2. Experimental methods and equipment

Measurement of the electrical conductivity of a material is generally deduced from measurement of the electrical resistance of a given volume of that material. Thermoconductivity measurements are therefore measurements of electrical resistance using conventional methods, adapted to a system that allows the temperature of the sample to be varied. These measurements pose a number of practical problems, and the accuracy and even validity of the results depend on how well these problems are resolved.

The technical difficulties vary according to the resistivity and temperature ranges to be explored, so there are a large number of techniques, each of which has its limitations both in terms of the device measuring the electrical resistivity and the device supporting the electrodes and sample at the temperature in question.

The range of resistances...