WO2010023971A1

WO2010023971A1 - Oxide and method for controlling electrical characteristics of electric conductor

Info

Publication number: WO2010023971A1
Application number: PCT/JP2009/053289
Authority: WO
Inventors: 直池田; 徳亮花咲
Original assignee: 国立大学法人岡山大学
Priority date: 2008-08-29
Filing date: 2009-02-24
Publication date: 2010-03-04
Also published as: JP5626946B2; JP2010053006A

Abstract

Disclosed is an oxide represented by formula (1), a part of R in formula (1) having been subjected to solid solution substitution by a positive divalent or lower element or a positive quadrivalent or higher element. (RM₂O₄)_m(RMO₃)_n (1) wherein R represents at least one element selected from the group consisting of Y, Dy, Lu, Er, Yb, Tm, Ho, Sc, and In; M represents at least one element selected from the group consisting of Mn, Fe, Co, and Ga; m is 1 or 2; and n is an integer of 0 or more.

Description

Method for controlling electrical properties of oxides and electrical conductors

The present invention relates to an oxide capable of controlling electrical properties of an electrical conductor and a method for controlling electrical properties of the electrical conductor.

The band gap of the electrical conductor is usually determined by the crystal structure that constitutes the conduction band and the forbidden band. For this reason, it is difficult to change the size of the band gap. Further, since the semiconductor material is a material having a specific band gap, such as Si or a compound semiconductor, the response by light absorption can respond only to a specific wavelength. Furthermore, it is impossible to control a wide band gap by doping.

In addition, compound semiconductors such as ZnSe and CdS, which are unstable or toxic substances, are used particularly in the wavelength band of the infrared region where energy is low, but the manufacturing method is difficult and there is a problem of toxicity. There is a problem that usage is restricted. Accordingly, there is a need for materials that can easily control electrical characteristics.

As a novel material system, for example, Non-Patent Document 1 reports the dielectric properties of LuFe ₂ O ₄ which is a two-dimensional triangular lattice iron double-charged oxide. LuFe ₂ O ₄ is ferroelectric, and its manifestation principle is thought to be due to the action mechanism such as charge order formation by frustrated electron correlation, for example, the polar electron configuration on Fe ³⁺ , and known dielectrics And reported that it is different.

Further, in Non-Patent Document 2, the recent first calculation principle regarding LuFe ₂ O ₄ points out the existence of metallic conductive characteristics. It has been reported that the electrical conductivity up to now has a semiconductor behavior.
N. Ikeda, et al. Nature 436 (2005) 1136. Xiang HJ, Whangbo MH, Phys. Rev. Lett. 98 (2007) 246403.

An object of the present invention is to provide an oxide capable of controlling an electric characteristic (semiconductor characteristic) such as a band gap to an arbitrary value and a method for controlling an electric characteristic to an arbitrary value.

According to the present invention, the following oxides and the like are provided. That is, the oxide according to the present invention is an oxide represented by the following formula (1), in which a part of R in the formula (1) is substituted with a solid divalent or lower element.
(RM ₂ O ₄ ) _m (RMO ₃ ) _n (1)
Here, R is at least one element selected from the group consisting of Y, Dy, Lu, Er, Yb, Tm, Ho, Sc and In, and M is Mn, Fe, Co and It is at least one element selected from the group consisting of Ga, m is 1 or 2, and n is an integer of 0 or more.

In the above oxide, M in formula (1) is preferably Fe. Moreover, it is preferable that the element of less than positive divalent is at least one element selected from the group consisting of Ca, Sr, Ba and Zn. Further, it is particularly preferable that the element having a positive divalent value or less is Ca.

The electric conductor according to the present invention is an electric conductor made of the above oxide. The p-type semiconductor according to the present invention is a p-type semiconductor made of the above oxide.

Alternatively, the oxide according to the present invention is an oxide represented by the following formula (1), in which a part of R in the formula (1) is replaced by a solid solution with an element having a positive tetravalence or higher.
(RM ₂ O ₄ ) _m (RMO ₃ ) _n (1)
Here, R is at least one element selected from the group consisting of Y, Dy, Lu, Er, Yb, Tm, Ho, Sc and In, and M is Mn, Fe, Co and It is at least one element selected from the group consisting of Ga, m is 1 or 2, and n is an integer of 0 or more.

In the above oxide, M in formula (1) is preferably Fe. Moreover, it is preferable that the element more than the positive tetravalent is at least one element selected from the group consisting of Ce, Ti, Zr, Hf, Sn, Ta, Sb and Re. Moreover, it is especially preferable that the element more than the positive tetravalent is Ce.

The electric conductor according to the present invention is an electric conductor made of the above oxide. An n-type semiconductor according to the present invention is an n-type semiconductor made of the above oxide.

The method for producing an oxide according to the present invention includes at least one of an oxide and carbonate of at least one element selected from the group consisting of Ca, Sr, Ba, and Zn, Y, Dy, Lu, Er, Yb, At least one oxide or carbonate of at least one element selected from the group consisting of Tm, Ho, Sc and In, and at least one element selected from the group consisting of Mn, Fe, Co and Ga. A step of preparing a raw material powder in which at least one of an oxide and a carbonate is mixed, and after the raw material powder is fired under heating in an atmosphere having an oxygen partial pressure of 10 ⁻⁶ to 10 ⁻¹¹ atm, And a step of cooling.

In the above production method, the raw material powder is fired at 1000 ° C. to 1400 ° C. for 1 to 100 hours in an atmosphere having an oxygen partial pressure of 10 ⁻⁷ to 10 ⁻⁸ atm, It is preferable to perform rapid cooling in a temperature range of 40 ° C.

Alternatively, the method for producing an oxide according to the present invention includes at least one of an oxide and carbonate of at least one element selected from the group consisting of Ce, Ti, Zr, Hf, Sn, Ta, Sb and Re, A group consisting of Mn, Fe, Co and Ga, and at least one of an oxide and carbonate of at least one element selected from the group consisting of Y, Dy, Lu, Er, Yb, Tm, Ho, Sc and In A step of preparing a raw material powder obtained by mixing at least one of oxides and carbonates of at least one element selected from the above, and an atmosphere having an oxygen partial pressure of 10 ⁻⁶ to 10 ⁻¹¹ atm. And a step of cooling after baking under heating.

In addition, the method for controlling electrical characteristics according to the present invention is a method in which a part of R of the oxide represented by the following formula (1) is substituted by a solid solution substitution of an element less than positive divalent or an element greater than positive tetravalent. This is a method for controlling the electrical characteristics of an object.
(RM ₂ O ₄ ) _m (RMO ₃ ) _n (1)
Here, R is at least one element selected from the group consisting of Y, Dy, Lu, Er, Yb, Tm, Ho, Sc and In, and M is Mn, Fe, Co and It is at least one element selected from the group consisting of Ga, m is 1 or 2, and n is an integer of 0 or more.

Further, in the above control method, it is preferable to control the band gap of the oxide by adjusting the amount of solid solution substitution of an element less than positive divalent or an element more than positive tetravalent.

According to the present invention, it is possible to provide a method for controlling the electrical characteristics of an oxide to an arbitrary value. Further, it is possible to provide an oxide which is a non-toxic material and can control the band gap from the far infrared region to the visible light region.

FIG. 1 is a flowchart showing a method for controlling electrical properties of an electrical conductor according to the present invention. FIG. 2 is an X-ray powder diffraction spectrum of the oxide produced in Example 6. FIG. 3 is a diagram illustrating an example in which a change in dielectric constant with temperature is measured. FIG. 4 is a diagram in which the reciprocal of the inflection point Tr is plotted on the horizontal axis and the measurement frequency is plotted on the vertical axis. FIG. 5 is a diagram showing the band gap Q and the electrical conductivity ρ of the oxides obtained in the examples and comparative examples.

The oxide of the present invention is represented by the following formula (1), and a part of R in the formula (1) is solid solution substituted by an element having a positive divalent value or less, or an element having a positive tetravalent value or more.
(RM ₂ O ₄ ) _m (RMO ₃ ) _n (1)
Here, in the above formula, R is at least one element selected from the group consisting of Y, Dy, Lu, Er, Yb, Tm, Ho, Sc and In, and M is Mn, Fe, Co , Ni, Cu, Zn, Al, Mg, and Ga, m is 1 or 2, and n is an integer of 0 or more.

The present inventors adjust the band gap because the band gap of the oxide represented by the formula (1) is dominated by the competition of the number of charges between elements less than positive divalent or more than positive tetravalent. I found out that I can do it.

Conventionally, since the band gap of an electric conductor is determined by the crystal structure constituting the conduction band and the forbidden band, it has been difficult to change the size of the band gap. On the other hand, in the electrical conduction of a substance whose charge configuration is competing by Coulomb force, such as an oxide represented by the formula (1), the amount of elements less than positive divalent or the amount of elements greater than positive tetravalent is adjusted. By adjusting the Coulomb force competition, it is possible to control physical properties depending on the size of the band gap, such as the temperature change of the electric conductivity of the oxide. Further, the oxide of the present invention has extremely low toxicity.

R in the formula (1) is at least one element selected from the group consisting of Y, Dy, Lu, Er, Yb, Tm, Ho, Sc and In. Y, Lu and Yb are preferred. In particular, Y or Yb is more suitable in the synthesis by firing.

M is at least one element selected from the group consisting of Mn, Fe, Co, and Ga. Fe and Mn are preferred. Fe is more preferable in terms of ease of control of the valence. m is 1 or 2. n is an integer of 0 or more, preferably an integer of 0 to 10, particularly preferably an integer of 0 to 6.

In the oxide of the present invention, a part of R in the formula (1) is replaced by a solid solution with an element having a positive divalent value or less or an element having a positive tetravalent value or more. By substituting an element having a positive divalent value or less for the oxide, electrical characteristics can be controlled from conductivity to p-type semiconductor properties, and an electrical conductor and p-type semiconductor can be realized. On the other hand, by substituting an element having a positive tetravalent or higher value for the oxide, the electrical characteristics can be controlled from conductivity to n-type semiconductor properties, and an electrical conductor and an n-type semiconductor can be realized.

Examples of the positive divalent or lower element include at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Na, K, Rb, Cs, and Zn. Moreover, this element less than positive divalent is preferably at least one element selected from the group consisting of Ca, Sr, Ba and Zn. Furthermore, Ca is more preferable in terms of ease of synthesis.

Examples of the positive tetravalent or higher element include at least one element selected from the group consisting of Ce, Ti, Zr, Hf, Sn, Ta, Sb, and Re. Moreover, this element more than the positive tetravalent is preferably at least one element selected from the group consisting of Ce, Ti, Zr and Sn. Furthermore, Ce is more preferable in terms of ease of synthesis.

In addition, the substitution ratio X (R _1−x A _x : atomic ratio) of R with respect to an element having a positive divalent or lower element or a positive tetravalent or higher element (A) may be appropriately adjusted so as to obtain desired electrical characteristics. . This substitution rate is usually greater than 0 and 0.3 or less, preferably 0.01 to 0.2, more preferably 0.01 to 0.10. The substitution ratio of R with respect to an element having a positive divalent value or less or an element having a positive tetravalent value or more can be adjusted by, for example, the charge ratio of raw materials when an oxide is synthesized.

The fact that a part of R in formula (1) is solid solution substituted by an element less than positive divalent or more than positive tetravalent means that the peak shift due to X-ray diffraction, that is, the change in lattice constant and the substitution element This can be confirmed by analysis by the XAFS method using the absorption edge. The confirmation of the substitution is performed by measuring the absorption edge of each element by the XAFS method, and from the radial distribution curve obtained by Fourier transform of the obtained spectrum and, for example, the XAFS spectrum of the Lu-K edge of LuFe ₂ O _4. This can be confirmed by comparing the obtained radial distribution curves. The substitution rate can be measured by plotting the lattice constant obtained from X-ray diffraction with the substitution amount.

The oxide of the present invention can be obtained, for example, by firing a mixture of raw materials. Examples of oxide raw materials include oxides, sulfides, sulfates, halides (chlorides, bromides, etc.) containing R or M in formula (1), elements less than positive divalent or elements more than positive tetravalent. And carbonates. It is preferable to use oxides or carbonates of the above elements so that they are completely thermally decomposed at a low temperature so that no impurities remain. The starting material is preferably sufficiently dried in advance.

As starting materials, at least one of oxides and carbonates of at least one element selected from the group consisting of Ca, Sr, Ba and Zn, and Y, Dy, Lu, Er, Yb, Tm, Ho, At least one of an oxide and carbonate of at least one element selected from the group consisting of Sc and In, and an oxide and carbonic acid of at least one element selected from the group consisting of Mn, Fe, Co, and Ga It is preferable to use a raw material powder in which at least one of the salts is mixed.

Alternatively, as starting materials, at least one of an oxide and carbonate of at least one element selected from the group consisting of Ce, Ti, Zr, Hf, Sn, Ta, Sb and Re, and Y, Dy, Lu, At least one selected from the group consisting of oxides and carbonates of at least one element selected from the group consisting of Er, Yb, Tm, Ho, Sc and In, and at least one selected from the group consisting of Mn, Fe, Co and Ga It is preferable to use a raw material powder in which at least one of an oxide of a seed element and a carbonate is mixed.

The raw materials can be mixed by, for example, a physical mixing method. A specific physical mixing method is not particularly limited, and a known device such as a ball mill can be used.

The oxide of the present invention is obtained by firing the raw material powder of the obtained raw material mixture under heating in an ultra-low oxygen partial pressure atmosphere and then cooling it. The raw material mixture may be uniaxially pressed into a form that is easy to handle before firing, for example, a pellet, and further molded by cold isostatic pressure (CIP) or the like. Moreover, you may calcine.

The firing conditions may be appropriately adjusted depending on the raw materials used. For example, the firing temperature is usually preferably 1000 ° C. to 1400 ° C., particularly preferably 1100 ° C. to 1300 ° C. The firing time is preferably 1 hour to 100 hours, particularly preferably 5 hours to 72 hours.

The atmosphere of firing, very low oxygen partial pressure atmosphere, it is preferable to adjust and more specifically an oxygen partial pressure of ¹⁰ -6 ^{to 10 -11} atm, further the oxygen partial pressure ^{of 10} -7 to 10 ^- It is particularly preferable to adjust to ⁸ atmospheres. In order to adjust the oxygen partial pressure, it is preferable to use a mixed gas of CO and CO _{2 or} a mixed gas of H ₂ and CO ₂ . When a mixed gas of CO and CO ₂ is used, the partial pressure of oxygen can be suitably adjusted by setting the range of CO ₂ / CO = 1 to 10.

After calcination, the obtained oxide is usually cooled in a temperature range of 15 to 40 ° C., and particularly rapidly cooled, so that the change in crystal structure can be suppressed, which is preferable. For cooling the oxide, for example, the temperature lowering rate is preferably about 100 ° C./min to 1000 ° C./min.

An oxide single crystal may be produced from the obtained oxide sintered body. A method for producing a single crystal can be produced by the following method, but is not necessarily limited to the following.

Examples of the method for producing the oxide single crystal include an optical FZ (floating zone: floating zone melting) method. Specifically, an oxide single crystal is grown using an infrared condensing heating furnace. The oxide sintered body is used as a raw material rod, and is placed on the upper axis of an infrared condensing heating furnace, and the oxide single crystal produced by another method as a seed crystal is placed on the lower axis. As the seed crystal, a single crystal portion obtained by preliminarily subjecting the oxide polycrystal to light heating zone melting is used.

The tips of the raw material rod and seed crystal are moved so as to be in the center of the furnace and brought into contact with melting, while the raw material rod and seed crystal are rotated in opposite directions to adjust the crystal growth rate. A single crystal is grown.

The crystal growth atmosphere is an ultra-low oxygen partial pressure atmosphere. Specifically, the oxygen partial pressure is preferably adjusted to 10 ⁻⁶ to 10 ⁻¹¹ atm, and the oxygen partial pressure is adjusted to 10 ⁻⁷ to 10 ⁻⁸ atm. It is particularly preferable to do this. In order to adjust the oxygen partial pressure, it is preferable to use a mixed gas of CO and CO _{2 or} a mixed gas of H ₂ and CO ₂ .

Moreover, it is preferable that the obtained oxide is cooled, particularly rapidly cooled after firing. Specifically, for example, the temperature lowering rate is preferably about 100 ° C./min to 1000 ° C./min.

In the oxide of the present invention, the electrical properties of the oxide can be controlled by solid solution substitution of a part of R in the formula (1) with an element less than positive divalent or an element more than positive tetravalent.

FIG. 1 is a flowchart showing a method for controlling electrical properties of an electrical conductor according to an embodiment. First, the amount of the positive divalent or lower element or the positive tetravalent or higher element contained in the oxide of the formula (1) is adjusted (step S1). Then, the electrical conductivity depending on the band gap of the oxide is changed and controlled (step S2).

In the present invention, the semiconductor property (electric property) of the oxide can be controlled to an arbitrary value by controlling the substitution rate of R with respect to an element having a positive or lower valence or an element having a positive or lower valence. For example, the band gap can be controlled from the far infrared region to the visible light region (0.1 eV to 2.5 eV).

In a substance that generates charge ordering due to competition of Coulomb force between charges, such as an oxide of formula (1), a current control element, a voltage signal storage element, a dielectric element, a photosensitive element using this characteristic, and Development of solar cells and the like becomes possible. In these electronic devices, by adjusting the competition between charges, it is possible to obtain the same effect as effectively changing the band gap and the electric conductivity. As a result, optimum characteristics necessary for design can be realized in the current control element, the voltage signal storage element, the dielectric element, the light sensing element, and the solar cell.

Here, the above-described oxide and the control of electric characteristics in the oxide will be described in some detail. However, the following description includes speculation from an academic point of view and does not affect the interpretation of the present invention. Further, in the following, for the substance represented by the general formula (RM ₂ O ₄ ) _m (RMO ₃ ) _n of the formula (1), characteristics and the like will be described using RFe ₂ O ₄ as an example for simplicity of explanation. Each of the substances represented by the above general formula has the same crystal structure and characteristics as RFe ₂ O ₄ .

In the conventional electric conductor, since the band gap is determined by the crystal structure, it is difficult to change the band cap. For example, since a conventional semiconductor material is a material having a specific band cap, the optical response can respond only to a specific wavelength, and it is difficult to control the band gap in a wide range by doping. Therefore, a material capable of easily controlling the electrical characteristics has been demanded.

In the present invention, since Fe ²⁺ and Fe ³⁺ are placed on a triangular lattice in the crystal structure of RFe ₂ O _4, a charge-ordered structure is formed by an electron correlation effect of charge-to-charge competition, thereby forming a band gap. It is the thing which pays attention to being done.

That is, a part of the trivalent rare earth ions (R) in RFe ₂ O ₄ are substituted with an element having a positive divalent value or less or an element having a positive tetravalent value or more. At this time, the valence of iron ions on the triangular lattice partially changes, thereby changing the charge-charge interaction and adjusting the charge order formation due to the charge-to-charge competition between the iron ions. It has been found that the size can be controlled, and the present invention has been achieved.

Furthermore, by substituting an element having a positive or lower valence in the oxide into a solid solution, the electrical characteristics of the oxide can be controlled from conductivity to p-type semiconductivity. It has been found that the electrical properties of the oxide can be controlled from conductivity to n-type semiconductor properties by substitution, and the present invention has been achieved.

Further, regarding RFe ₂ O ₄ , it is considered that the following two conditions are necessary for the background of the manifestation of the characteristics of the present invention.

First, there is a condition that the same number of Fe ²⁺ and Fe ³⁺ exist in a region called W-layer in the RFe ₂ O ₄ crystal. In the crystal structure of RFe ₂ O ₄ , as is the case with the entire crystal, the W-layer has a triangular lattice structure, and therefore the presence of the same number of Fe ²⁺ and Fe ³⁺ causes charge frustration. become.

That is, in the above crystal structure, since the average iron ion valence is 2.5, Fe ²⁺ has many electrons and plays a role of negative charge, while Fe ³⁺ has ^less electrons and plays a role of positive charge. Have. Further, in RFe ₂ O ₄ , the same number of positive charges and negative charges must be arranged on the W-layer triangular lattice, and as a result, the regular arrangement of Fe ²⁺ and Fe ³⁺ appears in the W-layer. . In this regular arrangement, as described above, a region rich in Fe ³⁺ has a role of positive charge, while a region rich in Fe ²⁺ has a role of negative charge. For this reason, the W-layer has an electric dipole (electric polarization), and the presence of this electric polarization is the origin of various characteristics.

As a second condition, in order for the same number of Fe ²⁺ and Fe ³⁺ to exist in the above substance, R is required to be 3+ as derived from the chemical formula RFe ₂ O ₄ . Therefore, from these conditions, the valence of R is 3+ in order to develop the characteristics of the substance of the present invention.

As a third condition, from the standpoint of crystal chemistry, in order for the crystal structure of this material to be established, the ratio of transition metal ions, oxygen ions, and rare earth ions must maintain the current ionic radius ratio. I guess it will be.

The present invention breaks down the first condition described above by substituting a small amount of divalent or tetravalent ions for R ³⁺ ions, and has physical properties such as optical properties, magnetic properties, electrical conductivity properties, and band gaps. It is based on finding that it changes markedly. Moreover, since the above-described crystal structure of RFe ₂ O ₄ is established, R ions known so far are Y, Dy, Lu, Er, Yb, Tm, Ho, Sc, and In. This is presumed to be restricted by the third condition described above.

It should be noted that the present invention does not exclude introducing a plurality of 3+ ions into R ions instead of one kind. It is speculated that dissolving ions with different ionic radii may further change the physical properties.

The essence of the present invention is based on the speculation that the first condition described above is modulated to adjust the charge frustration, and as a result, the physical properties including the band gap are changed. Moreover, in the example specifically described below as an example of the present invention, a small amount of Ca ²⁺ and Ce ⁴⁺ is substituted according to this idea, and the effect is confirmed.

Examples of oxides according to the present invention will be described.

Example 1 [Production of oxide]
Iron oxide powder having a purity of 99.99% (Fe ₂ O ₃ manufactured by Kojundo Chemical Laboratory Co., Ltd.), ytterbium oxide powder having a purity of 99.99% (Yb ₂ O ₃ manufactured by Kojundo Chemical Laboratory Co., Ltd.) and purity 99 99% calcium carbonate (CaCO ₂ manufactured by Kojundo Chemical Laboratory Co., Ltd.) is used. Fe ₂ O ₃ is prepared by baking at 600 ° C. for 12 hours in oxygen. Yb ₂ O ₃ is prepared by decarboxylation at 1000 ° C. in the atmosphere. The raw materials were weighed so that the atomic ratio (Yb: Ca: Fe) was 0.99: 0.01: 2, and pulverized and mixed to obtain a powder material.

This powder material was put into a press mold having a diameter of 10 mm, and was press-molded at a hydrostatic pressure of 60 MPa for 3 minutes and solidified into a cylindrical shape using a press machine. Next, the solidified powder material is taken out and used as a raw material body.

This raw material body was installed in a tubular electric furnace, and this mixed gas was supplied at a rate of 200 ml / min into the furnace tube as a mixed gas of CO and CO ₂ (CO ₂ / CO = 1: volume ratio). The heat treatment temperature was 1200 ° C., and the heat treatment time was 24 hours. After the heat treatment, the sample was taken out and rapidly cooled to room temperature (25 ° C.) to produce the oxide of the present invention.

The oxide obtained above was evaluated by ICP emission spectroscopy by quantitative analysis of composition analysis, and the atomic ratio (Yb: Ca: Fe) was 0.99: 0.01: 2.00. It was.

Examples 2 and 3
An oxide was produced in the same manner as in Example 1 except that the raw material charge ratio was changed as follows.
Example 2: Atomic ratio (Yb: Ca: Fe) = 0.95: 0.05: 2
Example 3: Atomic ratio (Yb: Ca: Fe) = 0.90: 0.10: 2

Example 4-6
An oxide was produced in the same manner as in Example 1 except that cerium oxide (manufactured by Kojundo Chemical Laboratory Co., Ltd.) was used instead of calcium carbonate as a raw material, and the raw material charge ratio was changed as follows. did.
Example 4: Atomic ratio (Yb: Ce: Fe) = 0.95: 0.05: 2
Example 5: Atomic ratio (Yb: Ce: Fe) = 0.90: 0.10: 2
Example 6: Atomic ratio (Yb: Ce: Fe) = 0.98: 0.02: 2

In Example 2-6, the composition and substitution of the obtained oxide were measured in the same manner as in Example 1, and it was confirmed that the composition was the same as the raw material charge ratio.

FIG. 2 shows an X-ray powder diffraction spectrum of the oxide produced in Example 6. As a result of analysis of peak shift by X-ray diffraction, it was confirmed that this oxide is a single phase of a crystal represented by YbFe ₂ O ₄ , and Yb was solid-substituted by Ce.

Comparative Example 1
An oxide was produced in the same manner as in Example 1 except that calcium carbonate was not added and the charging ratio was changed as follows.
Comparative Example 1: Atomic ratio (Yb: Fe) = 1: 2

[Evaluation 1]
With respect to the oxides manufactured in Example 1-5 and Comparative Example 1, the band gap was measured. Each oxide sintered body was polished into a cylindrical shape (cylinder diameter 7 mm, thickness 0.7 mm). Electrode surfaces were formed on the bottom and top surfaces of the sample using a conductive adhesive (silver paste). A sample was used as a measurement sample.

The temperature dependence of the dielectric constant of this measurement sample was measured, and the band gap was calculated from the dielectric dispersion of the measurement sample. The dielectric constant was measured according to the method described in JP-A-2007-223886.

FIG. 3 shows an example in which the temperature change of the dielectric constant of the sample is measured. From the obtained result, the inflection point Tr of each frequency is determined. FIG. 4 is a diagram in which the reciprocal of the inflection point Tr is plotted on the horizontal axis and the measurement frequency is plotted on the vertical axis. The obtained value is approximated by the following equation to obtain U.
f = f ₀ exp (−U / kT)
Here, f is a frequency, f ₀ is a constant, k is a Boltzmann constant, and T is an absolute temperature. By converting U to electron volts (eV), a band gap is obtained.

FIG. 5 is a graph showing the band gap Q and the electrical conductivity ρ of the oxides obtained in the above-described examples and comparative examples. The electrical conductivity is a value estimated from an electrical resistance near room temperature.

Curve C1 shows the relationship between the band gap Q and the amount X of elements less than positive divalent or more than tetravalent, and curve C2 shows the relationship between resistivity ρ and X at room temperature. Thus, in an electric conductor containing an oxide and an element having a positive or lower valence of 2 or more, and a positive or lower element having a positive or lower valence of 4 or more, by adjusting the amount X of the element having a positive or lower valence of 2 or higher and an element having a value of 4 or higher. The gap and resistivity ρ (electrical conductivity) can be controlled.

Note that the oxide of Comparative Example 1 (X = 0) has a band gap of 1.8 eV and an electric conductivity of about 100 kΩcm. The band gap of the oxide of Example 1 (X = 0.01) is 1.55 eV, and the electric conductivity is about 0.2 Ωcm.

[Evaluation 2]
The dielectric constant measurement sample prepared in Example 2 was irradiated with light separated by a splitter using an infrared light source, and light absorption characteristics were measured. In YbFe ₂ O ₄ to which no impurity is added, the absorption edge is mainly in the vicinity of 1.3 eV, but with the addition of Ca, the light absorption edge corresponding to the existence of the band gap is in the vicinity of 0.3 eV, 1 About 3 eV. This indicates that in this sample Yb _0.95 Ca _0.05 Fe ₂ O ₄ , the band gap was controlled by addition of impurities, and an absorption edge was formed in the vicinity of 0.3 eV.

On the other hand, in the Si single crystal having the same shape as in Example 2, the absorption edge is in the vicinity of 1 eV. Therefore, even when irradiated with light of energy smaller than this (for example, light of 0.3 eV (wavelength 4 μm)), light absorption is achieved. Does not happen. This indicates that there is no light absorption even when irradiated with light having energy smaller than the band gap of Si.

The oxide of the present invention can realize optimum characteristics necessary for design in current control elements, voltage signal storage elements, dielectric elements, light sensing elements, solar cells, and the like.

Claims

An oxide represented by the following formula (1), in which a part of R in the formula (1) is replaced by a solid solution with an element having a positive or lower valence of 2 or less.
(RM 2 O 4 ) m (RMO 3 ) n (1)
(Wherein R is at least one element selected from the group consisting of Y, Dy, Lu, Er, Yb, Tm, Ho, Sc and In, and M is from Mn, Fe, Co and Ga) (At least one element selected from the group consisting of m, 1 or 2 and n is an integer of 0 or more.)
The oxide according to claim 1, wherein M in the formula (1) is Fe.
The oxide according to claim 1 or 2, wherein the element of less than positive divalent is at least one element selected from the group consisting of Ca, Sr, Ba and Zn.
The oxide according to claim 1 or 2, wherein the element having a positive divalent value or less is Ca.
An electric conductor comprising the oxide according to any one of claims 1 to 4.
A p-type semiconductor comprising the oxide according to any one of claims 1 to 4.
An oxide represented by the following formula (1), wherein a part of R in the formula (1) is solid solution substituted with an element having a positive tetravalent or higher.
(RM 2 O 4 ) m (RMO 3 ) n (1)
(Wherein R is at least one element selected from the group consisting of Y, Dy, Lu, Er, Yb, Tm, Ho, Sc and In, and M is from Mn, Fe, Co and Ga) (At least one element selected from the group consisting of m, 1 or 2 and n is an integer of 0 or more.)
The oxide according to claim 7, wherein M in the formula (1) is Fe.
The oxide according to claim 7 or 8, wherein the element having a positive tetravalent or higher is at least one element selected from the group consisting of Ce, Ti, Zr, Hf, Sn, Ta, Sb and Re.
The oxide according to claim 7 or 8, wherein the element having a positive tetravalence or more is Ce.
An electric conductor comprising the oxide according to any one of claims 7 to 10.
An n-type semiconductor comprising the oxide according to any one of claims 7 to 10.
At least one of an oxide and carbonate of at least one element selected from the group consisting of Ca, Sr, Ba and Zn;
At least one of an oxide and carbonate of at least one element selected from the group consisting of Y, Dy, Lu, Er, Yb, Tm, Ho, Sc and In;
Preparing a raw material powder mixed with at least one of an oxide and carbonate of at least one element selected from the group consisting of Mn, Fe, Co and Ga;
A step of baking the raw material powder under heating in an atmosphere having an oxygen partial pressure of 10 −6 to 10 −11 atm and then cooling the raw material powder.
At least one of an oxide and carbonate of at least one element selected from the group consisting of Ce, Ti, Zr, Hf, Sn, Ta, Sb and Re;
At least one of an oxide and carbonate of at least one element selected from the group consisting of Y, Dy, Lu, Er, Yb, Tm, Ho, Sc and In;
Preparing a raw material powder mixed with at least one of an oxide and carbonate of at least one element selected from the group consisting of Mn, Fe, Co and Ga;
A step of baking the raw material powder under heating in an atmosphere having an oxygen partial pressure of 10 −6 to 10 −11 atm and then cooling the raw material powder.
A method of controlling the electrical characteristics of an oxide by replacing a part of R of the oxide represented by the following formula (1) with a solid solution or a non-positive divalent element or a positive tetravalent element or more.
(RM 2 O 4 ) m (RMO 3 ) n (1)
(Wherein R is at least one element selected from the group consisting of Y, Dy, Lu, Er, Yb, Tm, Ho, Sc and In, and M is from Mn, Fe, Co and Ga) (At least one element selected from the group consisting of m, 1 or 2 and n is an integer of 0 or more.)
The method according to claim 15, wherein the band gap of the oxide is controlled by adjusting a solid solution substitution amount of the element less than the positive divalent or the element more than the positive tetravalent.