RELATIONSHIP BETWEEN THERMAL-DIFFUSIVITY AND MEAN FREE-PATH

The thermal diffusivity is a parameter that determines the speed and a ttenuation of a thermal wave propagating through a material. In this p aper we show, using the kinetic model for thermal transport, that the thermal diffusivity is also proportional to the mean free path of the heat carriers. Thus, the thermal diffusivity has the added feature of being directly related to an important transport property of the excit ations that carry the heat. Thermal diffusivity and mean free path dat a are presented for an amorphous insulating solid, Pyrex 7740 glass, i n the temperature range from 25 to 300 K.