ENVIRONMENT SENSITIVE IMPEDANCE SPECTROSCOPY AND DC CONDUCTIVITY MEASUREMENTS ON NIWO4

Measurements of impedance spectroscopy and de conductivity over the te mperature range 300-1000K in atmospheres of dry and wet argon on antif erromagnetic NiWO4 are presented. The measured polycrystalline materia l was produced by a co-precipitation route. The conductivity was found to be sensitive to moisture over the temperature range 300-450 K. Imp edance spectroscopy measurements separated the contributions of the bu lk lattice and grain boundaries to the conductivity. These were separa ted over the temperature range 615-833K by equivalent circuit modellin g 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=49 2.7 exp(-1.15 eV/kT)Omega(-1) m(-1), above 625 K where K and T have th eir usual meaning.