Niobium oxide nanoparticles and the process for producing them

Abstract

D from approximately 100 nm to approximately 2 μm 50 A composition comprising nano-sized niobium oxide particles having the following: [Math 1] JPEG2026518376000018.jpg15166 Here, SSA is the BET specific surface area (unit: m²). 2 ( / g) and ρ is 4.6 g / cm³ 3 The density is such that the calculated particle size diameter D (in nm) differs by less than approximately 30% compared to the diameter of the observed particle size measured by SEM. This composition has properties beneficial for ceramic and electronic applications. Furthermore, this includes the manufacturing process of these particles and their applications.

Description

[Technical Field]

[0001] This application was filed on June 1, 2024, as a PCT international application, claiming priority and benefit to U.S. Provisional Patent Application No. 63 / 505,571, filed on June 1, 2023, and the entirety of its disclosure is incorporated herein by reference. [Background technology]

[0002] This application relates to compositions having nano-sized Nb2O5 particles, processes for manufacturing these compositions, and their applications in multilayer ceramic capacitors. The nano-sized Nb2O5 particles range in size from approximately 100 nm to approximately 2 μm. 50 It has a specific surface area (SSA) and a particle size diameter D (unit: nm) calculated from the SEM, where the difference compared to the measured particle size diameter measured by SEM is less than approximately 30%.

[0003] Niobium oxide particles have applications not only as catalyst supports but also in electrochromic devices, high-energy-efficiency windows, oxygen sensors, the photocatalyst industry, and multilayer ceramic capacitors.

[0004] These applications require nano-sized niobium oxide particles whose size, shape, crystal structure, and surface chemistry meet the requirements of such technological applications. However, the high surface energy associated with the ultrafine size of nanoparticles makes them prone to particle aggregation. Therefore, a high-yield and efficient process is needed to produce dispersed nano-sized niobium oxide particles. Consequently, research toward the preparation of nano-sized particles whose size, shape, dispersibility, crystal structure, and surface chemistry meet the requirements of such technological applications has been increasing in recent years.

[0005] The challenging task is to achieve an acceptable yield when synthesizing these nano-sized oxides while precisely controlling their highly dispersible morphology (size, shape, surface chemistry, particle size distribution, exposed crystal planes, etc.).

[0006] Therefore, there is still a need to develop simple and efficient methods for preparing nano-sized niobium oxide compositions with specific morphologies and particle sizes in high yield. [Overview of the Initiative]

[0007] The nano-sized Nb2O5 particles disclosed herein are D2O5 particles ranging in size from approximately 100 nm to approximately 2 μm. 50 The composition has a particle size diameter D (in nm) calculated from SSA, which is less than approximately 30% different from the diameter of the actual particle size measured by SEM. Therefore, this composition contains niobium oxide nanoparticles having a calculated particle size diameter D (in nm) determined by the following formula:

number

[0008] Furthermore, the present invention discloses a process for producing niobium oxide nanoparticles. These processes include (a) mixing a niobium salt, a polymer additive, and a precipitant in a solvent to provide a niobium precursor solution; (b) hydrothermally reacting the niobium precursor solution to form a precipitate; and (c) calcining the precipitate to provide niobium oxide nanoparticles having the following calculated particle size diameter D (in nm):

Number

Brief Description of the Drawings

[0009] [Figure 1] FIG. 1 illustrates a flowchart of one embodiment of the process for manufacturing Nb2O5 nanoparticles.

[0010] [Figure 2A] FIG. 2A is an SEM of the Nb2O5 particles of Comparative Example 1.

[0011] [Figure 2B] FIG. 2B is a graph illustrating the PSD profile of the Nb2O5 particles of Comparative Example 1.

[0012] [Figure 2C] FIG. 2C is an X-ray powder diffraction pattern (XRPD) of the Nb2O5 particles of Comparative Example 1 after firing.

[0013] [Figure 3A] FIG. 3A is an SEM of the Nb2O5 particles of Comparative Example 2.

[0014] [Figure 3B] FIG. 3B is a graph illustrating the PSD profile of the Nb2O5 particles of Comparative Example 2.

[0015] [Figure 4A] FIG. 4A is an SEM of the Nb2O5 particles of Example 1. [[ID=57]]

[0016] [Figure 4B]Figure 4B is a graph illustrating the PSD profile of the Nb2O5 particles of Example 1.

[0017] [Figure 5A] Figure 5A is a SEM image of the Nb2O5 particles from Example 2.

[0018] [Figure 5B] Figure 5B is a graph illustrating the PSD profile of the Nb2O5 particles of Example 2.

[0019] [Figure 5C] Figure 5C shows the X-ray powder diffraction (XRPD) map of the Nb2O5 particles of Example 2 after firing.

[0020] [Figure 6A] Figure 6A is a SEM image of the Nb2O5 particles from Example 3.

[0021] [Figure 6B] Figure 6B shows the X-ray powder diffraction (XRPD) map of the Nb2O5 particles of Example 3 after firing. [Modes for carrying out the invention]

[0022] This application discloses compositions and processes having nano-sized niobium oxide particles. Before describing them, it should be understood that this application extends to equivalents recognized by those skilled in the art, not to any specific structure, process step, or material disclosed herein. It should also be understood that the terminology used herein is used solely for the purpose of describing specific embodiments and is not intended to limit them. It should be noted that the singular forms “a,” “an,” and “the” used herein encompass multiple references unless the context clearly indicates otherwise. Thus, for example, “step” may include multiple steps, “producing” or “products” should not be interpreted as meaning all products in a reaction or treatment, and “treating” may encompass one or more such treatment steps. In this way, a “treating” step may include multiple or repeated treatments of the same material or fluid to produce a specified treatment product.

[0023] The term "approximately" encompasses typical experimental error. As used herein, "approximately" means within a statistically meaningful range, such as a given particle size, concentration range, time frame, molecular weight, temperature, or pH. Such ranges may be within orders of magnitude, typically within 10%, and more commonly within 5%. While sometimes occurring, such ranges may be within the normal experimental error of the standard methods used for measurement and / or determination of a given value or range. The permissible variation encompassed by the term "approximately" depends on the specific system under consideration and is readily understandable to a person of ordinary skill in the art. Where numerical ranges are described herein, all integer values ​​within the range are also encompassed as embodiments of the present invention.

[0024] This application relates to nano-sized Nb2O5 particles. These novel nano-sized particles exhibit a number of distinguishing physical properties, providing improved and advantageous physical properties for end applications, such as multilayer ceramic capacitors. These nano-sized Nb2O5 particles are highly dispersed (i.e., exhibit high dispersibility), meaning that the nanoparticles are discrete and not aggregated.

[0025] Dispersibility is a measure of the heterogeneity (or homogeneity) of particle sizes in a mixture. It can be indicated by the polydispersity index (PDI) parameter obtained from dynamic light scattering (DLS) or laser diffraction (LD) techniques. Specifically, the mean and standard deviation (stddev) are obtained from the particle size distribution (PSD) profile, and (standard deviation / mean) 2 The PDI value can be obtained by expressing it in the format shown. Information regarding this analytical technique can also be found at https: / / www.materials-talks.com / blog / 2017 / 10 / 23 / polydispersity-what-does-it-mean-for-dls-and-chromatography / and is incorporated into this application by reference as necessary. [Table 1]

[0026] As shown in Table A, the PDI value of a perfectly homogeneous sample is 0.0. In some embodiments, nano-sized Nb2O5 particles are "monodisperse," which means that the PDI value of the Nb2O5 particles is in the range of about 0.0 to about 0.1.

[0027] The Nb2O5 particles disclosed in this application are D2O5 particles ranging in size from approximately 100 nm to approximately 2 μm. 50 The particle also has a calculated particle size diameter D (in nm):

number

[0028] To apply the formula for determining the size by SSA, one important assumption is that the particles are discrete. A large difference between the calculated value and the observed value suggests that the formula is not applicable / inappropriate because the particles are not discrete (i.e., they are aggregates). In some embodiments, the Nb2O5 particles disclosed in the present application have a diameter D (unit: nm) of the calculated particle size that is less than about 25% different compared to the diameter of the observed particle size measured by SEM.

[0029] To derive this formula, the surface area of a sphere is πD 2 , and its volume is πD 3 / 6. Therefore, the surface area of a nano-sized material with a narrow particle size distribution is πD 2 ÷(πD 3 / 6×ρ). In the case of niobium oxide, ρ is 4.6 g / cm 3 .

[0030] Those skilled in the art will understand how to determine the diameter of observed particle sizes measured by a scanning electron microscopy. See National Institute of Standards and Technology (NIST) Special Publication 250-96, page 22 (September 2017), “Dimensional measurement of nanostructures with scanning electron microscopy,” KABertness, Applied Physics Division, Physical Measurement Laboratory. This can be found at https: / / doi.org / 10.6028 / NIST.SP.250-96, and its entire content is incorporated herein by reference. As described therein, scanning electron microscopy (SEM) is widely used for measuring the dimensions of nanostructures. SEM magnification calibration can be performed using the ASTM E766-14 implementation standard with NIST Reference Material (RM) and the calculation of dimensional uncertainty when measuring the dimensions of nanostructures manufactured using a calibrated SEM. Dimensional measurements can be performed according to NIST Special Test 15510S.

[0031] According to these techniques, samples are typically prepared by dispersing particles on a substrate. High-resolution images of the particles are obtained from a SEM, and individual particles are measured manually using machine software. Length is determined by measuring the longest distance from one side of the particle to the other using a straight line. Length refers to the measurement of the longest side of the particle. Width is perpendicular to length. Width is determined by measuring the distance from one side of the particle that defines the length to the other side that defines that length using a straight line. Width measures the distance between the shorter sides of the particle, or between parallel sides that define that length.

[0032] In some embodiments, the particles have an average particle length of about 50 nm to about 1 μm. In some embodiments, nano-sized Nb2O5 particles may have a single-peak profile size. In some embodiments, nano-sized Nb2O5 particles have a narrow particle size profile.

[0033] Particle size analysis was performed using a Microtrac S3500 particle size analyzer. A typical measurement was performed using approximately 0.1 g of the powder sample, to which 10 ml of 2% sodium hexametaphosphate solution was added. The sample + solution was then sonicated for approximately 3 minutes. A few drops of the sonicated solution were then added to the sample container of the instrument. The sample was again sonicated in the instrument for another 3 minutes. Three consecutive measurements were performed according to the instrument manufacturer's instructions. The results of the three measurements were averaged and recorded. Based on the above, the D of the sample was determined. 50 This will be decided.

[0034] Laser diffraction (LD) is used to measure particle size distribution (PSD). Dynamic light scattering (DLS) is another technique that can be used to measure PSD. Both LD and DLS can be used to measure PSD, but the models used are different. In DLS, the particle's velocity is a function of the particle size. In LD, the diffraction / scattering intensity versus angle (diffraction pattern) is a function of the particle size. Although the two are based on different models, the dispersion theory should be the same because it is merely a mathematical calculation based on PSD.

[0035] As described herein, the niobium oxide particles disclosed herein are nano-sized niobium oxide particles.

[0036] Niobium oxide particles can be crystalline. In some embodiments, crystalline niobium oxide particles are orthorhombic.

[0037] Nano-sized niobium oxide particles also have a desirable surface area. In some embodiments, the particles are about 5 m 2 From / g to approximately 100m 2 The composition has a BET specific surface area of ​​1 / g. The BET specific surface area of ​​the composition was determined using a Tristar II system from Micromeritics and nitrogen at approximately 77 Kelvin. Following generally accepted procedures, the application of the BET formula in determining the surface area used in this application was limited to the pressure range in which the term na(lP / Po) in the formula increased continuously with P / Po. The sample was degassed under nitrogen at approximately 350°C for approximately 2 hours.

[0038] Nano-sized Nb2O5 particles may also exhibit a desirable loss on ignition (LOI). In some embodiments, the nano-sized Nb2O5 particles disclosed herein have an LOI of less than 6% at the firing temperature. In certain embodiments, the LOI ranges from 0.1% to about 6%. As described herein, the LOI was determined by measuring the mass of the sample before and after firing the product at 1000°C for 1 hour.

[0039] These additional properties, including crystalline embodiments, BET, LOI, particle size profile, and particle length, may be combined with any of the embodiments described above. These additional embodiments may be combined individually or cumulatively with the general description of nano-sized Nb2O5 particles described above.

[0040] While not bound by any theory, the specific D described in this application 50Nano-sized niobium oxide particles with a specific particle size and diameter are considered to offer many beneficial technical effects, particularly when used in multilayer ceramic capacitors. The unique combination of shape and size provides better mixing and avoids significant aggregation. This improves efficiency in end applications such as multilayer ceramic capacitors. The shape and size described in particular may improve the electrical performance and reliability of the dielectric. The electrical properties and associated reliability may be attributable to the shape and size described in particular. The shape and size described in particular may improve the solubility and distribution of the niobium oxide particles described herein.

[0041] The nano-sized Nb2O5 particles disclosed herein range from approximately 100 nm to 2 μm in size. 50 The Nb2O5 particles disclosed in this application, having a diameter D (in nm) of a calculated particle size given by the following formula, are manufactured by a specific process:

number

[0042] This process includes (a) mixing a niobium salt, a polymer additive, and a precipitant in a solvent to provide a niobium precursor solution; (b) hydrothermally reacting the niobium precursor solution to form a precipitate; and (c) calcining the precipitate to provide niobium oxide nanoparticles having the following calculated particle size diameter D (in nm):

number

[0043] In step (a), the niobium salt, polymer additive, and precipitant are mixed in a solvent to provide a niobium precursor solution. The order of addition is not important, and any order of addition may be used. The solvent is water, particularly deionized water. The niobium salt in step (a) may be ammonium niobate, niobium chloride, or a mixture thereof. In certain embodiments, the niobium salt is ammonium niobate oxalate with an oxide content of 30.6%. In one embodiment, the niobium salt is first dissolved in water, and then the polymer additive and precipitant are added to this solution and dissolved in it. In other embodiments, the niobium salt, polymer additive, and precipitant may be dissolved individually in water, and these solutions may be mixed.

[0044] The precipitating agent may be selected from the group consisting of oxalic acid, tartaric acid, urea, ammonium phosphate, ammonium citrate, and mixtures thereof. In certain embodiments, the precipitating agent is oxalic acid, diammonium citrate, tartaric acid, or a mixture thereof.

[0045] The polymer additive may be selected from the group consisting of polyvinyl alcohol, polyvinylpolypyrrolidone, polyethylene glycol, polyethyleneimine, and mixtures thereof. In certain embodiments, the polymer additive is polyethylene glycol, polyvinylpolypyrrolidone, or a mixture thereof.

[0046] In certain embodiments, the precipitating agent is oxalic acid, tartaric acid, ammonium citrate, or a mixture thereof, and the polymer additive is polyvinylpolypyrrolidone, polyethylene glycol, or a mixture thereof.

[0047] In this embodiment, the niobium salt, polymer additive, and precipitant are Nb 5+ The mixture may be mixed to achieve a concentration of approximately 0.01 to 0.5 M.

[0048] The solution in step (a) is mixed. The solution may be thoroughly mixed by stirring for about 30 minutes to about 6 hours. In other embodiments, the solution may be mixed by ultrasonic treatment and then stirred. In additional embodiments, the ultrasonic treatment step may be omitted.

[0049] The mixed solution from step (a) is then subjected to a hydrothermal reaction to form a precipitate. The solution can be subjected to a hydrothermal reaction at a temperature of about 120°C to about 220°C for about 1 to 24 hours.

[0050] Before calcining the precipitate in step (c), the precipitate from step (b) may be collected. The precipitate can be collected by filtration or centrifugation. This precipitate can be collected and dried in an oven. The precipitate can be dried at approximately 50°C to approximately 100°C for approximately 3 to approximately 12 hours before calcination.

[0051] In one embodiment, the recovered precipitate may be washed with deionized water to an conductivity of less than about 200 μS / cm. In another embodiment, the recovered precipitate may be dehydrated. In an embodiment including dehydration, the recovered precipitate may be dehydrated with ethanol. In an embodiment including washing with water and / or dehydration, the process may further include drying the precipitate at about 50°C to about 100°C for about 3 to about 12 hours before calcination.

[0052] Finally, the precipitate is calcined to provide the niobium oxide nanoparticles disclosed herein. The precipitate can be calcined at a temperature of about 500°C to about 1000°C for about 1 to about 6 hours. The calcination should be sufficient to remove polymer additives. In certain embodiments, the precipitate is calcined at about 700°C for 1 hour.

[0053] The process disclosed herein provides nano-sized niobium oxide particles having the properties described herein.

[0054] Figure 1 is a flowchart of one embodiment of the process for producing nano-sized niobium oxide particles, as illustrated in the examples described later.

[0055] In the following examples, the preparation and characterization of nano-sized Nb2O5 particles are provided to illustrate the process in more detail, but the scope of the present invention is by no means limited in any way thereto.

[0056] In the following examples, a JEOL JSM6010LV was used to acquire SEM (scanning electron microscope) images to determine the particle size range and morphology. A Hitachi SU5000 FE-SEM was used to acquire high-resolution SEM images to determine the average particle size and morphology. Sample D 50 A Microtrac S3500 was used to determine the crystal structure of the final product. A Malvern Panalytical Empyrean X-ray diffractometer was used to determine the crystal structure of the final product. Micromeritics Tristar was used to determine the specific surface area (SSA) of the final product. Finally, the sample was calcined at 1000°C for 1 hour using a muffle furnace to determine the Line of Interest (LOI).

[0057] The comparative examples disclosed herein illustrate Nb2O5 particles in which the calculated particle size diameter D is measurably larger than approximately 30% compared to the observed particle size diameter measured by SEM. This larger difference between the calculated particle size diameter D and the observed particle size diameter measured by SEM is a result of the nanoparticles being less discrete (i.e., more aggregated).

[0058] Comparative Example 1: Production of Nb2O5 nanoparticles without polymer additives. The following took place: 1) 2.5 g of ammonium niobate oxalate (oxide content = 30.6%) and 4.2 g of oxalic acid dihydrate were weighed and dissolved in 100 mL of deionized water (DI water). 2) 0.038 g of ammonium phosphate was added to the above solution along with 50 mL of DI water. 3) The mixture was stirred to obtain a clear, colorless solution. 4) The mixture was then transferred to a 200 mL hydrothermal reactor. 5) The mixture was subjected to hydrothermal treatment at 220°C for 2 hours. 6) The precipitate was recovered by centrifugation and washed with deionized water until the conductivity was less than 200 μS / cm. 7) The solid was dehydrated with ethanol to obtain a wet cake. 8) The wet cake was dried at 60°C. 9) The dried product was calcined at 700°C for 1 hour.

[0059] The Nb2O5 particles were spherical. The Nb2O5 particles were analyzed by SEM (Figure 2A). According to SEM observations, the average particle size of the Nb2O5 particles was approximately 147.0 nm (measured from 50 particles by SEM), and the BET size was approximately 30.3 nm. Figure 2B is a graph illustrating the PSD profile of the Nb2O5 particles. [Table 2]

[0060] The Nb2O5 particles were also analyzed by XRPD (Figure 2C), exhibiting the properties of orthorhombic Nb2O5.

[0061] Comparative Example 2: Manufacturing Nb2O5 nanoparticles The following took place: 1) 2.5 g of ammonium niobate oxalate (oxide content = 30.6%) was weighed and dissolved in 150 mL of DI water. 2) 4.2 g of oxalic acid, 3.8 g of polyvinylpolypyrrolidone (molecular weight (MW) approximately 1,300,000), and 0.048 g of tartaric acid were added to the above solution. 3) The mixture was stirred for 60 minutes. 4) The mixture was then transferred to a 200 mL hydrothermal reactor. 5) The mixture was subjected to hydrothermal treatment at 220°C for 2 hours. 6) The precipitate was recovered by centrifugation and washed with DI water until the conductivity was less than 200 μS / cm. 7) The solid was dehydrated with ethanol to obtain a wet cake. 8) The wet cake was dried at 80°C for 12 hours. 9) The dried product was calcined at 700°C for 1 hour.

[0062] The Nb2O5 particles were nanoscale. The Nb2O5 particles were analyzed by SEM (Figure 3A). According to SEM observations, the average particle size of the Nb2O5 particles was approximately 171.8 nm (measured from 50 particles by SEM), and the BET size was approximately 247.9 nm. Figure 3B is a graph illustrating the PSD profile of the Nb2O5 particles. [Table 3]

[0063] Example 1: Manufacturing Nb2O5 nanoparticles The following took place: 1) 2.5 g of ammonium niobate oxalate (oxide content = 30.6%) was weighed and dissolved in 150 mL of DI water. 2) 4.2 g of oxalic acid and 0.048 g of tartaric acid were added to the above solution. 3) The mixture was stirred for 60 minutes. 4) The mixture was then transferred to a 200 mL hydrothermal reactor. 5) The mixture was hydrothermally treated at 220°C for 1.5 hours. 6) The precipitate was recovered by centrifugation and washed with DI water until the conductivity was less than 200 μS / cm. 7) The solid was dehydrated with ethanol to obtain a wet cake. 8) The wet cake was dried at 80°C for 12 hours. 9) The dried product was calcined at 700°C for one hour.

[0064] The Nb2O5 particles were nanoscale. The Nb2O5 particles were analyzed by SEM (Figure 4A). According to SEM observations, the average particle size of the Nb2O5 particles was approximately 184.2 nm (measured from 50 particles by SEM), and the BET size was approximately 143.7 nm. Figure 4B is a graph illustrating the PSD profile of the Nb2O5 particles. [Table 4]

[0065] Example 2: Production of Nb2O5 nanoparticles The following took place: 1) 2.5 g of ammonium niobate oxalate (oxide content = 30.6%) and 4.2 g of oxalic acid dihydrate were weighed and dissolved in 150 mL of DI water. 2) 0.3 g of polyvinylpyrrolidone (PVP) (molecular weight (MW) approximately 1300 K) was added to the above solution. 3) 0.3 g of diammonium citrate was added to the solution along with 50 mL of DI water. 4) The mixture was stirred until all components were dissolved. 5) The mixture was then transferred to a 200 mL hydraulic reactor. 6) The mixture was subjected to hydrothermal treatment at 220°C for 2 hours. 7) The precipitate was recovered by centrifugation and washed with deionized water until the conductivity was less than 200 μS / cm. 8) The solid was dehydrated with ethanol to obtain a wet cake. 9) The wet cake was dried at 60°C. 10) The dried product was calcined at 700°C for 1 hour.

[0066] The Nb2O5 particles were nanoscale. The Nb2O5 particles were analyzed by SEM (Figure 5A). According to SEM observations, the average particle size of the Nb2O5 particles was approximately 38.7 nm (measured from 50 particles by SEM), and the BET size was approximately 45.9 nm. Figure 5B is a graph illustrating the PSD profile of the Nb2O5 particles. [Table 5]

[0067] The Nb2O5 particles were also analyzed by XRPD (Figure 5C), exhibiting the properties of orthorhombic Nb2O5.

[0068] Example 3: Production of Nb2O5 nanoparticles The following took place: 1) 66.7 g of ammonium niobate oxalate (oxide content = 30.6%) was weighed and dissolved in 800 mL of DI water, and then the mixture was filled with DI water until the total volume reached 1 L. 2) 2.04 g of oxalic acid and 1.9 g of polyvinylpolypyrrolidone (molecular weight (MW) approximately 100,000) were added to 150 mL of the above Nb precursor solution. 3) The mixture was stirred at room temperature for 60 minutes. 4) The mixture was then transferred to a 200 mL hydrothermal reactor. 5) The mixture was subjected to hydrothermal treatment at 180°C for 36 hours. 6) The precipitate was recovered by centrifugation and washed with deionized water until the conductivity was less than 200 μS / cm. 7) The solid was dehydrated with ethanol to obtain a wet cake. 8) The wet cake was dried at 80°C. 9) The dried product was calcined at 700°C for 1 hour.

[0069] The Nb2O5 particles were nanoscale. The Nb2O5 particles were analyzed by SEM (Figure 6A). SEM observations revealed that the Nb2O5 particles had an average particle size of approximately 38.2 nm (measured from 50 particles by SEM) and a BET size of approximately 47.3 nm. The Nb2O5 particles were also analyzed by XRPD (Figure 6B), exhibiting the properties of orthorhombic Nb2O5. [Table 6]

[0070] Summary of calculated particle size diameters and observed particle size diameters in examples and comparative examples. The following table summarizes the calculated particle size diameter and the observed particle size diameter measured by SEM for the Nb2O5 nanoparticles manufactured in this application. The Nb2O5 particles of this application have a calculated particle size diameter D (in nm) given by the following formula:

number

[0071] The results show that the comparative example is significantly larger. [Table 7]

[0072] As shown, the Nb2O5 nanoparticles disclosed herein have a calculated particle size diameter D (in nm):

number

[0073] The Nb2O5 nanoparticles disclosed herein have a diameter D and size as described, and offer many beneficial technical effects, particularly when used in multilayer ceramic capacitors. Their unique shape, combined with their size, allows for better mixing and prevents significant aggregation. This improves efficiency in end applications such as multilayer ceramic capacitors.

[0074] Since devices such as multilayer ceramic capacitors are desired to be smaller and lighter, their components must contribute to achieving this end result. The shapes and sizes described in particular may improve the electrical performance and reliability of the dielectric. The electrical properties and associated reliability may be due to the solubility and distribution of rare earth oxides. The shapes and sizes described in particular may improve the solubility and distribution of rare earth oxide particles as described in this application.

[0075] The spherical morphology and, in particular, the particle size as defined herein may be beneficial for use as a powder, dispersion in liquid media, better mixing with BaTiO3 ceramics, and site occupancy. The particles disclosed herein may result in improved electrical performance and high reliability. The electrical properties and associated reliability of these capacitors may be due to the solubility, distribution, and site occupancy of the rare earth oxide in BaTiO3. Rare earth oxide particles having the spherical morphology and particle size disclosed herein may improve these properties.

[0076] Unless otherwise specified, all numerical values ​​used in the specification and claims, such as the amount of components, properties like molecular weight, and reaction conditions, are understood to always be modified by the word "about." Therefore, unless otherwise specified, the numerical parameters described in the following specification and appended claims are approximations and may vary depending on the desired properties to be obtained.

[0077] Although the numerical ranges and parameters representing the broad scope of this technology are approximations, the numerical values ​​described in specific examples are reported as accurately as possible. However, any numerical value inherently contains a certain degree of error, which is necessarily due to the standard deviation found in each test measurement.

[0078] It is clear that the compositions and methods described herein are suitable for achieving the described objectives and advantages, and the benefits inherent therein. Those skilled in the art will recognize that the methods and systems described herein can be implemented in a variety of ways and are therefore not limited by the exemplary embodiments and examples described herein. In this regard, any number of features of the different embodiments described herein can be combined into a single embodiment, and alternative embodiments having fewer or more features than all of the features described herein are also possible.

[0079] While various embodiments are described for the purposes of this application, various changes and modifications can be made within the scope envisioned by this application. Furthermore, there are many other modifications that are readily conceivable to those skilled in the art, and these are also included within the scope of the intent of this application.

Claims

1. D from approximately 100 nm to approximately 2 μm ５０ A composition comprising niobium oxide nanoparticles having a calculated particle size diameter D (unit: nm) given by the following formula: [Math 1] Here, SSA is the BET specific surface area (unit: m²). ２ ( / g) and ρ is 4.6 g / cm³. ３ Therefore, the diameter D (unit: nm) of the calculated particle size differs from the diameter of the observed particle size measured by SEM by less than approximately 30%.

2. The composition according to claim 1, wherein the particles have an average particle length of about 50 nm to about 1 μm.

3. The composition according to claim 1, wherein the niobium oxide particles have a diameter of calculated particle size that differs from the diameter of particle size observed by SEM by less than about 25%.

4. The aforementioned particles are approximately 5 m ２ From / g to approximately 100m ２ The composition according to any one of claims 1 to 3, having a BET specific surface area of ​​1 / g.

5. The composition according to any one of claims 1 to 4, wherein the particles are crystalline.

6. The composition according to claim 5, wherein the particles are crystallized in an orthorhombic system.

7. The composition according to any one of claims 1 to 6, wherein the composition has a loss on ignition (LOI) of about 0.1% to about 6%.

8. The composition according to any one of claims 1 to 7, wherein the particles are monodisperse.

9. A process for producing niobium oxide nanoparticles, (a) A step of providing a niobium precursor solution by mixing a niobium salt, a polymer additive, and a precipitant in a solvent. (b) The step of forming a precipitate by hydrothermally reacting the niobium precursor solution, and (c) A step of calcining the precipitate to provide niobium oxide nanoparticles having the following calculated particle size diameter D (unit: nm), Processes including: [Math 2] Here, SSA is the BET specific surface area (unit: m²). ２ ( / g) and ρ is 4.6 g / cm³. ３ Therefore, the calculated particle size diameter D (in nm) differs from the observed particle size diameter measured by SEM by less than approximately 30%.

10. The process according to claim 9, wherein the precipitating agent is selected from the group consisting of oxalic acid, tartaric acid, urea, ammonium phosphate, ammonium citrate, and mixtures thereof.

11. The process according to claim 9 or 10, wherein the polymer additive is selected from the group consisting of polyvinyl alcohol, polyvinylpolypyrrolidone, polyethylene glycol, polyethyleneimine, and mixtures thereof.

12. The process according to any one of claims 9 to 11, wherein in step (b), the niobium precursor solution is subjected to a hydrothermal reaction at a temperature of about 120°C to about 220°C for about 1 hour to about 24 hours.

13. The process according to any one of claims 9 to 12, wherein in step (c), the precipitate is calcined at a temperature of about 500°C to about 1000°C for about 1 hour to about 6 hours.

14. The process according to any one of claims 9 to 13, further comprising recovering the precipitate from step (b) by centrifugation, and washing the precipitate with deionized water before calcination to a conductivity of less than about 200 μS / cm.

15. The process according to claim 14, further comprising dehydrating the precipitate of step (b) before firing.

16. The process according to any one of claims 9 to 15, further comprising collecting the precipitate before firing and drying it at a temperature of about 50°C to about 100°C for about 2 hours to about 12 hours.

17. The process according to claim 9, wherein the mixing in step (a) is performed by stirring or ultrasonic treatment.

18. Nb of the solution in step (a) ５＋ The process according to claim 9, wherein the concentration is approximately 0.01 to approximately 0.5 M.

19. The process according to any one of claims 9 to 11, wherein the niobium salt is ammonium niobium oxalate with an oxide content of about 30.6%.

20. The process according to claim 19, wherein the precipitating agent is oxalic acid, tartaric acid, ammonium citrate, or a mixture thereof, and the polymer additive is polyvinylpolypyrrolidone, polyethylene glycol, or a mixture thereof.

21. Niobium oxide nanoparticles produced by the process described in any one of claims 9 to 20.

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