A complete computational route to predict reduction of thermal conductivities of complex oxide ceramics by doping: A case study of La2Zr2O7

Abstract

Rare-earth (RE) zirconate pyrochlores, of low thermal conductivity and high temperature stability, are widely considered as a candidate material group for thermal barrier coatings (TBCs). Doping of a RE zirconate pyrochlore has been shown to be one possible method towards additional reduction in the thermal conductivity. Focusing on lanthanum zirconate (La2Zr2O7) as a representative RE zirconate pyrochlore, we systematically investigated the effect of various doping elements, Gd, Y, Yb, In, Sc, Ce and Hf, on the thermal conductivity. A complete computational route, based on first-principles calculations, to predict the reduction of thermal conductivity by doping, has been developed. Employing first-principles calculations combined with thermodynamic modeling, the defects resulted from doping are explicitly clarified, with their concentrations determined considering the chemical environment. The phonon-defect scattering is then evaluated and the resultant reduction of thermal conductivity is determined from single-mode relaxation-time approximation. Good agreement has been achieved between our model predictions and available experimental data. The present study established a complete computational route, based on first-principles calculations, to predict the reduction of thermal conductivity by doping, not only for RE zirconate pyrochlores, but also for other complex oxide ceramics.