EFFECT OF ZIRCONIA DOPING ON THE ELECTRICAL BEHAVIOR OF YTTRIA

The ac electrical behavior of yttria doped with a zirconia concentrati on ranging from 0.15 to 20 mole % is investigated in the temperature r ange of 800 to 1300 degrees C. The ac electrical data, obtained in the range from 5 Hz to 13 MHz, indicated two distinct relaxations when an alyzed in the impedance plane. These relaxations are attributed to lum ped grains and trapping within grain boundaries, including possible el ectrode/sample effects. The admittance plane analysis revealed a semic ircular relaxation in the low-frequency region, indicating identical r esponse to that of the low-frequency relaxation of the impedance plane . The incorporation of zirconia into yttria is found to lower the acti vation energy of conduction in the grains and enhance ionic contributi on to the overall electrical conduction. The P-O2 studies and transfer ence number measurements near atmospheric region indicate that p-type conduction dominates for the lightly doped yttria. An ionic contributi on to the conduction processes becomes significant in heavily doped sa mples at/near atmospheric P-O2.