Synthesis and morphology of nanodisperse cerium oxide modified by gadolinium oxide

Stable sols were obtained in the CeO 2 –Gd 2 O 3 system using the stabilizing additive Hamulsion RUGLAP. The formation of phases in the CeO 2 –Gd 2 O 3 system with Gd 2 O 3 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 Gd 2 O 3 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 Gd 3+ 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 (CeO 2 –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 CeO 2 –Gd 2 O 3 –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 Ce 1− y Gd y O 2 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 CeO 2 sol, an average particle size decreases to 13 ± 2.8 nm. The nanoparticles are weakly agglomerated, if Gd 2 O 3 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. Highlights Stable sols in the CeО 2 –Gd 2 О 3 system were obtained by hydrolysis using a stabilizing additive containing proteins and carbohydrates. The electrokinetic potential has a positive value for all sols and decreases with increasing gadolinium oxide content. Compared to a crystalline CeО 2 in the CeО 2 –Gd 2 О 3 system, the band gap, unit cell parameters, and particle size change. Water in sols is held in the structure of the stabilizing additive.