Abstract
The conductivity of polycrystalline specimens of Mo03, measured using AC voltage, changes very considerably under the influence of superimposed d.c. voltage: this change is time-dependent. In some circumstances the change in conductivity is sudden and as great as several orders of magnitude, so that the impedance of the specimen of Mo03 changes its character from capacitive to almost pure resistive. This can be regarded as corresponding to some kind of switching process in the material, caused probably by carrier injection from electrode to material under the influence of space charge built up by carrier drift in the applied d.c. field.