Abstract Scope |
Low thermal conductivity is promoted by lattice defects and strong anharmonicity. Anharmonicity can be created through several strategies, e.g., introducing oxygen vacancies, lone pair electrons, resonant bonding, and rattling of atoms within the crystal lattice. Lattice defects increase phonon scattering which reduces thermal conductivity.
This investigation explores new defect lead ruthenate pyrochlores. The crystal structure contains oxygen vacancies and electron lone pairs in its A2O' sublattice. The backbone lattice (B2O6) consists of defect-free octahedra. Lowering lead on its A site by 0.2 increased cation and anion vacancies and reduced the lattice thermal conductivity, i.e., phonon scattering by a factor of 40 to a glass-like value. We left the A site fully occupied and replaced some Ru4+ with lead, which is expected to occupy the octahedral B site as Pb4+. The effect on phonon scattering was much less pronounced. All results will be shown together with underlying scattering mechanisms. |