Characterization of the high temperature properties of BaCe0.4Zr0.4Pr0.2O3−δ perovskite as a potential material for PC-SOFCs

Abstract

Compounds based on barium cerates and zirconates, Ba(Ce,Zr)O_3−δ, are oxides able to transport protons through their crystal lattice by proton hopping between oxygen sites. This feature makes them potential candidates as electrolytes for proton conducting solid oxide fuel cells (PC-SOFCs). Pr-doping this family of compounds decreases sintering temperature and introduces electronic conductivity. This work presents a systematic study of the high temperature properties of BaCe_0.4Zr_0.4Pr_0.2O_3−δ (BCZP) perovskite in view of its potential application as a PC-SOFC cathode. At room temperature, BCZP presents as a rhombohedral structure, which transforms reversibly to cubic at 550 °C in dry air. Electrical measurements under dry and wet air with water vapor (∼2% H₂O) and heavy water vapor (∼2% D₂O) were employed to study the conductivity over a wide temperature range. The total conductivity data exhibit behavior changes between 400 and 600 °C which could be associated with a crystal structure transition. BCZP presents low total conductivity (64 μS cm⁻¹ at 600 °C), which limits its application as single phase cathode material. However, the material has good thermomechanical compatibility with electrolytes (∼11 × 10⁻⁶ K⁻¹) and high CO₂ tolerance (T > 900 °C). These properties suggest that this compound could be used as an oxide support for composite, or backbone for impregnated, electrodes, or as a buffer layer to avoid degradation mechanisms improving the performance of another cathode material.