slurry conditioners, especially binders, plasticizers, dispersants, and antifoaming agents, to a minimum. It was found that it is easy to sinter in a flat and airtight manner. If the amount of the slurry conditioner is large, the formability of the green sheet will be improved, but if it is too large, the sintered body will have porosity. Furthermore, if the amount of the slurry conditioner is too small, the moldability will deteriorate and a flat green sheet will not be obtained.

(Function) The lanthanum chromite slurry, which has been adjusted to a desired viscosity by adding a slurry conditioner having the above-mentioned mixing ratio, is formed into a flat sheet having a desired thickness when passing through a doctor blade. In the temperature range from room temperature to 120°C, it should be 20"C/h or less and above 10"C/h.
Part of the organic solvent evaporates by increasing the temperature at a temperature increase rate of less than Gently stabilizes and evaporates organic solvents,
Prevents the generation of pores due to solvent gasification.

Next, in the temperature range from 120°C to 360°C, the rate is 20°C/h or less, preferably 1
By increasing the temperature at a rate of 0°C/h or less, some of the slurry conditioner burns, and the temperature is maintained in the 350-370°C temperature range for 2 hours or more, preferably 4 hours or more, without increasing the temperature. During this time, the slurry conditioner is stably burned. Thereafter, the material is maintained in a temperature range of 1,100 to 1,300° C. for 4 hours or more, preferably 10 hours or more, thereby creating a melt and exhibiting plasticity. The state in which this melt is created is as shown in the electron micrograph of FIG. This eliminates distortion in the lanthanum chromite film, making it flat and uniform in thickness. Furthermore, at 1300°C or higher for 4 hours or more, preferably 1
By maintaining the temperature for 00 hours or more, the lanthanum chromite film is densely fired.

This lanthanum chromite ceramic has the composition formula L a
N-zl Ca +x+yl Cr fl-yl O
A solid solution represented by s, where the values of x and y in the composition formula are O
<x≦0.4.0<y≦0.05. When y≦x is satisfied, a perovskite single phase having the composition X13' is obtained. When x and y do not satisfy the above values, a perovskite single phase with such a composition cannot be obtained,
In addition to perovskite, phases such as lanthanum oxide (La203) and calcium oxide (Cab) appear, resulting in a state of multiphase coexistence.

L a fl-ml Ca +x+yl Cr 1-F
IOx-based solid solutions also have excellent electrical conductivity, but CaO and La2O5 inhibit electrical conduction, and when either the value of x or y does not satisfy the above-mentioned value, the degree of sintering deteriorates significantly, The degree of sintering is less than 94% which prevents gas permeation.

(Example) Next, the structure of the present invention will be explained in detail based on the example shown in the drawings.

Lanthanum chromite membrane is produced by preparing a highly viscous slurry (mixing) in which lanthanum chromite powder is suspended in a solvent containing functional additives such as a plasticizer, binder, and antifoaming agent, and then using the doctor blade method. It is obtained by forming a film into a green sheet with a uniform thickness and then firing it.

To prepare the slurry used in the doctor blade method, first, lanthanum oxide (La208), calcium carbonate (CaCOs), and chromium oxide (Cr20s) are mixed together.
) in a predetermined ratio shown by the following formula (1), pulverized and mixed, and heated in air at a predetermined temperature, e.g.
Calcination is performed at 100° C. for about 10 hours to prepare a raw material powder of calcium-doped lanthanum chromite having a powder diameter of about 11a1.

L a Cr -ml Ca Cx+y+ Cr tl
-yl Os °°' (1) However, O<x≦0.4 0<y≦0.05 y≦x A binder pre-dissolved in a solvent is added to this lanthanum chromite powder. Then, the mixture is stirred and mixed using a ball mill, etc., a plasticizer is added thereto, further stirred and mixed using a ball mill, etc., an antifoaming agent is further added, and the defoaming is performed by holding the mixture still inside a pressure reducer, etc. to obtain slurry.

In addition, in such a slurry adjustment process, the slurry is reduced to a desired viscosity, for example, 500 to 700 g, by vacuum defoaming.
Adjust to /3・SeC.

Here, as a solvent, non-aqueous isopropanol [(
A mixed solution of Katayama Chemical Co., Ltd., - grade] and toluene [Katayama Chemical Co., Ltd., special grade] was used. In addition, as a binder, polyvinyl butyral [Tasui Kagaku Kogyo Co., Ltd., 5-LEC
, BM-11 was used.

As a plasticizer, a 0-grade dispersant (surfactant) using di-n-butyl phthalate [Nacalai Tesque Co., Ltd.]
As the surfactant, a nonionic surfactant [NOP-83RAT, manufactured by Nippon Oil & Fats Co., Ltd., fish oil] was used.

As an antifoaming agent, mono p-iso-octylphenyl ether [Nacalai Tesque Co., Ltd., Triton
-100° Characteristic Reagent by Application] was used. The amount used is 280~280g of solvent per 500g of lanthanum chromite.
460ml, binder 45-53g, plasticizer 45-5
5-ml, dispersant 13-18ml, antifoam agent 13-1
The range is 81.

The slurry having the desired composition and viscosity thus adjusted is then formed into a green sheet (a dense, flexible tape using a polymeric compound as a binder) with a desired thickness in a doctor blade device. The thickness of the slurry loaded into the slurry tank of the doctor blade device is regulated by a knife called a doctor, and the slurry is spread onto a conveyor tape that moves at a predetermined speed, and then moves inside the doctor blade device on the conveyor tape. Meanwhile, it is dried by heating with a heater or the like, and is peeled off from the conveying tape at the end of the device to maintain its shape as a green sheet. The doctor blade device is preferably one equipped with a two-stage doctor, and IP! The slurry cast by the i-th blade is finished to a more precise film thickness by the second blade.

Then, the unfired calcium-doped lanthanum chromite film formed into the desired shape is held under certain firing conditions, for example, in a temperature range of 1100 to 1300°C for 4 hours or more, preferably 10 hours or more during the firing process. It creates a melt and molds it into a flat shape.

Further, in the present invention, the temperature is raised at a rate of 20°C/h or less, preferably 10°C/h or less, from room temperature to 120°C, and preferably for 2 hours or more in the 110-130°C temperature range. Hold for more than 4 hours, temperature range from 120℃ to 360℃
20°C/h or less, preferably 10°C/h, until the temperature reaches
The temperature is raised at a temperature increase rate of 350 to 370°C for 2 hours or more, preferably 4 hours or more, and then 1 hour or less.
Dense and flat lanthanum chromite sintered under heating conditions of holding in a temperature range of 100 to 1300°C for 4 hours or more, preferably 10 hours or more, and further holding in a temperature range of 1300°C or more for 4 hours or more, preferably 10 hours or more. Obtain a membrane.

The lanthanum chromite membrane thus obtained is airtight and flat, as described below, and is therefore suitable for application in various fields, such as separators for fixed electrolyte fuel cells, gas diffusers, interconnectors, etc. but,
It is particularly suitable as a separator for a flat plate solid electrolyte fuel cell and a gas diffuser interconnector.

FIG. 1 shows an exploded perspective view of an example of a separator for a flat solid electrolyte fuel cell. In the fuel cell, flat unit cells 1 and separators 4 are alternately stacked with spacers 2.3 in between, and combustion is performed in an air supply space 5 and a combustion gas supply space 6 formed by the unit cells 1 and separators 4. Gas and air are supplied through a fuel gas supply pipe 7 and an air supply pipe 8, respectively. Furthermore, the unit cell 1 is formed by forming an air electrode 10 and a fuel electrode 11 on the front and back sides of a solid electrolyte 9. The lanthanum chromite membrane according to the present invention is used as the separator 4 of such a fuel cell.

There is also another example of a flat solid electrolyte fuel cell as shown in FIG. This flat plate type solid electrolyte fuel cell is made up of alternating layers of unit cells 1 and separators 4 having gas diffusers 12 and 13 on both sides. Gas Difuser 12.13 is made of lanthanum chromite ceramics with edge 14 formed.
Fuel gas and air are supplied to the fuel electrode and the air electrode through the groove 14.

Further, FIG. 3 shows an example of a cylindrical solid electrolyte fuel cell, which has a cylindrical support 2.
An air electrode 21, a solid electrolyte 22, and a fuel electrode 23 are formed concentrically around the air electrode 0, and an interconnector 24 formed on the air electrode 21 separates the solid electrolyte 22 and fuel electrode 23. It is provided so that a current of 21 flllll is taken out. A groove 25 is provided between the interconnector 24 and the fuel electrode 23 for electrical insulation. Air flows inside the support 20 and is supplied to the air electrode 21 through the porous support 20 .

(Left below) The starting materials on the order I of the order Aurizo are lanthanum oxide (L a20s ), calcium carbonate (CaCO, ), and chromium oxide (Cr20s).
were mixed at a predetermined molar ratio using a powder mixing method, and 1000
It was baked at ℃ for 20 hours. And x=0.3. y=0
．． 32. Calcium-doped lanthanum chromite raw material powder with an average particle size of 1- was obtained. A slurry was obtained by mixing this lanthanum chromite powder and a slurry conditioner in the proportions shown in Table 1.

Solvent Binder Plasticizer Dispersant Defoamer Table 1 Lanthanum Chromite 1500 Tono 112 Isopropanol 3601 (Mixing ratio 1.
2-2:1) Polyvinyl butyral 48Q phthalate di-n
-Butyl 501 nonionic surfactant (0P-83R8T) 13m
1 Mono-p-iso-octylphenyl ether 3m Lanthanum chromite powder and slurry conditioner were mixed in a rotary ball mill for 40 hours, defoamed in vacuum, and the viscosity was adjusted by evaporation of the organic solvent, resulting in a viscosity of 600 Q/C1a.・
It was used as a slurry for the doctor blade method of sec.

For mixing, a ball mill (manufactured by Dekozai Kogyo) with alumina balls and partially stabilized zirconia balls was used, and the raw material slurry was mixed with 1/3 of the volume of the ball mill through balls of different sizes (diameters 0°5 to 2°). .5c*) was the same <1/3, and the remaining 1/3 was a space, taking care to mix the slurry well. The rotation speed of the ball mill is approximately 60 rpm
And so.

(Margins below) λ The lanthanum chromite powder used in Example 1 was mixed with the slurry conditioner shown in Table 2 to obtain a slurry, and the viscosity was adjusted under the same conditions as in Example 1. Don't mix.

First, the lanthanum chromite powder used in Example 1 was mixed with the slurry conditioner shown in Table 3 to obtain a slurry, and the viscosity was adjusted under the same conditions as in Example 1, and the slurry was not mixed.

Table 2 Lanthanum chromite 500 Solvent Toluene + Isopropanol 4401 (mixing ratio 1:2 to 2:1) Binder Polyvinyl butyral 48Q Plasticizer Di-n-butyl phthalate 501 Dispersant Nonionic surfactant (0P-83RAT) 13 l Antifoaming agent
Mono p-iso-octylphenyl ether (blank below) Table 3 Lanthanum Chromite 1500 Solvent Toluene + Isopropanol 300ml (mixing ratio 1:2-2:1) Binder Polyvinyl butyral 53g Plasticizer Di-n-butyl phthalate 55- 1 Dispersant
Nonionic surfactant (OP-83RAT) 15mlml antifoaming non-p-iso-octyl phenyl ether The lanthanum chromite membrane produced by this manufacturing method has excellent flatness and airtightness, and is suitable for use as a solid electrolyte fuel using this lanthanum chromite. It has been found that the battery also has high performance.

The green sheet thus obtained is surrounded on all sides with ceramics such as alumina, and fired under the firing conditions shown in Tables 4 and 5 or under the firing conditions shown in Tables 6 and 7 to obtain a lanthanum chromite film. Ta.

Table 4 (Degreasing conditions) Room temperature to 130°C Temperature increase over 13 hours (temperature increase at 10°C/h or less) 130°C Hold for 13 hours 130 to 370°C Temperature increase over 24 hours (10°C/h
370°C Hold for 4 hours 370°C to room temperature Cool over 10 hours (blank below) Table 5 (Firing conditions) Room temperature to 1100°C Temperature rise over 11 hours (10°C/h
1100℃ Hold for 10 hours 1100-1500℃ Increase temperature over 4 hours (100℃
(Temperature rise at less than /h) 1500°C Hold for 10 hours 1500°C to room temperature Cool for 10 hours The degreasing process and baking process may be performed separately as in this example, but usually they are performed continuously. It will be done.

Table 6 (Degreasing conditions) Room temperature to 110°C Temperature increase over 11 hours (temperature increase at 10°C/h or less) 110°C Hold for 4 hours 110 to 350°C Temperature increase over 24 hours (temperature increase at 10°C/h or less) Temperature) 350'C Hold for 4 hours 350°C to room temperature Cool over 10 hours Table 7 (Firing conditions) Room temperature to 1100°C Increase temperature over 11 hours (100°C/
1100℃ Hold for 10 hours 1100-1500℃ Increase temperature over 4 hours (100℃
/h) 1500°C Hold for 10 hours 1500°C to room temperature 10 hours The cooling experiment used a mixed solution of non-aqueous isopropanol (x) and toluene (y), and the mixing ratio (volume ratio) was x: y=2~1
: 1 to 2, but no difference was found in the green sheets in that region even under the same conditions with other slurry conditioners. The amount of other slurry conditioners such as binders, plasticizers, dispersants, and antifoaming agents should be kept to a minimum;
In the firing process, we found that it was easier to fire the lanthanum chromite doctor blade film flat by surrounding the sample with ceramics such as alumina and not applying heat directly to the sample. The reason for this is that if too much slurry conditioner is added, the sintered body becomes porous, and the ceramic during sintering reacts sensitively to uneven temperatures, making the electrolyte membrane easily distorted.

Furthermore, if the firing conditions for ceramics are such that the rate of temperature rise and fall is fast, cracks or cracks will occur in the unsintered ceramic molded body, resulting in an extremely low yield rate.

Further, unless the temperature is maintained in the temperature range of 1100 to 1300°C for 4 hours or more, preferably 10 hours or more, it is not possible to create a sufficient melt to form the ceramic into a flat and uniform thickness.

Although the firing conditions shown in Tables 4, 5, 6, and 7 are suitable for producing lanthanum chromite doctor blade membranes up to a size of about 8 cm after firing, they are particularly limited to these. It is not a specific condition, but a flat sintered body can be obtained by raising and lowering the temperature to this degree, and there is no problem if the speed is slower than this. It is thought that it is necessary to perform degreasing at a rate of temperature rise and fall.

(Left below) Chestnut White Skin Yu The lanthanum chromite powder obtained in Example 1 was mixed with the slurry conditioner shown in Table 8 to obtain a slurry.

The lanthanum chromite powder obtained in Example 1 was mixed with the slurry conditioner shown in Table 9 to obtain a slurry.

Table 8 Solvent Toluene isopropanol 3601 Binder Polyvinyl butyral 53g Plasticizer Di-n-butyl phthalate 55+1 Dispersant Nonionic surfactant (0P-83R^T) 15111 Antifoaming agent
Mono p-iso-octylphenyl ether Table 9 Solvent Binder Plasticizer Dispersant Defoamer 00g Toluene Isopropanol 30011 Polyvinyl Butyral 48g Di-n-Butyl Phthalate
50IM nonionic surfactant (0P-83R^T) 1311 mono-p-
180-Octyl phenyl ether After mixing the lanthanum chromite powder with the above composition and a slurry conditioner in a rotary ball mill for about 40 hours, 600-octylphenyl ether was prepared by vacuum degassing.
After adjusting the viscosity to approximately g/(2)·sec, a film was formed by a doctor blade method.

The lanthanum chromite powder obtained in Example 1 was mixed with the slurry conditioner shown in Table 10 to obtain a slurry.

Table 10 Solvent Toluene isopropanol 440i Binder Polyvinyl butyral 53g Plasticizer Di-n-butyl phthalate 5511 Dispersant Nonionic surfactant (0P-83R^T) 15m Antifoam agent Mono p-iso-octylphenyl ether film formation The prepared green sheet is surrounded on all sides by ceramics such as alumina and subjected to the conditions in Tables 11 and 12 below, or the conditions in Table 1.
A firing process was performed under the conditions shown in Tables 3 and 14.

(Leaving space below) Table 11 (Degreasing conditions) Room temperature to 110℃ Increase temperature over 11 hours and increase temperature at 10℃/h or less) Hold for 4 hours Temperature increase over 24 hours (temperature increase at 10℃/h or less) 4 Time Hold Cool over 10 hours 110°C 350°C 110-350°C 350°C to room temperature 1st Room temperature to 1300°C 1300°C 1300-1500°C 1500°C 1500°C to room temperature Table 2 (Firing conditions) Increase temperature over 13 hours Hold for 10 hours, raise temperature over 4 hours (rise fA at 100°C/h or less) Hold for 10 hours, cool down over 10 hours (blank below) Table 13 (Degreasing conditions) Room temperature ~130℃ Increase temperature over 13 hours (temperature increase at 10℃/h or less) Hold for 4 hours, increase temperature over 24 hours, increase temperature at 10℃/h or less) Hold for 4 hours, cool down over 10 hours 130℃ 370℃ 130 ~370°C 370°C ~ Room temperature Table 14 (Firing conditions) Room temperature ~ 1300°C Temperature increase over 13 hours (100°C/
Temperature rise at 1300°C io hours (1300-1500°C) Temperature rise over 4 hours (100°C/
From these results, the doctor blade membrane containing the slurry conditioner mentioned above and satisfying the above firing conditions is able to absorb fuel gas and air. It is a dense membrane that does not pass through, has a conductivity equal to or higher than those made by other manufacturing methods, and can be formed flat, so when it is used as an electrolyte in solid electrolyte fuel cells, cross leakage in the electrolyte is prevented. It can be seen that there is no lag and the output current density exhibits better characteristics than the conventional product.

(Effects of the Invention) As is clear from the above description, according to the present invention, a flat lanthanum chromite film without warping can be formed by the doctor blade method. Furthermore, since the present invention utilizes the fact that a molten material is formed for firing, a flat lanthanum chromite film with excellent airtightness can be fired only once at a relatively low temperature in a short time and at low cost. Can be manufactured.

Therefore, it will greatly contribute to the realization of solid electrolyte fuel cells and other high-temperature operating bodies of lanthanum chromite conductive ceramics.

In addition, this lanthanum chromite membrane has excellent airtightness and high electrical conductivity, so it can be applied to a variety of applications that require operation at high temperatures, such as when used as a separator, interconnector, and gas diffuser for solid electrolyte fuel cells. Solid electrolyte fuel cells using these materials are highly practical.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing an example of a flat solid electrolyte fuel cell. FIG. 2 is an enlarged perspective view schematically showing another embodiment of the flat solid electrolyte fuel cell. FIG. 3 is a perspective view showing an example of a cylindrical solid electrolyte fuel cell. FIG. 4 is an electron micrograph showing the structure of calcium-doped lanthanum chromite of the present invention. Figure 1 ↑ 4...Separator, 12.13...Gas diffuser, 24...Interconnector. Patent applicant: Central Research Institute of Electric Power Industry, Institute of Industrial Technology

Claims (9)

[Claims] (1) La_(_1_-_x_) Ca_(_x_+_y
_)Cr_(_1_-_y_)O_3 However, 0<x≦0
．． 4 0<y≦0.05 y≦x For each 500 g of calcium-doped lanthanum chromite powder, 280 to 460 ml of solvent and 45 ml of binder
~53g, plasticizer 45-55ml, dispersant 13-18ml
Add 13-18 ml of antifoam and 500-700 g
A method for producing a calcium-doped lanthanum chromite film, comprising forming the film by a doctor blade method using a slurry adjusted to a viscosity of /cm/sec. (2) A mixed solution of toluene and isopropanol with a volume ratio of 1:2 to 2:1 as the solvent, polyvinyl butyral as the binder, and di-n-phthalate as the plasticizer.
The method for producing a calcium-doped lanthanum chromite membrane according to claim 1, characterized in that butyl is used as a dispersant, a nonionic surfactant is used as a dispersant, and mono-p-isooctylphenyl ether is used as an antifoaming agent. (3) In the process of firing the unfired calcium-doped lanthanum chromite film formed into the desired shape,
A method for firing a calcium-doped lanthanum chromite film, characterized by holding the film in a temperature range of ~1300°C for 4 hours or more. (4) The unfired calcium-doped lanthanum chromite film obtained by the manufacturing method according to claim 1 is heated from room temperature to 12
Raise the temperature at a temperature increase rate of 20 ° C / h or less until it reaches a temperature range of 0 ° C, and hold it in a temperature range of 110 to 130 ° C for 2 hours or more,
20 to reach the temperature range from 120℃ to 360℃
Raise the temperature at a temperature increase rate of ℃/h or less, hold in the temperature range of 350 to 370℃ for 2 hours or more, and then raise the temperature to 1100 to 1300℃
A method for firing a calcium-doped lanthanum chromite film, characterized in that the firing is performed under heating conditions of holding the film in a temperature range of 1300° C. or higher for 4 hours or more, and further holding it in a temperature range of 1300° C. or higher for 4 hours or more. (5) A method for firing a calcium-doped lanthanum chromite film according to claim 3 or 4, characterized in that the unfired calcium-doped lanthanum chromite film is surrounded by ceramics and is not directly exposed to heat. (6) A calcium-doped lanthanum chromite-based conductive ceramic, which is fired by the firing method according to any one of claims 3 to 5. (7) A solid electrolyte fuel cell characterized in that the calcium-doped lanthanum chromite-based conductive ceramic membrane according to claim 6 is used as a separator. (8) A solid electrolyte fuel cell characterized in that the calcium-doped lanthanum chromite-based conductive ceramic membrane according to claim 6 is used as an interconnector. (9) A solid electrolyte fuel cell characterized in that the calcium-doped lanthanum chromite-based conductive ceramic membrane according to claim 6 is used as a gas diffuser.