Determining the Kapitza resistance and the thermal conductivity of polycrystals: A simple model

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Abstract
A simple model for the thermal conductivity of polycrystals is presented by incorporating the concept of the Kapitza resistance with an effective medium approach. By applying this model to a few thermoelectric alloys reported in the literature, we show that it quite well describes the often observed grain size-dependent thermal conductivity of polycrystals and also provides a simple and practical method to determine the Kapitza resistance. We estimate the Kapitza resistance in real polycrystals and the effects of microstructural scales, such as spatial variations in the grain size and grain shapes, on the thermal conductivity.