JPH08259346A - Porous sintered compact and its production - Google Patents

Abstract

PURPOSE: To obtain a porous sintered compact capable of controlling dimensional shrinkage by a heat cycle in a perovskite-type oxide porous sintered compact including lanthanum manganite. CONSTITUTION: This porous sintered compact is provided with a perovskite-type compound oxide phase and a crystal phase composed of one or more metals selected from among silver, zirconium, indium, molybdenum, niobrum, tungsten, silicon, tin and antimony or its compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous sintered body which is particularly suitable as a heat resistant electrode such as an air electrode material for a solid oxide fuel cell (SOFC).

[0002]

2. Description of the Related Art In SOFC development projects, it is important to search for stable materials at high temperatures. As a SOFC air electrode material, a lanthanum manganite sintered body is currently considered to be promising (Energy Engineering, 13, 2, 52).
~ P. 68, 1990). In such a lanthanum manganite sintered body, a lanthanum manganite sintered body having a substantially stoichiometric composition or A
It is known that the site (lanthanum site) is partially deleted (manganese-rich composition). In particular, a porous sintered body made of lanthanum manganite having A site doped with Ca or Sr is regarded as a promising material for an air electrode including a self-supporting air cathode tube.

However, the present applicant has disclosed that the perovskite type oxide porous sintered body including such lanthanum manganite has the following problems (see Japanese Patent Laid-Open No. 6-183856). That is, regarding the conventional lanthanum manganite porous sintered body,
A heating-cooling cycle was performed between the temperature of 1100 ° C and the temperature of room temperature to 600 ° C to test its stability. In this lanthanum manganite, the B site is not particularly replaced, and 10% to 20% of the A site is replaced by calcium, or 10% to 15% of the A site is replaced by strontium. It was something that

As a result, the dimensions of the porous sintered body are
It was found that each heat cycle caused shrinkage of about 0.01 to 0.04%. Moreover, the shrinkage due to this heat cycle does not converge even after 100 heat cycles,
It was found that the number of heat cycles could reach several percent. When the air electrode contracts in this manner, a crack may occur between the air electrode and other constituent materials of the unit cell, which may cause the unit cell to be broken.

Moreover, even when this unit cell was operated at 1000 ° C. for a long time, such cracks did not occur at all. Therefore, it is considered that this phenomenon is not due to the shrinkage of the porous sintered body during firing, but to the dimensional change due to the thermal cycle.

Furthermore, the researchers belonging to the present applicant further researched the mechanism of causing the dimensional shrinkage of the porous sintered body due to the above thermal cycle. As a result, it was found that when the temperature was raised from room temperature to about 1000 ° C., the weight of the porous sintered body slightly decreased, and when the temperature was lowered to room temperature again, this weight was restored. Further, the dimensional shrinkage rate of the porous sintered body due to the thermal cycle was slightly different depending on the temperature rising / falling rate during the thermal cycle and the oxygen partial pressure in the atmosphere.

The mechanism by which such a phenomenon occurs is currently unknown. However, it is speculated that oxygen goes in and out of the crystal in the temperature range of 800 ° C. or higher in the atmosphere due to the thermal cycle, and the crystal lattice is distorted as the oxygen goes in and out, promoting the mass transfer of metal atoms. It

[0008]

Therefore, it is required to suppress or prevent the dimensional shrinkage phenomenon due to the thermal cycle as described above. Therefore, the present inventor
JP-A-316471, JP-A-6-287048 and the like disclose that the dimensional shrinkage phenomenon of the porous sintered body can be suppressed or prevented by largely changing the composition of lanthanum manganite. However, since the characteristics required for the air electrode of the solid oxide fuel cell are diverse, it is necessary to further find a new perovskite type composite oxide capable of preventing the thermal cycle shrinkage.

An object of the present invention is to find a new microstructure capable of suppressing dimensional shrinkage due to the above-mentioned thermal cycle in a perovskite type oxide porous sintered body such as lanthanum manganite.

[0010]

The present invention relates to a perovskite type complex oxide phase, silver, zirconium, indium,
The present invention relates to a porous sintered body characterized by comprising a crystalline phase made of one or more metals selected from the group consisting of molybdenum, niobium, tungsten, silicon, tin and antimony, or a compound thereof. .

Further, the present invention is characterized by comprising a perovskite type complex oxide phase and a crystal phase comprising one or more metals selected from the group consisting of lanthanum, manganese and nickel or a compound thereof. The present invention relates to a porous sintered body.

When manufacturing the above-mentioned porous sintered body, a group of compounds containing a metal element constituting the perovskite type composite oxide after firing, or a single perovskite type composite oxide, silver, zirconium, indium, A step of firing a mixture with an additive substance containing one or more metal elements selected from the group consisting of molybdenum, niobium, tungsten, silicon, tin and antimony is provided.

Alternatively, a compound group containing a metal element forming the perovskite type composite oxide after firing, or an addition containing one or more metal elements selected from the group consisting of a perovskite type composite oxide simple substance and manganese and nickel. A step of firing a mixture with a substance is provided, wherein the ratio of the number of moles of the perovskite type complex oxide to the number of moles of the metal element contained in the additive substance is 1.00: 0.0.
2 to 0.50.

Alternatively, the method has a step of firing a mixture of the compound group or perovskite type complex oxide and an additive substance containing lanthanum, and is included in the additive substance and the number of moles of the perovskite type complex oxide. The ratio with the number of moles of the metal element is 1.00: 0.02 to 0.04.

The present inventor has made detailed studies on the composition of the composite oxide constituting the porous sintered body. That is,
Various metal elements have been added to powders of compounds such as La, Ca, Sr, and Mn, and the effect of the added metal elements on the porous sintered body has been investigated. If a specific metal element is added in this process, the metal element does not form a solid solution in the crystal phase of the perovskite-type composite oxide in the porous sintered body, and is precipitated as a second phase as a simple metal or a metal compound. I found a thing. Then, when the porous sintered body was subjected to the above-mentioned thermal cycle, it was confirmed that the dimensional shrinkage of the porous sintered body was remarkably suppressed, and the present invention was reached.

Specifically, as such a specific metal element, one or more metal elements selected from the group consisting of silver, zirconium, indium, molybdenum, niobium, tungsten, silicon, tin and antimony corresponded. . In particular, the number of moles of the perovskite complex oxide is 1.
When it was set to 00, this action and effect became remarkable by setting the molar ratio of the metal elements contained in the additive substance to 0.02 or more.

From this viewpoint, the molar ratio of the metal element contained in the additive substance is preferably 0.05 or more, more preferably 0.10 or more. In particular, in the region where the value is 0.10 or more, the change in dimensional shrinkage due to the heat cycle with respect to the increase in the addition amount of the metal element becomes small regardless of which metal element is added.

When the molar number of the perovskite type complex oxide is 1.00 and the molar ratio of the metal elements contained in the additive substance exceeds 0.50, the molded body is extremely burned during firing. It becomes easy to bind, and it has become difficult to manufacture a porous sintered body. For example, when lanthanum calcium manganite or lanthanum strontium manganite is taken as an example, the sintering temperature of these perovskite type complex oxides is preferably 1300 ° C. or higher, and more preferably 1400 ° C. When the ratio of the metal elements exceeds 0.50, the sintered body is significantly likely to be compacted even in the temperature range of 1400 ° C. or less, and the porosity of the sintered body is significantly reduced. It has become difficult to manufacture a porous sintered body having the same. Therefore,
The ratio of the number of moles of metal elements contained in the additive substance is 0.
It is preferably 5 or less.

From this point of view, it is more preferable that the ratio of the metal element contained in the additive substance is 0.4 or less.

Here, the substances forming the crystal phase other than the perovskite type complex oxide differ depending on the added metal.

From the viewpoint of preventing the dimensional shrinkage of the porous sintered body due to the heat cycle among the above-mentioned additional metal elements, it further comprises zirconium, indium, molybdenum, tungsten, silicon, tin, antimony and silver. One or more metal elements selected from the group are preferred.
That is, the addition amount of these metal elements is 0.20 at the above ratio.
When added, the dimensional shrinkage ratio per thermal cycle could be 0.01% or less. However, the "dimensional shrinkage rate per thermal cycle" refers to the average value of each dimensional shrinkage rate from the first thermal cycle to the tenth thermal cycle after sintering the porous sintered body. And

Further, one or more metal elements selected from the group consisting of zirconium, indium, tin, antimony and silver are preferable. That is, when the addition amount of these metal elements was 0.20 at the above ratio, the dimensional shrinkage per thermal cycle could be 0.005% or less. From this viewpoint, one or more metal elements selected from the group consisting of zirconium, indium and silver are more preferable.

When the porous sintered body is used as a heat resistant electrode, a high temperature electrode or a breathable electrode, it is necessary to improve the electric conductivity of the porous sintered body. From this viewpoint, in order to improve the electric conductivity of the porous sintered body, it is preferable to employ one or more metal elements selected from the group consisting of indium and silver among the above-mentioned additive metal elements. preferable. In particular, when silver is used, the surprising result is obtained in which the electric conductivity of the porous sintered body is significantly improved as compared with the case where the second phase is not precipitated.

The inventor of the present invention further added manganese, lanthanum and nickel to the group of compounds containing the metal element constituting the perovskite type complex oxide after firing. However, manganese and nickel are metal elements that can be substituted at the B site of the perovskite complex oxide, and lanthanum is a metal element that can be substituted at the A site of the perovskite complex oxide. Therefore, in the case where the A site and the B site have a molar ratio of about 1: 1 in the total sum of the compound group that should constitute the perovskite complex oxide and the additive substance added to the compound group, No phase precipitates.

Therefore, in order to produce the porous sintered body of the present invention, one or more compounds selected from the group consisting of compounds that should constitute the perovskite type complex oxide after firing and the group consisting of manganese, nickel and lanthanum. When the number of moles of the perovskite type complex oxide is set to 1.00 when firing the mixture with the additional substance containing the metal element, the number of moles of the metal element contained in the additional substance is set to 0.02 or more. It is necessary to precipitate the metal element contained in the additive substance.

Even when such an additive metal element is used, as in the case of the above-mentioned one, when the porous sintered body is also subjected to the above-mentioned thermal cycle, the size of the porous sintered body is changed. It was found that the contraction was significantly suppressed.

When the ratio of the number of moles of metal elements contained in the additive substance is less than 0.02, these metal elements form a solid solution with the crystal phase of the perovskite type complex oxide, and the durability against the dimensional shrinkage. Improvement of is not remarkable.

Of these, lanthanum has different properties from nickel and manganese, so it is necessary to mention it. That is, when lanthanum is added to the raw material powder of lanthanum manganite, the lanthanum is inserted into the A site of the perovskite type complex oxide, but when the amount of this lanthanum is excessive, lanthanum hydroxide precipitates as the second phase. Therefore, the porous sintered body collapses.

However, even if the lanthanum is added in excess and the lanthanum hydroxide is deposited as the second phase, the present inventor has found that if the amount of the lanthanum hydroxide deposited is within a certain range, It was discovered that the dimensional shrinkage of the porous sintered body can be significantly reduced, and the porous sintered body does not collapse. However, for this purpose, the ratio of the number of moles of the metal element contained in the additive substance is 0.02 or more, and 0.0
It was necessary to set it to 4 or less. If this exceeds 0.04, the structure of the porous sintered body may absorb water and collapse.

When manganese or nickel is used as the metal element contained in the additive substance, the ratio of the number of moles of the metal element contained in the additive substance is preferably 0.05 or more. It is more preferable to set the above. In particular, in the region where it was 0.10 or more, the dimensional shrinkage per thermal cycle could be remarkably reduced to 0.002% or less.

Further, if the ratio of the number of moles of the metal element contained in the additive substance exceeds 0.50 when the number of moles of the metal element contained in the compound group is set to 1.00, the reason as described above is caused. Therefore, the molded body becomes extremely easy to sinter during firing, which makes manufacture difficult. Therefore, the ratio of the metal element contained in the additive substance is preferably 0.5 or less.

From this viewpoint, it is more preferable that the ratio of the number of moles of the metal element contained in the additive substance is 0.4 or less.

When the porous sintered body is used as a heat resistant electrode, a high temperature electrode or a breathable electrode, it is necessary to improve the electric conductivity of the porous sintered body. From this point of view, in order to prevent the decrease in the electrical conductivity of the porous sintered body, among the above-mentioned additional metal elements, manganese,
It is preferable to employ nickel.

In the present invention, the second phase is precipitated in addition to the perovskite type complex oxide.
In some cases, it may be a simple metal composed of the above metal elements,
Alternatively, it may be a compound containing this metal. Further, an additive substance containing at least the metal element is added to the compound group to be formed after firing the perovskite type composite oxide, and the additive substance may be a simple metal or a compound containing the metal element. May be

Examples of compounds that should constitute the perovskite type complex oxide include oxides, carbonates, nitrates and sulfates of each metal element. Further, the above-mentioned additive substance can be mixed with the perovskite complex oxide.

[0036]

EXAMPLE To manufacture a porous sintered body according to the present invention,
In a preferred embodiment, each powder of the compound group that is a starting material of the perovskite-type composite oxide is mixed with the powder of the additive substance to produce a mixed powder, and the mixed powder is fired to produce a synthetic product. , Crush this compound. An appropriate organic binder and / or a pore-forming agent is added to this synthetic product and the product is molded to obtain a molded product.

The firing temperature of this molded body is 1300 ° C to
The temperature is preferably 1600 ° C. Baking temperature to 130
If the temperature is lower than 0 ° C, sintering will not be completed completely. 160
If the temperature is higher than 0 ° C, the structure of the porous sintered body will be too dense and the porosity will decrease.

Regarding the composition of the perovskite-type composite oxide and the second phase constituting the porous sintered body according to the present invention,
Further description will be made. The composition itself of the composite oxide can be applied to a known composition, but it is particularly preferable that the B site is occupied by at least manganese. More preferably, the A site of the composite oxide is occupied by at least one metal element selected from the group consisting of rare earth elements and alkaline earth metal elements. More preferably, the A site of the composite oxide is one or more metal elements selected from the group consisting of rare earth elements other than cerium and yttrium, and one or more metal elements selected from the group consisting of calcium and strontium. It is occupied by and.

The complex oxides that can be preferably used in the present invention are exemplified. This composite oxide preferably has a composition represented by the following general formula (I).

Embedded image R _1-X A _X MnO ₃ (I)

Here, R and A occupy the A site of the composite oxide, and Mn occupies the B site of the composite oxide.

R is a kind of metal element selected from the group consisting of rare earth elements other than cerium and yttrium. This group is the group consisting of yttrium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. As R, lantern, praseodymium, neodymium, samarium, dysprosium,
Those selected from the group consisting of gadolinium and yttrium are particularly preferred. A is one or more metals selected from the group consisting of calcium and strontium.

In this composition, 5% or more and 50% or less (x = 0.05 to 0.50) of the A site is replaced with calcium or strontium.

Further, a complex oxide having a composition represented by the following general formula (II) is also preferable.

Embedded image R _1-X A _X Mn _1-Z E _z O ₃ (II)

Here, R and A occupy the A site of the composite oxide, and Mn and E occupy the B site of the composite oxide. R
Is a metal element selected from the group consisting of rare earth elements other than cerium and yttrium. A is one or more metals selected from the group consisting of calcium and strontium.

In this composition, at least one metal atom E selected from the group consisting of aluminum, cobalt, copper, magnesium, chromium, nickel, iron, titanium and zinc is used to convert the manganese atom at the B site of the composite oxide. Some have been replaced.

The substitution ratio of the metal atom E other than the manganese atom at the B site is 0.02% or more and 20% or less (z
= 0.0002 to 0.20). By setting the substitution ratio to 0.02% or more, the effect of suppressing shrinkage due to the thermal cycle becomes more remarkable. However, if it exceeds 20%, the electric conductivity of the porous sintered body tends to decrease.

Further, in this composition, 5 of A site is added.
% Or more and 50% or less (x = 0.05 to 0.50) is replaced by calcium or strontium. If this substitution amount is less than 5%, the electric conductivity of the porous sintered body tends to decrease.

In another preferred composition, the A site of the composite oxide is selected from the group consisting of at least one first metal element selected from the group consisting of calcium and strontium, a rare earth element other than cerium, and yttrium. It is occupied by two or more selected second metal elements, 5 to 70% of the A site is occupied by the first metal element, and the B site of the composite oxide contains manganese. There is.

The composition of this composite oxide is preferably represented by the following general formula (III).

Embedded image R _1-X A _X MnO ₃ (III)

Here, R and A occupy the A site of the composite oxide, and Mn occupies the B site of the composite oxide.

A is one or more first metal elements selected from the group consisting of calcium and strontium.
R is a rare earth element other than cerium, and two or more second metal elements selected from the group consisting of yttrium. This group is a group consisting of yttrium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. The second metal element R is preferably selected from the group consisting of lanthanum, praseodymium, neodymium, samarium, dysprosium, gadolinium, and yttrium.

The substitution ratio X by the first metal element A is A
5 to 70% (x = 0.05 to 0.70) of the sites. From the viewpoint of electric conductivity of the porous sintered body, the substitution amount of calcium or strontium is preferably 50% or less.

The composition of the composite oxide is preferably represented by the following general formula (IV).

Embedded image R _1-X A _X Mn _1-z E _z O ₃ (IV)

A and R are the above-mentioned elements. E is one or more third metal elements selected from the group consisting of aluminum, cobalt, copper, magnesium, chromium, nickel, iron, titanium, and zinc, and the rest of the B site is occupied by manganese.

The substitution ratio X by the first metal element A is A
5 to 70% (x = 0.05 to 0.70) of the sites. If this substitution amount is less than 5%, the electric conductivity of the porous sintered body tends to decrease. The substitution ratio of the first metal element A is preferably 50% or less.

As described above, R is a rare earth element other than cerium and two or more second metal elements selected from the group consisting of yttrium. When one of the second metal elements is lanthanum, the proportion of lanthanum at the A site is preferably 1 to 94%. In this case, the proportion of the other second metal element R is preferably 1 to 80% of the A site, and 2
It is more preferable to set it to 0 to 50%.

The substitution ratio of the third metal element E is 0.
It is preferably set to 02% to 40%. 0.02 for this
When it is at least%, the effect of suppressing shrinkage due to the thermal cycle becomes more remarkable.

Since the perovskite type complex oxide can have a non-stoichiometric composition, the composition variation of the complex oxide due to some impurities inevitably mixed in the manufacturing process of the porous sintered body is allowed. To be done.

The porous sintered body of the present invention can be particularly preferably used as a high temperature electrode material which is stable against heat cycles. Examples of such high-temperature electrode materials include fusion reactors, MHD
There are electrode materials for power generation.

Further, the porous sintered body of the present invention is used as an air electrode material for SOFC because of its heat resistance and air permeability.
It can be used particularly preferably. Further, it is preferably used as a material for a self-supporting air electrode substrate. Such an air electrode base is used as a base material of a single cell, and each component such as a solid electrolyte membrane, a fuel electrode membrane, an interconnector and a separator is laminated on the air electrode base. At this time, the air electrode substrate has a cylindrical shape with both ends open,
The shape may be a bottomed cylindrical shape with one end open and the other end closed, a flat plate shape, or the like. Among them, any one of the above-mentioned cylindrical shapes is particularly preferable because thermal stress is hardly applied and gas sealing is easy.

The porosity of the porous sintered body is preferably 10 to 40%. When it is used as an air electrode material for SOFC, the porosity is further increased to 15-40%.
Is preferable, and it is more preferable that it is 25 to 35%. In this case, by setting the porosity of the air electrode to 15% or more, the gas diffusion resistance is reduced, and by setting the porosity to 40% or less, it is possible to secure some strength.

Hereinafter, more specific experimental results will be described. (Production of Experimental Sample) As a starting material, La ₂ O ₃ , C
Each powder of aCO ₃ and Mn ₃ O ₄ was selected as a compound group constituting the perovskite type complex oxide. However, the compounding ratio of these compound groups is La: Ca: Mn = 0.8: 0.2: in terms of the molar ratio of each metal element.
It was set to 1.0. This is La _0.8 Ca _0.2 M
Corresponds to the composition of nO ₃ .

For powders of this compound group, ZrO ₂ ,
_{In 2 O 3, MoO 3,} Nb 2 O 5, WO 3, Si
O ₂ , SnO ₂ , Sb ₂ O ₃ , Ag ₂ O, NiO, Mn
₃ O ₄ or La ₂ O ₃ Each additive substance powder is weighed,
Mixed. The mixing ratio of this additive substance is the above-mentioned La.
_0.8 Ca _0.2 MnO ₃ 1.00 mol, 0.0
2, 0.05, 0.10, 0.20, 0.30, 0.4
It was 0, 0.50 or 0.60 mol. However, La
_{When 2} O ₃ is added, the addition ratio is 0.01,
It was set to 0.02, 0.04, 0.06 or 0.20.

This mixed powder was dried and molded by a cold isostatic press method at a pressure of 1 tf / cm ² to prepare a molded body. This molded body was placed in the atmosphere for 15
Heat treatment was performed at 80 ° C. for 10 hours to produce a synthetic product.

This synthetic product was crushed with a trommel for 8 to 12 hours to obtain a synthetic powder having an average particle size of about 6 μm. Next, water and an organic binder (acrylic binder) were added to and mixed with this synthetic powder to prepare a slurry having a water content of 40%, and granulated with a spray dryer. With this granulated powder,
A pore-forming agent (acrylic powder) was dry-mixed and dry-press molded to produce a flat plate-shaped molded body having a length of 50 mm, a width of 25 mm and a thickness of 6 mm. This molded body is 1200 ° C
It was fired at 1600 ° C for 5 hours to obtain each porous sintered body.
However, the firing temperature was changed so that the porosity of each porous sintered body was about 30%. The porosity of each porous sintered body is
It was measured by the water displacement method.

Each porous sintered body was processed to produce a quadrangular prism-shaped sample having a length of 4 mm, a width of 3 mm and a length of 40 mm.
Using each of these samples, thermal cycle shrinkage and electrical conductivity were measured as described below.

(Measurement of Crystalline Phase and Chemical Composition) Part of the cut margin when the sample was cut out from each porous sintered body was embedded in the resin, the resin was polished, and the scanning electron microscope and EDX (X The size of the precipitation phase was measured by a line spectroscopy analyzer), and the type of each metal element was identified. Also,
The remainder of the cut portion of the porous sintered body was ground in an alumina mortar, the crystal phase was measured using an X-ray diffractometer, and the chemical composition was identified by fluorescent X-ray and inductively coupled plasma atomic spectroscopy.

As a result, the crystal phase of the second phase actually detected in the porous sintered body was related to the metal element in the additive substance as shown in Table 1.

[0069]

[Table 1]

As a result of observation with a scanning electron microscope and observation with an X-ray diffractometer, no crystal phase other than those shown in Table 1 could be identified. In addition, as a result of measurement by EDX, it is considered that the metal elements other than nickel, manganese, and lanthanum were not in solid solution in the composite oxide, and all the added metal elements were precipitated.

As a result of measurement with a scanning electron microscope photograph, an X-ray spectroscopic analyzer and an X-ray diffractometer, the solid solution range of nickel, manganese and lanthanum in the perovskite type complex oxide is shown by the above molar ratio. It was 0.02 or less.

Scanning electron micrographs of the ceramic structure of each porous sintered body are shown in FIGS. 1 to 12, respectively. However, FIG. 1 shows the ceramic structure of the porous sintered body when zirconia is added. Mn ₃ O ₄ is precipitated in the gray portion, and ZrO ₂ is precipitated in the light gray. FIG. 2 shows the case where indium was added, and the white part is the deposited indium. FIG.
Shows the case where molybdenum was added, and the gray portion is CaMoO ₄ . FIG. 4 shows the case where niobium was added, and the white portion is LaNbO ₄ . FIG. 5 shows the case where tungsten is added. FIG. 6 shows the case where silicon is added. FIG. 7 shows the case where tin is added. FIG.
Shows the case where antimony was added, and the white part is La.
₃ Sb ₃ O ₁₁ or Ca ₂ La ₃ Sb ₃ O ₁₄ is shown. Fig. 9 shows the case where silver is added, and the white part is Ag.
, And the gray portion shows Mn ₃ O ₄ . Figure 10
The case where nickel is added is shown, and the black portion is Mn ₃ O ₄
, And the gray part indicates NiMn ₂ O ₄ . Figure 11
Shows the case where manganese was added, and the black part is Mn ₃
Indicates O ₄ . FIG. 12 shows the case where lanthanum was added, and the white portion shows La (OH) ₃ .

(Measurement of Thermal Cycle Shrinkage) Each of the above-mentioned samples was subjected to 6 at a temperature rising rate of 200 ° C./hour in the atmosphere.
The temperature was raised to 00 ° C. After this, 600 ℃ and 1000 ℃
Between the and, a heat cycle was performed 10 times at a temperature rising / falling rate of 200 ° C./hour, and the temperature was lowered to room temperature. At this time, in each heat cycle, at 600 ° C. and 1000 ° C., a constant temperature was maintained every 30 minutes. Thereafter, the dimensions of each sample were measured using a micrometer, and the dimensional shrinkage before and after the heat cycle was calculated. FIG. 13 shows the dimensional shrinkage rate per 10 initial thermal cycles. However, FIG. 13 shows the measurement results when the molar ratio of each metal element is 0.20. In addition, the first 1 of La _0.8 Ca _0.2 MnO ₃ simple substance
The dimensional shrinkage after 0 thermal cycles is 0.19%.

As can be seen from these results, according to the porous sintered body of the present invention and the method for producing the same, the dimensional shrinkage ratio due to the heat cycle can be remarkably reduced. When lanthanum was added at a molar ratio of 0.20 and 0.06, the porous sintered body collapsed. The dimensional shrinkage was 0.04% when the molar ratio of lanthanum was 0.04.

Further, in FIG. 14, the thermal cycle when manganese, silver and tungsten are variously changed as described above with respect to the respective addition ratios of the metal elements is first shown as 1.
The dimensional shrinkage ratio of the porous sintered body when applied 0 times is shown. As can be seen from this result, the addition ratio of the metal element is 0.0
When it is 2 or more, the dimensional shrinkage is remarkably reduced, and when it is 0.05 or more, the dimensional shrinkage is further reduced. I can no longer. 0.2 more
It was found that when the ratio is 0 or more, the manganese and tungsten hardly show the change in the dimensional shrinkage ratio even if the addition ratio is further increased.

The overall trend is that other metal elements, namely zirconium, indium, molybdenum, niobium,
The same was true for silicon, tin, antimony and nickel. In particular, of these graphs, nickel and indium have almost the same graph as silver, and zirconium and antimony have almost the same graph as manganese. For tin, the graph was almost the same as for tungsten. Regarding lanthanum, when the molar ratio of 0.02 was added, the dimensional shrinkage ratio was remarkably reduced. However, when the lanthanum content exceeds 0.04, it was found that the porous sintered body starts to absorb water and start to deteriorate.
However, in the range of 0.02 to 0.04, the porous sintered body was stable.

(Measurement of Electric Conductivity) With respect to each of the above-mentioned square pole-shaped samples cut out from the porous sintered body to which 0.20 of each metal element shown in Table 2 was added, a direct current four-terminal method was performed in an oxidizing atmosphere. The electrical conductivity was measured at 1000 ° C.
The results are shown in Table 2.

[0078]

[Table 2]

As can be seen from Table 2, when silver was added, the electrical conductivity was remarkably improved as compared with La _0.8 Ca _0.2 MnO ₃ containing no added metal element. It is considered that this is due to the precipitation of silver as shown in Table 1. Also, when indium was added, the electric conductivity was almost the same as that of La _0.8 Ca _0.2 MnO ₃ as well. This is also considered to be due to the deposition of indium metal.

Further, among manganese, silver and indium among the metal elements shown in Table 2, the values of the electric conductivity when various addition ratios of the metal elements are changed as described above are shown in Table 3. .

[0081]

[Table 3]

As can be seen from these results, when manganese is added, its electric conductivity is La _0.8 Ca _0.2.
It has almost the same electrical conductivity as MnO ₃ and almost no dependence on the amount added. However, when silver is added, it can be seen that the electrical conductivity of the sample improves as the addition ratio of silver increases. Therefore, from the viewpoint of the electrical conductivity and the dimensional shrinkage ratio, it can be said that the addition ratio of silver is more preferably 0.20 or more and 0.50 or less. Also, with respect to indium, when the addition ratio is about 0.20, La _0.8 Ca _0.2 Mn
It was almost equal to the electrical conductivity of O ₃ , but this was 0.3.
It was found that when the value was 0 or more, the electrical conductivity of the sample was further increased. Therefore, from this viewpoint, it can be said that the addition ratio of indium is more preferably 0.30 or more and 0.50 or less. The reason for the upper limit of 0.50 is that, as described in the next section (Measurement of Porosity), when the addition amount of the metal element exceeds 0.50, the porosity sharply decreases.

(Measurement of Porosity) A porous sintered body was manufactured according to the manufacturing method described above. However, manganese or silver is selected as the additive metal element, and the firing temperature is 1400 ° C.
Fixed to. Then, the porosity of the obtained porous sintered body was measured. The result is shown in FIG. As a result, it was found that, particularly when the addition ratio of the metal element exceeds 0.50, the sintering of the porous sintered body proceeds and the porosity becomes 10% or less, and the porous body approaches a dense body. From this point of view, it is necessary to set the addition ratio of the metal element to 0.50 or less. Further, in the application of the air electrode of SOFC, if the porosity is less than 10%, the function cannot be achieved, and from this viewpoint, it is necessary to set the addition ratio of the metal element to 0.50 or less.

Also, when indium, zirconium and nickel were used, the same result was obtained.

[0085]

As described above, according to the present invention, it is possible to provide a new porous sintered body capable of suppressing the dimensional shrinkage due to the heat cycle.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph showing a ceramic structure of a porous sintered body when zirconia is added.

FIG. 2 is a scanning electron micrograph showing a ceramic structure of a porous sintered body when indium is added.

FIG. 3 is a scanning electron micrograph showing a ceramic structure of a porous sintered body when molybdenum is added.

FIG. 4 is a scanning electron micrograph showing a ceramic structure of a porous sintered body when niobium is added.

FIG. 5 is a scanning electron micrograph showing a ceramic structure of a porous sintered body when tungsten is added.

FIG. 6 is a scanning electron micrograph showing a ceramic structure of a porous sintered body when silicon is added.

FIG. 7 is a scanning electron micrograph showing a ceramic structure of a porous sintered body showing the case where tin is added.

FIG. 8 is a scanning electron micrograph showing a ceramic structure of a porous sintered body when antimony is added.

FIG. 9 is a scanning electron micrograph showing a ceramic structure of a porous sintered body when silver is added.

FIG. 10 is a scanning electron micrograph showing a ceramic structure of a porous sintered body when nickel is added.

FIG. 11 is a scanning electron micrograph showing a ceramic structure of a porous sintered body when manganese is added.

FIG. 12 is a scanning electron micrograph showing a ceramic structure of a porous sintered body when lanthanum is added.

FIG. 13 is a graph showing the relationship between each added metal element and the dimensional shrinkage rate of the porous sintered body due to the heat cycle, and the molar ratio of each metal element is 0.20.

FIG. 14 is a graph showing the relationship between the ratio of the number of moles of manganese, silver or tank steel and the dimensional shrinkage rate of the porous sintered body due to the heat cycle.

FIG. 15 is a graph showing the relationship between the molar ratio of manganese or silver and the porosity of the porous sintered body.

Claims (10)

[Claims] 1. A perovskite-type composite oxide phase and a crystal phase comprising one or more metals selected from the group consisting of silver, zirconium, indium, molybdenum, niobium, tungsten, silicon, tin and antimony or a compound thereof. A porous sintered body characterized by being provided. 2. The porous sintered body according to claim 1, wherein manganese is contained in the B site of the perovskite type composite oxide. 3. The porous sintered body according to claim 1, wherein the A site of the perovskite type complex oxide contains lanthanum. 4. A porous calcination comprising a perovskite type complex oxide phase and a crystal phase made of one or more metals selected from the group consisting of lanthanum, manganese and nickel or a compound thereof. Union. 5. The porous sintered body according to claim 4, wherein manganese is contained in the B site of the perovskite type composite oxide. 6. The porous sintered body according to claim 4, wherein lanthanum is contained in the A site of the perovskite type composite oxide. 7. A compound group containing a metal element forming a perovskite type complex oxide or a perovskite type complex oxide after firing, and a group consisting of silver, zirconium, indium, molybdenum, niobium, tungsten, silicon, tin and antimony. A method for producing a porous sintered body, comprising a step of firing a mixture with an additive substance containing one or more selected metal elements. 8. The ratio of the number of moles of the perovskite type complex oxide to the number of moles of the metal element contained in the additive substance is set to 1.00: 0.02 to 0.50. The method for producing a porous sintered body according to claim 7. 9. A compound group containing a metal element constituting a perovskite type complex oxide or a perovskite type complex oxide after firing, and an additive substance containing one or more metal elements selected from the group consisting of manganese and nickel. Of the perovskite-type composite oxide and the ratio of the number of moles of the metal element contained in the additive substance to the ratio of 1.00: 0.02 to 0.50.
And a method for producing a porous sintered body. 10. A step of firing a mixture of a perovskite-type composite oxide or a group of compounds containing a metal element constituting the perovskite-type composite oxide after firing and an additive substance containing lanthanum, the perovskite comprising: The ratio of the number of moles of the type composite oxide to the number of moles of the metal element contained in the additive substance is 1.00: 0.02 to 0.04, and the production of a porous sintered body. Method.