Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G33/00—Compounds of niobium

Definitions

• the present invention relates to a niobate dispersion aqueous solution and a method for producing the same.
• Patent Literatures 1 and 2 disclose alkali niobate-based piezoelectric ceramics manufactured by a liquid-phase manufacturing method as piezoelectric ceramics containing no lead-based material.
• Patent Document 3 discloses a flat plate-like crystal and an anisotropic powder produced from a crystal of niobium metal salt particles.
• Patent Document 4 discloses a KNN film-forming liquid composition capable of forming a dense film and a method of forming a KNN film using this liquid composition.
• the alkali metal niobate particles disclosed in Patent Documents 1 and 2 and the flat plate-like crystals and anisotropic powder disclosed in Patent Document 3 are manufactured at high temperature and high pressure. was required, and equipment such as an autoclave was required.
• the solvent of the KNN film forming liquid composition disclosed in Patent Document 4 contains 50% to 90% by mass of a specific carboxylic acid with respect to 100% by mass of the liquid composition, thereby reducing the environmental load. Therefore, a solution preparation using water as a solvent has been required.
• the present invention is to provide a niobate-dispersed aqueous solution with high dispersibility in water, good solubility in water, and high purity, and a method for producing the same.
• the niobate-dispersed aqueous solution of the present invention which has been made to solve the above problems, contains 0.1 to 40% by mass of niobium in terms of Nb 2 O 5 , contains sodium ions and/or potassium ions, and has dynamic light scattering properties. It is characterized by having a particle size (D50) of 3,000 nm or less as determined by particle size distribution measurement using a method.
• the niobate-dispersed aqueous solution of the present invention preferably contains 0.1 to 40% by mass of niobium in terms of Nb 2 O 5 from the viewpoint of improving dispersibility and solubility in water. Further, the content of the niobate-dispersed aqueous solution of the present invention is more preferably 1 to 20% by mass, and even more preferably 5 to 10% by mass.
• the niobium concentration in the niobate dispersed aqueous solution is determined by diluting the aqueous solution appropriately with dilute hydrochloric acid as necessary and measuring niobium oxide (Nb 2 O 5 ) Calculate by measuring the converted Nb weight fraction.
• the niobic acid in the niobate-dispersed aqueous solution of the present invention does not necessarily exist in the form of Nb 2 O 5 .
• the reason why the content of niobic acid is shown in terms of Nb 2 O 5 is based on the convention when showing the niobium concentration.
• the niobic acid in the niobate-dispersed aqueous solution of the present invention is presumed to be present in the aqueous solution as ions in an ionic bond with sodium ions or potassium ions.
• hydroxide ions are present as anions
• halide ions such as fluoride ions and chloride ions are scarcely present
• sodium ions and potassium ions are cations.
• niobic acid is considered to exist as an anion such as NbO 3 — or as a polyoxometalate (polyacid) ion in which a plurality of niobium atoms and oxygen atoms are bonded.
• the niobate-dispersed aqueous solution of the present invention may further contain lithium ions.
• the niobate-dispersed aqueous solution of the present invention may contain lithium ions instead of sodium ions or potassium ions, or contain lithium ions in addition to sodium ions and potassium ions. may It is presumed that the niobic acid in the niobate-dispersed aqueous solution of the present invention is present in the aqueous solution as ions in an ionic bond with lithium ions.
• the particle size (D50) is 3,000 nm or less as determined by particle size distribution measurement using a dynamic light scattering method, it is preferable in terms of improving the dispersibility and solubility in water.
• the particle diameter (D50) is more preferably 30 nm or less, and even more preferably 20 nm or less.
• the particle diameter (D50) may be 10 nm or less, 1 nm or less, or a detection limit of less than 1 nm.
• the particle diameter (D50) is preferably greater than 0 nm, more preferably 1 nm or more.
• the solution having a particle size (D50) of 3,000 nm or less as determined by the particle size distribution measurement using the dynamic light scattering method is defined as the "niobate dispersed aqueous solution" of the present invention.
• the particle size (D50) of the niobate particles in the niobate-dispersed aqueous solution of the present invention determined by particle size distribution measurement using a dynamic light scattering method is 3,000 nm or less.
• the thickness is preferably 30 nm or less, and even more preferably 20 nm or less, from the viewpoint of improving the properties and solubility.
• the particle diameter (D50) may be 10 nm or less, 1 nm or less, or a detection limit of less than 1 nm.
• the particle size (D50) of the niobate particles or the like measured by particle size distribution measurement using a dynamic light scattering method is preferably greater than 0 nm, more preferably 1 nm or more.
• the dynamic light scattering method measures the light scattering intensity from a group of particles moving in Brownian motion by irradiating a solution such as a suspension solution with light such as a laser beam.
• This is a method for determining the particle size and distribution.
• the particle size distribution evaluation method uses a zeta potential/particle size/molecular weight measurement system (manufactured by Otsuka Electronics Co., Ltd.: ELSZ-2000ZS), JIS Z 8828: 2019 "Particle size analysis-dynamic light scattering to comply with the law.
• the solution is filtered with a filter with a pore size of 10 ⁇ m, and ultrasonicated for 3 minutes with an ultrasonic cleaner (manufactured by AS ONE: VS-100III). Take action. Furthermore, the liquid temperature of the solution, which is the mode of measurement, was adjusted to 25°C.
• the particle diameter (D50) refers to the median diameter (D50), which is the particle diameter indicating the 50% integrated value of the integrated distribution curve.
• aqueous solution in the present invention is not limited to those in which the solute is dispersed or mixed in the state of a single molecule in pure water, which is a solvent, but an assembly in which a plurality of molecules are attracted by intermolecular interactions. , for example, (1) multimeric molecules, (2) solvate molecules, (3) molecular clusters, (4) colloidal particles, etc., dispersed in a solvent.
• the niobate-dispersed aqueous solution of the present invention contains 0.1 to 40% by mass of niobium in terms of Nb 2 O 5 , contains sodium ions and/or potassium ions, and was measured using a dry powder laser diffraction/scattering method. It is characterized by having a dry powder particle size (D10) of 1 ⁇ m or more as determined by particle size distribution measurement.
• the niobate-dispersed aqueous solution of the present invention preferably contains 0.1 to 40% by mass of niobium in terms of Nb 2 O 5 in terms of improved dispersibility and solubility in water.
• the content of the niobate-dispersed aqueous solution of the present invention is more preferably 1 to 20% by mass, and even more preferably 5 to 10% by mass.
• the niobic acid in the niobate-dispersed aqueous solution of the present invention is presumed to exist in the aqueous solution as ions in an ionic bond state with sodium ions or potassium ions.
• the niobate-dispersed aqueous solution of the present invention may further contain lithium ions.
• the niobate-dispersed aqueous solution of the present invention may contain lithium ions instead of sodium ions or potassium ions, or contain lithium ions in addition to sodium ions and potassium ions.
• the niobic acid in the niobate-dispersed aqueous solution of the present invention is present in the aqueous solution as ions in an ionic bond with lithium ions.
• the particle size of the dry powder is referred to as the dry powder particle size in order to distinguish it from the particle size obtained by measuring the particle size distribution using the dynamic light scattering method described above.
• the method for evaluating the particle size distribution of the dry powder obtained by drying the niobate-dispersed aqueous solution of the present invention is as follows. It is performed by the dynamic light scattering method according to JIS Z 8828:2019. Moreover, filtering is not performed, and the following dispersion processing using ultrasonic waves is performed.
• the dry powder particle size was measured by subjecting the dry powder obtained by vacuum-drying the niobate-dispersed aqueous solution of the present invention (drying conditions: heating temperature 80° C., heating time 7 hours) to It is the particle diameter after dispersion treatment by.
• the procedure of ultrasonic dispersion treatment performed on the obtained dry powder is as follows. First, as a pretreatment for dispersion treatment by ultrasonic waves, 1 mg of sample powder and 20 mL of pure powder are put into a PP wide-mouthed bottle with a capacity of 50 mL, and the PP wide-mouthed bottle is ultrasonically cleaned (manufactured by AS ONE: VS-100III). set. Next, in a state in which the inside of the washing machine is filled with pure water up to 5 cm above the floor surface of the tank, ultrasonic dispersion treatment is performed at a frequency of 28 kHz for 60 minutes.
• the dry powder particle size (D10) obtained by measuring the particle size distribution of the dry powder using the laser diffraction/scattering method described above is 1 ⁇ m or more because the dispersibility and solubility in water are improved.
• the dry powder particle size (D10) is more preferably 10 ⁇ m or more.
• the dry powder particle size (D10) exceeds 150 ⁇ m, the aggregation becomes excessively large, and the film-forming properties, film uniformity, and flatness during the formation of a compact such as a film are impaired.
• the dry powder particle size (D10) is preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less, and even more preferably 20 ⁇ m or less.
• the dry powder particle size (D50) is preferably 20 ⁇ m or more for the same reason as the dry powder particle size (D10).
• the dry powder particle size (D50) exceeds 200 ⁇ m, the aggregation becomes excessively large, and the film-forming property, film uniformity, and flatness during the formation of a molded body such as a film are impaired. 100 ⁇ m or less is preferable, and 50 ⁇ m or less is more preferable.
• the dry powder particle size (D90) is preferably 30 ⁇ m or more, more preferably 60 ⁇ m or more.
• the dry powder particle size (D90) exceeds 2,000 ⁇ m, the aggregation becomes excessively large, and the film-forming property, film uniformity, and flatness during the formation of a molded body such as a film are impaired. Therefore, it is preferably 1,000 ⁇ m or less, more preferably 500 ⁇ m or less, and even more preferably 200 ⁇ m or less.
• the dry powder particle size (D10) indicates the particle size of the dry powder up to 10% in terms of volume fraction.
• the dry powder particle size (D50) indicates the particle size of the dry powder up to 50% by volume fraction, and is referred to as the median size.
• the dry powder particle size (D90) indicates the particle size of the dry powder up to 90% by volume fraction.
• the aqueous niobate dispersion solution of the present invention contains 0.1 to 40% by mass of niobium in terms of Nb 2 O 5 , contains sodium ions and/or potassium ions, and is dried powder obtained by vacuum drying.
• the dry powder particle size ratio (D90-D10)/D50 is 0 or more and 6 or less, as determined by particle size distribution measurement using a laser diffraction/scattering method.
• the dry powder particle size ratio (D90-D10)/D50 is 0 or more and 6 or less, the smaller the dry powder particle size ratio (D90-D10)/D50, the narrower the dry powder particle size distribution. , from the viewpoint of improving dispersibility and solubility in water.
• the dry powder particle size ratio (D90-D10)/D50 is 1 or more and 3 or less.
• the niobic acid in the niobate-dispersed aqueous solution of the present invention is presumed to exist in the aqueous solution as ions in an ionic bond with sodium ions or potassium ions.
• the niobate-dispersed aqueous solution of the present invention may further contain lithium ions.
• the niobate-dispersed aqueous solution of the present invention may contain lithium ions instead of sodium ions or potassium ions, or contain lithium ions in addition to sodium ions and potassium ions. may It is presumed that the niobic acid in the niobate-dispersed aqueous solution of the present invention is present in the aqueous solution as ions in an ionic bond with lithium ions.
• Nb/K/Na 1/0.5/0.5, preferable.
• the niobate-dispersed aqueous solution of the present invention contains at least one selected from ammonia and/or organic nitrogen compounds.
• the niobate-dispersed aqueous solution of the present invention contains niobic acid, sodium ions, potassium ions, and lithium ions, as well as ammonia and an organic nitrogen compound.
• the "ammonia” and the "organic nitrogen compound” according to the present invention include those ionized in the niobate-dispersed aqueous solution of the present invention.
• a hydrous ammonium niobate which is a niobium-containing precipitation slurry
• a reverse neutralization method in which an acidic niobium solution is added to aqueous ammonia.
• the organic nitrogen compound is added and mixed to form the niobate dispersed aqueous solution of the present invention, thus replacing the alkali metal ions such as sodium ions, potassium ions, and lithium ions.
• Ammonia and organic nitrogen compounds are believed to be present in the solution as cations.
• the method of measuring the concentration of ammonium ions present in the solution includes adding sodium hydroxide to the solution, separating the ammonia by distillation , and quantifying the concentration of ammonium ions using an ion meter.
• a method of quantifying with a thermal conductivity meter, the Kjeldahl method, gas chromatography (GC), ion chromatography, GC-MS (mass spectrometry) and the like can be mentioned.
• organic nitrogen compounds include aliphatic amines, aromatic amines, amino alcohols, amino acids, polyamines, quaternary ammonium, guanidine compounds, and azole compounds.
• aliphatic amines include methylamine, dimethylamine, trimethylamine, ethylamine, methylethylamine, diethylamine, triethylamine, methyldiethylamine, dimethylethylamine, n-propylamine, di-n-propylamine, tri-n-propylamine, iso- Propylamine, diiso-propylamine, triiso-propylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, iso-butylamine, diiso-butylamine, triiso-butylamine and tert-butylamine, n-pentamine , n-hexylamine, cyclohexylamine, piperidine and the like.
• aromatic amines examples include aniline, phenylenediamine, and diaminotoluene.
• amino alcohols include, for example, methanolamine, ethanolamine, propanolamine, butanolamine, pentanolamine, dimethanolamine, diethanolamine, trimethanolamine, methylmethanolamine, methylethanolamine, methylpropanolamine, and methylbutanolamine.
• amino acids include, for example, alanine, arginine, aspartic acid, EDTA, and the like.
• polyamines include polyamines and polyetheramines.
• Examples of quaternary ammonium include alkylimidazolium, pyridinium, pyrrolidium, tetraalkylammonium and the like.
• alkylimidazolium include 1-methyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-propyl-3-methylimidazolium, 1-butyl-3-methylimidazolium.
• pyridinium and pyrrolidium include N-butyl-pyridinium, N-ethyl-3-methyl-pyridinium, N-butyl-3-methyl-pyridinium, N-hexyl-4-(dimethylamino)-pyridinium, Examples include N-methyl-1-methylpyrrolidinium and N-butyl-1-methylpyrrolidinium.
• tetraalkylammonium include tetramethylammonium, tetraethylammonium, tetrabutylammonium, and ethyl-dimethyl-propylammonium.
• anions that form salts with the above cations include OH ⁇ , Cl ⁇ , Br ⁇ , I ⁇ , BF 4 ⁇ , HSO 4 ⁇ and the like.
• Guanidine compounds include guanidine, diphenylguanidine, and ditolylguanidine.
• azole compounds include imidazole compounds and triazole compounds.
• specific examples of imidazole compounds include imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole and the like.
• Specific examples of triazole compounds include 1,2,4-triazole, methyl 1,2,4-triazole-3-carboxylate, and 1,2,3-benzotriazole.
• Methods for measuring the concentration of organic nitrogen compounds present in the solution include gas chromatography (GC), liquid chromatography (LC), mass spectrometry (MS), gas chromatography/mass spectrometry (GC-MS), and liquid chromatography. • Mass spectrometry (LC-MS) and the like may be mentioned, and a method of quantifying N 2 minutes in a gasified sample with a thermal conductivity meter may be used in combination.
• the niobate-dispersed aqueous solution of the present invention may contain oxide powders such as Li, Mg, Ca, Ti, Mn, Ni, Cu, Sr, Ba, Ta, W, and Bi as additives. This is because the niobate-dispersed aqueous solution of the present invention is a homogeneous solution, and therefore, even when these oxide powders are in a suspended state, improvement in uniformity and improvement in reactivity (reaction rate) can be expected. be. Moreover, if these oxide powders are dissolved in the niobate-dispersed aqueous solution of the present invention to form a uniform solution, the composite element can be brought into a state of the highest reactivity.
• oxide powders such as Li, Mg, Ca, Ti, Mn, Ni, Cu, Sr, Ba, Ta, W, and Bi as additives.
• the niobate-dispersed aqueous solution of the present invention contains components other than components derived from niobium or niobic acid, and components derived from ammonia and organic nitrogen compounds (referred to as "other components"), to the extent that the action and effect thereof are not impaired. .) may be contained.
• other components include Li, Mg, Si, Ca, Ti, Mn, Ni, Cu, Zn, Sr, Zr, Mo, Ba, Ta, W, and Bi. However, it is not limited to these.
• the content of other components in the niobate-dispersed aqueous solution of the present invention is preferably less than 5% by mass, more preferably less than 4% by mass, and even more preferably less than 3% by mass. It should be noted that the niobate-dispersed aqueous solution of the present invention is not intended, but is assumed to contain unavoidable impurities. The content of unavoidable impurities is preferably less than 0.01% by mass.
• the niobate film of the present invention is characterized by containing the niobate in the niobate-dispersed aqueous solution.
• the niobate film of the present invention that is, the niobate molded film contains the niobate contained in the niobate-dispersed aqueous solution described above.
• the niobate film of the present invention can be used as a piezoelectric film. A method for manufacturing the niobate film of the present invention will be described later.
• the niobate powder of the present invention is characterized by containing the niobate in the niobate-dispersed aqueous solution.
• the niobate powder of the present invention contains the niobate contained in the niobate-dispersed aqueous solution described above. The method for producing the niobate powder of the present invention will be described later.
• the niobate molded article of the present invention is characterized by containing the niobate in the niobate-dispersed aqueous solution.
• the niobate molded article of the present invention contains the niobate contained in the niobate-dispersed aqueous solution described above.
• the niobate compact of the present invention can be used as a piezoelectric material. The method for producing the niobate molded article of the present invention will be described later.
• the method for producing a niobate dispersed aqueous solution of the present invention contains 0.1 to 40% by mass of niobium in terms of Nb 2 O 5 and has a particle size (D50) determined by particle size distribution measurement using a dynamic light scattering method. It is characterized by mixing a niobic acid solution with a particle diameter of 3,000 nm or less and sodium and/or potassium hydroxide.
• niobic acid solution containing 0.1 to 40% by mass of niobium in terms of Nb 2 O 5 and having a particle size (D50) of 3,000 nm or less as determined by particle size distribution measurement using a dynamic light scattering method is produced.
• the steps to do are as follows.
• the niobium referred to in this specification includes niobate compounds unless otherwise specified.
• An acidic niobium solution containing fluoride ions is obtained by dissolving niobium in an acidic solution containing hydrofluoric acid and subjecting the resulting solution to solvent extraction.
• the acidic niobium solution containing fluoride ions eg, an aqueous niobium fluoride solution
• water eg, pure water
• the niobium concentration is 1 g/L or more in terms of Nb 2 O 5
• the niobate compound hydrate is easily soluble in water
• productivity is considered, 10 g/L or more is more preferable.
• the niobium concentration is 100 g/L or less in terms of Nb 2 O 5
• the pH of the niobium fluoride aqueous solution is preferably 2 or less, more preferably 1 or less, from the viewpoint of completely dissolving niobium or niobium oxide.
• a precipitation slurry containing niobium is obtained by adding the obtained acidic niobium solution containing fluoride ions to aqueous ammonia of a predetermined concentration, that is, by a reverse neutralization method (hereinafter referred to as a reverse neutralization step).
• the ammonia concentration of the ammonia water used for reverse neutralization is preferably 10% by mass to 30% by mass.
• the ammonia concentration is 10% by mass, niobium is less likely to remain undissolved, and niobium or niobium acid can be completely dissolved in water.
• the ammonia concentration is 30% by mass or less, it is close to a saturated aqueous solution of ammonia, which is preferable.
• the ammonia concentration of the ammonia water is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass.
• the ammonia concentration is preferably 30% by mass or less, more preferably 29% by mass or less, and even more preferably 28% by mass or less.
• the amount of the niobium fluoride aqueous solution added to the aqueous ammonia is preferably such that the molar ratio of NH 3 /Nb 2 O 5 is 95 or more and 500 or less, more preferably 100 or more and 450 or less. More preferably, it is 110 or more and 400 or less.
• the amount of the niobium fluoride aqueous solution added to the ammonia water is preferably such that the NH 3 /HF molar ratio is 3.0 or more from the viewpoint of generating amines and niobic acid compounds that dissolve in dilute ammonia water. It is more preferably 4.0 or more, and even more preferably 5.0 or more.
• the NH 3 /HF molar ratio is preferably 100 or less, more preferably 50 or more, and even more preferably 40 or more.
• the time required for adding the aqueous niobium fluoride solution to the aqueous ammonia is preferably within 1 minute, more preferably within 30 seconds, and even more preferably within 10 seconds. That is, instead of gradually adding the niobium fluoride aqueous solution over time, it is preferable to add the aqueous solution of niobium fluoride at once, for example, to the ammonia water in the shortest possible time for neutralization reaction.
• the neutralization reaction can be carried out while maintaining a high pH.
• the niobium fluoride aqueous solution and ammonia water can be used at room temperature.
• the method for removing the fluorine compound is arbitrary, but for example, a method by filtration using a membrane such as reverse osmosis filtration using ammonia water or pure water, ultrafiltration, or microfiltration, centrifugation, or other known methods. can be adopted.
• a membrane such as reverse osmosis filtration using ammonia water or pure water, ultrafiltration, or microfiltration, centrifugation, or other known methods.
• temperature control is not particularly required, and the removal may be performed at room temperature.
• the precipitation slurry containing niobium obtained by the reverse neutralization method is decanted using a centrifuge, and washing is repeated until the amount of free fluoride ions is 100 mg / L or less. , a niobium-containing precipitate from which fluoride ions are removed is obtained.
• the cleaning liquid used for removing fluoride ions is aqueous ammonia.
• ammonia water of 5.0 mass% or less is preferable, ammonia water of 4.0 mass% or less is more preferable, ammonia water of 3.0 mass% or less is further preferable, and ammonia of 2.5 mass% Water is particularly preferred. If the ammonia water content is 5.0% by mass or less, ammonia and ammonium ions are suitable for fluorine, and an unnecessary increase in cost can be avoided.
• niobium-containing precipitate from which fluoride ions have been removed is obtained.
• the niobium concentration of the niobium-containing precipitation slurry was determined by taking part of the slurry, drying it at 110°C for 24 hours, and then calcining it at 1,000°C for 4 hours to generate Nb 2 O 5 . .
• the weight of Nb 2 O 5 thus produced can be measured and the niobium concentration of the slurry can be calculated from the weight.
• niobium-containing precipitation slurry that is, containing 0.1 to 40% by mass of niobium in terms of Nb 2 O 5 , and the particle diameter
• the niobate-dispersed aqueous solution of the present invention can be obtained by mixing a niobic acid solution having a D50) of 3,000 nm or less with sodium and/or potassium hydroxide. Ammonia or an organic nitrogen compound may be added at the same timing as the niobic acid solution and the hydroxide of sodium and/or potassium are mixed, or at a timing before or after that.
• ammonia or an organic nitrogen compound is highly volatile and easy to remove, it does not interfere with the formation of a compound with elemental sodium or potassium, which is related to hydroxides of sodium and/or potassium.
• the niobic acid solution and lithium hydroxide may be mixed, and the sodium to be mixed with the niobic acid solution, and potassium hydroxide, the niobic acid solution may be mixed with lithium hydroxide.
• the final mixture contains 0.1 to 40% by mass of niobium in terms of Nb 2 O 5 , and the particle size (D50) measured by the particle size distribution measurement using the dynamic light scattering method is 3,000 nm.
• a translucent white slurry is obtained by mixing the resulting niobic acid solution with sodium and/or potassium hydroxide and pure water as follows. The liquid temperature is brought to room temperature while the translucent white slurry is stirred, and the liquid temperature is kept at room temperature for 1 hour to obtain the colorless, transparent, or white suspension, niobate-dispersed aqueous solution of the present invention.
• the method for producing the niobate film of the present invention that is, the niobate film-formed body, will be described below.
• the method for producing a niobate film of the present invention comprises the steps of applying the niobate-dispersed aqueous solution obtained by the above-described method for producing a niobate-dispersed aqueous solution of the present invention, and baking it to form a niobate film. It is characterized by
• the niobate-dispersed aqueous solution obtained by the above-described method for producing a niobate-dispersed aqueous solution of the present invention is, if necessary, filtered through a filter having a pore size of 10 ⁇ m, for example, and is applied onto a substrate using a syringe. It was dropped and applied by spin coating (1,500 rpm, 30 seconds). Then, the substrate coated with the niobate-dispersed aqueous solution of the present invention is placed in a stationary furnace, heated to 700° C. or higher, and baked for 1 hour to form the niobate film of the present invention. can get.
• the method for producing a niobate powder of the present invention comprises the steps of drying and firing the niobate-dispersed aqueous solution obtained by the above-described method for producing a niobate-dispersed aqueous solution of the present invention to produce a niobate powder. It is characterized by
• the niobate-dispersed aqueous solution obtained by the above-described method for producing a niobate-dispersed aqueous solution of the present invention is placed in a stationary furnace, and air-dried at a heating temperature of about 110° C. for 7 hours.
• a heating temperature of about 110° C. for 7 hours By removing the water in the niobate-dispersed aqueous solution of the present invention, an intermediate product of niobate powder containing the niobate particles contained in the niobate-dispersed aqueous solution of the present invention is obtained.
• the intermediate product of the niobate powder containing the obtained niobate particles is placed in a stationary furnace, heated to 650° C. or higher, and fired for 1 to 3 hours to obtain the present invention. of niobate powder is obtained.
• the heating temperature is preferably 500° C. or higher and 2,000° C. or lower. When the heating temperature is 500° C. or higher and 2,000° C. or lower, the temperature is sufficient for the growth of niobate particles, the firing cost can be suppressed, and the fired product obtained by firing becomes a hard lump. This is because the increase in the labor and cost of pulverization can be avoided. Furthermore, the heating temperature is more preferably 700° C. or higher and 1,500° C.
• the firing time is preferably 0.5 to 72 hours. This is because if the firing time is 0.5 to 72 hours, the time is sufficient for the niobate particles to grow, and unnecessary costs can be suppressed. Furthermore, the firing time is more preferably 0.5 hours to 50 hours, more preferably 0.5 hours to 30 hours.
• a pulverized baked product may be used as the niobate powder of the present invention.
• the sieved product fine particle side obtained by classifying the fired product with a sieve or the like may be used as the niobate powder.
• the sieve top coarse particle side
• a sieve when classifying using a sieve, it is preferable to use a sieve with an opening of 150 ⁇ m to 1,000 ⁇ m. If it is 150 ⁇ m to 1,000 ⁇ m, the proportion on the sieve does not become too large, the re-grinding is not repeated, and the niobate powder requiring re-grinding is not classified under the sieve.
• the method for producing a niobate compact according to the present invention is characterized by comprising the steps of drying a niobate-dispersed aqueous solution, filling the resulting dry powder into a mold, molding under pressure, and firing.
• the niobate-dispersed aqueous solution obtained by the above-described method for producing a niobate-dispersed aqueous solution of the present invention is dried at 60° C. for 7 hours under a reduced pressure of 0.1 atm, for example, to obtain a vacuum-dried powder. obtain. After that, the resulting vacuum-dried powder is filled into a mold. Then, the mold filled with the vacuum-dried niobate powder of the present invention is placed in a static furnace and heated to 500° C. to 1,500° C., for example, 700° C. or higher for 1 hour to 100 hours. For example, the niobate molded article of the present invention is obtained by pressure molding for 6 hours.
• the niobate-dispersed aqueous solution of the present invention may contain a dispersant, a pH adjuster, a colorant, a thickener, a wetting agent, a binder resin, etc., depending on the application.
• the niobate-dispersed aqueous solution of the present invention has high dispersibility in water, good solubility in water, and high purity.
• niobate-dispersed aqueous solution of the embodiment according to the present invention will be further described below with reference to the following examples. However, the following examples do not limit the present invention.
• reaction liquid was a slurry of niobate compound hydrate, in other words, a slurry of niobium-containing precipitates.
• this reaction liquid was decanted using a centrifuge and washed until the amount of liberated fluoride ions became 100 mg/L or less to obtain a niobium-containing precipitate from which the fluoride ions were removed. At this time, ammonia water was used as a cleaning liquid.
• the niobium-containing precipitate from which the fluoride ions were removed was diluted with pure water to obtain a slurry. A portion of this slurry was dried at 110° C. for 24 hours and then calcined at 1,000° C. for 4 hours to produce Nb 2 O 5 , and the concentration of Nb 2 O 5 contained in the slurry was calculated from its weight.
• the particle size (D50) of the resulting niobium-containing precipitate slurry was less than 1 nm as determined by particle size distribution measurement using a dynamic light scattering method.
• the slurry of the niobium-containing precipitate diluted with pure water was prepared so that the final mixture had a niobium concentration of 5% by mass in terms of Nb 2 O 5 and a molar ratio of Nb/K/Na of 1:0.5:0.
• a translucent slurry mixture was obtained by mixing potassium hydroxide monohydrate and sodium hydroxide monohydrate with pure water so as to obtain 5. While stirring this mixture, the liquid temperature was brought to room temperature, and after holding for 1 hour, a colorless and transparent niobate-dispersed aqueous solution according to Example 1 was obtained.
• the particle size (D50) of the obtained colorless and transparent niobate-dispersed aqueous solution according to Example 1 was 13.2 nm as measured by particle size distribution measurement using a dynamic light scattering method.
• the dry powder particle diameter (D10) of the dry powder obtained by vacuum-drying the niobate dispersed aqueous solution according to Example 1 was 11.97 ⁇ m.
• the powder particle size (D50) was 30.52 ⁇ m, and the dry powder particle size (D90) was 94.44 ⁇ m.
• the dry powder particle size (D10), the dry powder particle size (D50), and the dry powder particle size ratio (D90-D10)/D50 calculated from the dry powder particle size (D90) according to Example 1 is 2. .7.
• Example 2 In Example 2, a slurry of the niobium-containing precipitate diluted with pure water was mixed with potassium hydroxide monohydrate and sodium hydroxide so that the concentration of niobium in the final mixture was 1% by weight, calculated as Nb2O5 .
• a colorless and transparent niobate-dispersed aqueous solution according to Example 2 was obtained by carrying out the same manufacturing method as in Example 1, except that the monohydrate and pure water were mixed.
• the particle size (D50) of the obtained colorless and transparent niobate-dispersed aqueous solution according to Example 2 was 14.5 nm as measured by particle size distribution measurement using a dynamic light scattering method.
• the dry powder particle diameter (D10) of the dry powder obtained by vacuum-drying the niobate dispersed aqueous solution according to Example 2 was 16.39 ⁇ m.
• the powder particle size (D50) was 31.49 ⁇ m, and the dry powder particle size (D90) was 94.44 ⁇ m.
• the dry powder particle size (D10), the dry powder particle size (D50), and the dry powder particle size ratio (D90-D10)/D50 calculated from the dry powder particle size (D90) according to Example 2 is 1. .7.
• Example 3 In Example 3, a slurry of the niobium-containing precipitate diluted with pure water was mixed with potassium hydroxide monohydrate and sodium hydroxide so that the concentration of niobium in the final mixture was 3% by weight, calculated as Nb2O5 .
• a colorless and transparent niobate-dispersed aqueous solution according to Example 3 was obtained by carrying out the same manufacturing method as in Example 1 except that the monohydrate and pure water were mixed.
• the particle size (D50) of the obtained colorless and transparent niobate-dispersed aqueous solution according to Example 3 was 16.5 nm as measured by particle size distribution measurement using a dynamic light scattering method.
• the dry powder particle diameter (D10) of the dry powder obtained by vacuum-drying the niobate dispersed aqueous solution according to Example 3 was 14.89 ⁇ m.
• the powder particle size (D50) was 20.49 ⁇ m, and the dry powder particle size (D90) was 67.10 ⁇ m.
• the dry powder particle size (D10), the dry powder particle size (D50), and the dry powder particle size ratio (D90-D10)/D50 calculated from the dry powder particle size (D90) according to Example 3 is 2. .5.
• Example 4 In Example 4, a slurry of the niobium-containing precipitate diluted with pure water was mixed with potassium hydroxide monohydrate and sodium hydroxide so that the concentration of niobium in the final mixture was 10% by weight, calculated as Nb2O5 . A manufacturing method similar to that of Example 1 was carried out, except that the monohydrate and pure water were mixed, to obtain a niobate-dispersed aqueous solution of white suspension according to Example 4.
• the particle size (D50) of the white niobate-dispersed aqueous solution obtained in Example 4 was 2631.5 nm as determined by particle size distribution measurement using a dynamic light scattering method. Further, the dry powder particle diameter (D10) of the dry powder obtained by vacuum-drying the niobate dispersed aqueous solution according to Example 4 (drying conditions: heating temperature 80° C., heating time 7 hours) was 1.57 ⁇ m. The powder particle size (D50) was 20.85 ⁇ m, and the dry powder particle size (D90) was 111.41 ⁇ m. Furthermore, the dry powder particle size (D10), the dry powder particle size (D50), and the dry powder particle size ratio (D90-D10)/D50 calculated from the dry powder particle size (D90) according to Example 4 is 5 .3.
• Example 5 In Example 5, a slurry of the niobium-containing precipitate diluted with pure water was mixed with potassium hydroxide monohydrate and sodium hydroxide so that the concentration of niobium in the final mixture was 30% by weight calculated as Nb2O5 . A manufacturing method similar to that of Example 1 was carried out, except that the monohydrate and pure water were mixed, to obtain a niobate-dispersed aqueous solution of white suspension according to Example 5.
• the particle size (D50) of the resulting white suspension of the niobate-dispersed aqueous solution according to Example 5 was 2434.2 nm as determined by particle size distribution measurement using a dynamic light scattering method.
• the dry powder particle diameter (D10) of the dry powder obtained by vacuum-drying the niobate-dispersed aqueous solution according to Example 5 was 1.50 ⁇ m.
• the powder particle size (D50) was 22.49 ⁇ m, and the dry powder particle size (D90) was 94.68 ⁇ m.
• the dry powder particle size (D10), the dry powder particle size (D50), and the dry powder particle size ratio (D90-D10)/D50 calculated from the dry powder particle size (D90) according to Example 5 is 4. .1.
• Example 6 a slurry of the niobium-containing precipitate diluted with pure water was diluted with potassium hydroxide monohydrate so that the molar ratio of Nb/K/Na in the final mixture was 1:0.6:0.4. The same production method as in Example 1 was carried out, except that the sodium hydroxide and sodium hydroxide monohydrate were mixed with pure water, to obtain a white suspension niobate dispersion aqueous solution according to Example 6. .
• the particle size (D50) of the resulting white suspension of the niobate-dispersed aqueous solution according to Example 6 was 2463.2 nm as determined by particle size distribution measurement using a dynamic light scattering method.
• the dry powder particle diameter (D10) of the dry powder obtained by vacuum-drying the niobate dispersed aqueous solution according to Example 6 was 1.35 ⁇ m.
• the powder particle size (D50) was 43.74 ⁇ m, and the dry powder particle size (D90) was 143.22 ⁇ m.
• the dry powder particle size (D10), the dry powder particle size (D50), and the dry powder particle size ratio (D90-D10)/D50 calculated from the dry powder particle size (D90) according to Example 6 is 3. .0.
• Example 7 a slurry of the niobium-containing precipitate diluted with pure water was mixed with potassium hydroxide monohydrate and pure A manufacturing method similar to that of Example 1 was carried out, except that water was mixed, to obtain a white suspension niobate-dispersed aqueous solution according to Example 7.
• the particle size (D50) of the obtained white suspension of the niobate-dispersed aqueous solution according to Example 7 was 2557.3 nm as measured by the particle size distribution measurement using the dynamic light scattering method.
• the dry powder particle diameter (D10) of the dry powder obtained by vacuum-drying the niobate dispersed aqueous solution according to Example 7 was 5.50 ⁇ m.
• the powder particle size (D50) was 37.91 ⁇ m, and the dry powder particle size (D90) was 112.23 ⁇ m.
• the dry powder particle size (D10), the dry powder particle size (D50), and the dry powder particle size ratio (D90-D10)/D50 calculated from the dry powder particle size (D90) according to Example 7 is 2. .8.
• Example 8 combines a slurry of the niobium-containing precipitate diluted with pure water with sodium hydroxide monohydrate and pure A manufacturing method similar to that of Example 1 was carried out, except that water was mixed, to obtain a white niobate-dispersed aqueous solution according to Example 8.
• the particle size (D50) of the resulting white suspension of the niobate-dispersed aqueous solution according to Example 8 was 2469.4 nm as determined by particle size distribution measurement using a dynamic light scattering method.
• the dry powder particle diameter (D10) of the dry powder obtained by vacuum-drying the niobate dispersed aqueous solution according to Example 8 was 6.50 ⁇ m.
• the powder particle size (D50) was 39.44 ⁇ m, and the dry powder particle size (D90) was 100.48 ⁇ m.
• the dry powder particle size (D10), the dry powder particle size (D50), and the dry powder particle size ratio (D90-D10)/D50 calculated from the dry powder particle size (D90) according to Example 8 is 2. .4.
• Example 9 prepared a slurry of the niobium-containing precipitate diluted with pure water in potassium hydroxide monohydrate, such that the final mixture had a Nb/K/Na molar ratio of 1:0.5:0.14. The same production method as in Example 1 was carried out, except that the sodium hydroxide and sodium hydroxide monohydrate were mixed with pure water, to obtain a white suspension niobate dispersion aqueous solution according to Example 9. .
• the particle size (D50) of the resulting white suspension of the niobate-dispersed aqueous solution according to Example 9 was 2884.3 nm as determined by particle size distribution measurement using a dynamic light scattering method. Further, the dry powder particle diameter (D10) of the dry powder obtained by vacuum-drying the niobate dispersed aqueous solution according to Example 9 (drying conditions: heating temperature 80° C., heating time 7 hours) was 1.25 ⁇ m. The powder particle size (D50) was 34.56 ⁇ m, and the dry powder particle size (D90) was 116.41 ⁇ m. Furthermore, the dry powder particle size (D10), the dry powder particle size (D50), and the dry powder particle size ratio (D90-D10)/D50 calculated from the dry powder particle size (D90) according to Example 9 is 3. .3.
• Example 10 mixes a slurry of the niobium-containing precipitate diluted with pure water with lithium hydroxide monohydrate and pure water such that the final mixture has a Nb/Li molar ratio of 1:1.
• a white suspension niobate-dispersed aqueous solution according to Example 10 was obtained by carrying out the same manufacturing method as in Example 1 except that the above was performed.
• the particle size (D50) of the resulting white suspension of the niobate-dispersed aqueous solution according to Example 10 was 2843.4 nm as determined by particle size distribution measurement using a dynamic light scattering method. Further, the dry powder particle diameter (D10) of the dry powder obtained by vacuum-drying the niobate dispersed aqueous solution according to Example 10 (drying conditions: heating temperature 80° C., heating time 7 hours) was 5.54 ⁇ m. The powder particle size (D50) was 38.26 ⁇ m, and the dry powder particle size (D90) was 167.16 ⁇ m. Furthermore, the dry powder particle size (D10), the dry powder particle size (D50), and the dry powder particle size ratio (D90-D10)/D50 calculated from the dry powder particle size (D90) according to Example 10 is 4. .2.
• Example 11 A slurry of the niobium-containing precipitate diluted with pure water was mixed with sodium hydroxide monohydrate and hydroxide so that the final mixture had a Nb/Na/Li molar ratio of 1:0.5:0.5. A manufacturing method similar to that of Example 1 was carried out, except that lithium monohydrate and pure water were mixed, to obtain a niobate-dispersed aqueous solution of white suspension according to Example 11.
• the particle size (D50) of the resulting white suspension of the niobate-dispersed aqueous solution according to Example 11 was 2185.6 nm as determined by particle size distribution measurement using a dynamic light scattering method. Further, the dry powder particle diameter (D10) of the dry powder obtained by vacuum-drying the niobate dispersed aqueous solution according to Example 11 (drying conditions: heating temperature 80° C., heating time 7 hours) was 5.53 ⁇ m. The powder particle size (D50) was 36.11 ⁇ m, and the dry powder particle size (D90) was 166.22 ⁇ m. Furthermore, the dry powder particle size (D10), the dry powder particle size (D50), and the dry powder particle size ratio (D90-D10)/D50 calculated from the dry powder particle size (D90) according to Example 11 is 4. .5.
• Comparative example 1 In Comparative Example 1, niobium oxide powder, potassium carbonate powder, and sodium carbonate were mixed so that the final mixture had a niobium concentration of 5% by mass in terms of Nb 2 O 5 and a molar ratio of Nb/K/Na of 1:0. Carbonate mixed powder according to Comparative Example 1 was obtained by weighing so as to have a ratio of 5:0.5, mixing and pulverizing in a ball mill, and firing the obtained mixed powder in an air atmosphere.
• niobium oxide powder, potassium carbonate powder, and sodium carbonate were mixed so that the final mixture had a niobium concentration of 5% by mass in terms of Nb 2 O 5 and a molar ratio of Nb/K/Na of 1:0.5. : 0.5, and the mixed mixture was mixed for 30 minutes with a ball mill.
• stainless steel media of the ball mill having a diameter of about 5 mm were used, sieving was performed, and under-sieving powder was collected to obtain a mixed carbonate powder according to Comparative Example 1.
• the particle size (D50) of the obtained white suspended carbonate mixed powder according to Comparative Example 1 was not measurable by measuring the particle size distribution using the dynamic light scattering method because it was not a solution.
• the dry powder particle size (D10) of the carbonate mixed powder according to Comparative Example 1 was 0.39 ⁇ m
• the dry powder particle size (D50) was 13.29 ⁇ m
• the dry powder particle size (D90) was 84.00 ⁇ m. .
• the sample is appropriately diluted with dilute hydrochloric acid and analyzed by ICP emission spectrometry (Agilent Technologies: AG-5110) to determine the Nb weight fraction in terms of Nb 2 O 5 , K weight fraction, and Na weight fraction. and Li weight fraction were measured.
• ⁇ Dynamic light scattering method The particle size distribution of the niobate dispersed aqueous solutions of Examples 1 to 11 was evaluated using a zeta potential/particle size/molecular weight measurement system (manufactured by Otsuka Electronics Co., Ltd.: ELSZ-2000ZS) according to JIS Z 8828:2019. was performed by the dynamic light scattering method. Also, 10 ⁇ m It was filtered through a filter with a pore size and subjected to the above-described dispersion treatment using ultrasonic waves. Here, since the carbonate mixed powder according to Comparative Example 1 does not dissolve in the solvent, measurement was not possible.
• the particle diameter (D50) refers to the median diameter (D50), which is the particle diameter indicating the 50% integrated value of the integrated distribution curve.
• the dry powder particle size (D10), the dry powder particle size (D50), and the dry powder particle size (D90) are the particle sizes of the dry powder up to 10%, 50%, and 90%, respectively, in volume fraction. show.
• ⁇ Film formability test> Appearance evaluation of the coating film formed on the surface of the glass substrate, which is a substitute for the current collector plate, was performed by observing with an optical microscope.
• the niobate-dispersed aqueous solutions of Examples 1 to 11 or Comparative Example 1 were dropped onto a 15 mm ⁇ 15 mm glass substrate using a syringe, and applied by spin coating (1,500 rpm, 30 seconds). Then, the coated portion was air-dried with high pressure air to form a coating film on the glass substrate.
• the formed coating film was observed with an optical microscope (magnification: 100 times) and evaluated according to the evaluation criteria "A", "B", or "C".
• Evaluation criteria "A” indicates that no coarse particles are present in the coating film, and air bubbles, coating unevenness, and cracks are all absent.
• Evaluation standard “B” indicates that no coarse particles are present in the coating film, but at least one air bubble, coating unevenness, or crack is present.
• Evaluation standard “C” indicates that coarse particles are present in the coating film, and at least one air bubble, coating unevenness, or crack is present.
• niobate films (samples) according to Examples 1 to 11 produced by coating the niobate dispersed aqueous solutions according to Examples 1 to 11 on a glass substrate and firing them, or the mixed carbonate powder according to Comparative Example 1. was kneaded into an acrylic resin, coated on a glass substrate, and fired to measure the transmittance of a carbonate film (sample) according to Comparative Example 1 produced by a spectrophotometer.
• Transmittance measurement conditions ⁇ Equipment: UH4150 type spectrophotometer ⁇ Measurement mode: wavelength scan ⁇ Data mode: %T (transmission) ⁇ Measurement wavelength range: 200 to 2600 nm ⁇ Scan speed: 600 nm/min ⁇ Sampling interval: 2 nm
• the transmittance at a wavelength of 500 nm was calculated from the transmittance obtained by measurement.
• the niobate dispersed aqueous solutions according to Examples 1 to 11 have high dispersibility in water and solubility in water when the niobium concentration in the aqueous solution is 0.1 to 40% by mass. was also excellent.
• the niobate-dispersed aqueous solutions according to Examples 1 to 11 have high dispersibility in water when the particle size (D50) of the niobate in the aqueous solution is 3,000 nm or less by the dynamic light scattering method.
• the solubility in water was also excellent.
• the dry powder particle size (D10) of the dry powder obtained from the aqueous solution is 1 ⁇ m or more by the dynamic light scattering method. It had high dispersibility and excellent solubility in water. Further, in the niobate dispersed aqueous solutions according to Examples 1 to 11, the dry powder particle size (D50) of the dry powder obtained from the aqueous solution is 20 ⁇ m or more by the dynamic light scattering method. It had high dispersibility in water and excellent solubility in water.
• the dry powder particle size (D90) of the dry powder obtained from the aqueous solution (D90) measured by the dynamic light scattering method is 60 ⁇ m or more. It had high dispersibility in water and excellent solubility in water.
• the dry powder particle size ratio (D90-D10)/D50 of the dry powder obtained from the aqueous solution obtained by the dynamic light scattering method (D90-D10)/D50 is 0 or more and 6
• D90-D10/D50 the dry powder particle size ratio of the dry powder obtained from the aqueous solution obtained by the dynamic light scattering method (D90-D10)/D50
• niobate-dispersed aqueous solutions according to Examples 1 to 11 were evaluated as "A” or "B", and thus were excellent in film formability.
• the niobate-dispersed aqueous solutions according to Examples 1 to 11 had a transmittance of 80% or more, and thus had excellent transmittance.
• the niobate-dispersed aqueous solution according to the present invention has high dispersibility in water, good solubility in water, and excellent film-forming properties. It is also suitable for use in piezoelectric elements and piezoelectric thin films.
• the niobate dispersion aqueous solution according to the present invention can be produced at a low temperature (low energy) by mixing an aqueous solution, whereas conventional niobate is produced through high-temperature sintering, and is stable as a product. As such, it will lead to sustainable management, efficient use and decarbonization (carbon neutrality) of natural resources.

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