Electronic Conduction Mechanism in Yttria‐Stabilized Zirconia‐Titania under Reducing Atmospheres

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Abstract
Yttria [12 mole percent (m/o)] stabilized zirconia with 5 to 10 m/o titania (YZTi) exhibits oxygen‐ion and n‐type conductivity under reducing atmospheres at elevated temperatures. Electron paramagnetic resonance (EPR) measurements reveal that the concentration of YZTi increases with increasing temperature, increasing content, and decreasing oxygen pressures below at 830°C. Impedance measurements show that the total electrical (oxygen‐ion plus n‐type) conductivity of YZTi having 10 m/o follows the same behavior and increases at oxygen pressures below and at 573 and 838°C, respectively. The EPR and impedance results support an electron hopping mechanism between the 3+ and 4+ oxidation states of titanium. Modeling of the impedance data verifies that the n‐type conductivity occurs in the YZTi lattice and is not restricted to the grain boundaries. A percolation model shows that electron hopping can occur in YZTi when titanium ions occupy as few as 3 to 4% of the cation sites.

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