AN EXPERIMENTAL-STUDY OF NICKEL MOLYBDATE ELECTRICAL-CONDUCTIVITY

The electrical conductivity of nickel molybdate has been measured in the temperature range (400-800-degrees-C) on ceramic samples. The existence of two polymorphic forms b-NiMoO4 and a-NiMoO4 is confirmed. The temperature of transition (T = 690-degrees-C) corresponds to the modification of symmetry of the molybdenum cations which changes from O(h) to T(d). The electrical transport for both varieties takes place via a classical band conduction mechanism. The b-NiMoO4 variety behaves as a p-type semiconductor in the 450-650-degrees-C temperature range with an activation energy of 1, 3 eV. The a-NiMoO4 has two conduction regimes: within the metastable temperature range (450-650-degrees-C) it is a p-type semi conductor (E(a) = 1,3 eV). at higher temperatures (T > 700-degrees-C), it is a n-type semiconductor with a higher activation energy of conduction (E(a) = 1,9 eV).