JPH0741360A - Production of beta"-alumina powder and beta"-alumina - Google Patents

Abstract

PURPOSE:To easily enhance the reliability and improve heat conductivity by pulverizing heat-treated products each having a specific X-ray diffraction pattern. CONSTITUTION:A powdery starting material mixture is prepd. by blending Na2CO3 powder with Li2CO3 powder and Al2O3 powder in a desired ratio and this mixture is heat-treated at 1,300-1,600 deg.C to obtain a heat-treated product whose X-ray diffraction pattern has 0-0.3 ratio of the peak intensity of the (01,17) face of beta-Al2O3 phase having 2.04Angstrom (d) to that of the (20,10) face of beta''-Al2O3 phase having 1.97Angstrom (d), and whose X-ray diffraction pattern has 0-0.03 ratio of the peak intensity of the (121) face of Nalo2 phase having 2.94Angstrom (d) to that of the (20,10) face of beta''-Al2O3 phase having 1.97Angstrom (d) and having other desired pattern. The products are then pulverized to <=3mum particle diameter and the objective beta-alumina powder is produced.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing β ″ -alumina powder and a β ″ -alumina powder suitable as a raw material powder for producing a solid electrolyte which is a constituent element of a sodium-sulfur battery having high performance and long life. Regarding

[0002]

BACKGROUND OF THE INVENTION β-Aluminas are well known substances in industry and are widely used as a conductor of cations in electrochemically operated devices. In particular, metallic sodium and sulfur are used as reactants. It is expected to have a wide range of applications such as sodium-sulfur battery diaphragm materials and solid electrolytes, sodium sensors or display elements. Particularly in recent years, the energy problem has become a concern, and the application to sodium-sulfur batteries for electric power storage is drawing attention. Β-alumina is mainly used for the solid electrolyte of the sodium-sulfur battery. With this β-alumina, Na ₂ O.Al ₂ O _{3 is used.}
Of the compounds present in the system, Na ₂ O
11Al ₂ O ₃ is β-alumina and Na ₂ O · 5Al ₂
O ₃ is called β ″ -alumina.

The crystal structure of these β-aluminas is O.
(2-) is most closely packed, and this O (2-1) is Al in the gap between the octahedron and the tetrahedron generated by the closest packing.
(3+) forms a structure called spinel block (Al ₁₁ O ₆ ). In addition, as a symbol representing an ion, () is added after the corresponding neutral particle, and the sign (+ or −) of the charge (+ or −) is shown in () in the parentheses. We will use the ones that

The Na (+) ion has a slightly low density of O (2-) sandwiched between the spinel blocks [NaO].
Conduct in layers. β-alumina serves as a lattice unit in two stages of spinel blocks, and the [NaO] layer serves as a mirror surface.
Further, β ″ -alumina serves as a lattice unit in three stages of the spinel block, and Na (+) ions move along in this [NaO] layer. Also, it is used as a solid electrolyte of a sodium-sulfur battery. β-alumina is generally a polycrystalline substance, and when Li ₂ O is added, a sintered body rich in β-Al ₂ O ₃ phase can be stably produced.
A β ″ -alumina having a high (+) ionic conductivity is obtained.
As described above, β ″ -alumina has a higher ionic conductivity than β-alumina, so that a sodium-sulfur battery having excellent energy efficiency can be obtained.
There is a demand for a β ″ -alumina-based solid electrolyte that uses ₂ O or the like as a structure stabilizer.

Further, as described above, β ″ -alumina is
Since it is used as a solid electrolyte / diaphragm, the following desirable characteristics are required in addition to the characteristics of good Na (+) ion conductivity. That is, (1) high density and no air permeability, (2) high mechanical strength, (3) fine and uniform crystal grains, and (4) electrochemical stability.

The solid electrolyte used in the sodium-sulfur battery is generally cylindrical and has a tubular shape with one end closed, and the opening thereof is α-used for electrical insulation and complete sealing of the battery. An insulating ring of alumina (Al ₂ O ₃ ) is adhered by glass. In many cases, sodium is placed inside the β ″ -alumina tube and sulfur is placed outside the tube. The anode metal container and the anode metal terminal are joined via an α-alumina insulating ring.

In Japanese Patent Publication No. 57-15063, a method for uniformly mixing a Li component which is a structure stabilizer is to make the Li component into a form of Li ₂ O.nAl ₂ O ₃ (n is at least 5). A method of adjusting the β ″ -alumina raw material powder to be added has been proposed. Here, the proposal is described in detail. Na; 8.6 to 9.0 weight percent, Li ₂ O;
As a method for producing a β ″ -alumina solid electrolyte having a composition of 0.7 to 0.8 weight percent and the balance Al ₂ O _3, Li ₂ O · nAl ₂ O having a structure similar to spinel is first prepared.
Adjust ₃ (n is at least 5). This Li ₂ O ・ Al
_For adjustment of ₂ O ₃ , LiNO ₃ or Li ₂ CO ₃ and α-Al ₂ O ₃ are dry-type or wet-mixed using an acetone solution. This mixture is then preferably 1100-1
This is a method of calcining at a temperature of 250 ° C. Further, by using an appropriate amount of this adjusted Li ₂ O.Al ₂ O ₃ , Na ₂ CO ₃ which is a sodium compound having components necessary for producing β ″ -alumina and α-Al ₂ O ₃ are added. The mixture is prepared in the same manner as the above Li ₂ O.Al ₂ O ₃ compound and calcined. The temperature is maintained for 10 minutes or less at a temperature of 0 ° C. Further, an annealing treatment is performed after the sintering in order to further reduce the resistivity for Na (+) ion conductivity.

[0008]

The sodium-sulfur battery has a high energy density and is expected as a battery for storing electric power. However, the β ″ -alumina-based solid electrolyte may deteriorate and be damaged during charge / discharge of the battery, and there are still many problems to ensure a sufficient battery life. It must meet the conditions used: (1) high density, (2) high mechanical strength, (3) Na.
(+) Good ion conductivity, (4) Fine and uniform crystal grains, (5) Electrochemically stable, etc.

According to the prior art, the preparation of the β ″ -alumina raw material powder is performed by a Li ₂ O.nAl ₂ O ₃ synthesis powder step and a Li ₂ O.nAl ₂ O ₃ and Na source synthesized in the step. α-
Two steps are required, a step of synthesizing β ″ -alumina raw material powder by mixing with Al ₂ O ₃ and the steps are complicated. In addition, a Li ₂ O.nAl ₂ O ₃ compound and Li ₂ O are required.・ N
Na ₂ CO ₃ and α-Al ₂ O ₃ are added to an Al ₂ O ₃ compound and mechanically mixed, and this mixture is simply calcined, so that a uniform reaction is difficult. In addition, a large amount of solid electrolyte is required for practical use of the sodium-sulfur battery. Therefore, in order to produce a solid electrolyte, it is essential to apply it to a mass production sintering facility such as a continuous furnace. On the other hand, according to the prior art, according to the study by the inventors, it is difficult to control these conditions because the proper range of conditions such as temperature rising rate, sintering temperature, and sintering time is small. Became necessary. If the control is wrong, there is a problem that coarse grains grow in the sintered body.

Here, the difficulty due to the coarsening of the crystal grains of the β ″ -alumina sintered body will be described. That is, when the β ″ -alumina sintered body grown into coarse particles is used as a solid electrolyte of a sodium-sulfur battery, There is a problem that destruction occurs due to the concentration of excessive current on specific particles. In addition, it also causes mechanical strength reduction, making it difficult to secure the reliability of the battery. As described above, the above-mentioned problems remain in the conventional technology.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a highly reliable β ″ -alumina powder manufacturing method and β ″ -alumina powder as a solid electrolyte which is a component of a sodium-sulfur battery. To provide.

Another object of the present invention is to provide a β ″ -alumina-based sintered body obtained by sintering β ″ -alumina powder having good conductivity for the above solid electrolyte.

Still another object of the present invention is to provide a sodium-sulfur battery provided with a solid electrolyte made of the above β ″ -alumina sintered body.

[0014]

The above object is to obtain a heat-treated product obtained by heat-treating a powder mixture, which has an X-ray diffraction pattern of β-A.
The peak intensity Iβ of the d = 2.04Å (01,17) plane of the l ₂ O ₃ phase and d = 1.97Å (20,1) of the β ″ -Al ₂ O ₃ phase
0) plane peak intensity Iβ ″, which is the ratio of the peak intensity Iβ ″, is in the range of 0 to 0.3, and the X-ray diffraction pattern of the heat-treated product is d = 2.94Å (121) plane of NaAIO ₂ phase. Peak intensity INaAlO ₂ and β = -Al ₂ O ₃ phase d = 1.9
I, which is the ratio of the surface peak intensity Iβ ″ of 7Å (20,10)
When the NaAlO ₂ / Iβ ″ is in the range of 0 to 0.03, the X-ray diffraction pattern of the heat-treated product has an α-Al ₂ O ₃ phase d = 2.
The peak intensity Iα of the 085Å (113) plane and β ″ -Al
₂ O ₃ phase d = 1.97Å (20,10) plane strength Iβ ″
It is achieved by crushing a heat-treated product having a characteristic that Iα / Iβ ″, which is the ratio of the crushed powder, and 0, and pulverizing the pulverized powder particles to a size of 3 μm or less.

The above-mentioned raw material powder mixture contains Na as a Na source.
₂ to 12% by weight of ₂ CO ₃ powder in terms of Na ₂ O,
Li ₂ CO ₃ powder as a Li source is calculated to be 0.1 to 1 in terms of Li ₂ O.
It is desirable for the weight percent and the balance to consist of Al ₂ O ₃ powder.

The bulk density of the above raw material powder mixture is 1.0 g
It is desirable to compress it to / cm ³ or more and calcine it.

The heat treatment temperature of the raw material powder mixture is set to 130.
It is desirable that the temperature be 0 to 1600 ° C.

The heat treatment time of the raw material powder mixture is set to 0.1.
It is desirable that the time is 5 hours.

The above-mentioned object is to use α-Al ₂ O ₃ powder and Na ₂ C.
A mixing step of collectively mixing the three components of O ₃ powder and Li ₂ CO ₃ powder, a pressing step of applying mechanical pressure to the mixed powder, and a calcination step of calcining the pressed mixed powder. And a crushing step of crushing the calcinated bulk β ″ -alumina.

For the above-mentioned purpose, the X-ray diffraction pattern of the heat-treated product obtained by heat-treating the powder mixture is d = of the β-Al ₂ O ₃ phase.
Peak intensities Iβ and β ″-of the 2.04Å (01,17) plane
Iβ / Iβ ″, which is the ratio of the peak intensity Iβ ″ of the d = 1.97Å (20,10) plane of the Al ₂ O ₃ phase, is in the range of 0 to 0.3, and the X-ray diffraction of the heat-treated product is shown. The pattern is NaA
IO ₂ phase d = 2.94Å (121) plane peak intensity IN
aAlO ₂ and β ″ -Al ₂ O ₃ phase d = 1.97Å (2
INaAl, which is the ratio of the surface peak intensity Iβ ″ of 0, 10)
O ₂ / Iβ ″ is in the range of 0 to 0.03, and the X-ray diffraction pattern of the heat-treated product is d = 2.08 of α-Al ₂ O ₃ phase.
The peak intensity Iα of the 5Å (113) plane and β ″ -Al ₂ O ₃
The d = 1.97Å (20,10) plane strength Iβ ″, which is the ratio to the strength Iβ ″, is 0. It is achieved by being.

When the major axis of the powder particles is l and the minor axis is d, it is desirable that the powder particles have a plate shape with an aspect ratio defined by 1 / d of 2 to 8.

The β ″ -alumina-based sintered body has an average crystal grain size of 5 μm or less and a maximum crystal grain size of 5 μm.
It is preferably 0 μm or less.

The β ″ -alumina-based sintered body is 1500 to
What was sintered at a temperature of 1670 ° C. for 0.1 to 1 hour is desirable.

The β ″ -alumina-based sintered body is 1300 to
What was annealed at a temperature of 1500 ° C. is desirable.

An anode composed of an anode active material which is liquid at an operating temperature and a current collector, and an anode container for containing the anode,
A cathode made of a cathode active material that is liquid at an operating temperature, a cathode container containing the cathode active material, and a solid electrolyte of a sodium-sulfur battery having a diaphragm and a solid electrolyte between the anode and the cathode as described above. It is desirable to use a β ″ -alumina-based sintered body.

[0026]

In the present invention, substances that become β ″ -alumina by heating, such as Na ₂ CO ₃ , Li ₂ CO ₃ and α-A.
The mixture of l ₂ O ₃ powder is compressed to a bulk density of 1.0 g / cm ³ or more. By this compression, the particle distance between the mixed components is shortened and the reaction proceeds uniformly. Further, it is possible to prevent evaporation of the Na ₂ O component in the subsequent calcination step.

Then, calcination is performed at a temperature of 1300 ° C. or higher,
By adjusting the mechanical pulverization, the composition of the β ″ -alumina raw material powder becomes uniform, finely divided, or chemically active. That is, Li ₂ CO ₃ , Na ₂ CO ₃ , α-A is obtained by calcination.
A mixture of 1 ₂ O ₃ powder or the like undergoes a phase transition in the β ″ -Al ₂ O ₃ phase, and β ″ -Al ₂ O ₃ crystals grow preferentially in the a and b axis directions, which are weak in strength. . Therefore, the crystal a,
The b-side has a weakly fragile cleavage rupture property, and is easily miniaturized by mechanical pulverization by utilizing the cleavage rupture property. By this mechanical pulverization, the β ″ -Al ₂ O ₃ powder is chemically activated and the composition becomes uniform.

The β ″ -alumina raw material powder of the present invention is a fine powder which has a uniform composition and is active as described above. This means that a green compact formed by using this raw material powder is sintered. Then, the densification of the β ″ -alumina sintered body proceeds due to the diffusion of only the particles.

Generally, the characteristics of the β ″ -alumina sintered body depend on its raw material powder, but the raw material powder of the present invention is β-Al ₂ like the β ″ -alumina raw material powder in the prior art.
The amount of O ₃ phase and NaAlO ₂ phase mixed is small and β ″ -Al ₂ O ₃
With a powder that has undergone a considerable phase conversion into a phase, the densification of the β ″ -alumina sintered body is achieved by the diffusion phenomenon between the powder particles.
The conductivity can be improved by annealing at a temperature of ~ 1500 ° C for 0.1 to 5 hours.

[0030] Therefore, conventionally _{Na 2 O · Al 2 O 3} -Al 2 O 3 system emerged intervention liquid phase and the β "-Al ₂ O ₃ particles by co-melting during sintering as technology around β-Al ₂
There is no coarsening of crystal grains caused by absorption of O ₃ particles, the degree of freedom in adjusting the sintering temperature is expanded, β ″ having high density with fine crystal grains and good Na (+) ion conductivity. An alumina-based sintered body is obtained, and the β ″ -alumina-based sintered body is sufficiently applicable as a solid electrolyte for sodium-sulfur batteries.

[0031]

Embodiments of the present invention will now be described in detail with reference to the drawings.

First, the basic manufacturing process of the present invention will be described.

FIG. 1 is a flow chart showing the basic manufacturing process of the present invention.

As shown in the figure, first, three components of Na ₂ CO ₃ , Li ₂ CO ₃ and α-Al ₂ O ₃ which are raw materials of β ″ -alumina are weighed and added with acetone. The reason is that if water is used, the alkaline component (N
This is for preventing a, Li) from being dissolved and causing segregation. A dry method without using an organic solvent such as acetone is also possible.

Next, a mixture of three-component powder and acetone is mixed to form a three-component batch mixed powder.

Then, acetone in the three-component batch mixed powder is evaporated and dried.

Next, in order to shorten the intermolecular distance of the dried ternary batch-mixed powder, it is compressed by applying mechanical pressure. In addition to the method of using a press molding machine, the method of putting the mixed powder in a rubber bag and applying hydrostatic pressure is also possible for compression.

Further, the compressed three-component batch mixed powder is calcined. By calcination, a calcined body of β ″ -alumina is obtained.

Finally, the calcined body of β ″ -alumina is pulverized to obtain β ″ -alumina powder.

Example 1 8.5% by weight in terms of Na ₂ O and 0.1 in terms of Li ₂ O.
8% by weight, so the balance of the alpha-Al ₂ O ₃ composition _{Na 2 CO 3, Li 2 CO} 3, α-Al 2 O 3 powder in acetone was added, and 2 hours wet mixed in a rotary ball mill. Acetone in this mixture was evaporated to dryness, and the compressed mixture obtained by compressing the dried mixture with a cold isostatic press was placed in a MgO container and calcined while preventing evaporation of alkaline components. The conditions of calcination are 1100 to 1600 ° C in the temperature range,
It was 0.1 to 5 hours. Next, this calcined body was crushed with an alumina roll crusher and then pulverized with a vibrating ball mill for 2 hours to produce β ″ -alumina powder. The produced β ″ -alumina powder had an average particle size of 0.8. Was ˜3 μm. The aspect ratio of the particles of this β ″ -alumina powder was 2-8.

To the β ″ -alumina powder, 2% by weight of polyvinyl butyral, which is an organic binder, was added together with an acetone solvent, wet-mixed to form a slurry, and the slurry was spray-dried by a spray dryer to obtain granulated powder. This granulated powder was used as a raw material powder and was molded by a cold isostatic press at a pressure of 2500 Kg / cm ^{2. After} heating the molded body to remove the binder, the molded body was put into a magnesia container and exposed to an alkaline atmosphere. While maintaining, sintering
Outer diameter 15 mm, wall thickness 1.0 mm, length 130 mm tubular,
A pellet-shaped β ″ -alumina sintered body having an outer diameter of 16 mm and a thickness of 1 mm was manufactured.

Table 1 shows the above Na ₂ CO ₃ , Li ₂ CO ₃ and α.
-Al ₂ O ₃ various calcination conditions of the powder mixture, I beta / I beta calcined body obtained in the calcining ", INaAlO ₂ / Iβ"
And Iα / Iβ ″ are shown.

[0043]

[Table 1]

As is apparent from Table 1, Na ₂ CO ₃ , Li ₂ CO ₃ and α-Al ₂ O _{3 which} are raw material powders for β ″ -alumina.
The calcined body obtained by calcining the powder mixture of the components has the calcination temperature and time of 1300 to 1600 ° C. and 0.1 to 1, as shown in samples No. 3 to No. 15 according to the present example. When it is set to 5 hours, the calcination temperature is 1100 to 1200 ° C.
Compared with o.1 and No.2 samples, Iβ / Iβ ″ is 0
Range of 0.30, INaAlO ₂ / Iβ ″ is 0 to 0.03
And the range of Iα / Iβ ″ were 0, which were relatively small values.

Table 2 shows the calcination temperatures of green compacts having different bulk densities and Iβ / Iβ ″, INaAlO ₂ / of the obtained calcinated bodies.
The relationship between Iβ ″ and Iα / Iβ ″ is shown.

[0046]

[Table 2]

As is clear from Table 2, the mixture was pressed to a bulk density of 1.0, 1.5 and 2.0 g / cm ³ , respectively, and this was pressed at 1500, 1550 and 1600 ° C.
Iβ / Iβ ″ of the calcined body obtained by calcining for 5 hours is 0
Range of 0.15, INaAlO ₂ / Iβ ″ is 0 to 0.01
, Iα / Iβ ″ was 0, and these ratios were smaller than those of the calcined body obtained by calcining the mixture of Table 1 which was not compacted before calcination under the same conditions.

Table 3 is a table showing the characteristics of the β ″ -alumina sintered body. Sample No. 2 of the comparative example shown in Table 1 and No. of the present invention.
The characteristics of the β ″ -alumina sintered body obtained by sintering using the pulverized powders of the calcined bodies of No. 3 and No. 14 as raw materials are shown.

[0049]

[Table 3]

As is apparent from Table 3, the characteristics of the β ″ -alumina sintered body are as follows: Iβ / Iβ ″, INaA of the raw material powder
be affected by lO ₂ / Iβ "and Iα / Iβ",
As a comparative example, Iβ / Iβ ″ of the raw material powder = 0.50, IN
aAlO ₂ /Iβ″=0.05 and Iα / Iβ ″ = 0.
The density of the β ″ -alumina sintered body obtained by sintering using the powder of sample No. 2 (see Table 1) having a large value of 20 was 2.8.
5 g / cm ³ , relative density; low as 87.4%, and Iβ / Iβ ″ = 0.30 of sintered body and INaAlO ₂ / Iβ ″ =
It has a large value of 0.05 and a high resistivity of 12 Ω · cm. In addition, the crystal grains of the sintered body have an aspect ratio (ratio of major axis to minor axis) of 6.4, and many coarse particles occupying 90% of coarse crystal grains of 50 μm or more are generated, and the radial crushing strength is as low as 65 MPa. , It was found that these sintered bodies cannot be used as a solid electrolyte for sodium-sulfur batteries.

On the other hand, according to the present invention, the characteristic of the raw material powder is Iβ
/Iβ″=0.30, INaAlO ₂ /Iβ″=0.03
And sample No. 3 having a small value of Iα / Iβ ″ = 0
(See Table 1), or Iβ / Iβ ″ = 0, INaAl
O ₂ / Iβ ″ = 0 and Iα / Iβ ″ = 0 and Sample No. 14 (see Table 1) in which each value is all 0, the β ″ -alumina sintered body was obtained under the sintering conditions. Is the sintering temperature; 1
500 to 1670 ° C, sintering holding time; 0.2 hour, temperature rising rate; at 60 to 300 ° C / h, density; 3.20 to
3.24 g / cm ³ , relative density; 98.2 to 99.4%, crystal grain aspect ratio (ratio of major axis and minor axis); 1.7 to 3.3
Fine particles having no coarse particles of 50 μm or more, radial crushing strength; 200-270 MPa, Iβ / Iβ ″ and INaAlO ₂ / Iβ ″ values of the sintered body; 0-0.02 and 0
A value of 0.01, resistivity; 2.7 to 4.0 Ω · cm was obtained. Further, the samples obtained by annealing these sintered bodies at 1300 to 1500 ° C. were also examined. As a result, it was found that the resistivity was better than the as-sintered ones without lowering the strength.

As described above, according to this embodiment, fine and uniform crystal grains are formed, and high density, high strength and Na
A β ″ -alumina-based sintered body having a good (+) ion conductivity can be obtained and can be sufficiently applied as a solid electrolyte for sodium-sulfur batteries.

Example 2 In Table 2, sample No. 14 showing good characteristics (sintering conditions: temperature rising rate: 300 ° C./h, sintering temperature: 1620 ° C.)
Diameter: 16 mm, thickness: 1 mm Shape β ″ -alumina sintered body was used as a solid electrolyte, and the direct current resistance was measured by incorporating it into a Na / Na cell. FIG. 2 is a vertical sectional view of a general Na / Na cell. is there.

FIG. 3 is a chart showing the relationship between the amount of electricity and the resistivity of β ″ -alumina of this example.

The cells 1 and 2 are made of stainless steel, and are separated by β ″ -alumina 3.
The cells 1 and 2 are insulated by the α-alumina pedestal 4, and the α-alumina pedestal 4 and the β ″ -alumina solid electrolyte 3 are joined by glass solder.
/ Na cell, temperature; 330 ° C, current density;
An energization test of 500 Ah / cm ² was conducted by a method of repeating energization at 0.5 A / cm ² in both directions for 30 minutes. As a result,
As shown in Fig. 3, any β ″ -alumina sintered body had no change in resistivity and was in the range of 4 to 5 Ω · cm, and had good Na ion conductivity. It was confirmed that the bound body was sufficiently applicable as a solid electrolyte for sodium-sulfur batteries.

As described above, according to this embodiment, high density, high strength Na (+) composed of fine crystal grains is formed.
To obtain a β ″ -alumina-based sintered body with good ionic conductivity, it is only necessary to calcinate the raw material powder mixture once at a higher temperature than before, and the process is simpler than the conventional two-time calcination. In addition, since the heat-treated product is confirmed to have characteristics by X-ray diffraction analysis and then pulverized, a good quality β ″ -alumina powder can be obtained.

Further, under the condition that the sintering temperature and the temperature rising rate at the time of β ″ -alumina sintering are set in a wide range, it is possible to obtain a good β ″ -alumina-based sintered body without abnormal grain growth. . Therefore, the β ″ -alumina-based sintered body can be mass-produced and is sufficiently applicable to the solid electrolyte for sodium-sulfur batteries.

[0058]

According to the present invention, by mixing, compressing, calcining and pulverizing a three-component powder as a raw material of β ″ -alumina, it is possible to obtain reliability as a solid electrolyte material which is a constituent element of a sodium-sulfur battery. It is possible to manufacture β ″ -alumina powder having a high value in a simple process.

[Brief description of drawings]

FIG. 1 is a flowchart showing a basic manufacturing process of the present invention.

FIG. 2 is a vertical sectional view of a general Na / Na cell.

FIG. 3 is a table showing the relationship between the amount of electricity and the resistivity of β ″ -alumina according to an example of the present invention.

[Explanation of symbols]

 1 cell 2 cell 3 β ″ -alumina solid electrolyte 4 α-alumina pedestal 5 insulating material 6 gasket

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[Procedure amendment]

[Submission date] June 30, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0049

[Correction method] Change

[Correction content]

[Table 3]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sadao Mizuno 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Toshimi Shioda 3-chome, Saiwai-cho, Hitachi, Ibaraki No. 1 Hitachi Ltd., Hitachi Factory (72) Inventor Tetsuo Nakazawa 7-1, 1-1 Omika-cho, Hitachi City, Hitachi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor, Yasujiro Okajima Hitachi, Ibaraki Prefecture 3-1-1 Sachimachi, Hitachi Ltd., Hitachi Works

Claims (12)

[Claims] 1. An X-ray diffraction pattern of a heat-treated product obtained by heat-treating a powder mixture has a β-Al ₂ O ₃ phase of d = 2.04Å
(01,17) plane peak intensity Iβ and β ″ -Al ₂ O ₃ phase d = 1.97Å (20,10) plane peak intensity Iβ ″
The ratio of the I beta / I beta "is within the range of 0 to 0.3, X-ray diffraction pattern of the heat-treated product is NaAIO ₂ phases d
= 2.94Å (121) plane peak intensity INaAlO
₂ and β ″ -Al ₂ O ₃ phase d = 1.97Å (20,10)
Of the surface peak intensity Iβ ″ of INaAlO ₂ / I
When β ″ is in the range of 0 to 0.03, the X-ray diffraction pattern of the heat-treated product is α-Al ₂ O ₃ phase d
= 2.085Å (113) plane peak intensity Iα and β ″
-Al ₂ O ₃ phase d = 1.97Å (20,10) plane strength Iβ ", which is the ratio of Iα / Iβ", which is the ratio to 0, is crushed, and the crushed powder particles are Size is 3μ
A method for producing β ″ -alumina powder, which is characterized in that it is produced so as to be m or less. 2. The raw material powder mixture contains N as a Na source.
a ₂ CO ₃ powder 7-12% by weight in the terms of Na ₂ O, the Li ₂ CO ₃ powder as a Li source in Li ₂ O in terms of 0.1
The method for producing β ″ -alumina powder according to claim 1, wherein the weight ratio is ˜1.0 weight percent and the balance is Al ₂ O ₃ powder. 3. The bulk density of the raw material powder mixture is 1.0
The method for producing β ″ -alumina powder according to claim 1 or 2, which comprises calcination after compressing to g / cm ³ or more. 4. The heat treatment temperature of the raw material powder mixture is set to 13
The method for producing β ″ -alumina powder according to claim 2 or 3, wherein the temperature is set to 00 to 1600 ° C. 5. The heat treatment time of the raw material powder mixture is set to 0.
The method for producing β ″ -alumina powder according to claim 4, wherein the time is 1 to 5 hours. 6. An α-Al ₂ O ₃ powder, Na ₂ CO ₃ powder and L
a mixing step of collectively mixing the three components of i ₂ CO ₃ powder, a pressing step of applying mechanical pressure to the mixed powder, a calcination step of calcining the pressurized mixed powder, and a calcination step And a pulverizing step of pulverizing the lumped β ″ -alumina thus obtained. 7. The X-ray diffraction pattern of the heat-treated product obtained by heat-treating the powder mixture has a β-Al ₂ O ₃ phase of d = 2.04Å
(01,17) plane peak intensity Iβ and β ″ -Al ₂ O ₃ phase d = 1.97Å (20,10) plane peak intensity Iβ ″
The ratio of the I beta / I beta "is in the range of 0 to 0.3, X-ray diffraction pattern of the heat-treated product is NaAIO ₂ phases d
= 2.94Å (121) plane peak intensity INaAlO
₂ and β ″ -Al ₂ O ₃ phase d = 1.97Å (20,10)
Of the surface peak intensity Iβ ″ of INaAlO ₂ / I
β ″ is in the range of 0 to 0.03, and the X-ray diffraction pattern of the heat treated product is d of the α-Al ₂ O ₃ phase.
= 2.085Å (113) plane peak intensity Iα and β ″
-Size of powder particles obtained by pulverizing a heat-treated product exhibiting the above-mentioned respective characteristics such that the ratio Iα / Iβ ″ of the Al ₂ O ₃ phase d = 1.97Å (20, 10) plane strength Iβ ″ is 0. Β-alumina powder having a size of 3 μm or less. 8. The β according to claim 7, wherein the powder particles have a plate-like shape with an aspect ratio defined by 1 / d of 2 to 8 where the major axis is 1 and the minor axis is d. ″ -Alumina powder. 9. The β ″-according to claim 7 or 8.
A β ″ -alumina-based sintered body obtained by sintering a molded article formed of alumina powder, and having a crystal grain size of 5 μm on average.
A β ″ -alumina-based sintered body characterized in that the maximum grain size is 50 μm or less. 10. The β ″ -alumina-based sintered body according to claim 9, wherein the molded product is sintered at a temperature of 1500 to 1670 ° C. for 0.1 to 1 hour. 11. A β ″ -alumina-based sintered body obtained by annealing the β ″ -alumina-based sintered body according to claim 10 at a temperature of 1300 to 1500 ° C. 12. An anode composed of an anode active material that is liquid at an operating temperature and a current collector, an anode container that houses the anode, a cathode made of a cathode active material that is liquid at an operating temperature, and the cathode active material. A cathode container for accommodating the solid electrolyte, which is a diaphragm between the anode and the cathode.
1. A sodium-sulfur battery comprising the β ″ -alumina-based sintered body according to claim 1.