JPH08188465A - Electroconductive ceramic and its production - Google Patents

Abstract

PURPOSE: To obtain an electroconductive ceramic improved an ionic conductivity in a temperature range in which conventional Ba2 In2 O5 has extremely low ionic conductivity. CONSTITUTION: This electroconductive ceramic is an oxide ceramic shown by Ba-In-Sn-O in the molecular ratio of Ba:In:Sn of 1:(1-x):x (0<(x)<=0.6).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a conductive ceramic having a perovskite-related structure.

[0002]

_2. Description of the Related Art Ba ₂ In ₂ O ₅ is one of Brown Millerite type compounds (general formula A ₂ B ₂ O ₅ ), which has an order-disorder transition point of oxygen defects at about 930 ° C. It is known that, at a temperature higher than this temperature, oxygen defects are randomly arranged to form a defect perovskite type cubic crystal structure, and the ionic conductivity is several tens of times higher than that at a temperature lower than the transition point (J. B. Goodeno
Ugh, J. et al. E. FIG. Ruiz-Diag and Y.
S. Zhen, Solid State Ionic
s, 44, 21-31 (1990)).

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As mentioned above, Ba
₂ In ₂ O ₅ has a problem that good ionic conductivity cannot be obtained at a temperature below the order-disorder transition point of oxygen defects.

The present invention has been made in view of the above problems, and an object thereof is to provide a conductive ceramic having improved ionic conductivity in a temperature range where the ionic conductivity of Ba ₂ In ₂ O ₅ was extremely low. Is to provide.

[0005]

The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, Ba-In-
The oxide ceramics represented by Sn-O is Ba ₂ In ₂
The inventors have found that O ₅ can improve the ionic conductivity in the temperature range where the ionic conductivity is extremely low, and completed the present invention.

That is, the present invention is based on Ba-In-Sn-O.
An oxide ceramic represented by: Ba, In, S
The conductive ceramics are characterized in that the molar ratio of n is Ba: In: Sn = 1: 1-x: x (0 <x ≦ 0.6), and a method for producing the same.

The present invention will be described in detail below.

In the electroconductive ceramics of the present invention, as the Sn content, that is, the value of x is increased from 0, the order-disorder transition point of oxygen defects is lowered until the transition point becomes room temperature or lower. When x is in the range of 0.1 to 0.6, a cubic crystal defect perovskite structure in which the transition point is reliably maintained at room temperature or lower is obtained.

However, when the value of x exceeds 0.1, the lattice volume becomes small, oxygen defects gradually become ordered, and the ionic conductivity also begins to gradually decrease. The decrease in the value becomes non-negligible. Therefore, the order-disorder transition point of oxygen defects is set to Ba ₂ In ₂ O.
_{In order} to make it lower than ₅ and have high ionic conductivity, x must be larger than 0 and not more than 0.6, and in order to bring the order-disorder transition point of oxygen defects to room temperature or less, x
Is preferably in the range of 0.1 to 0.6, and the lattice volume is Ba ₂
In order to make it larger than In ₂ O ₅ , x is 0.02 to 0.2.
A range of 5 is preferred. Therefore, x is particularly preferably in the range of 0.1 to 0.25.

The method for producing the conductive ceramics of the present invention is not particularly limited. For example, compounds of Ba, In and Sn are mixed in a molar ratio of Ba: In: Sn = 1: 1-x: x (0 <x ≦ 0.6), then calcined and molded, Method of firing, mixing the solution of the inorganic salt of each of the above-mentioned constituent metal elements, to obtain a coprecipitate by adding ammonia or the like, the precipitate is separated, washed, dried, then calcined, molding Then, it can be synthesized by a method such as firing.
Depending on the case, it may be possible to convert Ba compound and In compound into Ba ₂
In ₂ O ₅ was first synthesized, and the Ba compound and Sn compound were added to the composition so as to have the above composition, and the mixture was calcined and molded,
You may bake.

When all the raw material mixed powders obtained are oxides, they may be molded as they are and then sintered, but otherwise, for example, when an inorganic salt of a constituent metal element is used as a raw material, etc. If molded and sintered as it is, it is accompanied by a thermal decomposition reaction, which hinders sintering and makes it difficult to obtain a dense sintered body. Therefore, it is preferable to calcine once before sintering.

The calcination temperature is not particularly limited as long as the powder obtained after calcination is all in the oxide state, but it is preferably 1400 ° C. or lower in order to prevent melting and evaporation of the In component.

The sintering temperature of the obtained raw material mixed powder or calcination powder is not particularly limited, but the reaction is sufficiently advanced, the sintered body is sufficiently densified, and melting and evaporation of the In component are performed. In order to prevent this, the range of 1300 ° C to 1400 ° C is particularly preferable.

The order-disorder transition point of oxygen defects can be confirmed by differential thermogravimetric analysis. That is, in the measurement temperature region, at the transition point, an endothermic reaction occurs without a weight change when the temperature is raised, and an exothermic reaction occurs without a weight change when the temperature is lowered. However, the temperature at which the exothermic reaction at the time of temperature decrease is observed may shift to a temperature lower than the temperature at which the endothermic reaction at the time of temperature increase is observed. Therefore, in the case where oxygen defects are randomly arranged at room temperature and the transition point is below room temperature, the above exothermic reaction or endothermic reaction is not observed in the differential thermogravimetric analysis in the temperature range above room temperature.

The mechanism of the effect of the present invention has not been sufficiently clarified, but in the conductive ceramics of the present invention, the brown mirror light type compound A ₂ B ₂ O thereof is used.
_It is considered that, by locating Sn at the B site of ₅ , the symmetry of the crystal structure was improved, the disordered arrangement of oxygen defects was promoted, and high conductivity was obtained from a relatively low temperature.
However, such an assumption does not bind the present invention.

The conductive ceramics of the present invention are very useful because they show good ionic conductivity even at relatively low temperatures.

[0017]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited thereto.

Example 1 Ba (NO ₃ ) ₂ (manufactured by Kishida Chemical), In ₂ O ₃ (manufactured by Kishida Chemical) and SnO ₂ (manufactured by Kanto Chemical) were mixed with Ba: In: Sn.
After mixing so that the molar ratio was = 1: 0.95: 0.05, the mixture was calcined at 1000 ° C. for 6 hours in the atmosphere. The powder obtained is preformed at a pressure of 500 kg / cm ² , and further 2
After molding by hydrostatic pressure of t / cm ² , 1 at 1400 ° C
It was fired for 0 hour to produce a sintered body.

The obtained sintered body was Ba ₂ (In _0.95 Sn)
_0.05 ) ₂ O _5.05 , and as a result of an X-ray diffraction test (CuKα ray), this crystal phase was an orthorhombic brown mirrorlite type compound single phase, but compared with conventional Ba ₂ In ₂ O ₅ The symmetry of the crystal structure was improved.

From the results of differential thermogravimetric analysis, it was confirmed that the order-disorder transition point of oxygen defects was about 700 ° C.

The obtained sintered body was ground to a thickness of 2 mm, coated with a platinum paste, and subjected to electrode baking treatment at 1000 ° C., followed by an AC two-terminal method (applied AC current 20 m
V, frequency 10 Hz to 1 MHz, in air), the complex impedance was measured to calculate the ionic conductivity. The results are shown in Table 1.

[0022]

[Table 1]

Examples 2 and 3 Ba (NO ₃ ) ₂ (manufactured by Kishida Chemical Co., Ltd.), In ₂ O ₃ (manufactured by Kishida Chemical Co., Ltd.) and SnO ₂ (manufactured by Kanto Chemical Co., Ltd.) were mixed with Ba: In: Sn.
= 1: 0.9: 0.1 (Example 2), Ba: In: Sn
The mixture was mixed at a molar ratio of = 1: 0.5: 0.5 (Example 3) and then calcined in the atmosphere at 1000 ° C. for 6 hours.
The obtained powder was preformed at a pressure of 500 kg / cm ² and further hydrostatically pressed at ² t / cm ² , and then 14
A sintered body was produced by firing at 00 ° C. for 10 hours.

The obtained sintered body was Ba ₂ (In _0.9 S
n _0.1 ) ₂ O _5.1 (Example 2), Ba ₂ (In _0.5 Sn _0.5 ).
₂ O _5.5 (Example 3), and as a result of an X-ray diffraction test, this crystal phase was a single phase of a cubic defect perovskite type compound.

Further, the results of the differential thermogravimetric analysis did not show any exothermic reaction when the temperature was lowered or an endothermic reaction when the temperature was raised.

The ionic conductivity of the obtained sintered body was calculated by measuring the complex impedance in the same manner as in Example 1. The results are also shown in Table 1.

Comparative Example Ba (NO ₃ ) ₂ (manufactured by Kishida Chemical Co., Ltd.) and In ₂ O ₃ (manufactured by Kishida Chemical Co., Ltd.) were mixed so as to have a composition of Ba ₂ In ₂ O ₅ , and then the same treatment as in Example 1 was performed. A sintered body was produced under the conditions, and the ionic conductivity was measured by the same method as in Example 1. The measurement results are shown in Table 1.

As a result of the X-ray diffraction test, the crystal phase of the obtained sintered body was an orthorhombic brown mirrorlite type compound single phase. From the results of differential thermogravimetric analysis, it was confirmed that the order-disorder transition point of oxygen defects was about 930 ° C.

As is apparent from Table 1, below 900 ° C., the ionic conductivity was about one digit lower than in Examples 1 to 3.

[0030]

The conductive ceramics of the present invention are Ba ₂ I
Since it exhibits good ionic conductivity at a lower temperature than n ₂ O ₅ , it can be expected to be applied to various electronic materials such as batteries and sensors.

Claims (2)

[Claims] 1. An oxide ceramic represented by Ba-In-Sn-O, wherein the molar ratio of Ba, In, and Sn is Ba: In: Sn = 1: 1-x: x (0 <x≤. 0.6) which is a conductive ceramic. 2. A barium compound, an indium compound and a tin compound are mixed in a molar ratio of Ba: In: Sn = 1: 1-x: x (0 <x ≦ 0.6), and the powder is used as it is. Alternatively, the powder obtained by calcination is molded, and subsequently 1300 to 14
The method for producing a conductive ceramic according to claim 1, wherein sintering is performed at 00 ° C.