Electrical Charge Transport in Single‐Crystal CaWO 4

A combination of ac and dc electrical conductivity measurements was used to characterize the charge transport in single crystals of CaW0 4 which were equilibrated with H 2 ‐H 2 O‐Ar gas mixtures. Measurements were made from 900° to 1300°C and at P H2O /P H2 ratios from 0.02 to 3.0. The ac conductivity at 1000°C varied from 51.4×10 −6 to 5.89×10 −6 mho/cm for P H2O /P H2 =0.02 and 2.0, respectively; the dc conductivity changed from 51.0±10 −6 to 5.42×10 −6 mho/cm under the same experimental conditions. The partial logarithmic derivative of dc conductivity with respect to P H2O /P H2 was −1/2 between 1000° and 1300°C. The results may be described by a paired‐defect model of oxygen vacancies and oxygen interstitials (majority defects and minority electrons).