The Formation of Stacking Faults in Barium Zirconate-Type Perovskites

Yttrium-doped barium zirconate (BZY) is a proton-conductingperovskitewith potential for use in a variety of energy applications, includingas a catalyst support and as an electrolyte for solid-state fuel andelectrolytic cells. Of interest to material performance is the presenceand character of defects in the material, which will influence materialproperties. The presented work discusses the discovery of stackingfaults in conventionally sintered BZY at different measured A/B ratios (Ba x Zr0.8Y0.2O3-& delta;, x = 0.989, 1.001, and 1.006). Two structurally unique stackingfaults are observed for the first time in BZY, i.e., Ruddlesden-Popper(RP) type and non-RP type. Characterization using S/TEM details thepresence of stacking faults and dislocations and provides insightinto the formation process of RP-type faults in BZY-type materials.Electrochemical impedance spectroscopy is performed to analyze theimpact of stacking faults on material conductivity. The stacking faultsare concluded to be blocking conductivity and are expected to impactthe mechanical properties of the material. The defects are also observedin a yttrium-doped barium zirconate/cerate (BZCY) with nickel oxideand are shown to be prevalent in close-to-stoichiometric BZY (A/B = 1.001), indicating that they arecommon defects for this material class.