Thermal Conductivity of Sodium Nitrite

Abstract

The thermal conductivity of sodium nitrite single crystals has been measured in the temperature range of 70∼190°C along the direction of three crystal axes. Thermal conductivities in the b- and a-directions show a gradual decrease on heating, over a rather wide temperature range of some fifty degrees below the transition temperature. This decrease has been analyzed as an additive thermal resistivity with the help of a measurement at lower temperatures. Any anomalous behavior has not been found in the temperature dependence of thermal conductivity in the c-direction. A tentative model of the order-disorder arrangement of NO₂⁻ radicals is proposed for the explanation of the origin of the additive thermal resistivity, in which uneven interatomic forces due to the disordered arrangement are considered as scattering centers of phonons. The predicted temperature dependence is in a qualitative accord with the experimental one.