The low-temperature thermal depolarization spectrum of polycrystalline magnesite revealed a unique broad dipolar relaxation peak which exhibited a maximum at about 140K. The relaxation mechanism was suggested to be related to a dipole defect population with a distribution of relaxation times. By using a partial heating technique, activation energies were found which ranged from 0.19 to 0.30eV. A review of dielectric relaxation in calcite-family materials showed that each sub-lattice type (Ca and Mg) favored a certain defect structure. It was concluded that Mn2+ and Sr2+ impurities, as well as H2O molecules or OH ions, were the most likely components of the dipole defect configurations.

A.N.Papathanassiou, J.Grammatikakis: Physical Review B, 1997, 56[14], 8590-8