It was found that, with decreasing temperature, a conductivity anomaly occurred at about 290K, followed by a weak thermal effect at about 270K. A peak appeared, at about 260K, in the temperature dependence of the value of the lattice a-axis parameter. The results were related to the crystal structure, and the conductivity channels were distinguished; under the assumption that a hopping conductivity mechanism was operating. A geometrical analysis of the structure revealed the special nature of the c-parameter; which was almost 2 times smaller than the a- and b-parameters. Also, the linear radicals were located along the c-axis. In addition, the results indicated the important role that was played by conductivity paths along the crystallographic a-axis. These were not optimum paths for ionic transfer because the conductivity increased in directions normal to the a-axis.

A.K.Ivanov-Schitz, I.A.Verin, O.Nakamura, T.Fujieda: Kristallografiya, 1995, 40[1], 191-2 (Crystallography Reports, 1995, 40[1], 173-4)