Substantial appearance of origin of conductivity decrease in Y-doped BaZrO3 due to Ba-deficiency

Y-doped BaZrO3 (BZY) is getting attention due to its high proton conductivity. But the proton conductivity decreased when Ba-deficiency was introduced. And we recently found that the system with an atomic ratio of Ba : Zr : Y of 0.9 : 0.8 : 0.2 contained two perovskite phases (Ba0.74Zr0.55Y0.45O3-delta and Ba0.90Zr0.88Y0.12O3-delta). In this work, by scanning transmission electron microscopy (STEM), accumulation of stacking faults with higher content of Zr, Y or vacancies than Ba was observed in the Ba0.74Zr0.55Y0.45O3-delta phase. We discuss the influence of the phase on the conductivity based on the results of water content and conductivity measurements, and therefore assume that the proton conduction in the Ba0.74Zr0.55Y0.45O3-delta phase might be very small.