Electrical and thermal evidence for a phase transition in potassium hydrogen tartrate

Abstract

Measurements are reported of the electrical conductivity [sgrave] and the relative permittivity ε, in addition to some calorimetric parameters (thermal specific heat capacity C_p and thermal conductivity λ, as a function of temperature in the range 300K < r < 475K 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.