JPH0437646A - Production of zirconia ceramics film and its calcination method as well as zirconia conductive ceramics produced by this method and solid electrolyte fuel battery utilizing this ceramics - Google Patents

Abstract

PURPOSE:To prevent warpage and crazing and to improve airtightness and electric conductivity by making a slurry contg. (partially) stabilized zirconia, solvent, binder, plasticizer, dispersant, and defoaming agent into a film by a doctor blade method. CONSTITUTION:The slurry having 500 to 700g/cm.sec viscosity is obtd. by mixing 500g (partially) stabilized zirconia having 200 to 300Angstrom primary particle size, 270 to 440ml solvent mixture composed of toluene and isopropanol at 1.2 to 2.1 volumetric ratio, 47 to 50g polyvinyl butyral as a binder, 47 to 50ml phthalic acid-n-butyl ester as plasticizer, 8 to 12ml nonionic surfactant as the dispersant, and 8 to 12ml defoaming agent (e.g.: mono-p-isooctyl phenyl ether). After this slurry is made into the film by the doctor blade method, the film is heated up at <=20 deg.C/h heating up rate from room temp. to 120 deg.C, is held at 110 to 130 deg.C for >=2 hours, is heated up at 120 to 360 deg.C with <=20 deg.C/h heating up rate, is held at 350 to 370 deg.C for >=2 hours, is heated up to 1000 to 1300 deg.C at <=70 deg.C/h heating up rate, and is calcined for >=4 hours at >=1500 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is directed to the use of yttoria (Y2O3), calcia (C
ab), a method for producing a zirconia (Zr02)-based ceramic film stabilized or partially stabilized with a number of stabilizers such as magnesia (MgO), a firing method thereof, and a zirconia-based conductive ceramic obtained by this firing method; This invention relates to a solid electrolyte fuel cell using the same.

(Prior art) Zirconia stabilized with various stabilizers is chemically stable in oxidizing and reducing atmospheres, has almost no electron conduction, and has high oxygen ion conductivity at high temperatures. Therefore, it is used in electrolytes of solid electrolyte fuel cells, oxygen sensors, electric furnace heaters, etc.

For example, in solid electrolyte fuel cells, it is used as an electrolyte membrane that separates fuel gas and air. Research has been conducted on two types of solid electrolyte fuel cells: a cylindrical type and a flat plate type, but the research and development of the cylindrical type, which has a lower output density per unit volume but has higher mechanical strength, has taken precedence. There is.

In this cylindrical solid electrolyte fuel cell, the lanthanum manganite air electrode material is deactivated at high temperatures of 1400°C or higher, so the zirconia electrolyte membrane is
It is manufactured using the electrogemical vapor deposition (EVD) method, which allows for airtight sintering at low temperatures below .degree.

On the other hand, under these circumstances, research and development on the flat plate type, which is expected to have higher output density, has been conducted in recent years. The solid electrolyte of the zirconia membrane used in this flat plate solid electrolyte fuel cell is airtight so that the fuel gas and oxidizer gas do not mix, and it is manufactured using other methods such as mold pressure molding. It is necessary that the film has a conductivity comparable to that of the film and is flat so that it can be easily bonded to other battery constituent materials. In addition, taking into account our experience in the development of cylindrical solid electrolyte fuel cells, we are developing zirconia ceramic 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 desired that this method be made possible.

The doctor blade method is a common manufacturing method that can produce a thin film similar to that of a solid electrolyte at low cost without the need for special equipment. The ceramic membrane was warped and the electrolyte surface was uneven. Therefore, taking advantage of the fact that zirconia has plasticity at high temperatures, after firing, heavy weights were sequentially placed on the zirconia ceramic membrane depending on the degree of warpage of the zirconia, and the temperature was raised to a temperature of 1400 to 1600℃. By repeating this process, it was made flat.

(Problems to be Solved by the Invention) However, the adoption of the EVD film formation method is difficult to implement in solid electrolyte fuel cells due to the slow film formation rate and the need to use expensive chlorine gas as a starting material. making it even more difficult.

In addition, in the conventional manufacturing method of zirconia ceramic membranes using the doctor blade method, it is necessary to raise the temperature to high temperatures many times depending on the degree of warpage of the membrane, and the warpage is not properly corrected, resulting in a flat electrolyte membrane. I want to be loved, and I want to be raised further.
The defective product rate was high because the membrane broke or cracked each time the temperature dropped.

Therefore, when producing a zirconia-based ceramic film using the doctor blade method, there is a need for a method that does not involve the process of placing a weight on it and raising and lowering the temperature, but instead allows the film to be made airtight and flat by only -degree firing.

An object of the present invention is to provide a method for producing zirconia-based ceramics by a doctor blade method in the form of a conductive, airtight, and flat film in a single firing process, and a method for firing the film.

Another object of the present invention is to provide a low-cost, high-yield zirconia-based conductive ceramic and a solid electrolyte fuel cell.

(Means for Solving the Problems) In order to achieve the above object, the method for producing a zirconia-based ceramic film of the present invention is to provide a method for producing a zirconia-based ceramic film in which 500 g of stabilized zirconia or partially stabilized zirconia having a primary particle size of about 200 Å to 300 ! 270~440ml, binder 47~
50g, add plasticizer 47-50ml, dispersant 8-1211 and antifoaming agent 8-121, 500-700g/■・S
The film is formed by a doctor blade method using a slurry whose viscosity is adjusted to about EC.

In addition, in the case of a riconic ceramic powder with a primary particle diameter of 500 Å to 600, the particle size is 200 Å to 300, except that the binder is in the range of 44 to 47 g and the plasticizer is in the range of 32 to 3511.
The condition ii can be obtained by making it the same as the case of the human primary particle size.

Furthermore, the present invention provides a doctor blade film made of a slurry using zirconia ceramic powder with a primary particle size of 200 Å to 300 particles obtained by the above-mentioned manufacturing method, and heated at 20°C/h until the temperature ranges from room temperature to 120°C. Below, the temperature is preferably increased at a rate of 10°C/h or less, and the temperature is increased to 110 to 13
Hold in a temperature range of 0"C for 2 hours or more, preferably 4 hours or more, and raise the temperature at a rate of 20°C/h or less, preferably 10°C/h, until the temperature ranges from 120°C to 360°C. and held in a temperature range of 350 to 370'C for 2 hours or more, preferably 4 hours or more, and then maintained at a temperature of 70°C/h or less, preferably 50"IC in a temperature range of 900 to 1300°C.
The temperature was increased at a temperature increase rate of less than /h, and further 13
The firing is performed under heating conditions in which the temperature is maintained at a temperature of 00° C. or higher for 4 hours or more, preferably 10 hours or more.

In addition, a doctor blade film consisting of the slurry obtained by the above-mentioned manufacturing method using zirconia ceramic powder with a primary particle size of 500 Å to 600 Å was heated from room temperature to 12 Å.
Up to 20℃/h or less until the temperature reaches 0℃
``C,'h or less temperature increase rate, 110-130℃
2 hours or more preferably 4 hours or more at a temperature range of 1
20℃ from 20℃ to 360℃
/h or less, preferably at a temperature increase rate of 10°C/h or less, and in a temperature range of 350 to 370°C for 2 hours or more, preferably 4
The temperature is maintained at a temperature of 1000 to 1300°C for at least 70°C/h or less, or 50°C/h or less, and the temperature is further increased to 1500°C.
The firing is performed under heating conditions in which the temperature is maintained in the above temperature range for 4 hours or more, preferably 10 hours or more.

Furthermore, in the production of the zirconia-based ceramic membrane of the present invention, the doctor blade membrane is surrounded by ceramics in the above-mentioned firing step so that it is not exposed to direct heat.

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

Further, the solid electrolyte fuel cell of the present invention is characterized in that the above-described zirconia membrane is used as an electrolyte.

In addition, the "viscosity" mentioned in this specification is a value measured at room temperature using a simple rotational viscometer.

Here, the size of the zirconia ceramic powder is small and its distribution is uniform, and since it is easier to sinter densely at a low temperature if the shape is as spherical as possible, the -order particle size is 200 Å. The use of ~600 people is preferred. Zirconia ceramic powders with these particle sizes are manufactured by Van der Waalska (Van der Waalska).
Regardless of the primary particle diameter, the size of the secondary particles agglomerated by the ALS force is about 1.5 to 8.04, and there is no significant difference in the properties of the zirconia ceramic membrane as a solid electrolyte.

In addition, as a stabilizer for zirconia, it depends on the use of the zirconia film, but for example, it can be added as long as it has compatibility and stability with the electrode material, and generally magnesia (MgO), Calcia (Cab), Ittria (
Y203) etc. are adopted, and Y2O3 is preferably adopted from the viewpoint of conductivity and price.

In addition, 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 isopropanol and toluene in a ratio of about 2 to 2:1 is preferred, and the amount added is in the range of 270 to 440 ml, more preferably 300 to 400 ml.

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. , and the amount added is 47 to 50 g when using zirconia ceramic powder with a primary particle size of 200 Å to 300 Å;
When using a zirconia ceramic powder with a thickness of 0 Å to 600 Å, the amount is in the range of 44 to 47 g. If the amount of binder in the winter rally 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 a wetting effect to the zirconia powder (contributing to the dispersibility and lubricity of raw material particles), a substitute effect for the binder, and a plasticizing effect to the dry sheet. However, among these, di-n-butyl phthalate is particularly preferred, and the amount added is 47 to 501 ml when using zirconia ceramic powder with a primary particle size of 200 Å to 300 Å, while the amount added is 47 to 501 ml, while the amount is 47 to 501 ml when the primary particle size is 500 Å to 300 Å. When using zirconia ceramic powder of 600 people, it is in the range of 32 to 351.

As the dispersant, a nonionic surfactant is used, and the amount used is about 8 to 121. With this dispersant, van der
Prevents agglomeration due to WARSCA and improves dispersibility, increasing the packing density of zirconia particles in the green sheet.

The antifoaming agent is not particularly limited, but is preferably mono-p-isooctylphenyl ether,
The amount used ranges from 8 to 121.

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 the green sheet can be easily sintered in a flat and airtight manner.If the amount of the slurry conditioner is large, the formability of the green sheet is improved, but if it is too large, the sintered body becomes porous. However, 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 slurry, which has been adjusted to a desired viscosity by adding a slurry conditioner in the above-mentioned mixing ratio, is formed into a flat sheet having a desired thickness when passing through a blade called a doctor blade of a doctor blade device. In the temperature range from room temperature to 120°C, part of the organic solvent evaporates by heating at a rate of 20°C/h or less, preferably 10°C/h or less. In the temperature range of ~130° C., by maintaining the temperature for 2 hours or more, preferably 4 hours or more without raising the temperature, the organic solvent is gradually stabilized and volatilized, thereby preventing the generation of pores due to gasification of the solvent. Next, in the temperature range from 120°C to 360°C, the rate is 20°C/h or less, preferably 1
Some of the slurry conditioner burns when the temperature is raised at a rate of 0"C/h or less, and while the temperature is maintained in the 350-370°C temperature range for more than 4 hours without raising the temperature. The slurry conditioner is stably combusted.Then, the temperature is further raised, but in the case of using ceramic raw materials with a primary particle size of 200 Å to 300, the temperature range is 900 to 1300''C; When using human ceramic raw materials, the temperature range of 1000 to 1500"C is a region that shows rapid contraction with respect to temperature, so ceramics can be made by heating at a rate of 70°C/h or less, preferably 50°C/h or less. It makes the temperature of the molded body uniform and suppresses the occurrence of distortion.
When using ceramic raw materials with -order particle size of 200 Å to 300 people, the temperature is 1300℃ or higher, and -order particle size of 500 Å is used.
15 when using Å~600 ceramic raw materials
The temperature is maintained at 00° C. or higher for 4 hours or more, preferably 10 hours or more to achieve dense firing.

(Actual Rejection) Next, the configuration of the present invention will be explained in detail based on embodiments shown in the drawings.

Zirconia membranes are produced by preparing a highly viscous slurry (slurry) in which zirconia ceramic powder is suspended in a solvent containing functional additives such as plasticizers, binders, and antifoaming agents, and then using the doctor blade method. It is obtained by forming a film into a green sheet of uniform thickness and then firing it.

To prepare the slurry used in the doctor blade method, the ceramic raw material must be approximately 200 Å or more.
A binder pre-dissolved in a solvent is added to a zirconia ceramic powder having a primary particle size of 600 mm. 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 step, the slurry is adjusted to a desired viscosity by vacuum defoaming.

The slurry having the desired composition and viscosity thus adjusted is then formed into a green sheet (a dense and flexible tape with a polymeric compound as a binder) of the desired thickness in a doctor blade machine. be done. 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 is carried inside the doctor blade device by riding on the conveyor tape. While moving, 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. In addition, as a doctor blade device,
It is desirable to have a two-stage doctor, in which the slurry cast by the first stage blade is finished to a more precise film thickness using the second stage blade. The green sheet thus obtained is then sintered under constant firing conditions to obtain a desired zirconia ceramic film.

The zirconia-based ceramic membrane thus obtained is airtight and flat, as described below, and is therefore suitable for various fields, such as electrolytes in solid electrolyte fuel cells, oxygen sensors, electric furnace heaters, etc. It is particularly suitable as an electrolyte for flat plate solid electrolyte fuel cells. FIG. 1 shows an example of the configuration of this flat plate type solid electrolyte fuel cell in an exploded perspective view.The solid electrolyte fuel cell consists of flat unit cells 1 and separators 4 stacked alternately with spacers 2.
Combustion gas and air are supplied to an air supply space 5 and a combustion gas supply space 6 formed by the unit cell 1 and the separator 4 via a fuel gas supply pipe 8 and an air supply vibrator 7, 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 zirconia ceramic membrane according to the present invention is used as an electrolyte in such a solid electrolyte fuel cell.

Zirconia membrane suitable as a solid electrolyte is Ittria (
Y203) as a stabilizer, 8-12no
When it contains about 1% Y203, it is chemically stable near the operating temperature of solid electrolyte fuel cells (about 1000° C.). Therefore, as the zirconia powder, stabilized zirconia containing 8101% of ittria as a solid solution, such as Tosoh Corporation's trade names: Tl-8Y and TZ-8YS, was used. TZ-
8Y and TZ-8YS have different primary particle sizes, and TZ
-8Y approximately 200-300 people, TZ-8YS approximately 500 people
~600 people. -Secondary particles or secondary particles agglomerated by van Chil-Walska are approximately 1.5
~8.0 μm. These powders are manufactured by a spray drying method, which produces zirconia powder with fewer impurities than Ike's manufacturing method (co-precipitation method, etc.). The following slurry conditioner is mixed with this zirconia powder.

As a dispersion medium or solvent, non-aqueous isopropanol (
Katayama Chemical Co., Ltd., - grade) and toluene (Katayama Chemical Co., Ltd.,
A mixed solution of 270 to 440 (II + preferably 300 to 400 ml) is used per 500 g of zirconia powder.

As the binder, polyvinyl butyral (5-LEC, BM-1, manufactured by Block Chemical Industry Co., Ltd.) was used. This binder has a primary particle size of 47 to 50 g for 200 to 300 people, -
It is preferable to use 44 to 47 g for secondary particle systems with 500 to 600 people.

As the plasticizer, di-n-butyl phthalate (-grade, manufactured by Nacalai Tesque Co., Ltd.) was used. This plasticizer has a primary particle size of 2
It is preferable to use 47 to 50 ml for 00 to 300 people, and 32 to 35 ml for 500 to 600 people.

The dispersant (surfactant) is Nonionic Surfactant (Co., Ltd.)
Nippon Oil & Fats, fish oil, OP-83RAT> were used. It is preferable to use 8 to 12 ml of this dispersant per 500 g of zirconia powder.

The antifoaming agent was mono p-iso-octylphenyl ether (Nacalai Tesque Co., Ltd., Triton X-10).
0, application-specific characteristic reagent) was used. It is preferable to use 8 to 12 oool of this antifoaming agent per 500 g of zirconia powder.

Table 1 T7-8Y1500 Solvent Toluene 180m Isopropanol 180m Binder Polyvinyl butyral 50 (1) Plasticizer Di-n-butyl phthalate 501B Dispersant Nonionic surfactant (0P-83RAT) 10 TD antifoaming agent
500 g of zirconia powder over 1 year old and a slurry conditioner are mixed in the proportions shown in Table 1 to obtain a slurry. The zirconia powder used in this example was TZ-8Y with a primary particle diameter of 277 mm.

(Left below) After mixing the zirconia powder and slurry conditioner in a rotary ball mill for 40 hours, vacuum defoaming and viscosity adjustment by evaporation of the organic solvent were performed to create a slurry with a viscosity of 600 g/sec for use in the doctor blade method. did. The experiment was carried out using a ball mill (manufactured by Tetsuzai Kogyo Co., Ltd.) or a ball mill made of alumina (<Al203) with partially stabilized zirconia-based holes, and the raw material slurry was mixed into 1/3 of the volume of the ball mill using balls of different sizes with a diameter of 0.5 mm. 5~2.5■) same <1/3, remaining 1
/3 was used as a space to ensure that the slurry was well mixed. The rotation speed of the ball mill was approximately 60 revolutions/city.

The doctor blade slurry thus obtained was fired under the following conditions to obtain a zirconia film.

Table 2 (Degreasing conditions) Room temperature (20°C) to 120°C, temperature raised over 110 hours (
Temperature increase at 10℃/h or less) 120℃, held for 4 hours 120-360℃, temperature increase over 10 hours (
Temperature increase at 10℃/h or less) Hold at 360℃ for 14 hours 360℃ to room temperature, cool over 5 hours (blank below) Table 3 (Firing conditions) Room temperature to 800℃ Heat up to 100℃ over 8 hours
/h or less) 800-1300°C Temperature raised over 10 hours (50'C/h or less)
(Temperature rise below h) 1300°C Hold for 4 hours 1300°C to room temperature 5 hours Cooling surface, degreasing process and baking process may be performed separately as in this example, but usually they are performed continuously. .

The experiment was conducted using non-aqueous isopropanol (x) and toluene (x).
Using a mixed solution of y), the mixing ratio (volume ratio) is x:y
= 2 to 1: 1 to 2, but no difference was found in the green sheets in that region even when other slurry conditioners were used under the same conditions. The amount of binders, plasticizers, dispersants, and antifoaming agents used in other slurry conditioners should be kept to a minimum, and in the firing process, the sample should be surrounded by ceramics such as alumina so that direct heat is not applied to the sample. We discovered that it is easy to fire a zirconia-based ceramic doctor blade film flat. The reason for this is that if too much slurry conditioner is used, the sintered body becomes porous, and the ceramics during sintering reacts sensitively to uneven temperatures, making the electrolyte membrane easily distorted.

If the rate of temperature rise and temperature drop during degreasing of a ceramic molded body is fast, cracks or cracks will occur in the unsintered ceramic molded body, resulting in an extremely low yield rate. The temperature increase/decrease rates shown in Tables 2 and 3 are not optimal, and a zirconia ceramic doctor blade film up to a size of about 8 mm after firing can be flattened with this temperature increase/decrease. These are the conditions for obtaining a sintered body, and there is no problem at all if the speed is slower than this. Also, when firing larger molded products,
It is considered necessary to perform degreasing at a slower rate of temperature rise and fall.

The zirconia molded body is fired in the low sintering temperature range (approximately 360
℃ or less), the heating rate is 100℃/h, and the high sintering temperature region (
(approximately 800° C. or higher), the temperature is raised to a temperature at which dense sintering is achieved at a rate of 50° C./h or lower, and held at that temperature for about 4 to 5 hours. - There were no problems even when the temperature drop rate of the pre-sintered film was about 300°C/h.

1 Self-discharge λ Table 2 shows the particle size of the primary particles as zirconia powder.
An example using five TZ-8YS is shown.

Table 4 Solvent Binder Plasticizer Dispersant Antifoamer IV-8Y1500 Toluene 1801 Isopropanol 1801 Polyvinyl Butyral 47.5g Di-n Phthalate
-Butyl 351 nonionic surfactant (0P-83RAT) 10 n mono-p-
1sO-octylphenyl ether 1.01 After mixing the zirconia powder with the above composition and a slurry conditioner in a rotary ball mill for about 40 hours, and adjusting the viscosity to about 600 Q/>・sec by vacuum degassing,
The film was formed by the doctor blade method.

The formed green sheets were surrounded on all sides by ceramics such as alumina and subjected to a firing process under the conditions shown in Tables 5 and 6 below.

Table 5 (Degreasing conditions) Room temperature to 100℃, temperature raised over 10 hours (10℃/
Temperature rise below h) 100-120℃, hold for 4 hours 120-360℃
°C Increase temperature over 124 hours (temperature increase at 10 °C/h or less) 360 °C, hold for 4 hours 360 °C to room temperature, cool over 5 hours (blank below) Table 6 (Firing conditions) Room temperature to 1200 °C, 12 Temperature increase over time (100℃/h or less) 1200-1500℃, Temperature increase over 6 hours (50℃/hour or less)
(Temperature rise below h) 1500℃, held for 5 hours Cooled from 1500℃ to room temperature for 5 hours Zirconia membranes produced by this manufacturing method have better conductivity than those produced by mold molding, and have excellent airtightness. Director 6M discovered that solid electrolyte fuel cells using this zirconia membrane also have high performance! The shrinkage rate of the doctor blade film is influenced by the initial slurry preparation conditions and the size and shape of the primary particles of the raw material. Therefore, unless the conditions (temperature, time) for precisely sintering the doctor blade film are determined, it is not only difficult to produce a compact with high dimensional accuracy, but also the conditions for cell production cannot be determined.

Therefore, using zirconia (TZ-8Y, TZ-8YS manufactured by Tosoh) having different sizes of primary particles, the relationship between the size of the primary particles and the sintering temperature was investigated by measuring the shrinkage rate. Sinterability was determined by preparing a doctor blade film under the conditions described above, holding it at each temperature from 500 to 1500°C for 10 hours at a heating rate of 100°C/h, and then decreasing it to room temperature at a cooling rate of 100°C/h. It was cooled, and the change in volume was taken as the shrinkage rate.

FIG. 2 shows the results of shrinkage rate measurements of the zirconia doctor blade films of TZ-8Y and TZ-8YS.

It can be seen that TZ-8Y, which has smaller secondary particles, is sintered more densely at a lower temperature. Sintering of TZ-8Y is 90
It starts at 0℃, rapidly increases from 1100℃ to 1200'C, and is densely sintered (relative density 94% or more) under the conditions of holding at 1300''C for 210 hours.However, T
Z-8YS is sintered at 1100℃ because the secondary particles are large.
It was found that sintering was still progressing at 1300'C, starting from 1500°C, and almost dense sintering occurred at 1500°C and 10 o'clock opening (relative density of 94% or more). From this, in order to produce a dense electrolyte membrane, TZ-8Y is heated at 1000°C for at least 4 hours, preferably for 10 hours.
It has become clear that conditions are required in which YS is held at 1500° C. for at least 4 hours, preferably 10 hours. Here, the inventors have found through experiments that the certain period of time to be maintained should be at least 4 hours or more.

If the zirconia-based ceramic film is not a completely dense sintered body, cross leakage will occur and the combustion scum and oxidizing gas will burn directly at 1000°C, resulting in a decrease in electromotive force and local high temperatures. It is expected that cell destruction will occur due to thermal stress caused by the generation of portions, and that the conductivity of the stabilized or partially stabilized zirconia will decrease due to the low relative density. Therefore, the gas permeability of a zirconia-based ceramic doctor blade film sintered with a relative density of 94% or more was measured. This scum permeability measurement is a type of pressure method, in which one side of the membrane being measured is kept in a vacuum and a constant scum pressure is applied to the other side, resulting in a low pressure example due to the scum passing through the membrane due to the pressure difference. This method detects the pressure rise with a pressure transducer and determines the transmittance.

With this device, it is difficult to measure in the temperature range of 200°C or higher, so the operating temperature of the solid electrolyte fuel cell (approximately 1000°C
) it is not possible to determine the gas permeability of the zirconia ceramic nx membrane. However, if a zirconia-based ceramic membrane allows gas to permeate even at room temperature, the molecular motion in the gas state will be intense and the viscosity of the gas will increase100
At 0° C., the zirconia-based ceramic membrane should allow gas to pass through it more easily. Therefore, it is essential that the membrane is impermeable to gas at room temperature, and it is important to measure the gas permeability at room temperature. In order to predict the gas permeability at 1000°C, measurements were made at room temperature of 200°C under more severe conditions (vacuum on one side, hydrogen gas injected on the other side, and detected by gas chromatography).

The scum transmittance of each zirconia ceramic doctor blade film (relative density of 94% or more) with a film thickness of 0.1 mm, 0.2 nm, and 0.3 mm is 3.0 × 10-" to 10-"
m2/Pa-s. For general gases, the gas permeability of the V membrane is 75x1. O-” ~10-
”~2/Pa-s, it can be said that the zirconia-based ceramic doctor blade membrane does not allow hydrogen and oxygen to pass through at all in an industrial sense. The measurement results of the gas permeability of the zirconia electrolyte produced by the plasma spraying method used in the production will be compared with the product of the present invention.

Table 7 Zirconia Ceramic Film Forming Method Doctor Blade Method Low Pressure Plasma Spraying Normal Pressure Plasma Spraying Gas Permeability (rrl'/Pax5 3, OX1O-1s~10-+6 Approx. 1.2 X10-' Approx. 1.1 X1O -10 When comparing normal pressure plasma spraying and low pressure plasma spraying, it has been reported that low pressure plasma spraying has lower gas permeability, improved density, and improved cell voltage. When comparing the gas permeability of the zirconia ceramic membrane produced by the doctor blade method of the present invention, it can be seen that the latter is four orders of magnitude lower.From this result, the doctor blade method is superior to other membrane fabrication methods. It has become clear that a denser zirconia film can be produced using this method.

Prefecture 1' [1] Conductivity measurement was performed by applying platinum paste (manufactured by Tanaka Massey, TR7905) on both sides of a zirconia ceramic doctor blade film fired at 1500°C for 54 hours.
Baked at 00°C for 11 hours and measured in air by AC impedance method.

The results of measuring the electrical conductivity of the zirconia ceramic doctor blade film (relative density of 94% or more) are shown in FIG. Zirconia has electrical conductivity at high temperatures (approximately 600°C or higher)
The area does not depend much on the particle size of the sample, but varies greatly due to differences in relative density due to the amount of stabilizer substituted, impurities, and firing temperature, as described above. However, the zirconia-based ceramic film produced by the method of the present invention exhibits almost the same electrical conductivity as the electrical conductivity of the zirconia pellet formed by mold pressure molding. The zirconia ceramic raw material used for this doctor blade film has high purity and the amount of stabilizer is constant, so the zirconia film formed by the doctor blade method and sintered at an appropriate temperature can be processed by mold processing. It is thought that it is not as dense as pressure molding.

Furthermore, the conductivity curve of this doctor blade film also has a bending point (change in activation energy) similar to mold pressure molding. This phenomenon is caused by oxygen ions (0'-) in zirconia.
It is thought that this is not due to a change in the conductive mechanism of the membrane, but is due to the measurable fat. In other words, the influence of the inductance caused by the energized platinum lead wire appears strongly in the high temperature region where the resistance of zirconia is low, and the inductance cannot be separated from the resistance of zirconia, and the actual resistance of zirconia is measured to be higher, so the conductivity Possible causes include the fact that the conductivity curve is curved due to a low value of conductivity, and that the temperature measurement is not perfect.

Cell 2. The single cell used in the power generation test had Nyragel zirconia cermet (Ni-ZrO2:40vo1%N) as a fuel electrode on one side of the zirconia-based ceramic doctor blade membrane.
i, 1400°C, 4 hours calcining) was applied by slurry coating method, and heated at 1500°C in air.
After baking for 2 hours, lanthanum manganite [(L ao7S r o
, s) o, e+M
C. Burning was made under the conditions of 4 hours. The size of the single cell is that the solid electrolyte size is 1.5C1φ, and the N size is 180 l.
lff1, effective electrode area 0゜30c&(0,6cz
φ). Single cell power generation test is fuel'! Hydrogen was flowed through fllP1 and air was flowed toward the air electrode side, and the temperature was 1000°C. At that time, seal only the fuel electrode side with Pyrex glass,
Current was collected using a platinum mesh.

The current-voltage characteristics of the obtained single cell after being sufficiently energized at 1.5 A/dl are shown in FIG. From this experiment,
A current density of 1.5 A/cj, a cell voltage of 049 V, and a power density of 0.74 W/- were obtained. This value is a current density of 300mA
/cJ, cell voltage 0.57V, output density 0. ]7W・′
When compared with a vertically assembled cylindrical solid electrolyte fuel cell (manufactured by Westinghouse, USA), it can be seen that the performance is already more than four times superior.

The breakdown of the voltage drop due to the resistance of each cell component material regarding this internal resistance was determined by the DC polarization method at a current density of 1.5A/c.
At time j, fuel electrode overvoltage 220 mV, air electrode overvoltage 44
I found out that it was mV.

These values include the voltage drop due to the resistance of each electrode, but the voltage drop due to the resistance of each electrode is so small that it cannot be separated individually. However, when comparing the electrical resistance with zirconia, the resistance is 1/100
~1/1000, and the thickness is 1/2~1~5, so
Assuming that the electrical resistance of each electrode can be ignored, FIG. 4 shows the voltage drop of the electrolyte, and the rest is the overvoltage of each electrode.

From these results, it was found that the doctor blade membrane that contains the slurry conditioner and satisfies the firing conditions described above is a dense membrane that does not allow fuel gas or air to pass through, and has a high conductivity even if it is manufactured using other manufacturing methods. , and can be formed flat, so when used as an electrolyte in solid electrolyte fuel cells, there is no cross leakage in the electrolyte and the output current density is about four times better than conventional products. I can understand that.

(Effects of the Invention) As is clear from the above explanation, when the green sheet obtained by the doctor blade method using the slurry of the present invention is fired by the firing method of the present invention, it becomes airtight and collapses.
A flat stabilized or partially stabilized zirconia film with high conductivity can be produced in a short time and at low cost by firing only once. Moreover, the stabilized or partially stabilized zirconia film obtained by the production method of the present invention has excellent airtightness, high conductivity, and is flat, so it can be applied to various applications that require operation at high temperatures, such as solid Suitable for use as an electrolyte in electrolyte fuel cells.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing an example of a flat solid electrolyte fuel cell. Figure 2 shows TZ-8Y of Example 1 and TZ-8Y of Example 2.
It is a graph showing a comparison of shrinkage rate with S. FIG. 3 is a graph showing the temperature dependence of the electrical conductivity of the stabilized zirconia film of Example 1. FIG. 4 shows the power generation characteristic of a single cell using a stabilized silicone membrane as an electrolyte, indicated by the solid line tJ1. 9... Electrolyte. Patent applicant Director of the Institute of Industrial Technology Patent issuer
Representative of the Central Research Institute of Electric Power Industry Patent Attorney Murase -mi! Figure ↑ Temperature ('C)

Claims (9)

[Claims] (1) Per 500 g of stabilized zirconia or partially stabilized zirconia having a primary particle diameter of approximately 200 Å to 300 Å, 270 to 440 ml of solvent, 47 to 50 g of binder, 47 to 50 ml of plasticizer, 8 to 12 ml of dispersant, and antifoaming agent. 8~
1. A method for producing a zirconia ceramic film, which comprises forming a film by a doctor blade method using a slurry having a viscosity of 500 to 700 g/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.
2. The method for producing a zirconia ceramic membrane according to claim 1, wherein 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) Per 500 g of stabilized zirconia or partially stabilized zirconia with a primary particle diameter of about 500 Å to 600 Å, 270 to 440 ml of solvent, 44 to 47 g of binder, 32 to 35 ml of plasticizer, 8 to 12 ml of dispersant, and antifoaming agent. 8~
1. A method for producing a zirconia ceramic film, which comprises forming a film by a doctor blast method using a slurry having a viscosity of 500 to 700 g/cm·sec. (4) A mixed solution of toluene and isopropanol with a volume ratio of 1:2 to 2:1 is used as a solvent, polyvinyl butyral is used as a binder, and phthalic acid di-n-
4. The method for producing a zirconia ceramic membrane according to claim 3, wherein 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. (5) The doctor blade film obtained by the manufacturing method according to claim 1 or 2 is heated at a temperature increase rate of 20°C/h or less until it reaches a temperature range of 120°C from room temperature.
Hold in a temperature range of 30°C for 2 hours or more, raise the temperature at a rate of 20°C/h or less until it reaches a temperature range of 120°C to 360°C, and maintain it in a temperature range of 350 to 370°C for 2 hours. After that, in the temperature range of 900 to 1300°C, the temperature was raised at a rate of 70°C/h or less, and then fired under heating conditions where it was held in the temperature range of 1300°C or more for 4 hours or more. A method for firing a zirconia ceramic film, which is characterized by: (6) The doctor blade film obtained by the manufacturing method according to claim 3 or 4 is heated at a rate of 20°C/h or less from room temperature to a temperature range of 120°C.
Hold in a temperature range of 30°C for 2 hours or more, raise the temperature at a rate of 20°C/h or less until it reaches a temperature range of 120°C to 360°C, and maintain it in a temperature range of 350 to 370°C for 2 hours. After that, in the temperature range of 1000 to 1300°C, the temperature is raised at a rate of 70°C/h or less,
A method for firing a zirconia-based ceramic film, further comprising firing under heating conditions of holding the film in a temperature range of 1500° C. or more for 4 hours or more. (7) A method for firing a zirconia ceramic film according to claim 5 or 6, wherein the doctor blade film is surrounded by ceramics and is not directly exposed to heat. (8) A zirconia-based conductive ceramic fired according to claim 5 or 6. (9) A solid electrolyte fuel cell characterized in that the fired zirconia ceramic membrane according to claim 5 or 6 is used as an electrolyte.