JPS6033254A - Manufacture of high ion conductivity leucite ceramics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing highly ionic conductive leucite-based ceramics.

Generally, when the crystals constituting a ceramic body have glabellar voids or pores, the ceramic body exhibits high ionic conductivity because alkali cations easily move through the layers, gaps, or pores. A typical example of such a crystal is β-
A1203. Examples include α-AgI, which are widely used as solid electrolytes in chemical potential sensors, batteries, and the like. From a practical standpoint, such ceramic bodies have excellent ionic conductivity, thermal and chemical stability, high mechanical strength, and moldability. It is necessary to have properties such as excellent sinterability and excellent sinterability. However, β-Ad2(:
)3 is thermally and chemically stable and has excellent mechanical strength, but the temperature during shaping and sintering is 1600℃.
The problem is that the sintered body has poor workability due to its extremely high temperature (°C or more) and high hardness.

On the other hand, solid electrolytes of silver halide threads such as α-AgI,
Although it has excellent ionic conductivity, it has poor thermal and chemical stability and low mechanical strength. Therefore, in order to develop a wide variety of functional electronic components in response to today's strict technical requirements, it is necessary to develop electronic components that are thermally and chemically stable, can be sintered at low temperatures, and have excellent processability. The emergence of highly ionic conductive ceramics with high mechanical strength is desired.

As a result of various studies based on the above-mentioned current situation, the present inventor has discovered a leucite solid solution obtained by press-molding a 20 series amorphous material into S 102-A1203- with a specific composition and sintering it. It was discovered that (KAl) 1-XS i2+X06 becomes a highly ionic conductive ceramic that satisfies the above requirements, and the present invention was completed. That is,
The present invention uses SiO2, Al2O3, and 20 as basic components, and has an atomic ratio of 0.5 to 0.6 expressed by St/Si 10K and an atomic ratio of 0.9 expressed by AIVK. A leucite solid solution C (KA
A' ) 1-XS i2 +

The leucite solid solution formed in the present invention has a form in which a part of the KAn02 component in pure leucite (KAlS i 206) is replaced by S r 02. The larger the amount of SiO2 substitution, the more vacancies are formed due to the lack of K+ cations in the leucite solid solution crystal framework, which facilitates the movement of K+ cations and makes the solid solution highly ionic conductive. Ceramics composed of the solid solution also exhibit high ionic conductivity.

The method of the present invention is carried out, for example, as follows.

First, methyl silicate (CH30)4St is dissolved in a water-soluble lower alkyl alcohol such as ethyltanol or ethanol to form a homogeneous solution, and then an aqueous potassium nitrate solution and water are added to form a homogeneous solution. When the solvent is methanol, the concentration of aluminum nitrate is preferably about 0.8 to 0.95y/10mJ as Al2O3, the concentration of potassium nitrate aqueous solution is preferably about 5%, and the total amount of ethyl silicate and aluminum nitrate alcohol solution A homogeneous solution can also be obtained by adding an aqueous potassium nitrate solution by adding about twice the amount of methanol.

The mixing ratio of ethyl silicate, aluminum nitrate alcohol solution, and potassium nitrate aqueous solution is such that the atomic ratio represented by St/Si + A# + K in the finally formed homogeneous solution is 0.5 or more and 0.6 or less. , and the atomic ratio represented by Al/K is 0.9 or more and 1.
The amount should be 1 or less. Next, aqueous ammonia is added dropwise to the homogeneous solution containing Si, A#, and a source obtained as described above while stirring the solution until the solution becomes alkaline to form a gel. The obtained gelled product is heated to about 80 to 120°C to dehydrate and dry, and then heated at 650 to 850°C, taking care not to crystallize, to decompose and remove residual ammonium nitrate. Or methyl silicate,
After dissolving an alkyl silicate such as ethyl silicate, an aluminum alcoholate such as aluminum isopropylate, and a potassium alcoholate such as potassium tert-butyrate in an alcohol such as butyl alcohol, and forming a gel by adding hydrochloric acid and water. , dehydration, drying and heating may be performed in the same manner as above.

The residue after heating is an anhydrous, homogeneous amorphous material of SiO□-A1203-20 series, which is Si due to instantaneous gelation.

Each element of Al and K is homogeneously mixed on the order of atoms. The anhydrous amorphous material thus obtained was finely pulverized using a ball mill, etc., and molded by a known method such as a pressure molding method, a slurry casting method, a tape molding method, etc.
By heating at about 1400° C. for 3 to 24 hours, sintering and crystallization is completed and a highly ionic conductive ceramic body is obtained.

In a homogeneous amorphous material before sintering, A13+ and St'0 are in a disordered state, but when the amorphous material is heated below the liquidus temperature of each composition making up the amorphous material and crystallized, A13+ and St'0 are in a disordered state. The arrangement of l 3+ and St'0 forms the crystal groove structure of leucite. At this time, the Si content (δ
) within the specified range, a part of KAn02 is replaced by SiO2, and a leucite solid solution containing an appropriate amount of SiO□ is obtained.

The 10 cations in such a leucite solid solution are partially missing, and vacancies are formed in the crystal, so the ionic conductivity is extremely high compared to that of leucite crystals. It becomes a material with

Examples and comparative examples will be shown below to further clarify the characteristics of the present invention.

Example 1 Ethyl silicate 83.39' and aluminum nitrate Al
(NO3)3.9H2069,8y and methanol 40
After uniformly dissolving in 0 ml, 416.5 ml of 5% potassium nitrate aqueous solution was added to form a homogeneous solution.

Next, aqueous ammonia was added to the homogeneous solution while stirring until it became alkaline to form a gel. After dehydrating and drying the obtained gelatinized product by heating it at 110°C for about 40 hours,
Ammonium nitrate was decomposed by heating at 800°C for 1 hour. The obtained anhydrous amorphous material having a molar ratio of S i /S i + An-)K of 0.505 was finely ground to approximately 50 μm or less using a ball mill, and then milled into a powder having a diameter of 20 mm and a thickness of 4 m.
The material was pressure-molded to a size of 1.2 ton/cm2 at a pressure of 1.2 ton/cm2, and fired at 1300°C for 10 hours to obtain a highly ionic conductive leucite-based ceramic of the present invention.

Table 1 shows the composition of the amorphous body before firing, and Table 2 shows the physical properties of the sintered body. In Table 1, δ means St/Si +
An represents the atomic ratio shown in 10. Further, in FIG. 1, the dependence of electrical conductivity on the reciprocal of absolute temperature is shown as curve A.

Examples 2 to 5 Highly ionic conductive ceramics of the present invention were obtained in the same manner as in Example 1, except that the amounts of aluminum nitrate and potassium nitrate were changed as shown in Table 1.

Table 2 shows the physical properties, and FIG. 1 shows the dependence of electrical conductivity on the reciprocal of absolute temperature as curve B (Example 2) and curve C (Example 4).

Comparative Examples 1-2 Ceramics were obtained in the same manner as in Example 1, except that the amounts of aluminum nitrate and potassium nitrate were changed as shown in Table 1. Table 2 shows the physical properties, and FIG. 1 shows the dependence of electrical conductivity on the reciprocal of absolute temperature. Incidentally, since the leucite crystals in the ceramics obtained in Comparative Examples 1 and 2 both have the theoretical composition (KAnS 1206),
In the figure, the curves are almost the same, and as shown in Table 2, the crystal transition temperature (α=β) is also constant at 620°C.

From the results shown in Tables 1 and 2, it is clear that the ceramics of the present invention are luxuriously superior to the comparative ceramics in terms of conductivity, mechanical strength, and heat resistance. It is.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the dependence of electrical conductivity on the reciprocal of absolute temperature of ceramics obtained in Examples and Comparative Examples of the present invention. (or more) Figure 1 103/T(K)

Claims (1)

[Claims] ■ 5in21A1203 and 20 as basic components,
An amorphous material whose atomic ratio expressed by St/Si + AA' + K is within the range of 0.5 to 0.6 and whose atomic ratio expressed by kl/K is within the range of 0.9 to 1.1. By sintering the molded product, a leucite intersolution [(
A method for producing ceramics, characterized by forming highly ionic conductive leucite-based ceramics containing crystals of O (X≦1) as a main component.