ELECTRICAL AND THERMAL EVIDENCE FOR A PHASE-TRANSITION IN POTASSIUM HYDROGEN TARTRATE

Measurements are reported of the electrical conductivity sigma and the relative permittivity epsilon, in addition to some calorimetric parameters (thermal specific heat capacity C-p and thermal conductivity lambda, as a function of temperature in the range 300K<T<475 K of potassium hydrogen tartrate, (KHC4H4O6) Accurate measurements of these parameters indicate that the compound undergoes a structural phase transition in the vicinity of 336 K. The phonon and electron contributions to the heat transfer are discussed. Differential scanning calorimetry and differential thermal analysis on the polycrystalline samples were undertaken in order to check the transition temperature. Thermogravimetric analysis indicates the absence of any weight loss in the region of the transition temperature. The data are correlated with the crystal structure and the arrangement of molecules in the unit cell.