EFFECT OF HYDROSTATIC-PRESSURE ON THE ELECTRICAL CONDUCTANCE OF POLYCRYSTALLINE MAGNESITE (MGCO3)

The room-temperature conductance of polycrystalline magnesite was meas ured, for different hydrostatic pressures up to 3 kbar. The electrical conductivity decreases with increasing pressure, indicating that the conductivity mechanism is dominantly ionic. The In G(P) plots are curv ed and obey a second-order polynomial law. The curvature is interprete d, in the usual manner, either in terms of a pressure-dependent activa tion volume model or by asserting that the pressure activates addition al conduction modes. Additionally, a theoretical In G(P) equation was derived, by assuming that the activation volume is not single valued, but follows a Gaussian distribution function. The three models were em ployed to analyze the experimental data and estimate the activation vo lume for the conduction mechanism. The analyses provided compatible ze ro-pressure values of the activation volume. The results are discussed in relation to those reported for dolomite.