Insights in the phase stability and performance enhancement mechanism of La2(Zr1-xCex)2O7 with reduced thermal conductivity

Abstract

This study proposes a molten salt method-based process for the synthesis of Ce-doped pyrochlore-phase La2(Zr1-xCex)2O7, aiming to develop materials with excellent comprehensive properties, particularly for thermal barrier coatings. The results indicate that by employing the proposed method, the Ce doping level (x) can reach 0.4 for pyrochlore-phase La2(Zr1-xCex)2O7. However, high-temperature testing reveals a reduction in the phase stability of the samples. As the value of x increases, the temperature at which the samples exhibit the fluorite phase gradually decreases. DFT calculations on the crystal formation energy of La2(Zr1-xCex)2O7 confirm that an elevated level of Ce doping leads to an increase in crystal formation energy, indicating a decrease in phase stability. Subsequent thermal conductivity tests on La2(Zr1-xCex)2O7, along with theoretical thermal conductivity fitting, reveal a significantly greater fitting error for Ce doping at the Zr site compared to La site doping with other rare earth elements. Finally, XPS and EPR tests conducted on the samples doped at the Zr and La sites confirm that oxygen vacancies induced by high Ce doping levels play a crucial role in reducting the thermal conductivity of La2(Zr1-xCex)2O7.