Thermal dependence of microstructure and electric properties in doped calcium tartrates

Polycrystalline samples of pure calcium tartrate [CaC4H4O6·2H2O]·2H2O (labelled CaT) and CaT doped with divalent cations (Sr, Ba, Co, Zn and Cd) were studied using thermal analysis, impedance measurements and X-ray powder diffraction. Cell parameters were calculated for all compounds at six temperatures, in the temperature range 323 to 398 K, by whole-pattern profile matching. Then microstructural parameters were obtained by refining patterns using a pseudo-Voigt function. The ac conductivity of these samples in the frequency range 400 Hz–200 kHz between 338 K and 373 K has been measured. These results show that the conduction mechanisms, thermal stability and microstructure differ, depending on whether the doping agent is earth alkaline or a transition metal.