JP3113913B1 - Electrically conductive cerium double oxide ceramics and its manufacturing method - Google Patents

Abstract

Abstract: A tetragonal structure containing cerium in an oxidation state of +3 because cerium oxide (CeO ₂ ) in an oxidation state of +4 is easily reduced by a solid-phase reaction with V ₂ O ₅ in air. generating a CEVO ₄ with, as well as compounds CEVO ₄
Based on the fact that is an electrically conductive ceramic,
To find a ceramic with a new composition that has the same crystal structure and exhibits high electrical conductivity by ionic substitution by the addition of a component oxide. [Configuration] formula _{Ce lx Ca x VO 4- (x} / 2) (0 <x ≦
_{0.41), Ce 1-y Sr} y VO 4- (y / 2) (0 <y ≦
0.21), Ce _1-z Pb _z VO _{4- (z / 2)} (0 <z ≦
0.1), Ce _1-w Bi _w VO ₄ (0 <w ≦ 0.67)
An electrically conductive cerium oxide ceramic having a tetragonal structure represented by: These oxide ceramics
It is obtained by heating the mixed starting materials in the air to cause a solid-phase reaction to produce solid solutions of oxide ceramics of the respective general formulas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a compound of the general formula _Celx C
a _x VO _{4- (x / 2)} (0 <x ≦ 0.41) An electrically conductive cerium calcium calcium having a tetragonal structure
Vanadium oxide ceramics and general formula Ce _1-y Sr
_y VO _{4- (y / 2)} (0 <y ≦ 0.21), an electrically conductive cerium-strontium-vanadium oxide ceramic having a tetragonal structure, and a general formula Ce _1-z P
_{b z VO 4- (z / 2} ) (0 <z ≦ 0.1) electrically conductive cerium, lead, vanadium oxide having the structure of tetragonal represented by ceramics and formula Ce _1-w Bi _w VO _Four
The present invention relates to an electrically conductive cerium-bismuth-vanadium oxide ceramic having a tetragonal structure represented by (0 <w ≦ 0.67) and a method for producing these oxide ceramics.

[0002]

2. Description of the Related Art Conventionally, rare earth / vanadium oxide compounds (LnVO ₄ , where Ln = Ce to Lu, Y) are shown in FIG.
Zircon (ZrSiO ₄ , a = 6.
It has a tetragonal crystal structure called 6164 angstrom, c = 6.0150 angstrom) type, the oxidation state of the rare earth atom (Ln) is +3, and its electric property is considered to be an insulator. ing. However,
Unlike the case where Ln is Pr-Lu or Y, the synthesis of cerium-vanadium oxide compound (CeVO ₄ ) is performed in air because the starting material ceria (CeO ₂ ) has an oxidation state of +4. vanadium pentoxide (V ₂ O ₅₎
By a wet method be produced directly in a solid phase reaction is considered to be difficult, many synthetic methods of reduction of the cerium by atmosphere control or CEC1 ₃ oxidation state and the like cerium +3 as a starting material and Things were common.

On the other hand, CeO ₂ and V ₂ O ₅ are mixed in a molar ratio of 2:
Although there is a report that CeVO ₄ having a tetragonal crystal structure is produced even when the starting material mixed in 1 is subjected to a solid-phase reaction in air, it is generally observed that oxides in an oxidizing atmosphere form a solid phase. Since the oxidation state +4 of Ce is stable in the phase reaction,
These reports were questioned.

[0004] The present inventor has previously reported that the molar ratio is 2: 1.
CeO_TwoAnd V_TwoO_FiveSolid phase reaction in air
X-ray diffraction as shown in Fig. 14
Zircon-type tetragonal crystal with pattern (using CuKα ray)
CeVO with systemic crystal structure _Four(A = 7.4016 on
Gstrom, c = 6.4980 angstroms)
Confirm that it is generated, establish the synthesis conditions,
CeVO_FourIs another isomorphic compound LnVO_Four(Ln = Pr ~
Lu, Y), as shown in FIG.
It was found that it was a conductive semiconductor ceramic.

[0005]

SUMMARY OF THE INVENTION The present invention relates to an oxidation state +
Cerium oxide (CeO ₂ ) of No. ₄ is easily reduced by a solid-phase reaction with V ₂ O ₅ in air to produce CeVO ₄ having a tetragonal structure containing cerium in an oxidation state of +3. Based on the fact that the compound CeVO ₄ is an electrically conductive ceramic, a new ceramic having the same crystal structure and exhibiting high electrical conductivity is found by ionic substitution by adding an oxide of the third component. The purpose is to do so.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventor examined whether or not a part of cerium of a conventional cerium-vanadium oxide compound can be replaced with another metal element. As a result, they have found that calcium, strontium, lead, and bismuth substitute a part of cerium to form a stable solid solution having a tetragonal crystal structure, and that its electric conductivity is higher than that of CeVO _4. Was.

That is, the present invention relates to the general formula Ce _lx Ca
_x VO _{4- (x / 2)} and the electrically conductive cerium calcium vanadium oxide ceramics having the structure of tetragonal represented by (0 <x ≦ 0.41), the general formula Ce _1-y Sr _y
VO _{4-(y / 2)} (0 <y ≦ 0.21), an electrically conductive cerium strontium having a tetragonal structure
Vanadium oxide ceramics and general formula Ce _1-z Pb
_{z VO 4- (z / 2)} (0 <z ≦ 0.1) electrically conductive cerium, lead, vanadium oxide having the structure of tetragonal represented by ceramics and formula Ce _1-w Bi _w VO
₄ An electrically conductive cerium-bismuth-vanadium oxide ceramic having a tetragonal structure represented by (0 <w ≦ 0.67).

[0008] With respect to the typical composition of the above-mentioned four kinds of oxide ceramics of the present invention, the change of the electric conductivity with temperature is shown in FIG. 1 in the case of cerium-calcium-vanadium oxide ceramics, and cerium-strontium-vanadium is shown in FIG. FIG. 2 shows the case of oxide ceramics, and FIG. 3 shows the case of cerium / lead / vanadium oxide ceramics.
FIG. 4 shows the case of cerium-bismuth-vanadium oxide ceramics. FIG. 5 shows the case of a cerium-vanadium oxide compound for reference. As is clear from FIGS. 1, 2, 3, and 4, the above four types of ceramics have semiconductor properties exhibiting high electrical conductivity, and thus are used as materials for electrodes, sensors, catalysts, and the like. Having.

Of the above four types of oxide ceramics, cerium-calcium-vanadium oxide ceramics are:
Ceria (CeO ₂ ) and calcium oxide (CaO) or a compound decomposed to calcium oxide by heating, and vanadium pentoxide (V ₂ O ₅ ) or a compound decomposed to vanadium pentoxide by heating The molar ratio of CeO ₂ : CaO: V ₂ O ₅ is (1-x): x: 0.5 (where 0 <x ≦ 0.4
1) The starting materials mixed so that
It is obtained by performing a solid-phase reaction at a temperature of not less than ° C. _{Cel x} Ca _x VO _{4- (x / 2) of} uniform composition (0 <x ≦ 0.
41) In order to synthesize a ceramic powder, it is desirable to heat the starting material mixture at 800 ° C. in air, then pulverize and mix again, and reheat at 850 ° C.

Cerium-strontium-vanadium oxide ceramics include ceria (CeO ₂ ) and strontium oxide (SrO) or a compound decomposed into strontium oxide by heating, and vanadium pentoxide (V ₂ O ₅ ) or heating. The compound which is decomposed into vanadium pentoxide by the treatment is expressed as CeO ₂ : SrO: V ₂ O _{5 in a} molar ratio of (1-y): y: 0.
5, (where 0 <y ≦ 0.21), and is obtained by subjecting mixed starting materials to a solid phase reaction at a temperature of 400 ° C. or more in air. Ce a uniform composition _1-y Sr _y
VO _{4- (y / 2)} (0 <y ≦ 0.21) In order to synthesize a ceramic powder, the starting material mixture is heated at 850 ° C. in air.
It is desirable to pulverize and mix again after heating at 900 ° C. and reheat at 900 ° C.

Cerium / lead / vanadium oxide ceramics include ceria (CeO ₂ ) and lead monoxide (PbO) or a compound decomposed into lead monoxide when heated, and vanadium pentoxide (V ₂ O ₅ ). Or a compound that is decomposed into vanadium pentoxide by heating,
The molar ratio of CeO ₂ : PbO: V ₂ O ₅ is (1)
-Z): It is obtained by performing a solid-phase reaction of starting materials mixed so that z: 0.5, where 0 <z ≦ 0.1, at a temperature of 480 ° C. or higher in air. In order to synthesize Ce _1-z Pb _z VO _{4- (z / 2)} (0 <z ≦ 0.1) ceramic powder having a uniform composition, after heating the above mixture at 800 ° C. in air, Crush and mix again, 830 ℃
It is desirable to re-heat.

Cerium, bismuth, vanadium oxide ceramics include ceria (CeO ₂ ) and bismuth oxide (B
i ₂ O ₃ ) or a compound which is decomposed into bismuth oxide by heating, and vanadium pentoxide (V ₂ O ₅ )
Alternatively, a compound which is decomposed into vanadium pentoxide by heating is mixed with a compound in a molar ratio of CeO ₂ : Bi.
₂ O ₃ : V ₂ O ₅ is (1-w) :( w / 2): 0.5,
(However, 0 <w ≦ 0.67) It is obtained by performing a solid-phase reaction of the starting materials mixed so as to satisfy the condition of 500 ° C. or more in air. Ce _1-w Bi _w VO with uniform composition
₄ (0 <w ≦ 0.67) In order to synthesize a ceramic powder, it is desirable to heat the above mixture at 800 ° C. in air, pulverize and mix again, and reheat at 830 ° C.

[0013]

BEST MODE _FOR CARRYING OUT THE INVENTION The general formula _{Cel x} Ca _x V
O _{4- (x / 2)} and the electrically conductive cerium calcium vanadium oxide ceramics having the structure of tetragonal represented by (0 <x ≦ 0.41), the general formula Ce _1-y Sr _y VO
_{4- (y / 2)} and the electrically conductive cerium strontium vanadium oxide ceramics having the structure of tetragonal represented by (0 <y ≦ 0.21), the general formula Ce _1-z Pb _z V
O _{4- (z / 2)} electrically conductive cerium, lead, vanadium oxide having the structure of tetragonal represented by (0 <z ≦ 0.1) ceramics and the general formula _{Ce 1-w Bi w VO 4} ( 0 <
w ≦ 0.67) The conditions of the solid-phase reaction in air to obtain an electrically conductive cerium-bismuth-vanadium oxide ceramic having a tetragonal structure represented by the following formula: The measurement results of the physical properties will be described.

<A> Cerium-Calcium-Vanadium Oxide Ceramics Observation of the process of the solid-phase reaction was performed by a thermal analysis method using a simultaneous measurement apparatus for differential heat and thermobalance. First, ceria (CeO
₂ ), calcium carbonate (CaCO ₃ ) and vanadium pentoxide (V ₂ O ₅ ) in a molar ratio of CeO ₂ : C
aO: V ₂ O ₅ is (1-x): x: 0.5 (provided that 0
<X ≦ 0.41) The starting materials mixed so as to satisfy the condition were heated and heated in the air. FIG. 6 shows the measurement results for the composition at x = 0.1, where the dotted line shows the differential thermal curve and the solid line shows the thermobalance curve.

Although the differential thermal curve does not show a clear thermal change up to around 650 ° C., the weight change by the thermobalance is 540.
The weight starts to decrease at around ℃ and ends at around 850 ° C.
Further, a clear endothermic peak at 650 ° C. in the differential thermal analysis is
It corresponds to the melting point of vanadium pentoxide (literature value, 690 ° C.), and it is clear from the result of the thermobalance that the endothermic peak and the thermal change of the mixed raw material are almost finished. The weight loss rate during that time was 4.07%, and the release of oxygen by the reduction of cerium in the following chemical reaction formula,
Emission of carbon dioxide from calcium carbonate (sum of calculated values,
(4.53%), but the fact that the measured value is slightly smaller is different from the synthesis process in which heat treatment is performed at a constant temperature for a long time, and the reaction reaches an equilibrium in the thermal analysis process while heating and raising the temperature. It depends.

0.9 CeO ₂ +0.1 CaCO ₃ +0.
_{5V 2 O 5 → Ce 0.9 Ca} 0 .1 VO 3.95 + 0.225O
₂ + 0.1CO ₂ Accordingly, the general formula _{Ce lx Ca x VO 4- (x} / 2) (0 <
cerium-calcium-vanadium oxide ceramics having a tetragonal structure represented by x ≦ 0.41)
Ceria (CeO ₂ ), calcium oxide (CaO), and vanadium pentoxide (V ₂ O ₅ ) are mixed in a molar ratio of C
eO ₂ : CaO: V ₂ O ₅ is (1-x): x: 0.5,
(Where 0 <x ≦ 0.41), and the starting materials mixed and mixed can be synthesized by performing a solid-phase reaction at a temperature of 540 ° C. or more in air.

The powder X-ray diffraction pattern of the cerium-calcium-vanadium oxide ceramic having a tetragonal structure is similar to FIG. 14, and the lattice constant is slightly different due to the difference in the composition x. Therefore, the solid solution region can be determined by measuring the change of the tetragonal lattice constants a and c depending on the composition x. From FIG. 10 in which the results are plotted, formation of a solid solution in which cerium atoms are replaced by calcium atoms until x = 0.41 is observed.

The solid solution Cel _x C thus obtained
a _x VO _{4- (x / 2)} (0 <x ≦ 0.41) An arbitrary composition powder is formed into a disc-shaped green compact, sufficiently sintered, and electrodes are formed on both surfaces of the sintered body. Then, the electric conductivity was measured by a DC two-terminal method while heating in an electric furnace. The result is x = 0.2
1 is shown in FIG. <B> Cerium / Strontium / Vanadium Oxide Ceramics Ceria (CeO ₂ ) and strontium carbonate (SrC)
O ₃₎ and a vanadium pentoxide _{(V 2 O 5), CeO} 2 the ratio is in a molar ratio of: SrO: V ₂ O ₅ is (1-y):
The starting materials mixed so that y: 0.5 (provided that 0 <y ≦ 0.21) were heated and heated in air as a sample for thermal analysis. FIG. 7 shows the measurement results for the composition at y = 0.1, in which the dotted line shows the differential heat curve, and the solid line shows the thermobalance curve.

Although the differential thermal curve does not show a clear thermal change up to around 650 ° C., the weight change by the thermobalance is 370.
The weight starts to decrease around ℃ and ends at around 900 ℃.
The clear endothermic peak at 650 ° C. in the differential thermal analysis corresponds to the melting point of vanadium pentoxide (literature value, 690 ° C.)
It is clear from the results of the thermobalance that the heat change of the mixed raw material has almost completely ended along with the end of the endothermic peak. During that time, the weight loss rate was 4.13%, and the release of oxygen due to the reduction of cerium and the release of carbon dioxide from strontium carbonate in the following chemical reaction formula (total calculated value, 4.10%).
(45%), but the measured value is slightly smaller than in the synthesis process where heat treatment is carried out at a constant temperature for a long time. by.

0.9 CeO ₂ +0.1 SrCO ₃ +0.
_{5V 2 O 5 → Ce 0.9 Sr} 0 .1 VO 3.95 + 0.225O
₂ + 0.1CO ₂ Accordingly, the general formula _{Ce 1-y Sr y VO 4-} (y / 2) (0 <
cerium-strontium-vanadium oxide ceramic having a tetragonal structure represented by y ≦ 0.21) is composed of ceria (CeO ₂ ) and strontium oxide (Sr).
O) and vanadium pentoxide (V ₂ O ₅ ) in a molar ratio of CeO ₂ : SrO: V ₂ O ₅ (1-y):
y: 0.5 (provided that 0 <y ≦ 0.21) and can be synthesized by subjecting the mixed starting materials to a solid phase reaction at a temperature of 370 ° C. or higher in air.

The powder X-ray diffraction pattern of the cerium-strontium-vanadium oxide ceramic having a tetragonal structure is similar to FIG. 14, and the lattice constant is slightly different depending on the difference in the composition y. Therefore, the solid solution region can be determined by measuring the change in the tetragonal lattice constants a and c depending on the composition y. From FIG. 11 in which the results are plotted, formation of a solid solution in which cerium atoms are replaced with strontium atoms until y = 0.21 is observed.

The solid solution Ce _1-y S thus obtained is obtained.
A powder having an arbitrary composition of r _y VO _{4- (y / 2)} (0 <y ≦ 0.21) is formed into a disc-shaped green compact, sufficiently sintered, and electrodes are formed on both surfaces of the sintered body. Then, the electric conductivity was measured by a DC two-terminal method while heating in an electric furnace. The result is x = 0.2
2 is shown in FIG. <C> Cerium-lead-vanadium oxide ceramic In the case of cerium-lead-vanadium oxide ceramic, ceria (CeO ₂ ), lead monoxide (PbO), and vanadium pentoxide (V ₂ O ₅ ) are used. The ratio is C
eO ₂ : PbO: V ₂ O ₅ is (1-z): z: 0.5,
(However, 0 <z ≦ 0.1), the starting materials mixed and mixed were used as a sample for thermal analysis, and heated and heated in air. FIG. 8 is a graph showing the measurement results for the composition at x = 0.05, in which the dotted line shows the differential heat curve, and the solid line shows the thermobalance curve.

Although the differential thermal curve does not show a clear thermal change, the weight change by the thermobalance starts decreasing around 480 ° C. and ends at around 750 ° C. The weight loss rate of 2.54% during this period corresponds to the release of oxygen due to the reduction of cerium in the following chemical reaction formula (calculated value, 2.86). Unlike the synthesis process in which the heat treatment is performed for a long time, the reaction does not reach an equilibrium in the thermal analysis process while heating and raising the temperature.

0.95 CeO ₂ +0.05 PbO + 0.
5V ₂ O ₅ → Ce _0.95 Pb _0.05 VO _3.975 +0.237
5O ₂ Therefore, the general formula Ce _1-z Pb _z VO _{4- (z / 2)} (0 <
cerium-lead-vanadium oxide ceramics having a tetragonal structure represented by z ≦ 0.1
eO ₂ ), lead monoxide (PbO), and vanadium pentoxide (V ₂ O ₅ ) in a molar ratio of CeO ₂ : Pb
O: V ₂ O ₅ is (1-z): z: 0.5 (provided that 0 <
z ≦ 0.1) and can be synthesized by subjecting the mixed starting materials to a solid phase reaction at a temperature of 480 ° C. or higher in air.

The powder X-ray diffraction pattern of the cerium-lead-vanadium oxide ceramic having a tetragonal structure is similar to FIG. 14, and the lattice constant is slightly different due to the difference in the composition z. Therefore, the solid solution region can be determined by measuring the change in the tetragonal lattice constants a and c depending on the composition z. From FIG. 12 in which the results are plotted, formation of a solid solution in which cerium atoms are replaced by lead atoms up to z = 0.1 is observed.

The solid solution Ce _1-z P thus obtained is
b _z VO _{4- (z / 2)} (0 <z ≦ 0.1) An arbitrary composition powder is formed into a disc-shaped green compact, sufficiently sintered, and electrodes are formed on both surfaces of the sintered body. Then, the electric conductivity was measured by a DC two-terminal method while heating in an electric furnace. FIG. 3 shows the result when x = 0.1. <D> Cerium bismuth vanadium oxide ceramic In the case of cerium bismuth vanadium oxide ceramic, ceria (CeO ₂ ) and bismuth oxide (Bi ₂ O
₃₎ and vanadium pentoxide _{(V 2 O 5), CeO} 2 the ratio is in a molar _{ratio: Bi 2 O 3: V 2} O 5 is (1-
w): (w / 2): 0.5 (provided that 0 <w ≦ 0.6)
7) The starting materials mixed and weighed so as to be as described above were used as a sample for thermal analysis, and heated and heated in air. FIG. 9 shows that w =
It is a graph which shows the measurement result regarding the composition of 0.1, a dotted line shows a differential heat curve, and a solid line shows a thermobalance curve.

The differential thermal curve is 506 ° C.
A change occurs at 6 ° C. Further, 645 of differential thermal analysis
The clear endothermic peak at ° C. corresponds to the melting point of vanadium pentoxide (literature value, 690 ° C.). Further, it is clear from the result of the thermobalance that the heat change of the mixed raw material is almost finished together with the end of the endothermic peak. The weight loss rate of 2.54% during this period corresponds to the release of oxygen due to the reduction of cerium in the following chemical reaction formula (calculated value, 2.86). Unlike the synthesis process in which the heat treatment is performed for a long time, the reaction does not reach an equilibrium in the thermal analysis process while heating and raising the temperature.

0.9 CeO_Two+ 0.05Bi_TwoO_Three+
0.5V_TwoO_Five→ Ce_0.9Bi_0.1VO_Four+0.225
O_Two Therefore, in the general formula, Ce_1-wBi_wVO_Four(0 <w ≦
0.67) Cerium having the tetragonal structure shown
Bismuth vanadium oxide ceramics
(CeO_Two) And bismuth oxide (Bi)_TwoO_Three) And pentoxide
Nadium (V_TwoO _Five) And the proportion thereof is CeO
_Two: Bi_TwoO_Three: V_TwoO_FiveIs (1-w): (w / 2):
0.5, where 0 <w ≦ 0.67
And mixing the starting materials in air at a temperature of 500 ° C or higher.
To obtain a solid phase reaction.

The powder X-ray diffraction pattern of the cerium-bismuth-vanadium oxide ceramic having a tetragonal structure is similar to that of FIG. 14, and the lattice constant is slightly different depending on the composition w. Therefore, by measuring the change in tetragonal lattice constants a and c depending on the composition w,
The solid solution region can be determined. Figure 13 plotting the results
From, the formation of a solid solution in which cerium atoms were replaced by bismuth atoms until w = 0.67 was observed.

The solid solution Ce _1-w B thus obtained is
A powder having an arbitrary composition of i _w VO ₄ (0 <w ≦ 0.67)
After being formed into a disc-shaped green compact and sufficiently sintered, electrodes were applied to both surfaces of the sintered body, and the electric conductivity was measured by a DC two-terminal method while heating in an electric furnace. The result is shown in FIG. 4 when x = 0.2.

[0031]

EXAMPLES Example 1 Ceria (CeO ₂ ) having a purity of 99.9% or more, calcium carbonate (CaCO ₃ ) of a reagent grade, and a purity of 99.9%
% Of vanadium pentoxide (V ₂ O ₅ ), 53.333 mol% of CeO ₂ , 13.333 mol% of CaO, V
_It was weighed so that ₂ O ₅ was 33.333 mol%, and mixed well in an agate mortar. The obtained mixture was filled in a platinum crucible and charged in an electric furnace equipped with a Kanthal wire heating element. In an electric furnace, the mixture is heated from room temperature to 850
C. for 80 hours. Next, the platinum crucible was taken out of the electric furnace, and the product was sufficiently pulverized and mixed in an agate mortar. Further, a heat treatment of holding at 950 ° C. for 83 hours was performed in the same procedure as above to synthesize a cerium-calcium-vanadium oxide ceramic having a uniform phase. As a result of analyzing the obtained product, the atomic composition was Ce _0.8 Ca _0.2
A phase belonging to the tetragonal system represented by VO _3.9 (a =
7.3092 Å, c = 6.4476 Å). FIG. 16 shows an X-ray powder diffraction pattern of this phase by CuKα radiation.

Example 2 A disc-shaped green compact of the powder obtained in Example 1 was
After sintering at 0 ° C, a platinum paste is applied as an electrode to both sides of the sintered body, and it is placed in an electric furnace equipped with a Kanthal wire heating element and a platinum lead wire, and the temperature dependence of the electric conductivity is obtained. It was investigated. FIG. 1 shows the relationship between the electrical conductivity and the reciprocal of the absolute temperature. From these results, the atomic composition Ce _0.8 Ca of the present invention was obtained.
It was confirmed that the cerium-calcium-vanadium oxide ceramic represented by _0.2 VO _3.9 was a good electric conductive semiconductor.

Example 3 Ceria (CeO ₂ ) having a purity of 99.9% or more, strontium carbonate (SrCO ₃ ) of a reagent grade, and purity of 9
9.9% or more of vanadium pentoxide (V ₂ O ₅ )
O ₂ was weighed to 53.333 mol%, SrO was 13.333 mol%, and V ₂ O ₅ was 33.333 mol%, and thoroughly mixed in an agate mortar. The obtained mixture was filled in a platinum crucible and charged in an electric furnace equipped with a Kanthal wire heating element. The mixture was heated from room temperature in an electric furnace and kept at 850 ° C. for 80 hours. Next, the platinum crucible was taken out of the electric furnace, and the product was sufficiently pulverized and mixed in an agate mortar. Further, a heat treatment was carried out at 950 ° C. for 83 hours in the same procedure as above to synthesize a cerium-strontium-vanadium oxide ceramic having a uniform phase. As a result of analyzing the obtained product, the atomic composition was C
It was a phase belonging to the tetragonal system represented by e _0.8 Sr _0.2 VO _3.9 (a = 7.3632 Å, c =
6.4868 angstroms). FIG. 17 shows a powder X-ray diffraction pattern of this phase by CuKα radiation.

Example 4 A disc-shaped green compact of the powder obtained in Example 3 was
After sintering at 0 ° C, a platinum paste is applied as an electrode to both sides of the sintered body, and it is placed in an electric furnace equipped with a Kanthal wire heating element and a platinum lead wire, and the temperature dependence of the electric conductivity is obtained. It was investigated. FIG. 2 shows the relationship between the electrical conductivity and the reciprocal of the absolute temperature. From these results, the atomic composition Ce _0.8 Sr of the present invention was obtained.
It was confirmed that the cerium-calcium-vanadium oxide ceramic represented by _0.2 VO _3.9 was a good electric conductive semiconductor.

Example 5 In each case, ceria (CeO) having a purity of 99.9% or more was used._Two)When
Lead monoxide (PbO) and vanadium pentoxide (V
_TwoO_Five) And CeO_TwoIs 60 mol% and PbO is 6.6.
66 mol%, V_TwoO_FiveIs 33.333 mol%.
Weighed and mixed well in an agate mortar. The resulting blend
The compound was filled in a platinum crucible and equipped with a Kanthal heating element
The electric furnace was charged. In an electric furnace, remove the mixture from room temperature
Heat and hold at 655 ° C. for 60 hours. Then, platinum
Remove the acupoints from the electric furnace and pour the product in an agate mortar.
Minutes and crushed and mixed. Further, 800
Heat treatment at 58 ° C for 58 hours
, Lead and vanadium oxide ceramics were synthesized.
As a result of analyzing the obtained product, the atomic composition was Ce._0.9P
b _0.lVO_3.95Belongs to the tetragonal solid solution represented by
(A = 7.3870 Å,
c = 6.4992 angstroms). CuK of this phase
FIG. 18 shows a powder X-ray diffraction pattern by α-rays.

Example 6 The disk-shaped green compact of the powder obtained in Example 5 was 860
After sintering at ℃, apply a platinum paste as an electrode on both sides of the sintered body and leave it in an electric furnace equipped with a Kanthal wire heating element and a platinum lead wire to reduce the temperature dependence of electrical conductivity. investigated. FIG. 3 shows the relationship between the electrical conductivity and the reciprocal of the absolute temperature. From these results, the atomic composition Ce _0.9 Pb of the present invention was obtained.
It was confirmed that the cerium / lead / vanadium oxide ceramic represented by _0.1 VO _3.95 was a good electric conductive semiconductor.

Example 7 Ceria (CeO ₂ ) having a purity of 99.9% or more, bismuth oxide (Bi ₂ O ₃ ) and vanadium pentoxide (V ₂ O ₅ ), and CeO ₂ of 51.852 mol were used. %, B
i ₂ O ₃ is 11.111 mol%, V ₂ O ₅ is 37.03
It was weighed to 7 mol% and mixed well in an agate mortar. The obtained mixture was filled in a platinum crucible and charged in an electric furnace equipped with a Kanthal wire heating element. The mixture was heated from room temperature in an electric furnace and kept at 800 ° C. for 50 hours. Next, the platinum crucible was taken out of the electric furnace, and the product was sufficiently pulverized and mixed in an agate mortar. Further, heat treatment was performed at 800 ° C. for 158 hours in the same procedure as above to synthesize a cerium-bismuth-vanadium oxide ceramic having a uniform phase. As a result of analysis of the obtained product, the product was a phase belonging to a tetragonal system represented by Ce _0.7 Bi _0.3 VO ₄ (a = 7.3733 angstroms, c = 6.4857 angstroms). The powder X-ray diffraction pattern of this phase by CuKα ray is shown in FIG.
Shown in

Example 8 A disc-shaped green compact of the powder obtained in Example 7 was 860
After sintering at ℃, apply a platinum paste as an electrode on both sides of the sintered body and leave it in an electric furnace equipped with a Kanthal wire heating element and a platinum lead wire to reduce the temperature dependence of electrical conductivity. investigated. FIG. 4 shows the relationship between the electrical conductivity and the reciprocal of the absolute temperature. From these results, the atomic composition Ce _0.7 Bi of the present invention was obtained.
_0.3 VO cerium bismuth vanadium oxide ceramics represented by ₄ it was confirmed that a good electrical conductivity semiconductor.

[0039]

As described above, the cerium-calcium-vanadium oxide ceramic, cerium-strontium-vanadium oxide ceramic, cerium-lead-vanadium oxide ceramic, cerium-bismuth-vanadium oxide ceramic of the present invention. Is
Since it is an excellent electric conductor with a novel composition having a tetragonal crystal structure, it is used as a highly functional electric conductive material for electrode materials, sensor materials, catalyst materials and the like.

[Brief description of the drawings]

FIG. 1 is a graph showing a change in electric conductivity depending on a temperature of a phase represented by an atomic composition Ce _0.8 Ca _0.2 VO _3.9 . The plots with a + mark indicate changes in the heating process, and Δ marks indicate changes in the cooling process.

FIG. 2 is a graph showing a change in electric conductivity depending on a temperature of a phase represented by an atomic composition Ce _0.8 Sr _0.2 VO _3.9 . The plots with a + mark indicate changes in the heating process, and Δ marks indicate changes in the cooling process.

FIG. 3 is a graph showing a change in electric conductivity depending on a temperature of a phase represented by an atomic composition Ce _0.9 Pb _0.1 VO _3.95 . The plots with a + mark indicate changes in the heating process, and Δ marks indicate changes in the cooling process.

FIG. 4 is a graph showing a change in electric conductivity depending on a temperature of a phase represented by an atomic composition Ce _0.7 Bi _0.3 VO ₄ . The plots with a + mark indicate changes in the heating process, and Δ marks indicate changes in the cooling process.

FIG. 5 is a graph showing a change in electric conductivity of a compound CeVO ₄ with temperature. The plots with a + mark indicate changes in the heating process, and Δ marks indicate changes in the cooling process.

FIG. 6: Starting powder mixture (0.9 CeO ₂ +0.1 Ca)
4 is a graph showing the results of simultaneous measurement of differential heat and thermobalance of CO ₃ +0.5 V ₂ O ₅ ).

FIG. 7: Starting powder mixture (0.9 CeO ₂ +0.1 Sr
4 is a graph showing the results of simultaneous measurement of differential heat and thermobalance of CO ₃ +0.5 V ₂ O ₅ ).

FIG. 8: Starting powder mixture (0.95 CeO ₂ +0.05)
7 is a graph showing the results of simultaneous measurement of differential heat and thermobalance of PbO ₃ +0.5 V ₂ O ₅ ).

FIG. 9: Starting powder mixture (0.9 CeO ₂ +0.05 B)
graph showing _{i 2 O 3 + 0.5V 2 O} 5) differential thermal and thermal balance Simultaneous measurements of.

FIG. 10 shows lattice constants a and c of an electrically conductive cerium-calcium-vanadium oxide ceramic having a tetragonal structure represented by the general formula Ce _1-x Ca _x VO _{4- (x / 2)} , depending on the composition x. The graph which shows the change of.

[11] Formula _{Ce 1-y Sr y VO 4-} (y / 2) lattice constant depending on the composition y of electrically conductive cerium strontium vanadium oxide ceramics having the structure of tetragonal represented by a and c The graph which shows the change of.

FIG. 12 shows a lattice constant a according to the composition z of an electrically conductive cerium-lead-vanadium oxide ceramic having a tetragonal structure represented by the general formula Ce _1-z Pb _z VO _{4- (z / 2)}
7 is a graph showing changes in c and c.

[13] Formula Ce _1-w Pb _w VO ₄ lattice constant depending on the composition z of electrically conductive cerium bismuth vanadium oxide ceramics having the structure of tetragonal represented by a
7 is a graph showing changes in c and c.

FIG. 14 is a powder X-ray diffraction pattern diagram of the compound CeVO ₄ .

FIG. 15 is a schematic view showing a crystal structure of zircon.

FIG. 16: Powder X of atomic composition Ce _0.8 Ca _0.2 VO _3.9
Line diffraction pattern diagram.

FIG. 17 is a powder X having an atomic composition of Ce _0.8 Sr _0.2 VO _3.9 .
Line diffraction pattern diagram.

FIG. 18: Powder X of atomic composition Ce _0.9 Pb _0.1 VO _3.9
Line diffraction pattern diagram.

FIG. 19 is a powder X-ray diffraction pattern diagram of an atomic composition Ce _0.7 Bi _0.3 VO ₄ .

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-17156 (JP, A) E. FIG. Greedan and Wenhe Gong, "The Series LnSrV04: syntheses is, crystal structure, crystal chemistry, rys, and sigm. Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/00-35/50 CA (STN) REGISTRY (STN)

Claims (8)

(57) [Claims] 1. The method according to claim 1, wherein the general formula Ce _lux Ca _x VO _{4- (x / 2)} (0
An electrically conductive cerium-calcium-vanadium oxide ceramic having a tetragonal structure represented by <x ≦ 0.41). 2. A general formula _{Ce 1-y Sr y VO 4-} (y / 2) (0
An electrically conductive cerium / strontium / vanadium oxide ceramic having a tetragonal structure represented by <y ≦ 0.21). 3. The general formula Ce _1-z Pb _z VO _{4- (z / 2)} (0
An electrically conductive cerium / lead / vanadium oxide ceramic having a tetragonal structure represented by <z ≦ 0.1). 4. The general formula Ce _1-w Bi _w VO ₄ (0 <w ≦
0.67) An electrically conductive cerium-bismuth-vanadium oxide ceramic having a tetragonal structure represented by the formula: 5. Ceria (CeO ₂ ) and calcium oxide (CaO) or a compound which is decomposed into calcium oxide by heating, and vanadium pentoxide (V
₂ O ₅ ) or a compound that is decomposed into vanadium pentoxide by heating,
₂ : Starting materials mixed so that CaO: V ₂ O ₅ becomes (1-x): x: 0.5 (where 0 <x ≦ 0.41) in air at a temperature of 500 ° C. or higher. And the general formula Ce
cerium characterized by producing an electrically conductive cerium-calcium-vanadium oxide solid solution having a tetragonal structure represented by _lx Ca _x VO _{4- (x / 2)} (0 <X ≦ 0.41) Manufacturing method of multiple oxide ceramics. 6. Ceria (CeO ₂ ) and strontium oxide (SrO) or a compound which is decomposed into strontium oxide by heating, and vanadium pentoxide (V
₂ O ₅ ) or a compound that is decomposed into vanadium pentoxide by heating,
₂ : Starting materials mixed so that SrO: V ₂ O ₅ becomes (1-y): y: 0.5 (where 0 <y ≦ 0.21) in air at a temperature of 400 ° C. or higher. And the general formula Ce
_{1-y Sr y VO 4- (} y / 2) and characterized in that to produce an electrically conductive cerium strontium vanadium oxide solid solution having the structure of tetragonal represented by (0 <y ≦ 0.21) For producing cerium double oxide ceramics. 7. Ceria (CeO ₂ ) and lead monoxide (Pb)
O) or a compound decomposed to lead monoxide by heating and a compound which is vanadium pentoxide (V ₂ O ₅ ) or a compound decomposed to vanadium pentoxide by heating, in a molar ratio of CeO ₂ : PbO: V ₂ O
₅ is (1-z): z: 0.5 (provided that 0 <z ≦ 0.
1) The starting materials mixed so that
Heated at a temperature of at least ℃ C, the general formula Ce _1-z Pb _z VO
Cerium double oxide ceramics for producing an electrically conductive cerium / lead / vanadium oxide solid solution having a tetragonal structure represented by _{4- (z / 2)} (0 <z ≦ 0.1) Manufacturing method. 8. Ceria (CeO ₂ ) and bismuth oxide (B)
i ₂ O ₃ ) or a compound which is decomposed into bismuth oxide by heating, and vanadium pentoxide (V ₂ O ₅ )
Alternatively, a compound which is decomposed into vanadium pentoxide by heating is mixed with a compound in a molar ratio of CeO ₂ : Bi.
₂ O ₃ : V ₂ O ₅ is (1-w) :( w / 2): 0.5,
(Where, 0 <w ≦ 0.67), mixed starting materials so as to be heated at a temperature above 500 ° C. in air, the general formula _{Ce 1-w Bi w VO 4} (0 <w ≦ 0. 67. A method for producing a cerium double oxide ceramics, which comprises producing an electrically conductive cerium-bismuth-vanadium oxide solid solution having a tetragonal structure shown in 67).