Comparison of the microstructure and oxygen storage capacity modification of Ce0.67Zr0.33O2 from CaO and MgO doping

Doping effect of CaO and MgO on the microstructure and dynamic oxygen storage capacity (OSC) of Ce0.67Zr0.33O2 was compared. XRD, Raman spectra and HRTEM observation confirmed that after MgO and CaO doping, more oxygen ion vacancies and lattice defect in the fluorite lattice were produced due to charge compensation and radius effect. On the other hand, improved phase thermal stability was obtained from doping. Results of dynamic OSC measurements showed that MgO and CaO doping enhance the dynamic OSC of Ce0.67Zr0.33O2. But after redox treatment difference was found between the two dopants. The improved OSC of CaO doping was due to the proper ionic radius and effective modification of microstructure. The decreased OSC of MgO doped Ce0.67Zr0.33O2 after redox treatment was due to the small solubility of Mg2+ in ceria lattice and collapse of the defective structure of Mg–Ce–Zr–O system.