Ionic and electron-hole conduction in BaZr0.93Y0.07O3−δ by 4-probe dc measurements

Porous samples of composition of BaZr0.93Y0.07O3−δ were fabricated. Electrical conductivity of porous samples was measured using a 4-probe dc method over a pO2 range from 7.3 × 10−6 to 1 atm and over a temperature range from 500 to 800 °C. The results showed that the electrical conductivity increases with increasing pO2, a characteristic of electron-hole conduction. Above pO2 of 0.01 atm, the measured total conductivity was fitted to σt=σi+fpO21/4, where σi is the ionic conductivity and fpO21/4 is the electronic (hole) conductivity. The activation energies were estimated to be ∼0.57 ± 0.15 and ∼1.01 ± 0.04 eV for oxygen ion and electron-hole conduction, respectively. The oxygen ion transference number ranged between ∼0.01 and 0.7 over the pO2 and the temperature ranges investigated. Electrical conductivity measurements were also carried out in H2O-containing atmospheres. It was observed that at a temperature below ∼550 °C, the predominant ionic conduction was due to protons.