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BR-102019025561-B1 - COMPOSITION FOR CERAMIC THIN FILMS, PROCESS FOR OBTAINING RESIN FOR CERAMIC THIN FILMS ON GLASS/FTO SUBSTRATE AND CERAMIC THIN FILMS ON GLASS/FTO SUBSTRATE OBTAINED

BR102019025561B1BR 102019025561 B1BR102019025561 B1BR 102019025561B1BR-102019025561-B1

Abstract

COMPOSITION FOR CERAMIC THIN FILMS, PROCESS FOR OBTAINING RESIN FOR CERAMIC THIN FILMS ON GLASS/FTOE SUBSTRATES, AND CERAMIC THIN FILMS ON GLASS/FTOE SUBSTRATES OBTAINED. A composition for ceramic thin films is described, comprising a precursor resin based on transition metal salts and alkaline earth salts or complex salts of lanthanum or derivatives and transition metal salts, said resin being added to the triblock copolymer OPE20OPP70OPE20, wherein the proportion of said triblock copolymer to each milliliter of precursor resin is at least 5 mg at room temperature. The process for obtaining thin-film resin involves heating and stirring the precursor resin and triblock polymer composition, adjusting the viscosities to around 10 cP, allowing the solution to stand for a few hours to release bubbles formed in the liquid phase, and recovering and storing the resin product. The resulting resin is used to obtain oxide films by deposition on a glass/FTO substrate followed by calcination. The oxide films are used in electrochemical, photovoltaic, and sensor processes.

Inventors

  • JEFERSON ALMEIDA DIAS
  • MARCOS ANTONIO SANTANA ANDRADE JUNIOR
  • MÁRCIO RAYMUNDO MORELLI
  • ROSARIO ELIDA SUMAN BRETAS
  • HUGO LEANDRO SOUSA DOS SANTOS
  • LUCIA HELENA MASCARO SALES
  • TANIA REGINA GIRALDI

Assignees

  • UNIVERSIDADE FEDERAL DE ALFENAS - UNIFAL-MG
  • FUNDAÇÃO UNIVERSIDADE FEDERAL DE SÃO CARLOS

Dates

Publication Date
20260317
Application Date
20191203

Claims (18)

  1. 1. Composition for thin ceramic films, comprising: a) A precursor resin based on an aqueous solution of one to three metallic salts, selected from transition metal salts in molar proportions from 1 to 99% among said salts for resins with two or three metals, or alkaline earth metal salts also in molar proportions from 1 to 99% among said salts for resins with two or three metals, according to the stoichiometry of the desired oxide after calcination, the metallic salts being selected from soluble salts of copper, zinc, titanium, nickel, cobalt, vanadium, manganese, iron, lanthanum, strontium, barium, niobium, zirconium, cerium and tungsten or pseudoperovskite precursors of the LaMO3 series, where M is one or two cations of transition metals of the third period, lanthanum or its variations by other rare earths or alkaline earth metals, in which said metallic salts are complexed with citric acid and polyhydroxylated alcohol; said composition being further characterized by comprising: b) Triblock copolymer polyethylene oxide (OPE)-polypropylene oxide (OPP) and polyethylene oxide (OPE) of minimum formula OPE20OPP70OPE20, and wherein the proportion of said triblock copolymer to each milliliter of the precursor resin of a) is at least 5 mg, at room temperature.
  2. 2. Composition according to claim 1, characterized in that the pseudoperovskite precursor salts of component a) comprise lanthanum salts and cobalt and iron salts.
  3. 3. Composition according to claim 1, characterized in that the proportion of triblock copolymer for each milliliter of precursor resin is a) between 5 and 50 mg of said triblock copolymer OPE20OPP70OPE20 per mL of precursor resin.
  4. 4. Composition according to claim 3, characterized in that the proportion of OPE20OPP70OPE20 triblock copolymer for each milliliter of precursor resin is a) between 5 and 40 mg of said OPE20OPP70OPE20 triblock copolymer per mL of precursor resin.
  5. 5. Process for obtaining resin for thin ceramic films on glass/FTO substrate based on the composition according to claim 1, wherein the preparation of the precursor solutions of said resin comprises separately dissolving each of the precursor metal cation salts in deionized water in a molar ratio of 1 to 99% relative to the first metal cation salt, complexing with an organic acid in excess relative to said cations, the complexation being carried out under heating, obtaining citrates of the metal cations, and combining said citrates of metal cations, followed by polymerization with polyhydroxylated alcohol under polymerization conditions, in excess relative to the acid used; eliminating the water by evaporation to obtain the precursor resin; adjusting the viscosity to around 10 cP; and recovering the precursor resin to be added to the triblock copolymer, said process being characterized by comprising the insertion, in a proportion of at least 5 mg of OPE20OPP70OPE20 triblock copolymer per mL of said precursor resin, of said OPE20OPP70OPE20 triblock copolymer into said precursor resin by heating and stirring said copolymer, viscosity adjustment around 10 cP and recovery and storage of said resin for ceramic thin films on glass/FTO substrate.
  6. 6. Process according to claim 5, characterized in that the metal cation salts for the preparation of the precursor solutions are selected from transition metal and alkaline earth metal salts selected from soluble salts of copper, zinc, titanium, nickel, cobalt, vanadium, manganese, iron, lanthanum, strontium, barium, niobium, zirconium, cerium and tungsten or pseudoperovskite precursors of the LaMO3 series, where M is one or more transition metal cations of the third period, lanthanum or its variations or alkaline earth metals.
  7. 7. Process according to claim 6, characterized in that the pseudoperovskite precursor salts comprise lanthanum salts and cobalt and iron salts.
  8. 8. Process according to claim 6, characterized in that the metal cation salts for preparing the precursor solutions comprise salts with partial substitution of the pseudoperovskite transition metal cations by rare earths or alkaline earth metals selected from Sr2+ and Ca2+.
  9. 9. Process according to claim 5, characterized in that the proportion of OPE20OPP70OPE20 triblock copolymer for each milliliter of precursor resin is between 5 and 50 mg of said triblock copolymer per mL of precursor resin.
  10. 10. Process according to claim 9, characterized in that the proportion of OPE20OPP70OPE20 triblock copolymer for each milliliter of said precursor resin is between 5 and 40 mg of said triblock copolymer per mL of precursor resin.
  11. 11. Thin ceramic films on glass/FTO substrates obtained from the composition according to claim 1, said films being characterized by comprising oxides with only one cation of transition metals selected from CuO, Cu2O, ZnO, TiO2, NiO, Co3O4, V2O5, MnO, MnO2, Fe2O3, Fe3O4, La2O3, BaO, SrO, Nb2O5, ZrO2, CeO2, WO3 and doped variants.
  12. 12. Thin ceramic films on glass/FTO substrates obtained from the composition according to claim 1, characterized by comprising complex oxides with two cations selected from the pseudoperovskites of the LaMO3 series, where M is one or more cations of third-period transition metals, lanthanum or its variations.
  13. 13. Ceramic thin films according to claim 12, characterized in that said complex oxides comprise LaFeO3 and LaCoO3.
  14. 14. Ceramic thin films on glass/FTO substrates obtained from the composition according to claim 1, characterized by comprising complex oxides with three cations with partial substitution of the pseudoperovskite transition metal cations by rare earths or alkaline earth metals selected from Sr2+ and Ca2+.
  15. 15. Ceramic thin films according to claim 14, characterized in that said complex oxides comprise Sr0.3La0.7CoO3 and LaFe0.5Co0.5O3.
  16. 16. Ceramic thin films according to claims 11, 12, 13, 14 and 15, characterized in that their use is in electrochemical processes, selected from electrocatalysts for Oxygen and Hydrogen Release Reactions.
  17. 17. Ceramic thin films according to claims 11, 12, 13, 14 and 15, characterized by their use in photovoltaic devices.
  18. 18. Ceramic thin films according to claims 11, 12, 13, 14 and 15, characterized in that their use is in sensors, selected from sensors for hydrocarbons, nitrogen oxides, molecular hydrogen and carbon monoxide.

Description

FIELD OF THE INVENTION [0001] The present invention pertains to the field of compositions for thin ceramic films on glass substrates coated with FTO (fluorine-doped tin oxide). The composition comprises polymeric precursors known in the field of ceramic films and powders, and the triblock copolymer Pluronic P123. The insertion of the copolymer into the precursor solution of the ceramic films allows for the production of oxide films with improved homogeneity, reproducibility, and a low number of defects. FUNDAMENTALS OF THE INVENTION [0002] The production of ceramic thin films by solution deposition depends on the proper preparation of precursors containing the metal cations. The conventional polymeric precursor method is based on U.S. patent 3,330,697, in which metal cations are complexed by an organic acid and polymerized with a polyhydroxylated alcohol. Citric acid and ethylene glycol are the reagents normally used. Obtaining a polyester allows cationic dispersion at the molecular level and the obtaining of complex ceramic phases after calcination, being a well-established method for powder production and extensible for thin film deposition. This method is promising for obtaining complex oxides such as LaFeO3 and LaCoO3 because it avoids cation segregation and the formation of undesirable oxide phases. Modifications to Pechini's patent, already established in the literature, that define the conventional polymeric precursor method include the preparation of metal complexes individually for oxides with more than one cation; variations in the ratio between organic acid and metallic cations and in the ratios between organic acid and polyhydroxylated alcohol. [0003] Lanthanum ferrite and cobaltite are structures related to perovskites, with rhombohedral (LaCoO3) and orthorhombic (LaFeO3) crystal systems. These pseudoperovskites have demonstrated enormous potential in electrochemical and photoelectrochemical processes due to their high catalytic action for water decomposition. There are reports of their potential for photovoltaic applications. For these processes, it is desirable to grow these oxides on the conductive substrate in the form of thin films; to achieve low resistance to charge transport and avoid current loss. The quality of the film will be important to ensure reproducibility; avoid current loss in defects and ensure that the entire area of the conductive substrate is covered with the functional layer. [0004] The growth of these materials in the form of thin films by various methods is presented in the literature, but almost no report employs the FTO substrate. The vast majority of published works use glass, SrTiO3, LaAlO3 and variants of the latter by doping or cationic substitution. These substrates do not allow the use of the films produced for photoelectrochemical and photovoltaic processes due to low conductivity (glass) or the lack of high transparency in the visible spectrum (other substrates). [0005] The production of LaFeO3 films on FTO is reported in a single work, see Nassar, I. M. et al., Facile preparation of n-type LaFeO3 perovskite film for efficient photoelectrochemical water splitting., Chem. Sel., v. 3, p. 968-972, 2018, doi:10.1002/slct.201702997, which obtained films by immersing the substrate in a solution obtained by the sol-gel technique. Thin films (submicrometer or nanometer thickness, less than 1 μm) could not be obtained, since their thickness was determined on a micrometer scale, which decisively impacts the resistance to charge transport. There are no reports of LaCoO3 films being directly grown on FTO by any technique. [0006] The production of LaFeO3 films by the conventional polymeric precursor method has already been reported on a platinum substrate, see Ranieri, M. G. A. et al., Electrical behavior of chemically grown lanthanum ferrite thin films., Ceram. Int., v. 42, p. 2234-2240, 2016.doi:10.1016/j.ceramint.2015.10.016, while that of LaCoO3 has already been carried out on a silicon substrate, see Liu, H. et al., Epitaxial growth of strain-induced ferromagnetic LaCoO3 thin films by simple sol-gel technique, Nano., v. 11, p. 1650030-1650039, 2016. doi:10.1142/s1793292016500302, and in stainless steel, see Popa, M.; Calderón-Moreno, J. M., Lanthanum cobaltite thin films on stainless steel., Thin Solid Films, v. 517, p. 1530-1533, 2009. doi:10.1016/j.tsf.2008.08.187, which confirms the potential of this method for generating the ceramic phases of interest in the form of films. However, there are no reports of the production of these materials on the substrate of interest (FTO) using the aforementioned preparation method, even without the insertion of the amphiphilic triblock copolymer Pluronic P123 into the precursor resins, which constitutes the present invention. [0007] The type of substrate impacts the physical and chemical characteristics of the surface and consequently the interface with the precursor used in the solution deposition process, and the quality of t