JP2010064923A - Method for producing niobium monooxide, and niobium monooxide - Google Patents

Abstract

The present invention provides a technique for producing niobium monoxide having a large specific surface area suitable for a capacitor material and comprising fine particles.
The present invention relates to a method for producing niobium monoxide by reducing and calcining niobium pentoxide or niobium dioxide to produce niobium monoxide, and wet-mixing niobium pentoxide or niobium dioxide and a salt containing a rare earth element. A firing process is performed, and after the firing process, a reduction firing process is performed by mixing a niobium oxide in a state in which a rare earth element is doped at a niobium atom position and a reducing agent.
[Selection figure] None

Description

  The present invention relates to a technique for producing niobium monoxide having a large specific surface area and composed of a fine particle size.

  In recent years, the amount of niobium oxide used as a raw material for electronic parts such as frequency filters and capacitors, a target material for sputtering, and the like is rapidly increasing. In particular, niobium monoxide (hereinafter sometimes referred to as “NbO”) has been adopted as a new type of capacitor raw material, and can achieve a large capacity with a small-sized chip, and has excellent electrical stability and flame retardancy. It has begun to spread widely as a capacitor with the characteristics.

  In recent years, niobium capacitors have been required to be downsized and thin (thinned), and accordingly, higher capacity has been demanded. The raw material powder parameter corresponding to the capacitance is the specific surface area, and the larger the specific surface area of the raw material powder as the dielectric and the anode, the larger the capacitance can be realized. Therefore, NbO used as a raw material for niobium capacitors is required to be a finer powder having a large specific surface area.

  For such niobium monoxide, various production methods have been proposed. For example, Patent Document 1 discloses a manufacturing method in which an activation agent such as an oxide, carbonate, nitrate, or organic substance is added to niobium monoxide obtained by reducing niobium pentoxide with magnesium, and an activation process is performed. Proposed. According to the production method using this activator, niobium monoxide having many pores can be obtained, and the specific surface area can be increased. However, in the prior art using this activator, an activator is added and a removal step by washing is required, and an increase in cost due to an increase in the number of steps can be considered. Further, depending on the degree of the removal step, a large amount of impurities may be mixed into niobium monoxide, which may cause deterioration of the electrical characteristics of the capacitor, which is not preferable.

International Publication WO2002 / 093596 Pamphlet

  The present invention has been made under the circumstances described above, and an object thereof is to provide a technique for producing niobium monoxide having a large specific surface area suitable as a capacitor material and comprising fine particles.

  In order to solve the above-mentioned problems, the present inventors have conducted extensive studies on a conventional method for producing niobium monoxide by reduction firing. As a result, the specific surface area is large and the particles are made of fine particles to improve the capacitor characteristics. We have found a technology to produce niobium monoxide that can be used. Specifically, the present invention relates to a method for producing niobium monoxide by reducing and firing niobium pentoxide or niobium dioxide to produce niobium monoxide, and mixing niobium pentoxide or niobium dioxide with a salt containing a rare earth element. The firing process is performed, and after the firing process, the reduction process is performed by mixing the niobium oxide in a state in which the rare earth element is doped at the niobium atom position and the reducing agent.

  According to the present invention, niobium pentoxide or niobium dioxide and a salt containing a rare earth element are mixed and fired in an inert atmosphere or an atmosphere containing oxygen, so that the rare earth element is placed at the position of the niobium atom. A rare earth element-containing niobium oxide in a partially substituted state is obtained. Then, when the rare earth element-containing niobium oxide and the reducing agent thus obtained are mixed and reduced and fired, the sintering suppression effect due to the contained rare earth element is produced, so that the niobium oxidation not containing the rare earth element occurs. The primary particles of niobium monoxide are clearly finer than when the product is reduced and fired. The niobium monoxide obtained according to the present invention contains a rare earth element, but is contained in a state where it is substituted at the atomic level. Therefore, removal work as in the prior art of Patent Document 1 described above is required. do not do. The baking conditions after mixing are preferably 700 ° C. to 1100 ° C. for 5 hours to 24 hours in the air, and the subsequent reduction baking conditions are 1200 ° C. to 1500 ° C. for 5 hours to 24 hours in a hydrogen atmosphere. The firing time is preferred.

  In the production method of the present invention, it is preferable to use at least one of carbonate, nitrate and oxalate as the salt containing the rare earth element. When a rare earth salt compound of any one of carbonate, nitrate and oxalate is mixed with niobium pentoxide or niobium dioxide and calcined, the carbonate, nitrate and oxalate radicals are vaporized and vaporized. This is because the elements are easily distributed uniformly at the positions of niobium atoms.

  In addition, the reducing agent in the production method of the present invention is preferably selected from the group of alkali metals, alkaline earth metals, niobium carbides, niobium nitrides, niobium sulfides, niobium hydrides, and niobium metals. This is because with these reducing agents, niobium monoxide can be efficiently produced from the niobium oxide containing the rare earth element subjected to the firing treatment.

  In the manufacturing method of the present invention, the rare earth element is selected from a group of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Is preferred. Furthermore, it is more preferable that at least one element is selected from Y, La, and Ce. If these rare earth elements are used, the rare earth element is substituted at the position of the niobium atoms, so that the sintering suppressing action becomes more effective. It is preferable to adjust the amount of the salt containing a rare earth element to be mixed with niobium pentoxide or niobium dioxide so that the final rare earth element content in the niobium monoxide obtained is 50 ppm to 1000 ppm. If it is less than 50 ppm, the sintering suppressing effect is reduced, and if it exceeds 1000 ppm, the rare earth element cannot be substituted at the position of the niobium atom, and a complex oxide of rare earth element and niobium is produced as an impurity. Because it will end up.

  Furthermore, in the production method of the present invention, when mixing niobium pentoxide and rare earth elements, either dry mixing or wet mixing may be used, but wet mixing is preferable in consideration of homogeneity and workability after mixing. In the case of wet mixing, an organic solvent such as pure water or alcohol can be used as a solvent.

  According to the production method of the present invention, the rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu is 50 ppm to 1000 ppm. Niobium monoxide containing can be produced. Since the niobium monoxide of the present invention is a powder of niobium monoxide having a large specific surface area, which is composed of fine primary particles, it is possible to improve the capacitance, which is a capacitor characteristic. When the content of the rare earth element is less than 50 ppm, the sintering suppressing effect is reduced and fine primary particles cannot be formed. When the content exceeds 1000 ppm, the complex oxide of rare earth element and niobium is used as an impurity. It is because it becomes what produced | generated.

  Since niobium monoxide of the present invention is incorporated in a state where the rare earth metal is substituted at the position of the niobium atom, the peak indicated by niobium monoxide obtained by X-ray diffraction shifts to the high angle side. Specifically, as a normal peak of niobium monoxide (NbO) obtained by X-ray diffraction, according to JCPDS card (71-2146), the first peak is 2θ = 36.9517 °, and the second peak is Although it appears at a position of 2θ = 42.9296 °, in the niobium monoxide of the present invention, the positions of the first peak and the second peak are shifted to the high angle side. The reason for this is that when the rare earth metal is substituted at the position of the niobium atom, a defect occurs at the position of the niobium atom for charge compensation, the unit cell is distorted, and the lattice constant is reduced, so that the peak is increased. It is thought to shift to the angle side. From the viewpoint of obtaining niobium monoxide that is doped with a rare earth element at the niobium atom position and has a large specific surface area, which is an effect of the present invention, and is composed of a fine particle size, the peak shift to the high angle side is 0. The angle is preferably 01 ° or more, and the peak shift to the high angle side is preferably 0.05 ° or less from the viewpoint of maintaining a uniform crystal structure.

  According to the method for producing niobium monoxide according to the present invention, niobium monoxide having a large specific surface area and comprising fine particles can be easily produced. In addition, since niobium monoxide according to the present invention has a large pore volume and specific surface area, it is possible to increase the capacitance of the capacitor characteristics.

  Hereinafter, the best mode for carrying out the present invention will be described based on examples. In addition, this invention is not limited to the following Example.

  In Example 1, a case where La (lanthanum) is used as a rare earth element will be described as an example.

First, 44.3 mg of lanthanum nitrate hexahydrate and 1000 mL of pure water were prepared and mixed with 100 g of powdered niobium pentoxide (Nb ₂ O ₅ ) (this lanthanum nitrate hexahydrate). Is equivalent to 50 ppm in terms of lanthanum with respect to the finally obtained niobium monoxide powder). Mixing was performed by a ball mill, and 1 mmφ zirconia balls were used as mixing media, and the mixing time was 60 min. Then, this mixture was subjected to solid-liquid separation, and the resulting cake was dried at 120 ° C. for 6 hours, and further baked in an air atmosphere at 800 ° C. for 6 hours. Niobium pentoxide in which lanthanum was substituted at the niobium atom position. I got a powder.

  80 g of this lanthanum-containing niobium pentoxide, 9.5 g of niobium carbide (NbC), and 100 mL of pure water were wet mixed. Mixing was performed by a ball mill, and 1 mmφ zirconia balls were used as mixing media, and the mixing time was 60 min. This mixture was subjected to solid-liquid separation, and the resulting cake was dried at 120 ° C. for 6 hours, and further subjected to a baking treatment at 1350 ° C. for 6 hours in a hydrogen atmosphere to produce niobium monoxide. In Example 1, niobium monoxide having lanthanum amounts of 50 ppm, 100 ppm, 500 ppm, and 1000 ppm with respect to the finally obtained niobium monoxide was prepared and evaluated.

  For comparison, niobium monoxide containing no rare earth element was produced as follows. Niobium monoxide as a comparative example was wet mixed with 50 g of niobium pentoxide, 5.9 g of niobium carbide (NbC), and 100 mL of pure water. Mixing was performed by a ball mill, and 1 mmφ zirconia balls were used as mixing media, and the mixing time was 60 min. This mixture was subjected to solid-liquid separation, and the resulting cake was dried at 120 ° C. for 6 hours, and further subjected to a baking treatment at 1350 ° C. for 5 hours in a hydrogen atmosphere to produce niobium monoxide.

  About each niobium monoxide obtained as mentioned above, the pore volume and the specific surface area were measured as the physical properties. Further, capacitors were formed, and CV values, capacitance, withstand voltage, and dielectric loss (Tan δ), which are capacitor characteristics, were examined. Each measurement condition is shown below.

Pore volume: After forming niobium monoxide powder into pellets (φ5mm x 4.5mm), the pellets were used to measure pore distribution with a mercury intrusion porosimeter (Micromerix, Auto Pore IV). It was measured.

Specific surface area: BET specific surface area measuring apparatus (Co., Ltd.) using a nitrogen-helium mixed gas containing about 30% by volume of nitrogen as an adsorption gas and about 70% by volume of helium as a carrier gas. Performed according to (3.5) single point method of 6.2 flow method of JIS R 1626 "Method of measuring specific surface area by gas adsorption BET method of fine ceramic powder" by Shimadzu Corporation, Micromeritics Flow Soap II2300) It was.

Capacitor characteristics: Capacitor characteristics such as CV value, capacitance, withstand voltage, and electrical characteristics of Tan δ were obtained by using the obtained niobium monoxide to produce the following porous sintered body. First, 0.25 g of niobium monoxide powder was put into a press mold in which a tantalum (Ta) wire having a diameter of 0.3 mm was inserted and molded into a pellet. The molded pellet (φ5 mm × 4.5 mm) was fired at 1400 ° C. for 10 minutes. Then, the pellets were immersed in an 80 ° C., 0.1M-H ₃ PO ₄ bath, and held at a constant current density of 0.375 A / m ² and a formation voltage of 30 V for 60 minutes to perform anodization. The pellets subjected to such anodizing treatment were soaked again in 80 ° C. and 0.1M-H ₃ PO ₄ and held at a current density of 0.1 A / m ² for 5 minutes to measure the withstand voltage. The anodized pellets were immersed in a 150 g / L ammonium adipate solution, held at room temperature for 30 minutes, and then measured for CV value, capacitance, and dielectric loss (Tanδ) under the condition of 120 Hz.

  Tables 1 and 2 show the evaluation results of physical properties and capacitor characteristics obtained in Example 1. In addition, about the physical-property value of Table 1, the average measurement result of three samples is shown.

  From Table 1, it was found that the specific surface area of niobium monoxide containing lanthanum was clearly larger than that of lanthanum. Regarding the capacitor characteristics, it has been found that niobium monoxide of Example 1 can achieve a substantially target CV value with respect to the target CV value of 80000 μFV / g.

  In the second embodiment, the case where Ce (cerium) is used as the rare earth element will be described as an example.

First, 44.3 mg of cerium nitrate hexahydrate and 1000 mL of pure water were prepared and mixed with 100 g of powdered niobium pentoxide (Nb ₂ O ₅ ) (this cerium nitrate hexahydrate). Is equivalent to 50 ppm in terms of cerium with respect to the finally obtained niobium monoxide powder). Mixing was performed by a ball mill, and 1 mmφ zirconia balls were used as mixing media, and the mixing time was 60 min. Then, this mixture was subjected to solid-liquid separation, and the obtained cake was dried at 120 ° C. for 6 hours, and further baked in an air atmosphere at 800 ° C. for 6 hours. Niobium pentoxide in which cerium was substituted at the position of niobium atoms I got a powder.

  80 g of this cerium-containing niobium pentoxide, 9.5 g of niobium carbide (NbC), and 100 mL of pure water were wet mixed. Mixing was performed by a ball mill, and 1 mmφ zirconia balls were used as mixing media, and the mixing time was 60 min. This mixture was subjected to solid-liquid separation, and the resulting cake was dried at 120 ° C. for 6 hours, and further subjected to a baking treatment at 1350 ° C. for 6 hours in a hydrogen atmosphere to produce niobium monoxide. In Example 2, niobium monoxide having a cerium content of 100 ppm and 500 ppm with respect to the finally obtained niobium monoxide was produced and evaluated.

For comparison, niobium monoxide containing no rare earth element was niobium monoxide for comparison in Example 1 above.

  The cerium-containing niobium monoxide obtained in this way was measured for its pore volume and specific surface area as its physical properties. Further, capacitors were formed, and CV values, capacitance, withstand voltage, and dielectric loss (Tan δ), which are capacitor characteristics, were examined. Each measurement condition was the same as in Example 1 above. Tables 3 and 4 show the evaluation results of the physical properties and capacitor characteristics obtained in Example 2. In addition, about the physical-property value of Table 3, the average measurement result of three samples is shown.

  From Table 3, it was found that the specific surface area of niobium monoxide containing 500 ppm of cerium was clearly larger than that containing no rare earth element. Regarding the capacitor characteristics, it was found that niobium monoxide of Example 2 can achieve the target CV value with respect to the target CV value of 80000.

Finally, the results of niobium monoxide powder observation will be described. 1 and 2 show the results of analyzing the niobium monoxide obtained in Example 1 and Example 2 by X-ray diffraction. X-ray diffraction measurement uses an X-ray diffractometer (MXP18: manufactured by Mac Science Co., Ltd.), a copper (Cu) target, and a diffraction X-ray intensity by a Cu-Kα ₁ line (tube voltage 40 kV, tube Current 150 mA, measurement range 2θ = 10 ° to 90 °, sampling width 0.02 °, scanning speed 4.0 ° / min) were measured. As a result, FIG. 1 shows the measurement of niobium monoxide corresponding to lanthanum content of 50 ppm, 100 ppm, and 500 ppm in the case of Example 1, and the top expanded the peak around 2θ = 36.9 °. The bottom shows an enlarged peak near 2θ = 42.9 °. Moreover, it measured similarly about the niobium monoxide which does not contain a lanthanum (no addition 1, no addition 2). FIG. 2 shows the results of measuring niobium monoxide with a cerium content equivalent to 500 ppm. The data for additive-free 1 and additive-free 2 are the same as in FIG. According to the JCPDS card, the first peak appears at 2θ = 36.9517 °, and the second peak appears at 2θ = 42.9296 °.

  As shown in FIGS. 1 and 2, niobium monoxide in Examples 1 and 2 has a first peak (2θ = 36.9517 °) indicating NbO and a second peak (2θ = 42.9296 °). ) Both have been found to have shifted to higher angles.

  3 to 8 show SEM observation photographs of niobium monoxide. 3 and 4 are niobium monoxide corresponding to 500 ppm of lanthanum in Example 1, and FIGS. 5 and 6 are niobium monoxide corresponding to 500 ppm of cerium in Example 2. FIG. 8 is a niobium monoxide which does not contain a rare earth element. As shown in FIGS. 7 and 8, the niobium monoxide of Examples 1 and 2 shown in FIGS. 3 to 6 has finer primary particles than niobium monoxide containing no rare earth element. It has been found. It was also found that niobium monoxide in Example 1 and Example 2 was much finer in terms of pore formation.

X-ray diffraction measurement chart. X-ray diffraction measurement chart. The SEM observation photograph (1000 time) of niobium monoxide of Example 1. SEM observation photograph (5,000 times) of niobium monoxide in Example 1. The SEM observation photograph (1000 time) of niobium monoxide of Example 2. SEM observation photograph (5,000 times) of niobium monoxide in Example 2. SEM observation photograph (1000 times) of niobium monoxide containing no rare earth element. SEM observation photograph (5,000 times) of niobium monoxide containing no rare earth element.

Claims (6)

In a method for producing niobium monoxide by reducing niobium pentoxide or niobium dioxide to produce niobium monoxide,
Niobium pentoxide or niobium dioxide and a salt containing a rare earth element are mixed and fired,
A method for producing niobium monoxide, comprising performing a reduction firing treatment by mixing a niobium oxide doped with a rare earth element at a niobium atom position and a reducing agent after the firing treatment. The method for producing niobium monoxide according to claim 1, wherein the salt containing a rare earth element is at least one of carbonate, nitrate, and oxalate. The production of niobium monoxide according to claim 1 or 2, wherein the reducing agent is selected from the group consisting of alkali metals, alkaline earth metals, niobium carbides, niobium nitrides, niobium sulfides, niobium hydrides and niobium metals. Method. The rare earth element is selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Of manufacturing niobium monoxide. Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, containing a rare earth element selected from a group of 50 ppm to 1000 ppm niobium. 6. Niobium monoxide according to claim 5, wherein the peak of niobium monoxide obtained by X-ray diffraction is shifted to a higher angle side.