Glass-like thermal conductivity and other thermoelectric properties of lead ruthenate pyrochlore

Electrical-(sigma) and for the first time, thermal conductivity (kappa) and Seebeck coefficients of lead ruthenate (Pb2Ru2O6.5) pyrochlore were measured. For the metal-like Pb2Ru2O6.5 electrical conductivity decreased with increasing temperature (25 degrees C to 300 degrees C). The Seebeck coefficients showed a maximum at 150 degrees C, which is explained in the text. Pb2Ru2O6.5 is a p-type conductor. Thermal conductivity increased with increasing temperature. Intrinsic defects (vacancies and a stereo-chemically active 6s(2) electron lonepair of Pb) caused glass-like behavior, i.e. low and increasing thermal conductivity. Electrical- and electronic thermal conductivity varied with T-1/2 and T-1/2, respectively, implying impurity scattering. The lattice contribution kappa(L) decreased with T-1 with increasing temperature, suggesting that 3-phonon (Umklapp) scattering lowered kappa(L), which supporting impurity scattering. (C) 2020 Elsevier B.V. All rights reserved.