JPH07106938B2 - Beta-alumina solid electrolyte - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beta-alumina solid electrolyte having both excellent mechanical strength and sodium ion conductivity.

[0002]

2. Description of the Related Art Beta-alumina tubes used in sodium-sulfur batteries are required to have mechanical strength and sodium ion conductivity above a certain level so as to withstand long-term use. And, as a raw material for producing the beta-alumina tube, like the raw materials for general ceramic products, magnetizing components such as iron and silica components are uniformly regarded as harmful components, and their content is reduced to a level of 10 ppm or less. When using expensive lower raw materials or cheap alumina raw materials containing magnetizing components, demagnetize the magnetizing components to a level of 10 ppm or less and use them as raw materials. Was there.

However, when the beta-alumina raw material in which the content of the magnetizing component and the silica component is lowered to the level of 10 ppm or less is used, the mechanical strength and sodium ion conductivity of a certain value or more and In order to obtain an excellent product, it is necessary to bake at a high temperature of 1650 ° C. or higher, and as a result, it becomes difficult to control the temperature and it becomes difficult to stably produce a beta-alumina tube of the same quality. However, there is a problem that it is not suitable for a large-scale furnace and that the furnace material becomes short-lived and the firing cost becomes high.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides a beta-alumina solid electrolyte capable of efficiently producing a high-quality beta-alumina tube equivalent to the conventional one. It was completed for that purpose.

[0005]

The beta-alumina solid electrolyte of the present invention, which has been made to solve the above-mentioned problems, is obtained by converting Fe into Fe ₂ O ₃ in sintered beta-alumina to 20%.
~600ppm and by converting the Si to SiO ₂ 20~600ppm
It is characterized by containing.

The present invention is applied to conventional ceramic products.
It is considered to be a toxic component uniformly and the amount of the impurities contained in the raw material is 10ppm or less.
Iron-like deposits that had been removed to the bell content
The magnetic component and silica component are actually when the beta-alumina tube is sintered.
Acts as a sintering aid for the beta-alumina raw material
It was clarified that it was a₂O ₃
And SiO₂To realize more precise sintering by the presence of
It was completed based on the knowledge that
Fe in beta-alumina tube₂O₃Content of 20-600ppm
And SiO₂The content should be 20-600ppm
The point is that iron removal processing and raw material adjustment are done before.

In the present invention, the content of Fe ₂ O ₃ which is a minor component in the sintered beta alumina is ₂₀ to 600 pp.
By setting m ₂ and the SiO ₂ content to 20 to 600 ppm, the firing temperature is from 1650 ° C to 1580 ° C of the conventional product.
It became possible to lower the temperature to a low temperature. If the content of Fe ₂ O ₃ and SiO ₂ in the beta-alumina thus sintered is within the predetermined amount range, it is equivalent to the conventional product in spite of firing at a lower temperature than the conventional product. Sodium ion conductivity and mechanical strength are obtained, and
_An inexpensive raw material containing a trace amount of ₂ O ₃ and SiO ₂ components can be used, and beta alumina can be economically produced. When the content of Fe ₂ O ₃ and SiO ₂ is less than 20 ppm, it is necessary to perform the calcination treatment at a high temperature of 1650 ° C. as in the conventional product, and to stably produce a high quality beta alumina tube. Will be difficult. On the other hand, if the content of Fe ₂ O ₃ and SiO ₂ is more than 600 ppm, defects occur in the microstructure of the sintered beta alumina tube, making it impossible to obtain sufficient mechanical strength. The radial crushing strength (220Mpa) set as the value cannot be cleared. In addition, the CaO and K ₂ O components, which are contained as minor components, do not have any adverse effect on the present invention as long as the content is less than 300 ppm.

[0008]

[Examples] Preparation of minor components in sintered beta alumina
Α-Al which is the main raw material of beta-alumina
Mina raw materials are expensive and high purity, and are cheap and low purity.
Prepare various things up to₂Various
Were added together. In addition, the raw material thus obtained is
Rallying and deironing with a 12000 gauss wet deironer
Give various Fe₂O₃Is adjusted so that the content of
It was All other trace ingredients are successful and special
No adjustment was made, but K₂The contents of O 2 and CaO are
Small value is within 10ppm and maximum value is within 300ppm.
It was Note that these K₂For trace components such as O and CaO
It must be present in the present invention
There is no. The raw material obtained as described above is manufactured by a conventional method.
Granulate, then form beta-alumina tube,
For these samples, the sintered compact has the highest density and the sintered compact
The firing temperature at which the strength was maximized was measured. In this way
Fe in the obtained sintered body₂O ₃And SiO₂Content and firing temperature
The result of summarizing the relationship is shown in FIG. Also, likewise Nato
Fig. 2 shows the results that summarize the relationship with the ionic conductivity.
You Furthermore, it also represents the mechanical strength of beta-alumina tubes.
FIG. 3 shows the result of the summary of the relationship with the radial crushing strength.

As is clear from FIG. 1, when the Fe ₂ O ₃ content and the SiO ₂ content in the sintered body were each 20 ppm or more, the firing temperature was lower than 1650 ° C. of the conventional product. Can be fired at 1580 ° C, while Fe ₂ O ₃
When the SiO ₂ content and the SiO ₂ content are set to be 600 ppm or less, respectively, as is clear from FIGS. 2 and 3, the sodium ion conductivity is the target value of 4.4 Ω · cm (330
In the case of ℃), the radial crushing strength can be set to 240MPa or more, which is the target value, and a beta alumina tube of the same quality as the conventional product can be produced at a lower temperature and a cheaper raw material. It was confirmed that it could be manufactured.

[0010]

As is clear from the above description, the content of Fe ₂ O ₃ and SiO ₂ which are the minor components in beta-alumina is set to 20 to 600 ppm, respectively, so that the firing at a temperature lower than the conventional temperature can be achieved. It is possible to efficiently produce a high-quality beta-alumina tube equivalent to the conventional one,
Further, it is possible to use an inexpensive alumina raw material containing a magnetizing component such as iron, and there is also an advantage that the production cost can be significantly reduced. Therefore, the present invention, as a beta-alumina solid electrolyte that eliminates the conventional problems, has a great contribution to the industrial development.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the Fe ₂ O ₃ and SiO ₂ contents in a beta-alumina fired body and the firing temperature in Examples of the present invention.

FIG. 2 is a graph showing the relationship between the content of Fe ₂ O ₃ and SiO ₂ in the beta-alumina fired body and the sodium ion conductivity in the example of the present invention.

FIG. 3 is a graph showing the relationship between the contents of Fe ₂ O ₃ and SiO ₂ in a beta-alumina fired body and radial crushing strength in Examples of the present invention.

Claims (1)

[Claims] 1. Fe ₂ O in sintered beta alumina
A beta-alumina solid electrolyte containing ₂₀ to 600 ppm in terms of ₃ and 20 to 600 ppm in terms of Si converted to SiO ₂ .