Anomalously Low Heat Conduction in Single?Crystal Superlattice Ceramics Lower Than Randomly Oriented Polycrystals

Heat conduction in ceramics is attributed to phonon propagation, which can be strongly suppressed at boundaries. Usually, polycrystals show lower thermal conductivity (?) than single crystals, as contain many grain For functional applications management technologies, with low are required. While boundary engineering effective for reducing ?, its utilization limited by the fact that other properties often damaged. Here it shown single-crystalline oxide of InGaO3(ZnO)m a natural superlattice structure exhibits anomalously ? polycrystals. Single-crystalline films (m = integer), has InO2?/GaO(ZnO)m+ stacking along c-axis controllable layer thickness m, fabricated. It found perpendicular superlattices decreases decreasing m-value, and minimum 1.1 W m?1 K?1 4, 5), randomly oriented polycrystalline InGaO3(ZnO)m. On hand, parallel have similar values those polycrystalline. The present finding suggests boundaries between different components inside crystal also function resistance, will useful material design technologies.