Electrical conductivity of hexagonal Ba(Ti0.94Ga0.06)O2.97 ceramics

Impedance spectroscopy is used to estimate the bulk conductivity, sigma b, of hexagonal (6H)-Ba(Ti0.94Ga0.06)O2.97 ceramics in air, N2 and 5% H2/95% N2 between 400 and 1000 C. Isothermal plots of log sigma b vs log pO2 in the temperature range between 700 and 1000 C show the presence of a p-n transition with slopes of about -1/4 and +1/4 in the n- and p-type regions indicating that the conductivity obeys the "extrinsic" model proposed by Smyth and co-workers for undoped and acceptor-doped cubic BaTiO3-based materials. The activation energy Ea for oxidation in the p-type region to produce free holes is similar for 6H-Ba(Ti0.94Ga0.06)O2.97 and cubic BaTiO3-based ceramics with an estimated value from sigma b data of about 0.8 eV. The band gap for 6H-Ba(Ti0.94Ga0.06)O2.97 ceramics is about 3.2 eV. 10 refs.