WO2007007587A1

WO2007007587A1 - ORIENTATION CONTROLLED Co OXIDE POLYCRYSTAL

Info

Publication number: WO2007007587A1
Application number: PCT/JP2006/313288
Authority: WO
Inventors: Hiroshi Fukutomi; Eisuke Iguchi
Original assignee: National University Corporation Yokohama National University
Priority date: 2005-07-07
Filing date: 2006-07-04
Publication date: 2007-01-18
Also published as: JP5656961B2; JP2013063906A; JPWO2007007587A1

Abstract

This invention provides a Co oxide polycrystal, which comprises a polycrystal of a Co oxide having a mismatching crystal structure, causes slip deformation on (001) plane of the polycrystal, and has undergone crystal rotation in a given direction. Further, a Co oxide polycrystal subjected to crystal rotation in a given direction can be produced by compressing a polycrystal of Co oxide having a mismatching crystal structure at 800 to 930ºC and at a strain rate of 1.0 × 10-5 to 1.0 × 10-3 s-1 to cause slip deformation. According to the above constitution, the crystal orientation of ceramics can be controlled, and ceramics, which have been subjected to crystal orientation control and have anisotropic electric resistance and can be utilized as thermoelectric conversion ceramics, can be provided.

Description

Specification

Oriented controlled Co oxide polycrystal

Technical field

The present invention relates to ceramics manufactured by controlling crystal orientation, and more specifically, (00

1) It relates to Co oxides with incommensurate crystal structures that have undergone in-plane slip deformation and plastic deformation.

Background art

[0002] Ceramics generally cause plastic deformation even when a large force is applied for the purpose of plastic deformation because the number of independent slip systems necessary for plastic deformation of a polycrystalline body having a high Peierls potential cannot be secured sufficiently. It is normal to destroy without. Therefore, unlike metal materials, ceramics did not have an orientation control technology by plastic working.

On the other hand, in order to increase the figure of merit of thermoelectric conversion ceramics by orientation control, a method has been proposed in which a part of the raw material is partially melted while being uniaxially pressed and then gradually cooled (Patent Document 1). In addition, anisotropically shaped powders such as needles and plates are present in the molded body at a relatively high degree of orientation, and this anisotropically shaped powder is used as a template or a reactive template for the growth and oxidation of oxides. It is also possible to adjust the orientation by synthesis and / or sintering. The usefulness of rolling in a slurry state is also presented (Non-Patent Literature)

2).

In addition, the present inventors have proposed a ceramic represented by the general formula Bi Pb Sr Y Co O as a thermoelectric characteristic.

2-x X 3-y y 2 9- δ

(Non-Patent Document 1).

[0003] Patent Document 1: JP 2001-19544 (Patent No. 3089301)

Patent Document 2: JP 2003-282965 A

Patent Document 3: J. Phys. D: Appl. Phys. 34 (2001) 1017-1024

Disclosure of the invention

Problems to be solved by the invention

[0004] Conventional ceramic crystal orientation control technology is limited in application only to material systems and compositions in which a desired crystal can be obtained by recrystallization. However, there were difficulties such as requiring complicated processes.

For metal materials, a variety of texture control technologies have been established that adjust the crystal orientation by applying large plastic deformation using plastic processing techniques such as rolling. However, even in ceramics, crystalline materials are aligned along specific crystal planes. It is considered that the orientation of the crystal can be adjusted if it can be greatly plastically deformed by slip, that is, crystal slip deformation.

An object of the present invention is to provide a method for controlling the crystal orientation of a ceramic and a ceramic produced by controlling the crystal orientation. Thus, the ceramic orientation whose crystal orientation is controlled has anisotropy, and in the case of thermoelectric conversion ceramics, it can be used as thermoelectric conversion ceramics with improved performance index by utilizing the direction of low electrical resistance. Means for solving the problem

[0005] In a Co oxide having a misfit structure (ceramics having a layered crystal structure) targeted by the present invention, there is a direction in which the distance between adjacent atoms is short in the (001) plane, If the temperature is close to the melting point and the temperature is raised, the complete dislocation can be activated by overcoming the Peierls potential. In this case, since there are only two independent slip systems in the (001) plane, it is difficult to greatly deform the polycrystal.

In the present invention, it has been found that large strain processing can be achieved by selecting a temperature and strain rate at which the deformation between crystal grains due to diffusion can occur, and the present invention has been completed.

[0006] That is, the present invention relates to a polycrystalline body of cobalt oxide having an incommensurate crystal structure, and the crystals are oriented in a certain direction due to slip deformation in the (001) plane of the polycrystalline crystal. It is a Co acid complex polycrystal. The polycrystal is compressed at a strain rate of 1.0 X 10 ^_5 to 1.0 X 10 ^_3 s ^_1 at a temperature range of 800 ° C or higher and a temperature of 30 ° C below the melting point of the crystal. This slip deformation can be caused by performing the above.

For this compression processing, plastic processing methods such as uniaxial compression processing, plane strain compression processing, rolling, and extrusion processing may be used.

The present invention is, 1. 0 X 10 ^_5 at a temperature range up to a temperature of 30 ° C under the melting point of the Co Sani匕物of polycrystalline whether we said crystals 800 ° C or higher with a mismatched crystal structure ~ 1.0 X 10 " ³ s" ^This is a process for producing Co oxides with a mismatched crystal structure with slip deformation in the (001) plane consisting of compression processing at a strain rate of ¹ .

In addition to this _Co oxide having an incommensurate crystal structure, annealing for 12 to 50 hours in the temperature range up to 30 ° C below the melting point of the crystal is also possible. Also good.

The invention's effect

[0007] The present invention has made it possible to provide a ceramic in which the orientation is aligned in a certain direction by plastically deforming a polycrystalline ceramic having a crystal grain force whose orientation direction is random. The Co oxide having an incommensurate crystal structure of the present invention undergoes plastic deformation by high-temperature processing, realizing densification and texture formation, and as a result, improved thermoelectric properties.

In addition, the material of the present invention is a high-temperature thermoelectric conversion material that can be used up to around 700 ° C. In addition to fossil fuel thermoelectric conversion generators, heat generated by combustion in factories and garbage incinerators can be removed. BEST MODE FOR CARRYING OUT THE INVENTION Best Mode for Carrying Out the Invention

[0008] The highly oriented polycrystalline ceramic of the present invention is a Co oxide having a mismatch crystal structure.

“Incommensurate crystal structure” refers to C composed of multiple layers including CoO electron conducting layers.

2

o Oxide is a stack of layers in the c-axis direction, with the a and b axes in the vertical direction, and the ratio of the lattice constant of the CoO layer in the b-axis direction to the lattice constant of the other layers in contact with this layer above and below Is an irrational number

2

Means a structure. However, all layers have the same lattice constant in the a-axis direction.

This ceramic has a layered crystal structure and is more than 10 times the maximum value of the average density in the positive pole figure measured by the Schulz reflection method. For example, as shown in FIG. 1, the layered crystal structure includes a first sublattice made of a Co 2 O layer and a layer different from Co 2 O.

twenty two

A structure in which the second sub-lattice is deposited in a predetermined cycle.

The incommensurate crystal structure can be confirmed by X-ray diffractometry, but can be confirmed more accurately by neutron beam analysis.

In addition, the composition can be confirmed by the EDX measurement method, and more accurately, it is generally difficult to determine the amount of oxygen that can be confirmed by wet analysis using either method. [0009] As a Co oxide having this incommensurate crystal structure, Bi Pb Sr Y Co O (wherein x

2-x x 3-y y 2 9_ δ

= 0.4-0.8, y = 0.4-0.8, δ = 0.2-0.6), [Ca CoO] CoO (where x = 0.2

2 3-x 1-y 2-z

~ 0, y = 0.4 ~ 0, z = 0.2 ~ 0), [(Ca Sr) CoO] CoO (where x = 0.2 ~ 0, y = 0.2

1-x x 2 3-y 1-z 2-w

~ 0, ζ = 0/4 ~ 0, w = 0.2 ~ 0), ((Ca (Co, Cu) O) CoO (where x =-0

2 2-x 4-y 0. 63-z 2-w

l, y = 0.3-0, z = -0.1-0.1, w = 0.2-0) or [Bi Sr O] CoO (where x =

1. 74-x 2-y 4-z 0. 25-w 2 ~ v

-0.05 to 0.05, y = -0.05 to 0.05, z = 0.2 to 0, w = 0.05 to 0, V = 0.2 to 0), etc., in the practice of the present invention, ((Ca Sr) CoO] CoO (Where x = 0.2-0, y = 0.2-0, z = 0.4

1-x x 2 3-y 1-z 2-w

~ 0, w = 0.2 ~ 0) and [Ca CoO] CoO (where χ = 0 · 2 ~ 0, y = 0.4 ~ 0, ζ = 0 · 2 ~ 0)

2 3-x 1-y 2-z

is important.

[0010] "Polycrystal" is a collection of a large number of the above single crystals having a size of about 1 to about L0 m in various directions. This polycrystal can be obtained by assembling and sintering powders of this composition.

[0011] "Compression processing" is a plastic processing method in which a shape is changed by applying a compression force to a target object.

When the "co-oxide polycrystal having an incommensurate crystal structure" of the present invention is subjected to compression processing, the (001) face of the crystal grains constituting this Co oxide polycrystal and facing in various directions Slip on top Deformation occurs. Slip deformation results in a plastic deformation that reduces the length of the polycrystalline body in the compression direction. As a result of this slip deformation, each crystal rotates to the position where the (001) plane is parallel to the compression plane. That is, the crystal rotates so as to coincide with the direction of the normal direction force compression processing of the (001) plane of the crystal grains constituting the polycrystal.

“Single-axis compression processing” is a plastic processing method in which a uniaxial compression force is applied.

`` Plane strain compression processing '' prevents deformation in one direction among deformations in the direction perpendicular to the compression force of the target object when a uniaxial compression force is applied, and deformation in only one direction. This is a compression processing method that allows

The temperature of this compressive force is over 800 ° C. The temperature range is up to 30 ° C below the melting point of the crystal. The temperature 30 ° C below the melting point of the crystal indicates the temperature at which the crystal close to the melting point of the crystal is in a solid state. The melting point of the crystal is measured by thermal analysis.

The strain rate of the compression processing is obtained by dividing the compression rate by the height of the object to be compressed, and is 1.0 X 10 ^_5 to 1.0 X 10 ^_3 s ^_1 , preferably 2.0 X 10 ^_5 to 8 OX 10 ^_5 s ^_1 . distortion If the speed is less than 1.0 X 10 ^_5 s ^_1 , the main deformation mechanism, which takes a long time to give sufficient strain, changes to crystal slip deformation force diffusion creep, and the crystal orientation is sufficiently aligned. If the strain rate is greater than 1.0 X 10 ^_4 s ^_1 , the contribution of diffusion to alleviate the lack of the slip system is insufficient.

[0013] Annealing is performed to remove lattice defects such as dislocations that have proliferated during crystal slip deformation, and in a temperature range of 800 ° C or higher up to 30 ° C below the melting point of the crystal. Heat. By annealing after the processing, recovery of dislocations and the like occurs, and the electrical resistance can be further reduced.

[0014] Hereinafter, the present invention will be illustrated by way of examples, but is not intended to limit the present invention.

In the following examples, X-ray diffraction was measured in the range of α = 0 ° (in the normal direction of the plate surface) to 75 ° using a semi-automatic diffractometer (manufactured by Mac Science), and the obtained diffraction intensity A positive dot diagram was obtained. The measurement method was the Schulz reflection method, using CuKo; wire, tube voltage 40 kV, tube current 30 mA.

Tissue photographs were taken using a scanning electron microscope (SEM). The unsintered specimen was thinly cut with a diamond cutter and the surface of the specimen was also observed, and the finished specimen was observed on a surface perpendicular to the compression surface of the specimen.

The electrical resistance was measured by a four-terminal method after attaching an electrode to the sample, connecting a copper wire to the sample with a silver paste. The measurement procedure was as follows. Place the prepared sample in a single bottle (manufactured by OXFORD), draw a vacuum with an oil rotary pump, and apply a current of 10 mA when rising from about 80 K to 340 K using liquid nitrogen as a medium. The voltage value of the hour (workpiece is 100mA) was measured under GP-IB control at a temperature interval of 1K. The temperature was measured using a copper-constantan thermocouple.

[0015] Production Example 1

Bi 0 (purity 99.9%, Wako Pure Chemical Industries, Ltd.), PbO (purity 97%, Nakarai Desk Co., Ltd.), Sr 0 (

2 3 2 2 3 Purity 99.9%, Soekawa Riken Co., Ltd.), Y 0 (Purity 99.9%, Wako Pure Chemical Industries, Ltd.) and Co 0 (Pure

2 3 3 4 degrees 99.9%, Soekawa Science Co., Ltd.), with a molar ratio of 45: 30: 51: 15: 40 to a total weight of about 15 g, using an agate mortar, Wet mixing was performed using methanol. Mixing time It was 1 hour 30 minutes.

Next, this mixture was dry-mixed for 60 minutes using an agate ball mill and a milling machine (SPEX, CertiPrep).

Next, the sample was put in an alumina boat and calcined at 790 ° C for 12 hours in a pine furnace.

Since the sample after the calcination finished grain growth, the powder was refined by dry grinding using an agate mortar.

The obtained powder was formed into a cylinder having a diameter of about 11 mm and a height of about 4 mm, placed in an alumina boat, and baked in air at 840 ° C for 24 hours in a Matsufur furnace.

The resulting crystal is a Co oxide with a mismatch crystal structure with a composition of Bi Pb Sr Y Co O.

1.5 0.5 1.7 0.5 2 9-δ

It was a polycrystal with about 1 to 10 μπι crystal grains assembled. The X-ray diffraction pattern is shown in Fig. 2, and a cross-sectional photograph (SEM) of the crystal is shown in Fig. 3. The melting point of this crystal is 930 ° C and 7 eyes.

Example 1

The sample produced in Production Example 1 was sandwiched between magnesia plates at right angles to the axial direction of the cylinder using a 2t autograph (manufactured by Shimadzu Corporation) and heated in an infrared image furnace. While the temperature rose to 840 ° C, the temperature of the sample was measured using a thermocouple. Even after the target temperature was reached, the jig continued to expand, so the temperature was held for about 70 minutes until it stopped.

After the temperature hold, constant cross head speed along the axial direction of the sample cylinder at 2t autograph ^{(5.0 X 10- 3 mm / min} , which corresponds to a strain rate 2.0 X 10- ⁵ s- ^1.) Compressing at Thus, high temperature uniaxial compression was performed. The results are shown in Table 1.

[table 1]

Fig. 4 and Fig. 4 show the diffraction pattern of the plane perpendicular to the cylinder axis of the test specimen and the positive dot diagram. Shown in 5. In the diffraction pattern, a large peak was confirmed by jumping to around 30 degrees. Imax was measured by taking a positive point map of this peak. From this positive pole figure, it can be seen that the (001) plane is oriented parallel to the compression plane and rotated around the normal of the (001) plane by various angles. A cross-sectional photograph (SEM) in the direction parallel to the cylinder axis of the obtained specimen is shown in FIG. From this photograph, it can be seen that the dimensions of the crystal grains differ between the direction perpendicular to the compression direction (longitudinal direction in the figure) and the direction parallel to the direction, and plastic deformation occurred in the compression direction.

Example 2

[0017] The same operation as in Example 1 was performed so that the final strains were 0.47, 0.9, 1.27, and 1.87. The density is shown in Fig. 7, the positive dot diagram is shown in Fig. 8, and the resistivity is shown in Fig. 9.

From the density change in Fig. 7, it can be seen that the density increases monotonously until the strain is near 0.9, and the sintered body is densified. Up to this stage is the hot press process used in the prior art. In this technology, by setting the processing conditions as described above, the compression was further continued, and a plastic cache with a maximum true strain of 1.87 was achieved. At this time, no cracks were observed in the product, confirming that it was a healthy material.

The maximum value of the pole density in the (001) pole figure (Fig. 8) determined by Schulz's reflection method was 1.0 before calorie, but increased to 11.7 as the amount of strain increased. As shown in Fig. 9, the resistance decreases monotonously with increasing strain (ε) due to processing up to true strain of 1.87. In addition, materials manufactured by plane strain compression show a lower specific resistance than workpieces with true strains up to 1.87. Furthermore, the electrical resistance of the material created by this method remains low even at high temperatures.

Example 3

[0018] The sample that had been subjected to the compression check in Example 2 (with a strain of 1.87) was annealed in air at 840 ° C for 24 hours in a Matsufur furnace. Figure 9 shows the resistivity. Annealing further reduced the electrical resistance, down to a maximum of 20: 1. That is, by realizing high orientation by the orientation control technology of the present invention, the figure of merit of thermoelectric characteristics has been dramatically improved by 20 times. Example 4

[0019] A magnesia plate used for uniaxial compression was cut into a strip of 5 mm width, which was then manufactured A high-temperature plane strain compressive force test was performed by applying a pressure vertically from the axial direction of the cylinder of the sample prepared in 1.

As in Example 1, at 840 ° C along the axial direction of the sample cylinder at 2t autograph cross-head speed constant ^{(5.0 X 10- 3 mm / min} , the strain rate 2.0 X 10- ⁵ ^s-1 High-temperature plane strain compression processing was performed. The results are shown in Table 2.

[Table 2]

[0020] Also, the diffraction pattern of the plane perpendicular to the axis of the cylinder of the obtained test piece and its positive electrode dot diagram are shown in FIG. 10 and FIG. In the positive pole figure (Fig. 5) of Example 1 (high temperature uniaxial compression processing), the force that the (001) plane is aligned, the direction was not aligned, but this example (high temperature flat strain compression) In the machining), from the positive point diagram, the (001) plane is not distributed concentrically with the surface normal, and the specific direction is just that this plane is oriented parallel to the compression plane. This indicates that the plane and direction could be aligned by plane strain compression. In other words, it is considered that a material with a structure orientation close to that of a single crystal has been produced, and it is considered that it has excellent thermoelectric properties.

[0021] Ironmaking example 2

CaCO (manufactured by Wako Pure Chemical Industries, Ltd., purity 99.9%), Co 0 (manufactured by Rare Metallic Co., Ltd., purity)

3 3 4

99 (9%), SrCO (manufactured by Wako Pure Chemical Industries, Ltd., purity 99.9%)

3 0.9 0.1 2 3

] Weighed to CoO, wet-mixed and calcined at 920 ° C for 12 hours. Crush after calcining

0.62 2

After being powdered, it was press-molded into a cube shape with a side of 6 mm and sintered at 920 ° C for 24 hours. Furthermore, final annealing was performed for 12 hours at 700 ° C in an oxygen atmosphere. The melting point of this crystal was 1350 1400 ° C.

Example 5

[0022] Using the 2t autograph (manufactured by Shimadzu Corp.) It was sandwiched between magnesia plates at right angles to the direction and heated in an infrared image furnace. While the temperature rose to 880 ° C., the temperature of the sample was measured using a thermocouple. Even after the target temperature was reached, the jig continued to expand, so the temperature was held for about 70 minutes until it stopped.

After the temperature hold, constant cross head speed along the axial direction of the prismatic sample 2t autograph (. Which 2.0 X 10- ² mm / min, which corresponds to a strain rate 5.5 X 10- ⁵ s- ¹⁾ at true strain - By compressing to 1.14, high temperature uniaxial compression was performed. Figure 12 shows the (001) positive pole figure measured for this sample. The projection plane is a compression plane and the average pole density is 1. Accumulation of high pole density exceeding the maximum pole density of 12 is confirmed at the center of the figure, that is, at the normal to the compression plane. Also, the accumulation of extreme density is spreading concentrically. This result is the same as in Example 2.

[0023] Example 3

[Ca CoO] 11mm in diameter and 5mm in height using CoO powder (Seimi Chemical Co., Ltd.)

2 3 0.62 2

A cylindrical base material was made by press molding and then sintered at 920 ° C for 24 hours.

Example 6

[0024] Using a 2t autograph (manufactured by Shimadzu Corporation), the sample produced in Production Example 3 was sandwiched between magnesia plates at right angles to the axial direction of the cylinder and heated in an infrared image furnace. While the temperature rose to 920 ° C, the temperature of the sample was measured using a thermocouple. Even after reaching the target temperature, the jig continued to expand, so the temperature was maintained for about 70 minutes until it reached the target temperature.

After the temperature hold, constant cross head speed along the axial direction of the cylinder of the sample at 2t autograph (. Which 2.0 X 10- ² mm / min, which corresponds to a strain rate 6.7 X 10- ⁵ s- ¹⁾ at true strain - By compressing to 1.01, high-temperature uniaxial compression was performed. Figure 13 shows the (001) positive pole figure measured for this sample. The projection plane is a compression plane and the average pole density is 1. Accumulation of high pole density exceeding the maximum pole density of 17 is confirmed at the center of the figure, that is, at the normal to the compression plane. Also, the accumulation of extreme density is spreading concentrically. This result is the same as in Examples 2 and 5, and shows that the conductive surface is frequently oriented parallel to the compression surface.

The electrical resistance of Example 6 was measured by a four-terminal method after attaching an electrode to the sample and then connecting a copper wire to the sample with a silver paste. The results are shown in Figs.

Figure 14 shows the measurement results of the specific resistance of [Ca CoO] CoO. b Sr Y Co O results in low resistivity, -1.87 force-working material and plane strain compression material

0.5 1.7 0.5 2 9-δ

These results are shown together. [Ca CoO] CoO is the result of heating and cooling.

2 3 0.62 2

The results are shown. [Ca CoO] CoO with controlled orientation is the number of Bi Pb Sr Y Co O

2 3 0.62 2 1.5 0.5 1.7 0.5 2 9- δ Shows a low electrical resistivity up to 1000K. Figure 15 shows [Ca CoO] Co

2 3 0.62

The result of 0 is shown enlarged. The electrical resistivity reaches a minimum of 2 mΩcm or less.

2

Yes.

[0025] The crystal structures of Example 2 (Bi-Sr-Co-O) and Example 5 and Example 6 (Ca-Co-0), which are layered oxides having a misfit structure, are also shown in FIG. Shown in

Figure 17 shows the results of confirming the crystal structure of [Ca CoO] CoO by X-ray diffraction. [(Ca

2 3 0.62 2 0

Sr) CoO] CoO is a material in which Ca in [Ca CoO] CoO is partially substituted with Sr.

.9 0.1 2 3 0.62 2 2 3 0.62 2

The crystal structure is the same as [Ca CoO] CoO. In Example 2, four layers of insulation between CoO layers

2 3 0.62 2 2

There is a difference in the presence of three insulator layers between the CoO layers in the body layers, Examples 5 and 6.

2

The crystal orientation can be controlled by this method even when V, V, and misalignment.

Brief Description of Drawings

[0026] FIG. 1 is a diagram showing a crystal structure of Bi Pb Sr Y Co 2 O. In the figure, vertical direction (crystal c

1.5 0.5 1.7 0.5 2 9- δ

The atomic plane whose normal is (axial direction) is the (001) plane.

FIG. 2 is a diagram showing a diffraction pattern of a polycrystal prepared in Production Example 1.

FIG. 3 is a cross-sectional photograph (SEM) of a polycrystal prepared in Production Example 1.

FIG. 4 is a diagram showing a diffraction pattern of a crystal subjected to high-temperature uniaxial compression processing in Example 1.

FIG. 5 is a diagram showing a positive electrode dot diagram of a crystal subjected to high-temperature uniaxial compression processing in Example 1. The concentric curve indicates the position where the average pole density is 1, 2, 3, 4, 5 or 6 times higher from the outside.

FIG. 6 is a cross-sectional photograph (SEM) of a crystal subjected to high-temperature uniaxial compression processing in Example 1. The vertical direction in the figure is the compression direction.

FIG. 7 is a graph showing changes in density of crystals subjected to high-temperature uniaxial compression processing in Example 2. The vertical axis represents density (g / cm ² ), and the horizontal axis represents strain.

FIG. 8 is a diagram showing a positive electrode dot diagram of a crystal subjected to high-temperature uniaxial compression processing in Example 2.

FIG. 9 is a graph showing the resistivity of crystals subjected to high-temperature uniaxial compression processing in Example 2. FIG. 10 is a diagram showing a diffraction pattern of a crystal subjected to high-temperature plane strain compression processing in Example 4.

FIG. 11 is a diagram showing a positive electrode dot diagram of a crystal subjected to high-temperature plane strain compression processing in Example 4. Concentric curves indicate the positions where the average pole density is 1, 2, 3, 4, 5, 6, 7 times as many as the order from the outside.

FIG. 12 is a diagram showing a positive electrode dot diagram of a crystal subjected to high-temperature uniaxial compression processing in Example 5.

FIG. 13 is a diagram showing a positive electrode dot diagram of a crystal subjected to high-temperature uniaxial compression processing in Example 6.

FIG. 14 is a graph showing the results of measuring electrical resistance of the crystal prepared in Example 6.

FIG. 15 is a diagram showing the results of measuring electrical resistance of the crystal prepared in Example 6.

[Fig. 16] Bi Pb Sr Y Co O prepared in Example 2 (right figure) and [P

1.5 0.5 1.7 0.5 2 9- δ (

Sr) CoO] CoO and the [Ca CoO] CoO prepared in Example 6 (left)

.9 0.1 2 3 0.62 2 2 3 0.62 2

FIG.

FIG. 17] A diagram showing an X-ray diffraction pattern of a polycrystal prepared in Production Example 3.

Claims

The scope of the claims

[1] Co-acidic polycrystal having an incommensurate crystal structure, wherein the crystal is oriented in a certain direction due to slip deformation in the (001) plane of the polycrystal Polycrystal.

[2] The slip deformation, the 1. 0 X 10 one ^{5-polycrystalline} from 800 ° C or more at a temperature range of a temperature or under 30 ° C of the melting point of the crystal 1. 0 X 10 ^The cobalt oxide having an incommensurate crystal structure according to claim 1, which is generated by performing a compressive force test at a strain rate of ^_3 s ^{_ 1} .

[3] The Co oxide having a mismatched crystal structure according to claim 1 or 2, wherein the compression processing is uniaxial compression processing.

[4] The Co oxide having a mismatch crystal structure according to [1] or [2], wherein the compression process is a plane strain compression process.

[5] Further, according to any one of claims 1 to 4, wherein annealing is performed for 12 to 50 hours in a temperature range of 800 ° C or higher up to a temperature of 30 ° C below the melting point of the crystal. Co oxide with an incommensurate crystal structure.

[6] The Co oxide having the incommensurate crystal structure is Bi Pb Sr Y Co O (where x = 0.

2-x x 3-y y 2 9_ δ

4 to 0.8, y = 0.4 to 0.8, δ = 0.2 to 0.6), [Ca CoO] CoO (where χ = 0 · 2 to 0

2 3-x 1-y 2-z

, Y = 0.4-0, z = 0.2-0), ((Ca Sr) CoO] CoO (where x = 0.2-0, y = 0.2-0

1-x x 2 3-y 1-z 2-w

, Z = 0.4-0, w = 0.2-0), [(Ca (Co, Cu) 2 O] CoO (where x = -0.1-0.1,

2 2-x 4-y 0. 63-z 2-w

y = 0.3-0, z = -0.1-0.1, w = 0.2-0) or [Bi Sr O] CoO (where x = -0.

1.74- x 2-y 4-z 0. 25-w 2-v

5 to 0.05, y = -0.05 to 0.05, z = 0.2 to 0, w = 0.05 to 0, V = 0.2 to 0), the mismatch crystal structure according to any one of claims 1 to 5. Have Co acid.

[7] Claims 1-6! A thermoelectric conversion material comprising a Co oxide having a mismatched crystal structure according to any one of the items.

^{[8] 1. 0 X 10 _5} ~1 month or more 800 ° C and Co Sani匕物force also comprising polycrystalline with mismatched crystal structure even at temperatures ranging temperature under 30 ° C of the melting point of the crystal A process for producing Co oxides with incommensurate crystal structures with slip deformation in the (001) plane, consisting of compression processing at a strain rate of 0 X 10 ^_3 s ^{_ 1} .

[9] The process according to claim 8, further comprising annealing for 12 to 50 hours in a temperature range of 800 ° C. or more and a temperature of 30 ° C. below the melting point of the crystal.