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Rahman T, Martin NP, Jenkins JK, Elzein R, Fast DB, Addou R, Herman GS, Nyman M. Nb 2O 5, LiNbO 3, and (Na, K)NbO 3 Thin Films from High-Concentration Aqueous Nb-Polyoxometalates. Inorg Chem 2022; 61:3586-3597. [PMID: 35148102 DOI: 10.1021/acs.inorgchem.1c03638] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Synthesizing functional materials from water contributes to a sustainable energy future. On the atomic level, water drives complex metal hydrolysis/condensation/speciation, acid-base, ion pairing, and solvation reactions that ultimately direct material assembly pathways. Here, we demonstrate the importance of Nb-polyoxometalate (Nb-POM) speciation in enabling deposition of Nb2O5, LiNbO3, and (Na, K)NbO3 (KNN) from high-concentration solutions, up to 2.5 M Nb for Nb2O5 and ∼1 M Nb for LiNbO3 and KNN. Deposition of KNN from 1 M Nb concentration represents a potentially important advancment in lead-free piezoelectrics, an application that requires thick films. Solution characterization via small-angle X-ray scattering and Raman spectroscopy described the speciation for all precursor solutions as the [HxNb24O72](x-24) POM, as did total pair distribution function analyses of X-ray scattering of amorphous gels prior to conversion to oxides. The tendency of the Nb24-POM to form extended networks without crystallization leads to conformal and well-adhered films. The films were characterized by X-ray diffraction, atomic force microscopy, scanning electron microscopy, ellipsometry, and X-ray photoelectron spectroscopy. As a strategy to convert aqueous deposition solutions from {Nb10}-POMs to {Nb24}-POMs, we devised a general procedure to produce doped Nb2O5 thin films including Ca, Ag, and Cu doping.
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Affiliation(s)
- Tasnim Rahman
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Nicolas P Martin
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Jessica K Jenkins
- School of Chemical, Biological, and Environmental Engineering, 116 Johnson Hall, 105 SW 26th St. Corvallis, Oregon 97331, United States
| | - Radwan Elzein
- School of Chemical, Biological, and Environmental Engineering, 116 Johnson Hall, 105 SW 26th St. Corvallis, Oregon 97331, United States
| | - Dylan B Fast
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Rafik Addou
- School of Chemical, Biological, and Environmental Engineering, 116 Johnson Hall, 105 SW 26th St. Corvallis, Oregon 97331, United States
| | - Gregory S Herman
- School of Chemical, Biological, and Environmental Engineering, 116 Johnson Hall, 105 SW 26th St. Corvallis, Oregon 97331, United States
| | - May Nyman
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
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