DIELECTRIC RELAXATIONS AND CRYSTAL WATER STOICHIOMETRY OF ROCHELLE SALT

Various dispersions of the dielectric permittivity of Rochelle Salt, which are caused by crystal imperfections, are known to occur at low frequencies. On the other hand some properties of Rochelle Salt point out that at room temperature rather high concentrations of crystal water defects are present. Therefore the dependence of the relaxation strengths on the content of crystal water is investigated in the case of two different dispersions. One of them shows no connection with the stoichiometry as far as the water of crystallization is concerned, whereas the relaxation strength of the other decreases by about two decades, if the relative humidity, at which the crystals are stored, is increased from 9 to 54 per cent. This dependence is explained quantitatively by concentration changes of water vacancies in the lattice. The energy of activation of the corresponding dielectric relaxation and the energy necessary to create a water vacancy are determined as 0.5 eV. © 1969 Springer-Verlag.