JP2003012327A - Thermoelectric oxide material of layered alkali titanate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoelectric oxide material of a layered alkali titanate, its use and its producing method. SOLUTION: The starting raw materials of a titanate are such materials as titanium oxide, a chemical seed of a transition metal and an alkali compound. The titanate material is obtained by a flux or a solid phase reaction of the mixture of them in an atmosphere or an inert gas atmosphere, and furthermore it is changed to be conductive by conductive carrier controlling through different metallic ion doping or a partial reduction treatment of titanium. The above material is used for an elemental material of thermoelectric energy changing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrically conductive titanate material, its use, and a method for producing the same. More specifically, it has a transition metal ion or the like in its skeleton structure, and is mainly titanium. Alkali titanate compound having a low dimensional layered crystal structure consisting of, a new oxide material having conductivity imparted by doping titanium to a crystal of a different metal ion or by partial reduction of titanium by high temperature firing in an inert atmosphere, The present invention relates to use in a thermoelectric energy conversion element material and the like utilizing the electrical and thermal characteristics, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A thermoelectric energy conversion material directly converts thermal energy, which cannot be recovered as energy, which is generated by burning of fossil fuels such as an energy engine or incineration of dust into electrical energy. It is a device material intended to be converted and used. Thermoelectric conversion
Two types of semiconductor materials, p-type and n-type, are joined, and a potential difference caused by a difference in conductive carrier mobility in each material under overheating, and the potential difference causes movement between electrodes taken out from the material (n-type). Electric current is generated from thermal energy (temperature difference) due to the current caused by electron transfer from electron to p-type. At present, about 8 to 10% of thermoelectric materials are used as practical elements such as cells, but they are known to have high thermoelectric conversion efficiency as thermoelectric materials. It is an alloy-based material such as Fe or Si, and has room temperature to 2 due to the problem of thermal stability of the material.
It is mainly used at low temperatures such as 00 ° C. Thermoelectric materials using these alloy-based materials are used in power generation equipment for spacecraft such as space shuttles, generators for portable wristwatches, and also for practical use such as conducting pilot tests using waste heat generated in waste treatment facilities. It is also known to be used as a typical element material.

On the other hand, in order to obtain higher energy using a material having a constant thermoelectric conversion efficiency, it is important to utilize a large temperature difference generated in a higher temperature environment. Furthermore, in order to use it as a generator at high temperature, it is necessary to maintain the performance even if the element material is exposed to high temperature for a long time. However, existing alloy-based materials have a problem in long-term use at a high temperature because oxidation proceeds from the surface at a high temperature of 600 ° C. or higher and the material properties deteriorate. On the other hand, in recent years, oxide materials having conductivity and semiconductor characteristics are known,
Furthermore, among them, the thermoelectric conversion efficiency is 8 which is equivalent to alloy type.
A material having a value of about 10% and usable as a thermoelectric material has also been found. In them, n-type high-concentration carriers with large effective charge mass and low mobility are generated due to peculiar overlap of d-electron orbitals in the layered oxide layer, and thus they are classified as a strongly correlated material. These oxide materials are unlikely to deteriorate in material properties due to oxidation even in a high temperature atmosphere of 600 ° C. or higher which is the temperature of automobile exhaust gas.
Further, in an oxide semiconductor, the carrier mobility generally increases with an increase in temperature, so that the conductivity is improved even in a high temperature atmosphere.

To obtain high performance as a thermoelectric material, 1)
High conductivity (low electric resistance), 2) High electromotive voltage (Seebeck coefficient μV / K) in the material at a constant temperature difference, and 3) Maintaining the temperature difference on the device as high as possible. It is important that the material has low thermal conductivity. However, a material having a high conductivity has a high carrier mobility in the material, which leads to an improvement in heat conduction at the same time, so that the above 1) and 2) have opposite properties.
At present, it is known that in a material having high properties as a thermoelectric oxide material, the balance between electrical properties and thermal properties affects the thermoelectric properties due to the material crystal structure.

As an attempt to make such an oxide material coexist with high electric characteristics and low heat conduction characteristics, at present,
Utilization of anisotropy of electrical conductivity or thermal conductivity based on the structural regulation by the crystal structure, and use of a phonon scattering effect by containing a heavy element have been performed. Also,
For polycrystalline materials, simultaneous control of electrical conductivity and thermal conductivity has been studied by controlling the arrangement of crystal grains and the structure control of the nanostructure at the grain interface. The structure-controlled thermoelectric conversion materials that have been reported so far are mainly p-type materials, and in order to use them as thermoelectric elements, it is particularly necessary to develop n-type materials. Also, due to resource issues, it is necessary to use cheaper and resource-rich raw materials.

Under such circumstances, it is important to develop an n-type thermoelectric oxide material capable of simultaneously controlling the crystal structure and the polycrystalline material structure composed thereof. n
A series of titanates is known as a type semiconductor oxide material having a two-dimensional layered crystal structure. Titanate crystals have been used in automobile bumpers and the like for strengthening plastics and the like because they easily grow into a plate shape or a fibrous shape. It is expected to be used together with titanium oxide as an environmental material in the field of energy conversion catalysts and the like. In addition, since they have a nano-sized ion-exchangeable alkali ion layer between the layers of the titanium layer, it is possible to control the semiconductor properties by chemical modification by intercalation into the nano space between the layers, which improves the properties. Has been reported.

On the other hand, by utilizing such a specific crystal structure and controlling the electrical conductivity of the titanium oxide layer, it can be expected to be used as a thermoelectric oxide material. At the interface near the alkali metal or alkaline earth metal layer between the titanium oxide layers in these layered titanate materials,
It can be expected that a phonon scattering layer similar to that of a p-type transition metal thermoelectric layered oxide material is formed, and further improvement of thermoelectric characteristics can be expected due to deterioration of heat conduction characteristics. Furthermore,
In general, layered titanates are known to be plate-shaped crystal particles, so it is considered that the thermoelectric conversion material properties can be increased by controlling the texture in a polycrystalline material composed of these particles. . From these, if it is possible to utilize the improvement in conductivity and the decrease in thermal conductivity due to phonon scattering in the alkali metal or alkaline earth metal layers sandwiching the titanate, it is expected to create a new thermoelectric conversion oxide material. it can. Further, the material containing titanium oxide as a main raw material is relatively abundant in terms of resources and is important as a low-cost industrial material.

Crystal in which a titanium oxide layer is arranged in a two-dimensional layer form
It has a structure, especially the titanium oxide layer unit is a triangular lattice type
Crystal structure that is connected by the sharing of the oxygen atoms of the
As a structure, solid solution of transition metals such as iron, nickel and cobalt
Α Titanate crystalline Na_x Mx Ti_2-xO_Four (X =
0.2-0.4) and the like are known. These layered compounds
Products can usually be synthesized by the alkali flux method, but
Most of them show conductor-like electrical characteristics. These materials
10 is used as a thermoelectric material.³ S / m or more
Has DC conductivity and several hundreds μV / S or more thermoelectromotive force
Is desirable. Furthermore, low heat transfer of 5.0 W / mK or less
Conductivity is also important. For that, titanic acid
Making the oxide layer conductive is an important issue.

[0009]

Under these circumstances, the present inventors have been conducting various studies on a method for making the titanate compound layer conductive, and have made α-titanic acid containing a transition metal into a solid solution. As a result of synthesizing a salt and investigating the thermoelectric properties of the polycrystalline sintered body, we obtained a new finding that an oxide material having high electrical conductivity and low thermal conductivity was obtained, and completed the present invention. It was It is an object of the present invention to provide a layered titanate material in which the conductivity of a titanic acid layered structure in which a transition metal is dissolved is improved. Another object of the present invention is to provide a method for making layered titanate conductive. It is another object of the present invention to provide a polycrystalline sintered body material whose conductivity is controlled by partially reducing titanium of the above-mentioned layered titanate.
A further object of the present invention is to provide a thermoelectric energy conversion element which is a combination of the above polycrystal and p-type polycrystal.

[0010]

The present invention for solving the above-mentioned problems comprises the following technical means. (1) A two-dimensional layered structure containing titanium as a main component, which is obtained by starting a mixture of titanium oxide, a transition metal chemical species, and an alkali compound as a starting material and subjecting the mixture to a flux or a solid phase reaction in the atmosphere or an inert atmosphere. A titanate material, characterized in that the crystal structure compound is further made conductive by controlling a conductive carrier by doping with a different metal ion or partially reducing titanium. (2) The titanate material according to the above (1), which comprises a monovalent or divalent ion-exchangeable alkali metal layer at an interlayer site of a two-dimensional layered crystal structure. (3) The titanate material according to (1) above, which contains transition metal species of iron, nickel, or cobalt, or alkali metal sodium. (4) The titanate material according to (1) above, which has a two-dimensional layered structure having a transition metal ion in a skeleton structure and has n-type thermoelectric properties. (5) The titanate material as described in (1) above, wherein the two-dimensional layered crystal structure compound is further made conductive by doping with a different metal ion by a solid phase reaction, a flux reaction, a uniform precipitation reaction, or a liquid phase reaction. (6) The titanate material according to the above (1), which is made conductive by further sintering the two-dimensional layered crystal structure compound in an inert atmosphere. (7) A thermoelectric energy conversion element material utilizing high conductivity and low thermal conductivity characteristics resulting from the molecular structure of the titanate described in (1) above, wherein the titanate material and p-type Bi-Te are used. A thermoelectric energy conversion element material comprising a combination of a base metal alloy, a CoSb ₃ -based skutterudite compound, NaCo ₂ O ₄ , a Ca ₃ Co ₄ O ₉ -based layered cobalt oxide compound, or a nickel oxide polycrystal. (8) A two-dimensional layered crystal structure compound containing titanium as a main component by starting a titanium oxide, a transition metal chemical species, and an alkali compound as a starting material and subjecting the mixture to a flux or a solid phase reaction in the air or an inert atmosphere. Is produced and is then fired in an inert atmosphere to make it electrically conductive, which is a method for producing a titanate material. (9) The method for producing a titanate material according to (8) above, wherein the transition metal chemical species is a transition metal oxide or a transition metal nitrate, and the alkali compound is an alkali carbonate or an alkali nitrate. (10) The method for producing a titanate material according to the above (8), which comprises firing a mixture having an excessive alkali metal composition. (11) The method for producing a titanate material according to (8), wherein the mixture is reacted in an inert atmosphere of nitrogen gas or argon gas.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail. In the present invention, in order to solve the above problems,
The following technical measures are adopted. 1. Synthesis of Transition Metal Solid Solution Layered Alkali Titanate by Alkali Flux Method Titanium oxide, a transition metal species such as its nitrate or oxide, and an alkali compound such as sodium carbonate or sodium nitrate are mixed according to a predetermined composition, N
a _x M _x Ti _2-x O ₄ (M: transition metal, x = 0.2 to
0.4), and reacted at 900-1350 ° C. in air or in an inert gas atmosphere such as argon gas to obtain a transition metal solid solution titanic acid having a rhombohedral or hexagonal layered crystal structure. Salt, Na _x M _x Ti _2-x O ₄
(M: transition metal, x = 0.2 to 0.4).

The titanium oxide, the transition metal chemical species and the alkali compound are preferably titanium oxide (TiO ₂ ) in the rutile or anatase phase and triiron tetraoxide (Fe ₃ O).
₄ ), tricobalt tetroxide (Co ₃ O ₄ ), nickel oxide (NiO) or a nitrate containing a high temperature decomposable transition metal,
Examples thereof include carbonates, chlorides, oxalates, and the like, sodium carbonate, sodium nitrate and sodium chloride, sodium oxalate, etc., but are not particularly limited, and appropriate ones can be used. This synthetic reaction
In order to suppress the partial decomposition of the layer structure due to the oxidation of the transition metal compound, the reaction in an inert atmosphere such as argon gas is desirable. Sodium is partially evaporated in the temperature rising process of the above synthetic reaction, and if the interlayer alkali metal ion, for example, sodium ion is insufficient, the layered structure becomes unstable. Therefore, preferably, the alkali metal in the charge, for example, Excess sodium is added and the product is washed with water or methanol to remove excess sodium.

2. Conducting electric conductivity of layered titanate by partial reduction Since the polycrystalline body obtained by sintering the powder prepared by the above method 1 is a semiconductor, it has low DC conductivity. Therefore, this polycrystal is further subjected to solid phase reaction, flux reaction, uniform precipitation reaction,
Alternatively, the polycrystal is made conductive by doping with a different metal ion by a reaction such as a liquid phase reaction or by sintering the polycrystalline body in an inert atmosphere. In the α phase, it is considered that the transition metal ions in the structure exist in a trivalent state to stabilize the two-dimensional layered structure (FIG. 1). Therefore, for example, the solid solution of metal ions such as Nb ⁵⁺ may increase the carrier concentration. By controlling or by, for example, firing under reduced pressure-Ar substitution to directly partially reduce titanium in the structure and create an oxygen ion overdoped state, the conductivity is controlled as n-type (electron carrier). can do. More specifically, for example, as a simple reduction method,
The layered titanate molded body is placed on a graphite dish and sintered at a high temperature of 1250 to 1300 ° C. in an argon gas atmosphere, whereby the layered titanate can be made electrically conductive, whereby a black multicolored titanate can be obtained. A crystal sintered body is obtained,
Further, a material having direct current conductivity even at room temperature can be obtained. The carrier concentration control and the partial reduction of titanium in the structure can be performed by an appropriate method.

3. Thermoelectric Material Properties of α-Phase Layered Titanate Polycrystal The polycrystalline sintered body obtained in the above 2 is an n-type by measuring its DC conductivity, thermoelectromotive force, and thermal conductivity of the polycrystalline body. As a result of evaluating the characteristics as a thermoelectric oxide material,
It was found that it is a polycrystal having a relatively large thermoelectric output factor and a low thermal conductivity as a conductive ceramic, and can be used as an n-type thermoelectric element material.

4. Thermoelectric element evaluation n-type α-phase layered titanate polycrystal obtained in the present invention and p
A thermoelectric element can be produced by electrically bonding the pn interface using a type polycrystalline body. For example, the n-type α-phase layered titanate polycrystal (for example,
And _{Na 0.2 Co 0. 2 Ti 1.8 O} 4), a similar p-type a layered compound NaCo ₂ O ₄ polycrystal were prepared respectively, the elements were electrically joined the p-n interface at Au paste A thermoelectric element having a maximum electromotive force of 0.12 V and a maximum of about 18 μW can be obtained by heating the joining side in an electric furnace to, for example, 800 ° C. and cooling the other side by blowing air.

The material of the present invention obtained as described above has the following characteristics. (1) A material that can be used as a new n-type conductive material or the like can be obtained by utilizing the layered crystal structure of titanium oxide, making it conductive by controlling the conductive carriers, and utilizing the low thermal conductivity due to the layered structure. . (2) The above materials can be manufactured at low cost because titanium oxide is the main raw material and can be synthesized mainly by the alkali flux method and the composition and the like can be easily controlled. (3) Use as an n-type polycrystalline oxide thermoelectric material can be expected. (4) By utilizing firing under an inert atmosphere,
It is possible to stably synthesize a compound having a layered crystal structure, and it is possible to control the generation of electron carriers by the partial reduction of titanium sites.

[0017]

EXAMPLES Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. (1) Preparation of α-phase layered sodium titanate and polycrystals Commercially available TiO ₂ (mainly anatase), Na ₂ CO ₃
(Or Na ₂ NO ₃ ) and a transition metal oxide (or nitrate), Na: M: Ti = 3: 2: 18 to 9: 6: 14.
(Na _x M _x Ti _2-x O ₄ , x = 0.2 to 0.4) was mixed in a ball mill for 24 hours (in this case, a 50 mol% excess was added in order to suppress evaporation of sodium salt). Were mixed), and reacted in a platinum crucible at 900-1350 ° C. in air or in an argon gas atmosphere for 6 to 24 hours to synthesize. The product was then ground and washed in methanol. As a result, in the reaction at 1000 ° C. or higher, cobalt, nickel or rhombohedral sodium α-phase titanate Na _x M _x Ti _{2- x} O ₄ (x = 0.2 to
0.4) was produced. In Fig. 2, 10 by the flux method
3 shows an XRD pattern of α-phase layered sodium titanate in which cobalt, nickel, or iron was solid-solved, which was synthesized at 00 ° C. Further, in the X-ray diffraction peak in the product, the peak intensity on the low angle side due to the layered structure was stronger and the compound having a more stable layered structure was obtained by firing in an argon atmosphere.

Next, the obtained powder is treated with about 4 × 10 × 20 m.
m, and CIP molding at 200 MPa, then place it on a graphite dish in an argon atmosphere and put it at 1200-135.
Firing was performed at 0 ° C. for 6 to 24 hours. After the reaction was completed, it was cooled to room temperature in about 4 hours. The sample obtained in the inert atmosphere was black. As shown in FIG.
An XRD pattern of a sintered body of α-phase layered sodium titanate synthesized at 0 ° C. is shown in FIG. 4, and an SEM of the surface of the polycrystalline sintered body is shown in FIG. Since the XRD pattern (FIG. 3) of the sample sintered in the inert atmosphere was the same as before the reaction, no phase change was observed. In the obtained polycrystalline sintered body, voids were observed here and there as shown in FIG.
Coupling between particles was sufficiently advanced. In addition, as a characteristic fine structure, a structure in which plate-like particles were arranged and arranged in one direction was observed.

(2) Evaluation of Thermoelectric Properties of α-Phase Layered Sodium Titanate Polycrystalline Material In the α-phase layered sodium titanate polycrystalline material sample fired in air at 1300 ° C., no DC conductivity was observed at room temperature. However, on the other hand, in the α-phase layered sodium titanate polycrystal sintered at 1200 ° C. or higher in an argon atmosphere, iron,
For both nickel- and cobalt-based samples,
DC conductivity was confirmed at room temperature. FIG. 5 shows 20 mol of iron, nickel and cobalt produced in an argon atmosphere.
The temperature changes of the DC conductivity, the thermoelectromotive force, and the calculated thermoelectric power factor (= thermoelectric power squared × conductivity) of the α-phase layered sodium titanate polycrystalline body containing 100% are shown. These measurements were carried out in a He gas atmosphere using a vacuum processing machine ZEM-1. α-phase layered sodium titanate Na _0.2 Co _0.2 T
The DC conductivity and thermoelectromotive force of i _1.8 O ₄ at 600 ° C are
It was about 4 × 10 ³ S / m and −180 μV / K, respectively, and it was observed that the conductivity and the thermoelectromotive force increased as the temperature increased. The performance factor of the thermoelectric material and the output factor that serves as one guide can be calculated to be about 1.0 × 10 ⁻⁴ W / mK ² . Further, the thermoelectromotive force has a negative value, and further, the electric conductivity increases as the temperature increases, so that the conductive characteristics of an n-type semiconductor are shown. This is due to the electron carrier conductivity resulting from the partial reduction of titanium under an inert atmosphere. In addition, when the change in electrical characteristics due to repeated firing at 1000 ° C. in the atmosphere was examined, it was found that Na _0.2 Co _0.2 Ti _1.8 O
_No significant decrease in conductivity was observed for ₄ and Na _0.2 Ni _0.2 Ti _1.8 O ₄ , indicating that the reduced titanium was stable.

On the other hand, when Na _0.2 Fe _0.2 Ti _1.8 O ₂ was repeatedly fired, a decrease in conductivity due to oxidation was observed. FIG. 6 shows the temperature change of the thermal conductivity of the α-phase layered sodium titanate polycrystalline sintered body synthesized at 1250 ° C. in an argon atmosphere, which was measured by a laser ablation method. Laser flash method (Vacuum Riko TC-700
The apparent thermal conductivity of α-phase layered sodium titanate polycrystals such as Na _0.2 Co _0.2 Ti _1.8 O ₄ measured in 0) is 08 to 1.5 W / mK and the conductivity is 0.8 to 1.5 W / mK as shown in FIG. The oxide polycrystal was relatively small. This is smaller than that of titanium oxide and is considered to be due to the layered crystal structure in which an alkali layer is sandwiched.
600-7 calculated from the measured output factor and thermal conductivity
The thermoelectric figure of merit ZT at 00 ° C. was about 0.15 (energy conversion efficiency of about 2%).

(3) Thermoelectric power generation test Na _0.2 Co _0.2 Ti prepared in the above (1) to (2)
An α-phase layered sodium titanate polycrystal such as _1.8 O ₄ was used as an n-type element, and a NaCo ₂ O ₄ polycrystal produced by the flux method and pressureless sintering (930 ° C., 6 h) was used as a p-type. As a mold element, a thermoelectric element was prepared by cutting each into a flat plate of about 1 × 3 × 15 mm and electrically joining the tip of about 1 mm with a gold paste at 600 ° C. Next, the electric power generated by the device was measured by heating the junction to various temperatures and cooling the other with an air-cooling fan. FIG. 7 shows the output voltage (V), current (mA) and thermoelectric power (W) at various temperatures. As shown in FIG. 7, 700-800
When the element is overheated at 0 ° C, a temperature difference of 590 to 670 ° C is formed on the element, and 5 to 18 µW (maximum electromotive force of 0.09
Power generation of ~ 0.12V) has become possible. Also, for example,
By connecting 10 elements in series, a power generation element of about 1.2V-0.2mW could be produced under heating at 800 ° C.

[0022]

As described in detail above, according to the present invention, titanium oxide, a transition metal chemical species, and an alkali compound are used as starting materials, and a mixture thereof is subjected to a flux or solid phase reaction in the air or an inert atmosphere. A titanate material characterized in that the two-dimensional layered crystal structure compound containing titanium as a main component obtained by the above method is further made conductive by controlling a conductive carrier by doping with a different metal ion or partially reducing titanium. According to the present invention, according to the present invention, the use thereof and the production method thereof are as follows: 1) easily using a titanium oxide which is inexpensive and rich in resources, a flux reaction to easily synthesize an α-phase layered sodium titanate having a layered crystal structure. 2) The carrier concentration is controlled by a partial reduction treatment of titanium sites, for example, high temperature treatment in an inert gas atmosphere. And makes it possible to n-type and conductivity titanate hydrochloride product is synthesized, 3) can be expected use as a novel n-type thermoelectric oxide material, 4)
Utilizing the coexisting properties of high conductivity and low thermal conductivity by forming an array structure of titanium oxide layer with high conductivity property generated in layered crystal structure and layer of alkali metal etc. whose thermal conductivity is structurally reduced 5) This polycrystalline material can be
By producing a power generation element which is used as a mold and is joined to another p-type polycrystalline oxide element, it is possible to obtain a special effect that it can be used as an oxide thermoelectric power generation element.

[Brief description of drawings]

FIG. 1 shows a crystal structure of α-phase layered sodium titanate.

FIG. 2 shows an XRD pattern of α-phase layered sodium titanate in which cobalt, nickel or iron is solid-solved, which was synthesized by a flux method at 1000 ° C.

FIG. 3: α synthesized at 1250 ° C. in an argon atmosphere
Phase Layered Sodium Titanate Na _0.2 Co _0.2 Ti _1.8
The XRD pattern of the O ₄ sintered body is shown.

FIG. 4: α synthesized at 1250 ° C. in an argon atmosphere
Phase Layered Sodium Titanate Na _0.2 Co _0.2 Ti _1.8
O ₄ shows the SEM of a surface of the polycrystalline sintered body.

FIG. 5: Direct current conductivity (S / m) thermoelectromotive force (μV / K) of α-phase layered sodium titanate polycrystal solid solution of cobalt, nickel or iron synthesized at 1250 ° C. in argon atmosphere And the temperature change of the thermoelectric power factor (W / mK ² ) are shown.

FIG. 6: α synthesized at 1250 ° C. under an argon atmosphere
Phase Layered Sodium Titanate Na _0.2 Co _0.2 Ti _1.8
The temperature change of the thermal conductivity of the O ₄ polycrystal sintered body by the laser ablation method is shown.

FIG. 7: α-phase layered sodium titanate Na _0.2 Co
Trial production using a _0.2 Ti _1.8 O ₄ polycrystalline sintered body (n-type Na _0.2 Co _0.2 Ti _1.8 O ₄ −p-type NaCo ₂ O ₄ ).
The output voltage (V), electric current (mA), and thermoelectric power generation (W) of the oxide polycrystalline thermoelectric element at various temperatures are shown.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 35/16 H01L 35/16 35/18 35/18 35/22 35/22 35/34 35/34 F Term (reference) 4G002 AA06 AB01 AD02 AE05 4G031 AA01 AA04 AA11 AA21 AA22 AA23 BA02 CA01 GA01 GA08 4G048 AA03 AB01 AB05 AC08 AD06 AE05

Claims (11)

[Claims] 1. A titanium-containing main component obtained by subjecting titanium oxide, a transition metal chemical species, and an alkali compound as a starting material to a flux or solid-phase reaction of a mixture thereof in the air or an inert atmosphere, and containing titanium as a main component. A titanate material characterized in that a three-dimensional layered crystal structure compound is further made conductive by controlling conductive carriers by doping with a different metal ion or partially reducing titanium. 2. The titanate material according to claim 1, wherein a monovalent or divalent ion-exchangeable alkali metal layer is included in an interlayer site of a two-dimensional layered crystal structure. 3. The titanate material according to claim 1, which contains the transition metal species iron, nickel, or cobalt, or the alkali metal sodium. 4. A compound having a transition metal ion in a skeleton structure, 2.
The titanate material according to claim 1, which has an n-type thermoelectric property in a dimensional layer structure. 5. The titanate material according to claim 1, wherein the two-dimensional layered crystal structure compound is further made conductive by doping a different metal ion by a solid phase reaction, a flux reaction, a uniform precipitation reaction, or a liquid phase reaction. . 6. The titanate material according to claim 1, wherein the two-dimensional layered crystal structure compound is made electrically conductive by further sintering in an inert atmosphere. 7. A thermoelectric energy conversion element material utilizing the high conductivity and low thermal conductivity characteristics resulting from the molecular structure of the titanate according to claim 1, wherein the titanate material and p-type Bi- are used. A thermoelectric energy conversion element material characterized by combining a Te-based metal alloy, a CoSb ₃ -based skutterudite compound, NaCo ₂ O ₄ , Ca ₃ Co ₄ O ₉ -based cobalt oxide layered compound, or a nickel oxide polycrystal. . 8. A two-dimensional layered crystal comprising titanium oxide, a transition metal chemical species, and an alkali compound as a starting material, and a mixture thereof is subjected to a flux or solid phase reaction in the atmosphere or an inert atmosphere to cause titanium as a main component. A method for producing a titanate material, characterized in that a structural compound is produced and further made conductive by firing in an inert atmosphere. 9. The method for producing a titanate material according to claim 8, wherein the transition metal chemical species is a transition metal oxide or a transition metal nitrate, and the alkali compound is an alkali carbonate or an alkali nitrate. 10. The method for producing a titanate material according to claim 8, wherein the mixture having an excessive alkali metal composition is baked. 11. The method for producing a titanate material according to claim 8, wherein the mixture is reacted in an inert atmosphere of nitrogen gas or argon gas.