Exceptional high ionic conductivities have been well documented in the Bi2VO5.5-based materials. However, the poor phase and redox stabilities under a reducing atmosphere hindered their wide applications. Herein, with the aim to improve the phase and redox stabilities under a reducing atmosphere, a high-entropy strategy of multiple-metal-doping was applied to prepare series Bi2V1–4x(GaSiTaZr)xO5.5-δ (0 ≤ x ≤ 0.1) materials by a traditional solid state reaction method. The results revealed that multiple-metal-doping could stabilize the tetragonal phase of Bi2VO5.5 to room temperature and shown good phase and structural stabilities under inert or high oxygen partial pressure atmospheres, as well as pure oxide ion conduction which was about two orders of magnitude higher than that of the parent material, e.g. ∼2.0×10−2 S/cm at 400 ºC for the x = 0.05 sample while ∼1.5×10−4 S/cm for the x = 0 sample. Although the Bi2V1–4x(CuNiNbTi)xO5.5-δ materials would still be readily reduced under a reducing environment and introduce strong electronic conduction, the phase stability was apparently improved. Thus, improving the redox stability and suppressing the electronic conduction of the stabilized Bi2VO5.5-based materials under a reducing atmosphere is still the direction we should strive for.
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