Understanding the thermodynamic properties of 20% CeO2 stabilized ZrO2 coatings with atomistic modeling and simulations

Abstract

To understand the improved stability and reduced thermal conductivity of 20% CeO2 stabilized ZrO2 coatings compared to pure zirconia, different Ce doped ZrO2 systems are modeled. The Ce insertion in ZrO2 lattice elongates the lattice parameters and the elongation is proportional to the Ce doping concentration. Moreover, the cell volume linearly increases with the Ce doping level. X-ray diffraction analysis confirmed the Zr0.84Ce0.16O2 phase, describing the substitutional Ce doped at Zr sites. Ce doping modified the electronic band structure of ZrO2 without creating any isolated states in the band gap. The Ce4Zr12O32 modeled system with Ce doping concentration of 8.33% provided the stable phonon density of states curves compared to the pure and doped systems. Ce doping reduced the thermal conductivity of ZrO2. Increasing Ce doping level further reduced the thermal conductivity reaching the maximum reduction at 8.33% doping concentration. Further increase in the Ce level has no effective reduction in the thermal conductivity values. The reduced thermal conductivity is attributed to the enhanced phonon scattering due to the substitutional Ce4+ dopant and optimal doping concentration. The experimental observation could be satisfactorily explained by the calculations results.