Synthesis and morphology of nanodisperse cerium oxide modified by gadolinium oxide
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ORIGINAL PAPER: SOL-GEL AND HYBRID MATERIALS FOR CATALYTIC, PHOTOELECTROCHEMICAL AND SENSOR APPLICATIONS
Synthesis and morphology of nanodisperse cerium oxide modified by gadolinium oxide S. I. Niftaliev1 I. V. Kuznetsova ●
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Yu. N. Vlasov2 L. V. Lygina1 V. Yu. Tuneekov1 C. S. Gadzhiyeva3 ●
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Received: 7 April 2020 / Accepted: 3 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Stable sols were obtained in the CeO2–Gd2O3 system using the stabilizing additive Hamulsion RUGLAP. The formation of phases in the CeO2–Gd2O3 system with Gd2O3 content of up to 0.07 mol occurs already at the stage of synthesis by the Krekke method. The electrokinetic potential is positive for all samples. A sharp increase in the electrokinetic potential (with Gd2O3 content of over 0.07 mol) is connected with a change in the nature of potential-determining ions of the electrical double layer and the diffusion of excess Gd3+ ions from the solid core of a colloidal particle into its surface. The absorption spectra were analyzed to determine the band gap of colloidal sol particles. With an increase in the cerium oxide content in the sol with the stabilizer (CeO2–Stab), the value of the band gap energy for direct and indirect transitions increases. An additional absorption band appears in the sol spectra based on the CeO2–Gd2O3–Stab system in the 265 ÷ 275 nm wavelength range, the value of the band gap energy for direct transitions 4.46–4.62 eV, presumably, corresponds to solid solutions of Ce1−yGdyO2 type. The suggested stabilizer, which contains silicon oxide, guar gum, and gelatin, is neutral with respect to positively charged sol particles. It is adsorbed on the surface of dispersed particles and isolates them from each other, without causing coagulation of the sol. When gadolinium oxide (0.01 mol) is added to the CeO2 sol, an average particle size decreases to 13 ± 2.8 nm. The nanoparticles are weakly agglomerated, if Gd2O3 content in the sol is up to 0.05 mol; with increasing gadolinium oxide content the size of agglomerates increases. The processes of sol dehydration proceed in the range of 65–90 °C. The activation energy of these processes is in the range of 51–54 kJ/mol. The values of activation energies indicate the presence of moisture in a bound state in the structure of the stabilizing additive Hamulsion RUGLAP. Graphical Abstract
Keywords CeO2–Gd2O3 sols Electrokinetic potential Band gap width Optical properties Stabilizer Agglomeration of nanoparticles ●
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* I. V. Kuznetsova [email protected] 1
Department of Inorganic Chemistry and Chemical Technology, Voronezh State University of Engineering Technologies, Pr. Revolyutsii, 19, Voronezh 394036, Russia
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Department of Physics, Heat Engineering and Power Engineering, Voronezh State University of Engineering Technologies, Pr. Revolyutsii, 19, Voronezh 394036, Russia
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Department of Histology, Cytology and Embryology, I.M. Sechenov Moscow State Medical University, Ul. Bolshaya Pirogo
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