LATTICE THERMAL-CONDUCTIVITY OF YBA2CU3O7-DELTA

We report a systematic study of the ab-plane thermal conductivity (kappa) on single crystal and liquid-phase processed (LPP) specimens of YBa2Cu3O7-delta (delta less-than-or-equal-to 0.16) in the temperature range 10 K less-than-or-equal-to T less-than-or-equal-to 300 K. From measurements of electrical conductivity on the same specimens and application of the Wiedemann-Franz law we estimate the relative contributions to the heat conduction from the carriers and the lattice. The normal-state phonon scattering mechanisms are quantified by calculations which employ the conventional theory of lattice heat conduction by longitudinal acoustic phonons. Differences in the magnitude and temperature dependence of kappa for the LPP and crystal specimens are accounted for by differences in the relative weight of phonon-defect, phonon-carrier, and phonon-phonon scattering. For all specimens phonon-defect scattering predominates throughout most of the temperature range.