Interfacial Thermal Resistance and Thermal Conductivity in Nanograined SrTiO3

A series of nanograined dense SrTiO 3 ceramics were examined for thermal conductivity, $\kappa$, as a function of average grain size $d$. The $\kappa$ decreased gradually with decreasing $d$, primarily due to a significantly increased number of interfaces as heat transport barriers. Lowest $\kappa$ 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 $\kappa$ on grain size was formalized, which shows the theoretical minimum $\kappa$ could be achieved at $d$ of about 10 nm.