Sintering mechanism and electrical conductivity of ZnO added BaCe0.8Zr0.1Y0.1O3-δ proton conducting perovskites

Abstract

The sintering mechanism and electrical conductivity of ZnO added BaCe0.8Zr0.1Y0.1O3-δ (BCZY) proton conducting perovskites were investigated. The additions of 0.1 to 3 wt% ZnO to BCZY promoted the sintering of the BCZY pellet samples, and the samples with ZnO showed impermeable bodies with relative densities ≥90% after firing at 1400 °C for 6 h. First-principles calculations suggest that Ba in BaZnO2 is more stable than in perovskites, and Zn is hardly soluble in BCZY. These theoretical results indicate that ZnO reacts with Ba in the BCZY perovskites. The melting points of the BaO and ZnO mixtures were approximately 1100 °C. Because their liquid phase should react with excess Y component in the perovskite, the liquid phase containing Y component enhances the densification of the doped perovskite by the liquid phase sintering. The electrical conductivities of BCZY perovskites with ZnO content ranging between 0.1 wt% and 3 wt% varied from 1.3 × 10−2 to 1.5 × 10−2 S/cm at 600 °C in an atmosphere of 3.0% H2O, 19.4% H2 and 77.6% N2. The electrical conductivities of BCZY perovskites with ZnO were comparable to those of the dense BCZY perovskite without ZnO. The present result suggests that addition of a small amount of ZnO is appropriate for enhancing the sintering and retaining the high electrical conductivity of BCZY.