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 (Ba_0.74Zr_0.55Y_0.45O_3−δ and Ba_0.90Zr_0.88Y_0.12O_3−δ). 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 Ba_0.74Zr_0.55Y_0.45O_3−δ 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 Ba_0.74Zr_0.55Y_0.45O_3−δ phase might be very small.