Environment sensitive impedance spectroscopy and dc conductivity measurements on NiWO4

Measurements of impedance spectroscopy and de conductivity over the temperature range 300-1000K in atmospheres of dry and wet argon on antiferromagnetic NiWO4 are presented. The measured polycrystalline material was produced by a co-precipitation route. The conductivity was found to be sensitive to moisture over the temperature range 300-450 K. Impedance spectroscopy measurements separated the contributions of the bulk lattice and grain boundaries to the conductivity. These were separated over the temperature range 615-833K by equivalent circuit modelling and an activation energy for the bulk lattice conductivity obtained. Conductivity measurements indicated that the compound is an intrinsic semiconductor and obeys the Arrhenius conductivity equation; sigma=492.7 exp(-1.15 eV/kT)Omega(-1) m(-1), above 625 K where K and T have their usual meaning.