Hydrogen Reduction Properties of RuO 2 Electrodes

The thermodynamic stability of RuO2 under a reducing atmosphere containing hydrogen gas was investigated. The RuO2 electrode is reduced to Ru metal at 200°C in 0.3% H2 and at 300°C in 0.03% H2, even when the electrode is stacked with a (Ba, Sr)TiO3 dielectric layer. The reduction decreases the electrode volume. Our findings indicate that application of the RuO2 electrode in device integration will be difficult because of the thermodynamic instability as long as the thermal equilibrium state of reduction is attained during hydrogen sintering.