The thermal conductivity of sodium chloride at elevated temperatures

The thermal conductivity of solids has been attributed to a combined effect of the quantized vibration of the lattice points, called phonons, and the flow of valence electrons. In nonconductors the thermal conductivity is due almost entirely to phonons, as was shown by Debye, whereas in metals the conductivity is due mostly to the flow of valence electrons. After Debye, Peierls calculated the lattice conductivity at elevated temperatures using quantum mechanics and demonstrated that it is proportional to 1/T. There are not enough data available to substantiate any theory but what data there are seem to indicate a mixed conductivity with temperature dependence between 1/T and 1/T[superscript 3/2]. Thus it is the purpose of this experiment to extend the data on insulating single ionic crystals from room temperature up to about 1000 degrees centigrade, or near the melting point of the material. The present experimenter was concerned mostly with putting the apparatus into a better operating condition by eliminating small deficiencies in the apparatus as it was left by Weisbrod, obtaining some data, and comparing it with values obtained by previous experimenters. The experiment utilizes an absolute steady state method of measurement. This method was chosen because dynamic methods require elaborate equipment and it appears to be more difficult to eliminate or account for all errors as was the case with Clarke and Kingston and Beatty. The information required for calculating the conductivity of the material was obtained by passing a known amount of heat across a specimen of known size and temperature --Introduction, pages 1-2