Tuning the phase composition and particle characteristics of partially stabilized yttria and ceria co-doped zirconia nanocrystals via a sol–gel process with sodium chloride as an additive

The aim of the current work was to prepare partially stabilized yttria and ceria co-doped zirconia nanocrystals (PS-YCZ-NCs) with a controlled phase state and morphology. PS-YCZ-NCs were prepared via the sol–gel method based on the direct reaction of metal nitrates with ethylene glycol in the presence of sodium chloride. The effect of the NaCl dosage on the particle morphology and phase state was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The addition of NaCl in the sol–gel process was determined to improve the formation of tetragonal zirconia at calcination temperatures of less than 600   °C and to induce a phase transformation from tetragonal to monoclinic at temperatures above 600   °C. Therefore, PS-YCZ-NCs with different tetragonal and monoclinic phase ratios can be prepared by changing the dosage of NaCl and the calcination temperature. In addition, the optimal synthesis conditions for PS-YCZ-NCs with pseudo-sphere morphology and a particle size ranging from 15 to 30   nm have been determined.