Synthesis and Characterization of BaCe0.4Zr0.4Pr0.2O3−δ Mixed Conductor Perovskite

Abstract

<jats:title>Abstract</jats:title> <jats:p>Compounds based on barium cerates and zirconates Ba(Ce,Zr)O<jats:sub>3−δ</jats:sub> are oxides able to transport protons through their crystal lattice by proton hopping between oxygen sites. This feature makes them potential candidates as hydrogen sensors, membranes for hydrogen purification and isotopic exchange, and electrolyte for Proton Conducting Solid Oxide Fuel Cell (PC-SOFC) and Solid Oxide Electrolyzer Cells (PC-SOEC). Pr-doping on these family compounds decreases sintering temperature and introduces electronic conductivity. This work presents a systematic study of the high temperature properties of the BaCe<jats:sub>0.4</jats:sub>Zr<jats:sub>0.4</jats:sub>Pr<jats:sub>0.2</jats:sub>O<jats:sub>3−δ</jats:sub> (BCZP) perovskite in view of its potential use for these applications. At room temperature, BCZP presents rhombohedral structure, which transforms reversibly to cubic at 550 °C in dry air. Electrochemical measurements under dry air, wet air with water vapor (~ 2% H<jats:sub>2</jats:sub>O) and heavy water vapor (~ 2% D<jats:sub>2</jats:sub>O) were employed to describe bulk ionic and electronic transport above 200 °C. The total conductivity data exhibit behavior changes between 400 and 600 °C which could be associated to a crystal structure transition. Below 600 ºC BCZP presents low total conductivity, which limits its applications as single phase cathode material for electrochemical applications. However, the material has good thermomechanical compatibility with electrolytes (~ 11 × 10<jats:sup>− 6</jats:sup> K<jats:sup>− 1</jats:sup>) and high CO<jats:sub>2</jats:sub> tolerance (T &gt; 900 ºC). These properties suggest that this compound could be used as oxide support for composite or impregnated electrodes, buffer layer to improve the performance of another cathode material or gas separation co-ionic membranes.</jats:p>