Thermophysical performances of (Sm1-xLux)3TaO7 (x = 0, 0.1, 0.3 and 0.5) ceramics

Abstract

To optimize thermophysical performances, Sm3TaO7 was doped with Lu3+ and pressureless sintered at 1600 ?C. It was shown that Sm3+ is partly substituted by Lu3+ cations and the (Sm1-xLux)3TaO7 ceramics with a single pyrochlore structure are obtained.With increasing x value from 0 to 0.5, the band gap increases gradually from 4.677 to 4.880 eV. Owing to the enhanced phonon scattering caused by Lu3+ doping, the thermal conductivities at 800 ?C of the prepared samples are in the range of 0.95-1.44W?K?1?m?1. It was also confirmed that the phase transition is restrained effectively by substituting Sm3+ with Lu3+. Due to the reduction of crystal lattice energy and average electro-negativity difference, the thermal expansion coefficient (TEC) is heightened with increasing Lu content. TEC achieves the highest value (10.45 ? 10?6 K?1 at 1200 ?C) at the equal molar ratio between Sm3+ and Lu3+ cations (i.e. x = 0.5), which is much higher than those of 7YSZ and Sm2Zr2O7 ceramics.