Interfacial thermal resistance and thermal conductivity in nanograined SrTiO₃

A series of nanograined dense SrTiO₃ ceramics were examined for thermal conductivity, κ, as a function of average grain size d. The κ decreased gradually with decreasing d, primarily due to a significantly increased number of interfaces as heat transport barriers. Lowest κ at 300 and 1000 K, obtained in a 55-nm-grained sample, were about 50 and 24% smaller than those of a bulk single crystal. The Kapitza-type interfacial thermal resistance was estimated, and the dependence of κ on grain size was formalized, which shows the theoretical minimum κ could be achieved at d of about 10 nm.