Synthesis, sintering behavior and electrical properties of Ba(Zr0.1Ce0.7Y0.2)O3−δ and Ba(Zr0.1Ce0.7Y0.1Yb0.1)O3−δ proton conductors

Perovskite-type Ba(Zr0.1Ce0.7Y0.2)O3−δ (BZCY) and Ba(Zr0.1Ce0.7Y0.1Yb0.1)O3−δ (BZCYYb) proton conductor powders were synthesized by a novel solid–liquid composite method. The resultant powders were characterized by XRD, SEM, XRF, BET and particle size distribution (PSD) analysis. High-purity, single-phase and slightly aggregated powders with a particle size smaller than 400 nm were obtained by using polyvinyl pyrrolidone (PVP) as the surfactant and calcining at 1150 °C once. The sintering behavior and ionic conductivity of the sintered BZCY and BZCYYb powders were studied and compared with each other. The results indicated that the sintering behavior of BZCY was inhibited after introducing 10 mol% Yb, which was manifested as hindered grain growth, a delayed sintering process and an increase in densification temperature from 1400 °C to 1500 °C. Conductivity results showed that the conductivities of BZCY were determined to be 0.80×10−2 Scm−1, 0.97×10−2 Scm−1 and 1.21×10−2 Scm−1 in air, H2 and wet H2, respectively, at 600 °C. After doping with 10 mol% Yb, the value increased to 1.41×10−2 Scm−1, 1.63×10−2 Scm−1 and 2.14×10−2 Scm−1 in air, H2 and wet H2, respectively. Both BZCY and BZCYYb displayed mixed ionic conductivity and the proton conductivities were higher than their oxygen-ion conductivities and were improved after introducing 3 vol% H2O. These trends observed for the conductivities of the powders were explained. Finally, the oxygen-ion conductivities of BZCY and BZCYYb were compared with GDC, 8YSZ and 10Sc1CeSZ. The results indicate that the BZCY and BZCYYb are excellent low-temperature proton and oxygen ion mixed conductors.