Variations in the thermal conductivity of La2Zr2O7 and Gd2Zr2O7 with variable La/Gd concentrations.

The phonon density of states and thermal conductivity of La 2 Zr 2 O 7 and Gd 2 Zr 2 O 7 are tuned to get materials with improved thermal insulation properties. In this study, pure and doped models of La 2 Zr 2 O 7 and Gd 2 Zr 2 O 7 were developed and simulated based on density functional theory. Doping Gd at La sites in La 2 Zr 2 O 7 was observed to modify the band structure. The density of states analysis showed that Gd d states were introduced in the band gap. With increasing Gd concentration, the band gap of La 2 Zr 2 O 7 was initially populated and then, a clear band gap was observed at high Gd/La ratios. Smoothness in the phonon density of states curves was observed with an increase in Gd concentration. However, irregular phonon density of states curves was obtained for the Gd 2 Zr 2 O 7 system. Among the simulated models, the La 16-5 Gd 5 Zr 16 O 56 system with Gd/La ratio of 0.454 provided minimum thermal conductivity. [ABSTRACT FROM AUTHOR]