Crystallization process of (ZrO ₂ ) _0.9 (Sc ₂ O ₃ ) _0.1 nanoparticles synthesized by a sol‒gel method for SOFC electrolyte

Abstract The zirconia (ZrO 2 )‐based electrolyte with fine grain size obtained from nanoscale powders is of crucial importance for high‐performance intermediate‐temperature solid oxide fuel cells (SOFC). Although the sol‒gel method for obtaining the nanoparticles of ZrO 2 ‐based electrolyte has been extensively studied, the detailed crystallization process of this method has not been systematically investigated. Here, we prepared scandia‐doped zirconia (10ScSZ) nanoparticles by a sol‒gel method employing nitrate as the precursor, ethylene glycol as the solvent, and acetic acid as the catalyst. The chemical reactions between metal nitrates and ethylene glycol are described by the theoretical calculation of enthalpy of formation, which is firstly reported for the sol‒gel preparation of ZrO 2 ‐based nanoparticles. The decomposition of the residual solvents, organics and carbon as well as the generation of CO 2 , ZrO 2 · x H 2 O, and Zr‒O during the calcination from 200°C to 800°C are carefully determined through Thermogravimetric and differential scanning calorimetry and Fourier transform infrared characterizations. X‐ray diffraction (XRD) refinements with the analyses of crystallinity and grain growth activation energy confirm the crystallized temperature of 750°C with the average grain size of 13.91 nm. Notably, the grain growth activation energy was determined to be as low as 0.28 eV, significantly lower than values typically reported for solid‐state or co‐precipitation methods, highlighting the advantage of the sol–gel route. The detailed lattice features of 10ScSZ nanoparticles by transmission electron microscopy measurements are consistent with those obtained from XRD refinements. Finally, the spherical and well‐dispersed 10ScSZ nanoparticles synthesized by our sol‒gel method are confirmed by scanning electron microscopy observations, with the average particle size of 86.43 nm at the crystallized temperature of 750°C.