Effect of Pr-doping on structural, electrical, thermodynamic, and mechanical properties of BaCeO3-d as proton conductor

Abstract

The effect of partial substitution of Ce by Pr ions in BaCe1−xPrxO3−δ (0 ≤ x ≤ 0.8) perovskite was studied to improve the proton conductor capability, including transport and mechanical properties, thermodynamic stability, CO2 tolerance and sintering. The stability under oxidizing and reducing (5% H2/Ar and 10% CO2/Ar) atmospheres was evaluated by thermogravimetry. The conductivity was studied by Electrical Impedance Spectroscopy (EIS) under wet (2% H2O) flow of 20% O2/Ar and 10% H2/Ar as a function of temperature between 100 and 600◦C. The mechanical stiffness and fracture load were measured by a Small Punch Testing (SPT) method at room temperature. It was found that the Pr doping improves the sintering capacity, and increases the conductivity. However, the stability under reducing and carbon dioxide atmospheres decreases. A correlation between electrical conductivity, CO2 tolerance, thermodynamic stability under reducing atmospheres and mechanical properties was found. Dense BaCe0.8Pr0.2O3−δ obtained at 1350◦C presents low porosity (5 ± 1%), an improvement of 30% in stiffness and 56% in fracture load, good stability under oxidizing and reducing atmosphere, slightly higher CO2 tolerance range and an increase of electrical conductivity respect to that of the un-doped compound.