Modification of Properties and Study of Electrical Conductivity of Citrogypsum

Due to a complex chemical composition and microstructure of many functional materials the problem of optimizing their parameters for applied purposes is associated with determining of charge carrier transport mechanisms. To modify the properties of CaSO4 ⋅ 0.5H2O we prepared composite samples: (CaSO4 ⋅ 0.5H2O)0.95–(FeSO4 ⋅ 7H2O)0.05 and (CaSO4 ⋅ 0.5H2O)0.90–(FeSO4 ⋅ 7H2O)0.10. In a dry atmosphere all studied samples also had a specific conductivity of about 10–9 S cm–1. It has been established that with an increase in relative humidity (RH) of the environment the specific conductivity increases according to a power law up to 10–7 S cm–1. The measurements were carrying out at a constant temperature of 28 °C and RH range of 35–90%. To study a proton conductivity of studied compounds a method of impedance spectroscopy was using. Conductivity was measuring in the frequency range 20 Hz–5 MHz. In (CaSO4 ⋅ 0.5H2O)0.95–(FeSO4 ⋅ 7H2O)0.05 samples and (CaSO4 ⋅ 0.5H2O)0.90–(FeSO4 ⋅ 7H2O)0.10 at above 40% RH granular conductivity was observed, an additional linear section was observed in (CaSO4 ⋅ 0.5H2O)0.90–(FeSO4 ⋅ 7H2O)0.10 samples which is responsible for the conductivity along grain boundaries.