Perovskite nanoparticle, composition comprising same and method for obtaining a perovskite nanoparticle

Abstract

The present invention pertains to the fields of materials engineering and nanotechnology. More specifically, the invention discloses a perovskite nanoparticle, a composition comprising said nanoparticle and a method for obtaining same. In one embodiment, the perovskite nanoparticle is selected from CaTiO3, AgNbO3, AgTaO3, KNbO3, NaNbO3, CsSnCl3, or combinations thereof. The composition of the invention comprises perovskite nanoparticles, other non-perovskite nanoparticles, submicrometric particles, or combinations thereof. The method of the invention comprises at least one prior, joint or sequential comminution step for one or more cation sources. In one embodiment, the method of the invention is conducted in a liquid medium. The invention provides perovskite nanoparticles with a specific granulometric profile, which are useful in a variety of applications and solve various technical problems.

Description

Descriptive Report of Invention Patent PEROVSKITE NANOPARTICLE, COMPOSITION COMPRISING THE SAME AND PROCESS FOR OBTAINING PEROVSKITE NANOPARTICLE Field of Invention

[0001] The present invention is in the field of Materials Engineering and Nanotechnology. More specifically, the invention discloses a perovskite nanoparticle, a composition comprising the same, and a process for obtaining the same. In one embodiment, the perovskite nanoparticle is selected from CaTiOa, AgNbOa, AgTaOa, KNbOa, NaNbOa, CsSnCh, or combinations thereof. The composition of the invention comprises perovskite nanoparticles, other non-perovskite nanoparticles, submicron particles, or combinations thereof. The process of the invention comprises at least one step of prior, joint, or sequential comminution of one or more cation sources. In one embodiment, the process of the invention is conducted in a liquid medium. The invention provides perovskite nanoparticles with a specific particle size profile, being useful in a variety of applications and solving several technical problems. Background of the Invention

[0002] Perovskite was discovered in the Ural Mountains of Russia by Prussian Gustav Rose in 1839 and named after the Russian mineralogist Lev A. Perovskite (1792–1856). Perovskite is a relatively rare mineral, occurring as orthorhombic (pseudocubic) crystals in metamorphic rocks and associated with mafic intrusions, nepheline syenites, and rarely with carbonatites.

[0003] The term "perovskite" currently refers to a large group of compounds with a crystal structure that resembles the structure of the perovskite mineral calcium titanate. Its general formula is ABC3, where A and B are cations and C is an anion, which is usually the oxide ion O 2-, or halide ions (Cl-, Br, F'), a non-limiting example being CaTiOa. The A and B cations are of different sizes, as is the case with LaMnOa. The approximate structure is that of a face-centered cube, but the difference between the A and B cations can distort this structure, tilting it. The perovskite structure exhibits the characteristic ferroelectric effect, like garnet and olivine. Many superconducting ceramics have the perovskite structure.

[0004] Nanotechnology is a rapidly expanding science and has generated significant expectations due to the unusual properties of nanoparticles made from various materials. However, its large-scale use still faces multiple limitations, including the difficulty in obtaining nanoparticle preparations with high concentrations, purity, and a precise particle size profile. Furthermore, several other technical issues limit the industrial use of nanoparticles, including their tendency to aggregate, difficulty in dispersion, and the assumption that only high-value-added products justify investment in technology to obtain nanoparticles and prepare formulations containing them. Nanoparticles obtained through synthesis or bottom-up processes are limited to certain chemical species that are reaction products and generally have low purity, making them technically and / or economically unviable on a large scale.

[0005] The present invention provides a significant advance by providing perovskite nanoparticles. The composition of the invention comprises the aforementioned perovskite nanoparticles and other excipients and / or non-perovskite nanoparticles, and solves several technical problems in a surprising way, notably in the magnitude of the benefits.

[0006] In the search for the state of the art in scientific and patent literature, the following documents were found that relate to the topic, without, however, anticipating or suggesting it:

[0007] US patent 2,220,966, entitled Titanium Oxide Suspensions, was filed by DuPont in the 1940s. This document reveals a A method for preparing aqueous suspensions of colloidal titanium oxide using oxygen-containing monobasic compounds and subsequent coagulation of the mixture with titanium particles. These oxygen-containing compounds include chloric, perchloric, hydrobromic, perbromic, iodic, periodic, sulfamic acids, or their barium salts. The document does not disclose perovskites or a process for obtaining them.

[0008] Patent application PI 9306825, titled "Stable Aqueous Suspension of Colloidal Particles and Process for its Preparation," was filed by Eka Nobel and published in 1998. The document describes the particles as silica (anionic) and smectite-type sludge, which are water-swellable and used in combination with polymers in paper production. The document does not disclose perovskites or a process for obtaining perovskites.

[0009] Patent application PI 9801050, entitled Colloidal Metal Oxides Having Blocked Isocyanate Groups, was filed by Bayer AG and published in 1999. This document discloses colloidal metal oxides having blocked isocyanate groups, which are based on a reaction product of A) silanes containing blocked isocyanate groups with B) colloidal metal oxides selected from Al, Si, Ti, Ta, W, Hf, Zr, Sn and Y. The use of said modified metal oxides, alone or in combination with compounds containing at least two reactive isocyanate groups, for the preparation of coating agents, lacquers or optionally expanded polyurethane plastics is also described. The document does not disclose perovskites or a process for obtaining perovskites.

[0010] EP 1052225, entitled Titanium Oxide Colloidal Sol and Process for the Preparation of Titanium Oxide, was filed by Nihon Parkerizing and published in 2000. This document discloses a neutral colloidal sol of titanium dioxide with high stability in the neutral range, which forms a transparent and colorless coating even after drying at room temperature. The colloidal sol is obtained by mixing an acidic titanium dioxide sol comprising 50 to 100 parts by weight of TiO2 colloidal particles with 5 50 parts by weight of a titanium ion chelating agent with 1 to 50 parts by weight of an alkaline substance, adjusting the pH of the mixture between 5 and 10 and then carrying out a deionization treatment to charge the TiO2 colloidal particles with a negative charge.

[0011] Patent application JP200405081 1 A, titled "Ink Jet Recording Material," was filed by Mitsubishi Paper Mills and published in 2004. The document discloses an approach to solving the problem of inkjet recording materials, namely, providing gloss, ink absorption, abrasion resistance, and good surface coating. The proposed solution involves incorporating a layer of fine, anionic inorganic particles and a layer containing colloidal silica into the recording material. The document does not disclose perovskites or a process for producing them.

[0012] Document JP2008285613A, entitled Aqueous Dispersion of Titanium Oxide Composite Particle and Method for Producing the Same, was filed by Achiles Corp. and Toyota and published in 2008. This document discloses a method for producing a dispersion of TiO2 particles that suppresses the oxidative decomposition, caused by TiO2, of surfaces such as fabrics, in addition to providing TiO2 stability. The method involves the steps of (i) using 0.3 to 3% by weight (relative to the weight of TiO2) of ammonium polyacrylate or polyacrylic acid triethylamine as a dispersing agent; (ii) and add 10 to 75% by weight of colloidal silica converted to oxide, with an average particle diameter between 1 and 30nm (measured by dynamic light scattering), so that the colloidal silica particles are absorbed by the TiO2 particles, forming a composite particle.

[0013] Patent application JP2013177307A, titled Colloidal Titanium Dioxide Sol, was filed by Millenium Inorganic Chem and published in 2013. This document discloses a method for preparing stable and transparent colloidal titanium dioxide sols. The process involves the steps of (i) obtaining a titanium dioxide precursor in solution, (ii) hydrolyzing said precursor to form TiO2, which is then precipitated from the solution in amorphous form with particles with an average size of less than 50nm; (iii) isolating the TiO2 particles from the previous step; and (iv) forming a liquid dispersion with said particles with an organic liquid containing a mono-, di-, or trialkylamine base.

[0014] The article entitled "Nb-doped Colloidal T1O2 Nanocrystals with Tunable Infrared Absorption" was published by Trizion et al. in 2013 in Chem. Mater. 25(16): 3383-3390. This document reveals the synthesis of Nb-doped TiO2 nanocrystals (anatase), yielding TiO2 nanocrystals approximately 10 nm in size and with Nb concentrations of up to 14%. The article indicates that the incorporation of Nb ions leads to the appearance of a broad absorption peak that ranges from the visible to the mid-infrared and is tunable; that is, the incorporation of Nb affects the optical properties of the material. The article also reveals that the addition of Nb alters the shape of the TiO2 nanocrystals. The document refers to bottom-up processes and does not disclose perovskites or a process for obtaining perovskites by mechanosynthesis.

[0015] Document US 2015024529A, entitled Formulation of Colloidal Titanium Oxide Solutions Composition for Coating and Printing Methods, and Improvement of the Output and Lifespan of Organic PlN / NlP Photovoltaic Cells, was filed by the University of Nantes and published in 2015. Said document discloses a method for preparing a solution of colloidal nanoparticles comprising: (i) dissolving a TiO2 precursor and one or more solvents; (ii) chemically converting said precursor, preferably by hydrolysis, to form TiO2 nanoparticles dispersed in said solvent, so that the colloidal solution has a viscosity dynamically 4 and 54 cP at 20 °C. e C and 101,325 Pa. The uses in the preparation of photovoltaic cells and in the generation of energy using a semiconductor prepared with said solution are also described.

[0016] The article by Petrovic, V., entitled “Synthesis calcium-titanate (CaTiOa)”, The Advanced School of Electrical Engineering, Belgrade, Vojvode Stepe 283, SCG, describes a process for obtaining calcium titanate (CaTiOa). This process uses the agglomeration method, through the reagents in calcium carbonate (CaCOa) powder and titanium dioxide (TiO2) are combined using mechanosynthesis to initiate the reaction, and the mixture is then calcined. The resulting perovskite is reduced in size compared to its precursors due to grinding. However, the aforementioned document does not reveal perovskite nanoparticles.

[0017] Carmo, João R.'s thesis, entitled "SYNTHESIS, MICROSTRUCTURAL AND ELECTRICAL CHARACTERIZATION OF CERAMIC COMPOUNDS BASED ON SOLID SOLUTIONS OF STRONTIUM TITANATE, CALCIUM TITANATE AND IRON OXIDE", was presented at the Institute for Energy and Nuclear Research (IPEN), University of São Paulo (USP), São Paulo, in 2011. The document describes the synthesis of different compositions based on iron-doped SrTiOa and CaTiOa, through mixing in an alcoholic medium and drying the material, preparation of polymeric precursors, analysis of ceramic powders of these compositions, preparation of sintered ceramic compacts of the compositions, characterization of them and evaluation of the electrical response of the compacts under oxygen. However, this document does not reveal perovskite nanoparticles.

[0018] The work of Gralik, G. et al., entitled “Processing and characterization of CaTiOa perovskite ceramics”, UFSC, Florianópolis, Santa Catarina, was published in 2014. The document describes the production of calcium titanate perovskite (CaTiOa) through the solid-state reaction method with grinding of the reactants calcium carbonate (CaCOa) and titanium dioxide (TiO2), followed by calcination of the final mixture, which is characterized. However, this document does not reveal perovskite nanoparticles.

[0019] The work of Silva, Ana R. de Q., entitled “SYNTHESIS AND CHARACTERIZATION OF PEROVSKITES CaTiOa AND Ca1 -x-yErxYbyTiOa, was presented at the Federal University of Maranhão (UFMA) in 2016. The referred document describes the synthesis of calcium titanate by the solid state reaction in powder form, synthesis and doping of the ceramic system with rare earth oxides Er 3+ and Yb 3+ by the solid state reaction, made from the materials of starting Ca(OH)2, TiO2, Er2Ü3 and Yb2O3, with grinding, then calcination and sintering, characterization of the ceramic system by X-ray diffraction, identifying the crystalline phases formed, refining, characterization of the ceramic system by Raman Spectroscopy and Scanning Electron Microscopy. However, this document does not reveal perovskite nanoparticles.

[0020] The work by Sugak, D. et a!., entitled “Mechanosynthesis, Structure and Photoluminescent Properties of the Pr 3+ Doped LiNbO3, LiNbO3:Mg, LiTaOs Nanopowders”, was published on 21 Jul 2023 in the journal Powders 2, 562-577. This paper describes the synthesis of nanocrystalline powders of LiO.9sPro.o2Nb03 (LN:Pr), LiO.93Mgo.osPro.o2Nb03 (LN:Mg,Pr), and Lio.98Pro.o2TaO3 (LT:Pr) was obtained by high-energy ball milling followed by high-temperature reheating. The photoluminescent spectrum showed characteristics of Pr3+ ions in the crystal structure of LiNbOs and LiTaOs, and they are more efficiently excited by UV light. It is considered the closest document to the present invention. However, this document does not reveal perovskite nanoparticles like those of the present invention.

[0021] International patent application PCT / BR2021 / 050346, entitled "Niobium Nanoparticle Preparation, Use and Process for Obtaining It," was filed by Fras-le. The document describes a niobium nanoparticle preparation obtained using a top-down approach. This preparation also includes the following technical characteristics: particles entirely in the nanometer particle size range; high purity; and industrial-scale production, with a cost-effective approach. This nanometric powder preparation has very high purity, as the process does not add impurities or lead to the formation of reaction products, as is the case with state-of-the-art bottom-up (or synthesis) processes. The document does not disclose perovskites or a process for obtaining perovskites.

[0022] International patent application PCT / BR2021 / 050337, entitled Tantalum Nanoparticle Preparation, Process for Obtaining and Using, was filed by the Hercílio Randon Institute. This document describes a A tantalum nanoparticle preparation obtained by a comminution or top-down approach. This preparation simultaneously includes the following technical characteristics: particles entirely in the nanometer particle size range; high purity; and industrial-scale production, with a cost-effective approach for economic viability. This nanometric powder preparation has very high purity, as the process does not add impurities or lead to the formation of reaction products, as is the case with state-of-the-art bottom-up (or synthesis) processes. The document does not disclose perovskites or a process for obtaining perovskites.

[0023] From what can be inferred from the literature researched, no documents were found anticipating or suggesting the teachings of the present invention. Summary of the Invention

[0024] The present invention solves several prior art problems and provides perovskite nanoparticles with a defined particle size profile. Additionally, new processes for obtaining perovskite are highly desired, as it is a high-value compound and can be used for a variety of applications. The inventive concept common to the objects of the invention is to use a precursor (containing the central cation of the subsequently obtained perovskite) comminuted to the nanometer range to enable its reaction with another precursor containing another cation and the anion necessary for the formation of the perovskite structure. This solution, in addition to enabling the production of perovskites with unique and advantageous physical properties, provides simpler and more scalable production processes.

[0025] It is an object of the invention to provide perovskite nanoparticles. In one embodiment, the perovskite nanoparticles. In one embodiment, the perovskites comprise titanium, niobium, tantalum, and / or tin. In one embodiment, the perovskite nanoparticles of the invention are selected from CaTiOa, AgNbOa, AgTaOa, KNbOa, NaNbOa, CsSnCh, or combinations thereof.

[0026] Another object of the invention is a composition comprising the perovskite nanoparticles of the invention and other non-perovskite nanoparticles, submicron particles, or combinations thereof.

[0027] Another object of the invention is to provide a process for preparing perovskite nanoparticles. In one embodiment, the process of the invention comprises a step of prior, concomitant, or sequential comminution of one or more cation sources, optionally followed by one or more heating steps. In one embodiment, the process of the invention is conducted in a liquid medium.

[0028] These and other objects of the invention will be readily appreciated by those skilled in the art and will be described in detail below. Brief Description of the Figures

[0029] The following figures are presented:

[0030] Figure 1 shows the XRD data of TiO2 samples after different grinding times in a high-energy mill TiO2 - AR (as received, 0h), TiO2- 1h, TiO2- 6h and TiO2- 12h. On the x-axis the angles 20 are shown and on the y-axis the intensity (ua).

[0031] Figure 2 shows the crystallinity (A) and crystallite size (B) according to milling time for the same samples described in Figure 1. On the x-axis is shown the milling time in hours, on the y-axis to the left is % crystallinity, and on the y-axis to the right is the crystallite size in nm.

[0032] Figure 3 shows the particle size distribution of calcite limestone particles before grinding, presenting the volume density (%) on the y-axis by the size classes (pm) on the x-axis.

[0033] Figure 4 shows the particle size distribution of the agricultural input formulation particles after grinding, presenting the volume density (%) on the y-axis by the size classes (pm) on the x-axis.

[0034] Figure 5 shows an x-ray diffraction spectrum under Cu-Ka1 radiation for a sample of the product of the process of the present invention, illustrating the presence of perovskite. The x-axis illustrates the 20 (theta) angle and the y-axis illustrates the photon count.

[0035] Figure 6 shows Powder X-ray Diffraction patterns for different syntheses of AgNbOs using nanometric Nb20s. The x-axis shows the angles 20 and the y-axis shows the intensity (in 10 3 counts).

[0036] Figure 7 shows a Powder X-ray Diffraction pattern for the synthesis of AgNbOa with submicron Nb20s. The x-axis shows the angles 20 and the y-axis shows the intensity (in 10 3 counts).

[0037] Figure 8 shows a Powder X-ray Diffraction pattern for the synthesis of AgTaOa with nanosized Ta2Os. The x-axis shows the angles 20 and the y-axis shows the intensity (in 10 3 counts).

[0038] Figure 9 shows a powder X-ray diffraction pattern for the synthesis of AgTaOa with micrometer Ta20s. The x-axis shows the angles 20 and the y-axis shows the intensity (in 10 3 counts).

[0039] Figure 10 shows the XRD data of the nanosized niobium precursor (Nb206-12h), with 26% crystallinity (Nb20s phase 1, monoclinic CIF #29). The x-axis shows the 20 angles and the y-axis shows the intensity (ua).

[0040] Figure 1 1 shows the XRD data of the submicron niobium precursor (Nb20s-SM), with 81% crystallinity (Nb20s phase 1, monoclinic CIF #29). On the x-axis the angles 20 are shown and on the y-axis the intensity (ua).

[0041] Figure 12 shows the XRD data of the potassium precursor (K2CO3) with 53.9% crystallinity (phase 1: 99.1% K2CO3(H2O)IS monoclinic CIF #0222257; phase 2: 0.9% K2CO3 monoclinic CIF #66943). The x-axis shows the angles 20 and the y-axis shows the intensity (ua).

[0042] Figure 13 shows the XRD data of the sodium precursor (Na2CO3) with 75.6% crystallinity (phase 1: 68.4% monoclinic Na2COs CIF #6031 1 ; phase 2: 31.6% monoclinic Na2CO3.H2O CIF #34886). The x-axis shows the angles 20 and the y-axis shows the intensity (ua).

[0043] Figure 14 shows the XRD data of the K2CO3 mixture with niobium submicron (Nb20s-SM), with a crystallinity of 25.4% (Nb20s phase 1, monoclinic CIF #29). The angles 20 are shown on the x-axis and the intensity (ua) on the y-axis.

[0044] Figure 15 shows the XRD data of the K2CO3 mixture with nanosized niobium (Nb20s-12h), with a crystallinity of 10.9% (Nb20s phase 1, monoclinic CIF #29). The angles 20 are shown on the x-axis and the intensity (ua) on the y-axis.

[0045] Figure 16 shows the XRD data of the Na2COa mixture with submicron niobium (Nb20s-SM), with crystallinity of 60.7% (phase 1: 59.4% Nb20s, monoclinic CIF #29; phase 2: 40.6% Na2COa monoclinic CIF #6031 1 ). On the x-axis the angles 20 are shown and on the y-axis the intensity (ua).

[0046] Figure 17 shows the XRD data of the mixture Na2COa with nanosized niobium (Nb20s-12h), with crystallinity of 27% (phase 1: 98.2% Nb20s, monoclinic CIF #29; phase 2: 1.8% Na2COa monoclinic CIF #6031 1 ). On the x-axis are shown the angles 20 and on the y-axis the intensity (ua).

[0047] Figure 18 shows the XRD data of the KNbOa-SM sample obtained after the first calcination, with a crystallinity of 56.4% (KNbOs phase 1, orthorhombic CIF #39869). The x-axis shows the angles 20 and the y-axis shows the intensity (ua).

[0048] Figure 19 shows the XRD data of the KNbO3-12h sample obtained after the first calcination, with a crystallinity of 56.2% (phase 1 KNbOs, orthorhombic CIF #39869). The x-axis shows the angles 20 and the y-axis shows the intensity (ua).

[0049] Figure 20 shows the XRD data of the NaNbOs-SM sample obtained after the first calcination, with a crystallinity of 56.4% (phase 1 NaNbOs, orthorhombic CIF #264747). The angles 20 are presented on the x-axis and the intensity (ua) on the y-axis.

[0050] Figure 21 shows the XRD data of the NaNbO3-12h sample obtained after the first calcination, with a crystallinity of 56.5% (phase 1 NaNbOs, orthorhombic CIF #264747). The x-axis shows the 20-angle and the δ-axis shows the ya intensity (ua).

[0051] Figure 22 shows the XRD data of the KNbOa-SM sample obtained after the second calcination, with a crystallinity of 55.2% (KNbOa phase 1, orthorhombic CIF #39869). The x-axis shows the angles 20 and the y-axis shows the intensity (ua).

[0052] Figure 23 shows the XRD data of the KNbO3-12h sample obtained after the second calcination, with a crystallinity of 57.3% (phase 1 KNbOa, orthorhombic CIF #39869). The x-axis shows the angles 20 and the y-axis shows the intensity (ua).

[0053] Figure 24 shows the XRD data of the NaNbOa-SM sample obtained after the second calcination, with a crystallinity of 54.7% (phase 1 NaNbOa, orthorhombic CIF #264747). The x-axis shows the angles 20 and the y-axis shows the intensity (ua).

[0054] Figure 25 shows the XRD data of the NaNbO3-12h sample obtained after the second calcination, with a crystallinity of 57% (phase 1 NaNbOa, orthorhombic CIF #264747). The x-axis shows the angles 20 and the y-axis shows the intensity (ua).

[0055] Figure 26 shows a TEM image of the KNbO3-12h sample obtained after the first calcination cycle.

[0056] Figure 27 shows a representation of the crystal structures of CsSnCh. In (a) the cubic lattice of perovskite is represented and in (b) the monoclinic lattice is represented, with the cesium (Cs) atoms represented in larger diameter, the tin (Sn) atoms represented in intermediate size and the chlorine (Cl) atoms represented in smaller size.

[0057] Figure 28 shows photos of the materials obtained in each of the different steps (E.1 to E.6) of the process described in example 5 (paragraphs

[0184] the

[0189] ).

[0058] Figure 29 shows a diffractogram of the CsSnCh material of 1 â generation. On the x-axis the angles 20 are shown and on the y-axis the intensity (ua).

[0059] Figure 30 shows a diffractogram of the cubic phase of the perovskite CsSnCh (ICSD #678994). On the x-axis the angles are shown 20 and on the y-axis the intensity (ua).

[0060] Figure 31 shows a diffractogram of the monoclinic phase CsSnCh (ICSD #14199). On the x-axis the angles 20 are shown and on the y-axis the intensity (ua).

[0061] Figure 32 shows a TEM image of CsSnCh nanoparticles (left) and the particle size distribution (in nm) (right).

[0062] Figure 33 shows an SEM image (left) and chemical composition map of the compound CsSnCh from 1 â generation (right).

[0063] Figure 34 shows a Tauc-plot for determining the bandgap value of the CsSnCh material of 1 âgeneration (approximately 3 days after synthesis). The x-axis shows the energy data in eV and the y-axis shows the bandgap values ​​in (Ea) 2 .

[0064] Figure 35 shows an enlargement of the main region of the diffractograms of the produced material. In decreasing order of representation (from the top) is the elapsed time - 1 h (hour), 1w (week), 1 to 8m (months) for the sample of 1 â generation, followed by the two diffraction patterns for each phase.

[0065] Figure 36 shows the behavior of the mass percentages of the cubic (blue) and monoclinic (orange) perovskite phase.

[0066] Figure 37 shows an enlargement of the main region of the material after the reversibility process. In A, the material data of 1 âgeneration 8 months after acquisition; in B the data from the 2nd generation material are shown. The x-axis shows the angles 20 and the y-axis shows the intensity (ua).

[0067] Figure 38 shows from the top (A): diffraction profile of the starting material with only the monoclinic phase; below (B) the diffraction profile of the sample after the reversibility process; and in the last profiles below the patterns of the cubic and monoclinic phases, respectively.

[0068] Figure 39 shows a comparison between the percentages of cubic and monoclinic phase in the material of 1 â generation (A) and 2nd generation (B).

[0069] Figure 40 shows the X-ray diffraction results of a sample containing CaCOa, TiO2, and CaTiOa. In 1) the peaks corresponding to CaCOa are shown, in 2) the TiO2 peaks, and in 3) the CaTiOa peaks. On the x-axis the angles 20 ( s ) and on the y-axis intensity (cps).

[0070] Figure 41 shows a correlation between the X-ray diffraction peaks of the sample in Figure 40, showing the diffraction profile of the sample compared to specific known profiles. The x-axis illustrates the angle 20 (theta) and the y-axis illustrates the photon count.

[0071] Figure 42 shows the X-ray diffraction results of a sample containing CaCOa, TiO2, CaTiOa. In 1) the peaks corresponding to CaCOa are shown. In 2) the TiO2 peaks and in 3) the CaTiOa peaks. On the x-axis the angles (°) are presented and on the y-axis the intensity (cps).

[0072] Figure 43 shows a correlation between the X-ray diffraction peaks of the sample in Figure 42, showing the diffraction profile of the sample compared to specific known profiles. The x-axis illustrates the angle 20 (theta) and the y-axis illustrates the photon count. Detailed Description of the Invention

[0073] The present invention solves several problems in the prior art and provides perovskite nanoparticles with a defined particle size profile. Additionally, new processes for producing perovskite are highly desired, as it is a high-value compound and can be used for a variety of applications.

[0074] In a first aspect, the present invention provides a perovskite nanoparticle with a defined particle size profile. In one embodiment, the perovskite nanoparticles comprise titanium, niobium, tantalum, and / or tin. In one embodiment, the perovskite nanoparticles of the invention are selected from CaTiOa, AgNbOa, AgTaOa, KNbOa, NaNbOa, CsSnCh, or combinations thereof.

[0075] In a second aspect, the present invention provides a composition comprising perovskite nanoparticles, other non-perovskite nanoparticles, submicron particles, or combinations thereof.

[0076] In a third aspect, the present invention provides a process for preparing perovskite nanoparticles. In one embodiment, the process of the invention comprises a step of prior, concomitant, or sequential comminution of one or more cation sources, optionally followed by one or more heating steps. In one embodiment, the process of the invention is conducted in a liquid medium.

[0077] The invention is also defined by the following clauses:

[0078] 1) Perovskite nanoparticle having an equivalent diameter between 10 and 500 nanometers (nm).

[0079] 2) Perovskite nanoparticle according to clause 1 in which the particle size distribution profile of said nanoparticles is: d10 from 10 to 10nm; d50 from 50 to 150nm; d90 from 100 to 250nm.

[0080] 3) Perovskite nanoparticle according to clause 1 selected from CaTiOa, AgNbOa, AgTaOa, KNbOa, NaNbOa, CsSnCh or combinations thereof.

[0081] 4) Composition comprising perovskite nanoparticles of equivalent diameter between 10 and 1000 nanometers (nm) and an excipient or other non-perovskite nanoparticles, submicron particles, or combinations thereof.

[0082] 5) Composition according to clause 4 in which the said excipient is selected from: water, aqueous solutions, organic solutions, emulsions, suspensions or combinations thereof.

[0083] 6) Process for obtaining perovskite nanoparticles comprising at least one step of prior, concomitant or sequential comminution of one or more cation sources, optionally followed by one or more heating steps.

[0084] 7) Process according to clause 6 in which the source of the central cation of the (subsequent) perovskite structure is selected from titanium dioxide, niobium pentoxide, tantalum pentoxide, tin chloride, or combinations thereof.

[0085] 8) Process according to clause 6 or 7 in which the comminution step is carried out in a liquid medium.

[0086] Examples

[0087] The examples shown here are intended only to exemplify some of the various ways of carrying out the invention, without, however, limiting its scope.

[0088] Example 1 - Obtaining CaTIOs perovskite nanoparticles

[0089] In this embodiment, CaTiOa perovskite nanoparticles were obtained from CaCOa and TiOa precursors without requiring a calcination step, which is surprising in the art. Consequently, the energy required to obtain the perovskite nanoparticles was entirely supplied in the high-energy comminution process, in contrast to the prior art.

[0090] TiO2 is a ceramic material with exceptional chemical, physical, optical, and electronic properties. These properties make TiO2 a versatile material, with a wide range of technological applications, such as catalysis systems, charge transport layers in photovoltaic devices, pigments, sunscreens, and other applications. TiO2 can exist in three main crystalline phases: anatase, rutile (both tetragonal), and brookite (orthorhombic). The formation of these phases is influenced by several factors, including temperature, heat treatment time, specific surface area, impurity levels, and interactions with other components. The anatase and brookite phases are thermodynamically stable at room temperature, while the rutile phase is more stable at higher temperatures. At higher heat treatment temperatures, the anatase-rutile or anatase-brookite-rutile phase transformation can be observed.In the present invention, at least part of the TiO2 is amorphous. or amortized by the previous or concomitant comminution stage.

[0091] To analyze the effects of comminution on the crystal structure, degree of amortization, and particle size profile, samples of particulate TiO2, including TiO2 - AR (as received, micrometer-sized), and batches of nanoparticle suspensions comminuted in a high-energy mill with the following grinding times: 1 h, 3 h, 6 h, 9 h, and 12 h, were analyzed. To obtain particulate material, each of the nanoparticle suspensions was oven-dried for 24 h at 35°C. After drying the suspensions, each batch of material was named according to the conditions indicated above.

[0092] The following results describe the samples TiO2 - AR, TiO2 - 1 h, TiO2 - 6 h, and TiO2 - 12 h. According to the diffractograms presented in Figure 1 and based on the crystallinity estimate presented in Figure 2, the TiO2 - AR sample revealed the presence of the rutile and anatase phases, which are two of the three most common polymorphs of TiO2, totaling 71% crystallinity. Additional analyses performed through Rietveld refinement allowed an estimate that 81% of the crystalline phase is associated with the anatase phase, while 19% is related to the rutile phase. The final composition can be estimated as 29% amorphous phase, 57.5% anatase, and 13.5% rutile. After one hour of grinding, the anatase phase disappeared, and the crystalline fraction of the ground samples exhibited only the rutile phase. The TiO2 samples did not show a significant reduction in crystallinity compared to the AR sample.Although this structural stability was observed with the sample preparation method used, there was a tendency for crystallite size to decrease as milling time increased, decreasing from 23 nm (in the AR sample) to approximately 4.5 nm after 12 hours of milling.

[0093] The degree of comminution also impacts the band gap (Eg) value of TiO2, as shown in Table 1.

[0094] The optical properties of the TiO2 samples were evaluated by means of reflectance measurements obtained in the UV-Vis range, with the AR sample presented low reflectivity for wavelengths below 350 nm and high reflectivity for wavelengths above 400 nm, indicating the presence of an energy band gap of approximately 3.53 eV, characteristic of the anatase phase. Similarly, samples subjected to different milling times also exhibited high reflectivity. However, a shift toward longer wavelengths (red-shift) was observed in these samples, resulting in high reflectivity for wavelengths above 420 nm. These data are related to oscillations in the optical band gap values, which are smaller compared to the AR sample (Table 1). This change may be associated with variations in the percentage of phases or the presence of structural defects and impurities that affect crystallite size and can reduce the crystallinity of the samples, as observed in the structural characterization.

[0095] Table 1: Band gap energy (Eg) values ​​of TiO2 samples after different comminution times.

[0096] Table 2: Summary of physical properties of TiO2 nanoparticles after different comminution times.

[0097] Once these characterizations were made, calcitic limestone particles (CaCOa or calcite) were obtained, which were characterized for granulometric distribution as can be seen in figure 3, which shows the volume density (%) on the y-axis by the size classes (pm) on the x-axis.

[0098] The results of the analysis of CaCOa particles before the grinding process can be seen in Table 3.

[0099] Table 3: Calcitic limestone particles before the grinding process.

[0100] These particles were milled in a high-energy mill for several 1-hour cycles. The results of the sequential grinding of limestone nanoparticles after the grinding process can be seen in Table 4.

[0101] Table 4: particle size of limestone nanoparticles after the grinding process.

[0102] When comparing the specific surface area of ​​the input limestone and the specific surface area of ​​the limestone in the form of nanoparticles, it is found that there was an increase of greater than 14,000% in the specific surface area.

[0103] Then, a batch of 1.125 kg TiO2 particles with particle size distribution of D90 1.320 pm, D50 0.6098 pm and D10 0.153 pm was fed to the aforementioned high-energy mill containing the limestone nanoparticles, in water, and containing 3.65 kJ / L 0.2-0.4 mm zeta beads. The grinding parameters were, Tmax 60 eC, solids content 18.36%. Operating the high-energy mill for several cycles, from 1 to 8 cycles of 1 hour each, at a pressure of 1.1 to 1.2 bar, pump speed of 90 min-1, flow rate of 51 kg slurry / h, agitator speed of 3700 min 1 , inlet material temperature varying between 21.3 and 37.1 S C and outlet material temperature varying between 22.4 and 49.2 S In the respective cycles, the gross energy was 2.4 kW and the grinding energy was 1.8 to 14.4 kWh in the respective cycles. The particle size distribution profile obtained is described in Table 3.

[0104] Table 5 - particle size distribution profile of particles obtained after multiple comminution cycles under the conditions indicated above.

[0105] For 0 cooling, the parameters were 7.3 and 1 1.4 inlet temperature SC, respectively in the grinding chamber, mechanical seal, circulation tank and chiller, each of these stages with a flow rate of 1000 liters per hour of cooling water, totaling 4000 liters per hour.

[0106] Figure 4 shows the particle size distribution of the particles present obtained. The results of the particle analysis after the grinding process can be seen in Table 6.

[0107] Table 6: particles obtained after the grinding process.

[0108] Example 2 - Characterization of CaTiOs perovskites

[0109] Figure 5 shows the X-ray diffraction results for a sample of the product obtained in example 1. According to the diffraction profile, the pattern coinciding with the CaTiOa perovskite produced from the grinding of limestone (CaCOa) together with titanium dioxide TiOa, in the proportion of 10:1 (CaCO3:TiO2) is observed.

[0110] Figure 5 shows a correlation between the X-ray diffraction peaks, showing the diffraction profile of the sample in comparison with specific profiles already known, such as entry 96-901-6707, corresponding to the calcite (CaCOa) profile, entry 96-153-0151 corresponding to the Titanium dioxide (TiO2) profile and entry 96-900-6174 of Calcium Titanate (CaTiOa) which is an example of perovskite.

[0111] Table 7: X-ray diffraction results

[0112] The formation of CaTiOa perovskite nanoparticles confirmed by analysis in the X-ray diffractometer is surprising, not only due to the starting reagents, but also due to the way it was produced, i.e., mechanosynthesis by high-energy milling without the need for a calcination step.

[0113] Example 3 - Ag(Nb,Ta)Os perovskite nanoparticles and their production process

[0114] This example discloses nanoparticles of silver-niobium and / or silver-tantalum perovskites (Ag(Nb,Ta)O3) and a process for obtaining them. The inventive concept common to the other objects of the invention, of using a precursor comminuted to the nanometer range, was applied in the present example to obtain the aforementioned perovskites, which have peculiar and advantageous physical properties, solving some technical problems.

[0115] In this example, Niobium(V) and Tantalum(V) oxide particles were used as precursor materials, which are the subject of co-pending patent applications PCT / BR2021 / 050346 and PCT / BR2022 / 050337, respectively. These precursors have different physical properties, which impact or may impact the final products obtained from these materials.

[0116] Niobium pentoxide nanoparticle preparations were made from grinding in a high-energy mill, as described in PCT / BR2021 / 050346, obtaining the following particle size distribution profiles (particle size in nm). AR material (as received, without grinding): 1400nm; Grinding for 1 h: D90=147, D50=82, D10=43; grinding for 6h: D90=98, D50=56, D10=32; grinding for 12h: D90=138, D50=49, D10=7.

[0117] Tantalum pentoxide nanoparticle preparations were made from grinding in a high-energy mill, as described in PCT / BR2022 / 050337, obtaining the following particle size distribution profiles (particle size in nm). AR material (as received, without grinding): 500nm; Grinding for 1 h: D90=450, D50=245, D10=83; grinding for 6h: D90=375, D50=148, D10=52; grinding for 11 h: D90=263, D50=113, D10=39.

[0118] Unlike known prior art processes, which involve sol-gel synthesis, such as the Pechini process, the present invention involves the use of precursors comminuted to the nanometer range and subsequent contact with a solid-phase silver salt in the presence of a solvent, followed by heat treatment. The contact step of the precursors containing silver, niobium, and / or tantalum is performed mechanically, as in a mechanosynthesis process. The heat treatment step is performed at a temperature above 600°C. e C, with gradual heating ramps up to the aforementioned temperature. The heat treatment time at the final temperature depends on several factors, including the amount of material and the heat exchange efficiency of the heat exchanger used, such as a muffle furnace. Times of 0.5 to 10 hours are suitable for the process of the invention.

[0119] In one embodiment, the following precursors were used: Silver Carbonate (Ag2CO3) (99.5% purity) and nanosized Niobium(V) Oxide (Nb20s).

[0120] In one embodiment, said niobium pentoxide comprises a degree of amortization of at least 15%. In one embodiment, said niobium pentoxide comprises a degree of amortization of at least 20% to 75%. Surprising and particular results are obtained when niobium pentoxide nanoparticles have a high degree of amortization.

[0121] In this embodiment, 1.0 g of Ag2CO3 (Silver Carbonate) powder was placed in an agate mortar along with 0.9639 g of Nb2Os (Niobium Pentoxide) in nanometric powders, in addition to 1.0 ml of isopropanol. These powdered materials were manually macerated until completely homogenized and dried in an oven at 80°C overnight. The mixture was then taken to a muffle furnace for heat treatment for 2 h at 850°C, with a heating ramp of 5°C min -1 . The material thus obtained, after cooling to room temperature, was again manually macerated in an agate mortar for homogenization purposes, and then stored. This material was analyzed by Powder X-Ray Diffraction (PXRD) analysis.

[0122] PXRD data were acquired using the equipment and settings described in Table 6. After acquisition, Rietveld refinement was performed using GSAS-II, an acronym for General Structure Analysis System (TOBY; VON DREELE, 2013). The main purpose of Rietveld refinement is to use a least-squares method to simulate an X-ray (or neutron) diffraction pattern that fits the measured pattern, varying parameters related to the sample contribution, preparation, or the equipment itself. For Rietveld refinement, a Crystallographic Information File (CIF) obtained from the online library ICSD (Inorganic Crystal Structure Database) is required.

[0123] Table 8. Parameters of the X-ray diffractometer used in the analysis of PXRD.

[0124] In addition to the physical parameters of each sample, Rietveld refinement provides values ​​that indicate the proximity between the calculated points and the observed points. These parameters include Rwp, presented as wR in GSAS-II, and X 2 RED. Good values ​​for Rwp and X 2 RED are, respectively, below 10% and close to 1. However, these parameters should be interpreted with caution, since, as highlighted by TOBY (2006), there are good published articles in which the value of X 2 RED is much greater than 1. Therefore, understanding the model and the reasons for a poor statistical fit is much more important than obtaining good values ​​of Rwp and X 2 RED.

[0125] To facilitate understanding, the samples were named following a pattern S_E_g_Q, where: S: Solvent Used, I for isopropanol and A for acetone; E: Oxide Used, Nb for Nb20s and Ta for Ta2Os; g: Granulometry of the oxide used, pm or nm; Q: Amount of solvent used A, 10, 15 or 20. A for Arbitrary amount, 10 for 1.0 ml, 15 for 1.5 mL and 20 for 2.0 mL.

[0126] AgNbOs (SILVER NIOBATE) perovskites

[0127] To determine the influence of the solvent and its quantity on the synthesis, three different experiments were carried out, at different times and using nanometric Nb20s, the results being presented in the diffraction patterns in figure 6, which shows the Powder X-ray Diffraction patterns for different syntheses of AgNbOs using Nb20s.

[0128] Figure 6 shows that the diffraction patterns of the three samples do not show significant differences in peak intensity and shape, indicating that the phases formed in all syntheses were the same, with little variation in their relative amounts. This evidence is confirmed by Rietveld refinement, where, as shown in Table 9, three phases were identified: a majority phase of AgNbOs, in the desired perovskite form, and two minority phases of Ag and orthorhombic Nb20s, corresponding to the precursors. Furthermore, the lattice parameters obtained for the majority phase, presented in Table 9, show no differences. significant to each other.

[0129] Table 9 - Fraction of phase formed (by mass) for each sample and agreement parameters of the Rietveld refinement.

[0130] Table 10. Lattice parameters for the majority phase of AgNbOs of space group Pbcm (#57).

[0131] In the synthesis using micrometric Nb2O5, 1.0 ml of isopropanol was used as solvent. The obtained X-ray diffraction pattern is shown in Figure 7. As before, Rietveld refinement identified three phases: 99.3% AgNbOs in the perovskite phase and space group Pbcm (#57), indicating an orthorhombic structure; 0.3% metallic silver; and 0.5% orthorhombic NbsOs. The refinement agreement parameters were a wR of 5.997% and an X 2 RED of 9.65, indicating a good statistical fit between the experimental data and the simulated / expected curve.

[0132] Furthermore, the network parameters for the majority phase were refined, obtaining values ​​of 5.552 93(16) Â, 5.605 17(14) Â and 15.662(4) Â for a, b and c, respectively.

[0133] AgTaOs (SILVER TANTALATE) perovskites

[0134] In this embodiment, the following precursors were used: Silver Carbonate (Ag2CO3) (99.5% purity) and nanosized Tantalum(V) Oxide (Ta2Os). In this embodiment, 1.0 g of Ag2CO3 (Silver Carbonate) powder was placed in an agate mortar along with 1.6025 g of Ta2Os (Tantalum Pentoxide) in nanometric powder, in addition to 1.5 ml of isopropanol. These powdered materials were manually macerated until completely homogenized and dried in an oven at 80°C overnight. The mixture was then taken to a muffle furnace for heat treatment for 2 h at 850°C, with a heating ramp of 5°C min' 1. The material thus obtained, after cooling to room temperature, was again manually macerated in an agate mortar for homogenization and then stored. This material was analyzed by Powder X-Ray Diffraction (PXRD). AgTaOs perovskites were obtained in the same manner as described for AgNbOs. For comparison purposes, nanometric and micrometric Ta2Os were used, and the X-ray diffraction patterns of the obtained powders are shown in Figures 8 and 9, respectively.

[0135] Comparing Figures 8 and 9, we can see that in Figure 8, referring to the synthesis with nanometric Ta2Os, the same peaks observed in Figure 9, which refers to the synthesis with micrometric Ta2Os, are present, but less intense. Furthermore, another set of peaks, although present in Figure 8, appears with greater intensity in Figure 9. This indicates the presence of a secondary phase in greater quantity in the synthesis with nanometric Ta2Os.

[0136] In one embodiment, the tantalum pentoxide has a degree of amortization of at least 18%. In one embodiment, said tantalum pentoxide has a degree of amortization of at least 20% to 75%. Surprising and particular results are obtained when the tantalum pentoxide nanoparticles have a high degree of amortization.

[0137] Rietveld refinement confirmed that the phases formed in both cases are metallic silver, AgTaOs in the form of rhombohedral perovskite, and Ag2Ta40n, another double oxide of silver and tantalum, also called silver tantalate, but with a different crystal structure. desired perovskite. To clarify, in this work, when we refer to silver tantalate, we are referring to the perovskite phase with molecular formula AgTaOa.

[0138] The results obtained for the phase percentage and network parameters are presented in Tables 1 and 12.

[0139] Table 1 1. Fraction of phase formed (by mass) for each sample and agreement parameters of the Rietveld refinement.

[0140] Table 12. Lattice parameters for the majority phase AgTaOa of space group R-3c (#167), obtained with respect to the rhombohedral axis.

[0141] Table 12 shows very similar lattice parameters for both syntheses, that is, for both nanometric and micrometric Ta2Os. The difference in phase concentrations for each synthesis can be attributed to suboptimal synthesis conditions that do not take into account how reactant particle sizes affect reaction rates and compound stability with respect to temperature.

[0142] Example 4 - Nanoparticles of potassium (KNbO3) and sodium (NaNbO3) niobate perovskites and their production process

[0143] Potassium (KNbO3) and sodium (NaNbO3) niobates belong to the alkali niobate family, along with lithium niobate (LiNbO3). These oxides, mainly KNbO3 and NaNbO3, are structurally classified as Perovskites, generally in their orthorhombic form, have sparked growing interest in advanced materials research due to their piezoelectric and pyroelectric properties. These materials have shown promise for applications in sensors and actuators, where the ability to convert electrical or mechanical stimuli into detectable signals is required. They are highlighted in the literature as alternatives to lead zirconate titanate (PZT). The need to replace PZT is due to its high lead content, which leads to environmental and health problems.

[0144] This example describes nanoparticles of these niobates and a solid-phase production process that allows control over the phases and crystal structure. Niobium pentoxide (Nb206) nanoparticles obtained by the process described in co-pending patent application PCT / BR2021 / 050346 are used as one of the precursors. These nanoparticles are distinguished by a high percentage of amorphous phase, in contrast to nanoparticles obtained by other known methods or techniques. The amorphous nature of these nanoparticles can confer unique properties to the niobates synthesized from them, resulting in materials with distinct characteristics compared to niobates produced with micrometric and crystalline niobium precursors.

[0145] In this embodiment, the solid-phase reaction process involves simple mixing of the precursors and subsequent heat treatment, which can be repeated depending on the desired conditions. Alternatively, as described in Example 1, the reaction can occur in a high-energy mill, eliminating the need for subsequent heat treatment.

[0146] In the experiments described below, the precursors were initially evaluated for moisture content. The following particulate materials were used as precursors: submicron Nb20s (Nb20s-SM), nanometric Nb20s (Nb20s-12h), K2CO3 (99.0%), and Na2CO3 (99.5%). Approximately 10 g of each of them were individually inserted into porcelain crucibles and subjected to a temperature of 200°C for 20 hours. The sample mass was measured at the beginning (mi) and end (mf) of this process, in order to determine the percentage of moisture by mass (% mass) of the precursors. Table 13 presents the values ​​obtained. Based on these data, in the subsequent precursor mixing step, a correction factor was applied when calculating the mass of the non-heat-treated precursors to obtain the desired stoichiometry.

[0147] Table 13 - Initial and final mass values ​​(mi and mf) of the samples after heat treatment at 200°C for 20 hours, to determine the percentage of moisture by mass of the precursors (% mass)

[0148] The precursors were mixed to enable the reactions described in equations 1 and 2, which describe the synthesis reactions of potassium and sodium niobates, respectively: K2CO3 + Nb2O52KNbO3+ CO2 (1 ) Na2CO3+ Nb2O52NaNbO3+ CO2 (2)

[0149] To obtain approximately 10 g of K2CO3 and Na2CO3 from niobium pentoxide at submicron and nanometric scale, the samples of Nb2O6-SM and Nb2O5-12 were mixed with K2CO3 or K2CO3 respectively, in stoichiometric proportions, taking into account the purity and moisture content determined in the previous step.

[0150] In this embodiment, the mixtures were mixed in a porcelain mortar and pestle for 10 minutes, using 10 ml of isopropyl alcohol as the dispersion medium. The mixture was then heated to 80°C for 20 minutes in an oven to promote alcohol evaporation.

[0151] The particulate material, after the drying process, was subjected to uniaxial compaction with a force of 9 tons, forming a tablet. Compaction took place in a cylindrical die with a diameter of 13 mm. The resulting pressure, expressed in SI units, was calculated to be approximately 660 MPa.

[0152] The compacted samples (pellets) were placed in porcelain crucibles and subjected to the initial calcination process in a muffle furnace. Heating was carried out at a rate of 5°C / min until reaching 775°C, maintaining this temperature for 5 hours. Cooling occurred within the furnace without specific time control, until reaching room temperature. The calcined samples were then placed in a porcelain mortar and subjected to a pestle pulverization step. After pulverization, the particulate material was mixed for 10 minutes using 10 ml of isopropyl alcohol as the dispersion medium, following the same methodology adopted in the precursor mixing step.

[0153] The mixture made with the product from the first calcination and isopropyl alcohol was subjected to a temperature of 80°C for 20 minutes in an oven to promote alcohol evaporation. The same parameters for drying the mixture, described above, were used.

[0154] After drying, the material was subjected to uniaxial compaction with a force of 9 tons, forming a pellet. Compaction took place in a cylindrical die with a diameter of 13 mm. The resulting pressure, expressed in SI units, was calculated to be approximately 660 MPa.

[0155] A second calcination was performed using the same parameters as the first calcination, in which the compacted samples were placed in porcelain crucibles and subjected to the second calcination process in a muffle furnace. Heating was carried out at a rate of 5°C / min until reaching 775°C, maintaining this temperature for 5 hours. Cooling occurred inside the furnace without specific time control, to room temperature.

[0156] Structural Characterization of the Precursors and Products Obtained

[0157] The structural characterization of both the precursors and mixtures, as well as the calcined materials obtained, was performed via X-ray diffraction (XRD). The analyses were performed on a Rigaku - MiniFlex 600 equipment in Bragg-Brentano geometry operating in the 6 - 2 6 mode, using Cu Ka radiation (À = 1.54059 nm). The Inorganic Crystal Structure Database (ICSD) provided the initial structural models that were used as input to the GSAS-I software to perform the Rietveld refinement. To analyze the degree of crystallinity, the method proposed by Hinrichsen was used. The diffractograms of the precursors can be seen in Figures 10-14.

[0158] The Nb2O5-12h sample (figure 10) presented a degree of crystallinity of 26.0% (or degree or % of amortization of 74%), with the crystalline fraction corresponding to the monoclinic structure (CIF #29). In contrast, the Nb2O5-SM sample (figure 11) presented a significantly higher crystallinity, reaching 81.0% of the same monoclinic structure (CIF #29), which suggests a greater structural ordering. Potassium carbonate (figure 12) presented a crystallinity of 53.9%, corresponding to the monoclinic structure of two distinct chemical phases: 99.1% of the K2CO3.H2OI.5 phase (CIF #022257) and 0.9% of the K2CO3 phase (CIF #66943). Sodium carbonate (figure 13) presented a crystallinity of 75.6%, which also corresponds to the monoclinic structure of two distinct chemical phases: 68.4% of the Na2COs phase (CIF #6031 1 ) and 31.6% of the Na2CO3.H2O phase (CIF #34886).

[0159] These results highlight differences in the degree of crystallinity between the precursors, especially those that are niobium sources, which may impact the properties of the niobates resulting from the synthesis processes and subsequent applications. Table 14 presents a summary of the information on crystallinity, crystal structure, and lattice parameters of the phases found through Rietveld refinement of the precursors used.

[0160] Table 14 - Crystallinity, crystal structure and lattice parameters of the precursors used.

[0161] The diffractograms of the mixtures of niobium precursors with potassium and sodium carbonates were analyzed. The crystallinity of the mixture of K2CO3 with Nb206-SM (Figure 14) was 25.4%. However, when Nb20s-12h was used in the mixture with K2CO3 (Figure 15), the crystallinity value was 10.9%. In the mixtures with potassium carbonate, only crystalline peaks corresponding to the Nb20s phase (CIF #29) could be identified. In the mixture of Na2CO3 with Nb206-SM (Figure 16), the crystallinity was 60.7%, while with Nb20s-12h (Figure 17), the crystallinity value decreased to 27%. In these cases, despite Due to the low crystallinity of the mixtures, peaks relating to the Na2COa phase (40.6% and 1.8%, respectively - CIF #60301 1 ) were identified in addition to the Nb20s peaks (CIF #29).

[0162] The data obtained show that all mixtures presented lower crystallinity values ​​than those observed in the precursors prior to this step. This may indicate that the mortar mixing process led to amortization of the crystalline structure of the precursors, especially potassium carbonate, since no peaks of this phase were identified in the corresponding diffractograms. Table 15 summarizes the information on crystallinity, crystal structure, and lattice parameters of the phases found in the mixtures.

[0163] Table 15: Crystallinity, crystal structure and lattice parameters of mixtures of niobium pentoxide (Nb2O5-SM and Nb20s-12h) with potassium and sodium carbonates (K2CO3 and Na2CO3).

[0164] Structural Characterization of Calcination Products The X-ray diffractograms of the calcined materials to form potassium and sodium niobates are presented in the figures below. To facilitate sample identification, potassium niobates obtained from the mixture of K2CO3 and Nb2O6-SM will be called KNbOa-SM and KNbOa-12h when Nb2O6-12h was the precursor. Using the same logic for sodium niobates, they will be called NaNbOs-SM and NaNbOa-12h when synthesized from Nb2O6-SM and Nb2O6-12h, respectively.

[0165] During the synthesis process, two successive calcinations were performed to form the phases of interest. In the first calcination, the formation of the desired phases was observed in both cases, that is, for both potassium niobate (Figures 18 and 19) and sodium niobate (Figures 20 and 21), regardless of the type of niobium precursor used. The diffractograms of the samples obtained after the second calcination (Figures 22-25) showed no significant differences in relation to those obtained from the samples resulting from the first, indicating that the formation of the KNbO3 and NaNbO3 phases was already complete after the first calcination cycle.

[0166] In all samples calcined once or twice, the identified crystal structure was orthorhombic perovskite (CIF #39869 for KNbOa-SM and KNbOa-12h, and CIF #264747 for NaNbOs-SM and NaNbOs-12h). The crystallinity of the samples was evaluated and the results showed a consistent value of approximately 56% for the products of the first calcination and between 54.7 and 57.3% for the products of the second calcination, suggesting that 0 degree of structural ordering was maintained between the different calcination cycles.

[0167] These data indicate that, despite repeated calcinations, the formation process and crystal quality of KNbO3 were stable and there was no significant improvement in crystallinity after the first cycle. The information on crystallinity, crystal structure and lattice parameters of the phases found after the first calcination cycle is presented in Table 16.

[0168] Table 16 - Crystallinity, crystal structure and lattice parameters of potassium and sodium niobates obtained in the first calcination.

[0169] Table 17 presents the information for the samples resulting from the second cycle.

[0170] Table 17 - Crystallinity, crystal structure and lattice parameters of potassium and sodium niobates obtained in the second calcination.

[0171] Microstructural Characterization The KNbO3-12h sample, obtained after the first calcination cycle, was analyzed in terms of microstructure via Transmission Electron Microscopy (TEM). The image obtained is shown in Figure 26, which shows the presence of particles with irregular morphology and others that are more elongated. The particles are around 250 nm in size, but smaller particles and agglomerates can also be observed.

[0172] The use of Nb20s nanoparticles produced by the topdown process described in co-pending patent application PCT / BR2021 / 050346 provides an innovative approach for the synthesis of alkali niobates. This route not only enriches the potential applications of niobates but also opens up new possibilities for the production of advanced materials. The results demonstrated the production of perovskite nanoparticles with the phases of interest, KNbO3 and NaNbO3, using both Nb2O5-SM and Nb2O5-12h as precursors. In the subsequent sintering steps, which are crucial for the processing of piezoelectric ceramics, microstructural characteristics such as morphology, grain size, and distribution can undergo substantial changes and significantly impact the electrical and piezoelectric properties of the materials, influencing their applications in sensors and actuators.

[0173] Example 5 - CsSnCh perovskite nanoparticles, CsSnCh nanoparticles in monoclinic phase, and their production process

[0174] This example reveals CsSnCh perovskite nanoparticles smaller than 80 nm, CsSnCh nanoparticles with a monoclinic structural phase. Perovskites have good properties for use in photovoltaic devices, featuring low bandgap values, efficient photon absorption in the UV-Vis region, and generation of charge carriers (excitons). Furthermore, this example also details a process for obtaining such materials, providing cost reduction, increased industrial scalability, and eliminating the need for uncontrolled environments.

[0175] In this example, CsSnCh nanoparticles with structure are provided mixed crystalline: cubic perovskite (bandgap value of approximately 1.5 eV) and monoclinic crystalline structure (bandgap value ~3.5 eV) (figure 27).

[0176] The process of this embodiment uses a mechanical mixing step of the precursors. Optionally, a chemical substitution step of elements to form other materials is also included. This approach optimizes the physical properties associated with different technological applications, in particular, the production of 3-cell photovoltaic cells. a generation.

[0177] In one embodiment, a powdered material is obtained from a process with the following steps:

[0178] - dissolve cesium chloride (CsCI) in a solvent, optionally using auxiliary grinding until complete dissolution, forming a solution;

[0179] - add tin chloride (SnCh) to the previous solution and homogenize, optionally using auxiliary grinding until complete dissolution; and

[0180] - heat the homogeneous mixture obtained at a temperature above 100°C until the reaction is complete.

[0181] Optionally, the process includes an additional grinding step after the heating referred to above and / or a second heat treatment under conditions similar to those of the first heat treatment.

[0182] A more specific embodiment of the process was carried out as follows, obtaining a powder material of CsSnCh nanoparticles with stability of 1 month:

[0183] The precursor materials cesium chloride - CsCl and stannous chloride - SnCh were weighed, for a molar ratio of CsCl and SnCh of 1 : 1 . The following steps are illustrated in conjunction with Figure 28.

[0184] Step 1 (E.1) Dissolving the CsCI in distilled and deionized water in a mortar, through manual grinding, in which the volume ratio of distilled and deionized water to the molar mass of the precursors is 1:5:5;

[0185] Step 2 (E.2) After complete dissolution, add SnCk to the previous solution;

[0186] Step 3 (E.3) Continue grinding manually in a mortar for 10 minutes, counting the time from the addition of SnCh to the solution in step 2;

[0187] Step 4 (E.4) Heat the mixture in a muffle furnace at a temperature of 150°C (423 K) for 30 minutes (oven previously at temperature);

[0188] Step 5 (E.5) Remove the mixture from the oven and continue grinding manually in a mortar for 10 minutes, without prior cooling of the powder;

[0189] Step 6 (E.6) Heat the mixture in a muffle furnace at a temperature of 150°C (423 K) for 30 minutes (oven previously at temperature);

[0190] The material obtained is then removed from the oven and placed in an Eppendorf tube.

[0191] The precursor materials used in the synthesis of CsSnCh perovskite nanoparticles have the following characteristics: cesium chloride is 99.9% pure, stannous chloride is 98% pure, and distilled and deionized water was obtained through a Milli-Q water purification system.

[0192] Example 6 - Identification of the crystal structure and size / morphology of nanoparticles

[0193] To identify the crystal structure and size / morphology of the nanoparticles produced according to example 5, the X-ray diffraction technique - XRD - was used. Two crystal structures were identified in the synthesis process of CsSnCh nanoparticles: cubic perovskite and monoclinic phase.

[0194] Figure 29 shows the diffractogram of the newly obtained material. The peaks related to the cubic perovskite phase CsSnCh (ICSD #678994) are marked (main peak (110) at approximately 22.4°). The unmarked peaks refer to the monoclinic phase CsSnCh (ICSD #14199) (main peak (400) at approximately 22.1°). No additional peaks related to element segregation, precursor materials, or spurious phases were identified.

[0195] Figures 30 and 31 represent the diffractograms of the cubic perovskite phase and monoclinic phase, respectively.

[0196] The material obtained was also analyzed by electron microscopy. transmission, observing that the material is composed of spherical nanoparticles (Figure 32). The particle size distribution calculation indicates that the produced material has a bimodal size distribution, with an average diameter of 15 nm (D10 of 9.6 nm and D90 of 22.6 nm).

[0197] For correct identification of the elements present in the material, the EDS (energy dispersive spectroscopy) technique was used using a scanning electron microscope (SEM) (figure 33). The atomic percentages of the elements present and identified are shown in table 18, confirming the expected stoichiometry for the CsSnCh phase.

[0198] Table 18: evaluation of the chemical composition of CsSnCh perovskite nanoparticles in two different clusters observed in figure 33.

[0199] The optical band gap value was determined using the UV-VIS optical absorbance technique. Absorbance spectra were obtained for subsequent determination of the band gap values ​​using the Tauc-plot method. Figure 34 illustrates the extrapolation of the linear region of the absorbance spectrum expressed in eV (2.85 eV). This value is higher than that reported in the literature for the cubic perovskite phase CsSnCh (approximately 1.5 eV) and lower than that reported for the monoclinic phase (approximately 3.5 eV).

[0200] Example 7 - Monitoring the temporal evolution of the crystal structure of CsSnCh nanoparticles

[0201] The structural stability of the compound produced according to Example 5 was monitored using XRD. The sample was placed in an Eppendorf tube and stored in a desiccator throughout the study. No moisture measurement technique was used inside the desiccator, nor was an inert atmosphere used.

[0202] Figure 35 shows, in decreasing order of representation (top to bottom), the diffraction profile of the sample measured 1 hour after obtaining the product, observing the presence of the main peaks corresponding to the cubic (26 wt.%) and monoclinic (74 wt.%) perovskite phases. Immediately below, the diffractogram for the sample 1 week after its acquisition, stored in a desiccator, is shown. The presence of the cubic phase (23.4 wt.%) is still noted, despite the small decrease in the percentage of this phase. After 1 month of the sample being stored in a desiccator, the amount of the cubic perovskite phase in the sample decreased to 10 wt.%. After 4 months of the sample being stored in a desiccator, peaks corresponding to the cubic perovskite phase were no longer observed, being only peaks corresponding to the monoclinic phase. After 8 months, there was no change in the diffraction profile of the material. No spurious phases were observed up to this point.

[0203] Figure 36 shows the variation in the percentages of the cubic perovskite phase and monoclinic phase.

[0204] Study of structural reversibility

[0205] To evaluate the structural reversibility of the nanoparticles after 8 months of synthesis, the following process was adopted:

[0206] A) Selection of material aged for 8 months presenting only the monoclinic phase;

[0207] B) Heat the material in a muffle furnace at a temperature of 150°C (423 K) for 30 minutes (oven previously at temperature);

[0208] C) Remove the material from the oven and continue grinding manually in a mortar for 10 minutes, without prior cooling of the powder;

[0209] D) Heat the material in a muffle furnace at a temperature of 150°C (423 K) for 30 minutes (oven previously at temperature);

[0210] E) Remove the material from the muffle furnace and place it in an Eppendorf tube.

[0211] The material thus obtained was analyzed by X-ray diffraction, and the reappearance of the cubic perovskite phase CsSnCI3 was observed. Figure 37 represents the enlargement of the diffractogram of this new material (in red), where the peak corresponding to the cubic phase is marked and the diffraction profile of the material after 8 months of synthesis is also shown (in black).

[0212] Figure 38 shows the diffractogram of the starting sample (top), followed by the diffraction profile of the sample after undergoing the reversibility test: the diffraction patterns of the cubic perovskite phase in blue and the monoclinic phase in orange. Through Rietveld refinement, the percentage of each phase was calculated, now obtaining 49 wt.% for the cubic perovskite phase CsSnCh, a value higher than that of sample 1. â generation (26 wt.%) (figure 39).

[0213] This example demonstrates a combination of CsSnCh perovskite nanoparticles in the cubic phase, associated with nanoparticles with a monoclinic structure. The stability of the CsSnCh perovskite was evaluated under ambient temperature, humidity, and light conditions, with the presence of the cubic phase observed up to 1 month after synthesis. The monoclinic phase was observed up to 8 months after the material was obtained (the test time limit), without the presence of other phases.

[0214] The material of this embodiment of the invention is particularly useful for applications in photovoltaic devices of 3 â generation, in which the cubic phase can be used as the active layer and the monoclinic phase as the transport layer in the device architecture.

[0215] Example 8 - Impact of the HO2 ratio on the production of CaTIOs perovskites

[0216] In one embodiment, conditions similar to those described in examples 1 and 2 were repeated, now using two different ratios of CaCCh and TiCh to verify the impact on the amount of CaTiC perovskite obtained (in this case, TiO2:CaCCh at 1:10 and at 3:8 by mass).

[0217] Figure 40 shows the X-ray diffraction results (LabX XRD-6100 diffractometer, Shimadzu) for a sample of the product obtained using a TiO2:CaCCh ratio of 1:10 by mass. In the example in question, ground 50g of TiO2 with 500g of CaCOs.

[0218] Phase identification is obtained by comparing the results with the diffractograms contained in the Crystallography Open Database (COD 2018) using Match !3 software. Phase percentage values ​​are for qualitative purposes. The final result is obtained from the X-ray diffractogram with the identified phases, with data processing in Origin 2019 Professional software. According to the diffraction profile, a pattern coinciding with CaTiOs perovskite produced from grinding limestone (CaCOa) together with titanium dioxide TiO2 is observed.

[0219] Figure 41 shows a correlation between the X-ray diffraction peaks, showing the diffraction profile of the sample in comparison with specific profiles already known, such as entry 96-900-0966, corresponding to the profile of calcite (CaCOa), entry 96-153-0151 corresponding to the profile of titanium dioxide (TiO2) and entry 96-900-2802 of calcium titanate (CaTiOa) which is an example of perovskite. The relative proportion of each is shown in Table 19.

[0220] Table 19: X-ray diffraction results

[0221] Figure 42 shows the X-ray diffraction results (LabX XRD-6100 diffractometer, Shimadzu) for a sample of the product obtained using a TiO2:CaCO3 ratio of 3:8 by mass. In the example in question, 150 g of TiO2 were ground with 400 g of CaCOa.

[0222] Phase identification is obtained by comparing the results with the diffractograms contained in the Crystallography Open Database (COD 2018) using Match !3 software. Percentage values ​​of the phases are for qualitative purposes. The final result is obtained from the diffractogram. X-rays with the phases identified, with data processing in the Origin 2019 Professional software. According to the diffraction profile, the pattern coincides with the perovskite CaTiOa produced from the grinding of limestone (CaCOa) together with titanium dioxide TiO2.

[0223] Figure 43 shows a correlation between the X-ray diffraction peaks, showing the diffraction profile of the sample in comparison with specific profiles already known, such as entry 96-900-0966, corresponding to the profile of calcite (CaCOa), entry 96-153-0151 corresponding to the profile of titanium dioxide (TiO2) and entry 96-900-2802 of calcium titanate (CaTiOa) which is an example of perovskite. The relative proportion of each is shown in Table 20.

[0224] Table 20: X-ray diffraction results

[0225] The formation of CaTiOa perovskite nanoparticles, demonstrated by X-ray diffractometer analysis under various conditions (examples 1-3 and 8), is surprising, not only because of the starting reagents but also because of the method of production—i.e., mechanosynthesis by high-energy milling without the need for a calcination step. Furthermore, it shows that varying the proportion of TiO2 used has a significant impact on the perovskite content obtained.

[0226] Those skilled in the art will appreciate the knowledge presented herein and will be able to reproduce the invention in the presented embodiments and in other variants and alternatives, covered by the scope of the following claims.

Claims

Claims 1. Perovskite nanoparticle characterized by having an equivalent diameter between 10 and 500 nanometers (nm).

2. Perovskite nanoparticle according to claim 1, characterized in that it is selected from CaTiOa, AgNbOa, AgTaOa, KNbOa, NaNbOa, CsSnCh, or combinations thereof.

3. Perovskite nanoparticle according to claim 1 or 2, characterized in that the particle size distribution profile of said nanoparticles is: d10 from 10 to 100nm; d50 from 50 to 150m; d90 from 100 to 250nm.

4. Perovskite nanoparticle according to claim 1 or 2, characterized in that it has an equivalent diameter below 100nm.

5. Composition comprising perovskite nanoparticles characterized by the fact that it comprises perovskites of equivalent diameter between 10 and 500 nanometers (nm) and an excipient, other non-perovskite nanoparticles, submicrometric particles, or combinations thereof 6. Composition according to claim 5, characterized in that said excipient is selected from: water, aqueous solutions, organic solutions, emulsions, suspensions or combinations thereof.

7. Process for obtaining perovskite nanoparticles characterized by comprising at least one step of prior, concomitant or sequential comminution of one or more cation sources, optionally followed by one or more heating steps.

8. Process according to claim 7, characterized in that the source of the central cation of perovskite structure is selected from titanium dioxide, niobium pentoxide, tantalum pentoxide, tin chloride or combinations thereof.

9. Process according to claim 7 or 8, characterized in that the comminution step is carried out in a liquid medium.

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