B. Xiao

Mechanical properties of rare earth stannate pyrochlores

The RE2Sn2O7 series compounds (REu2009=u2009La, Nb, Sm, Gd, Er, Yb) with a pyrochlore structure are prepared by co-precipitation method. The bulk, shear, Young’s moduli, B/G, and Poisson’s ratios are calculated using density functional theory and also measured by ultrasonic resonance method. The theoretical values of lattice constants and mechanical moduli are smaller than experimental results. The electronic structures of RE2Sn2O7 are analogous to RE2Zr2O7. La2Sn2O7 exhibits stronger ionic bonds than others. The covalent interactions are slightly enhanced in the heavy rare earth stannate pyrochlores. The Vickers harnesses of RE2Sn2O7 are measured experimentally, which are smaller than theoretical predictions.

LiRE2Si3 (RE = Nd, Sm, and Eu) as potential photovoltaic materials

The equilibrium lattice properties, electronic and optical properties of LiRE2Si3 (RE = Nd, Sm, and Eu) compounds have been investigated. LiRE2Si3 compounds show strong absorption in the entire range of solar spectrum. The conversion efficiencies are 52.4, 70.2, and 63.9% for LiNd2Si3, LiSm2Si3, and LiEu2Si3, respectively. The efficiencies of LiSm2Si3 and LiEu2Si3 are about twice of GaAs (34%), and they are three times higher than Si (20%). The presence of 4f shell and the unoccupied π* states enhance the electron transportation invoked by photon adsorption. The LiRE2Si3 compounds are the excellent candidates of photovoltaic materials so far.