Synthesis and electrochemical assessment of Ce0.5Yb0.5O1.75 ceramics and derived composite electrolytes

•Ce0.5Yb0.5O1.75 prepared for the first time through solid state reaction.•High energy milling needed to assist the ceramic route.•Ce0.5Yb0.5O1.75 is oxide-ion conductor in air and n-type conductor at low pO2.•Ce0.5Yb0.5O1.75 decomposes slightly when exposed to alkaline carbonates.•Composites based on Ce0.5Yb0.5O1.75 show standard electrical performance.

Ce0.5Yb0.5O1.75 was prepared for the first time through high temperature (1600 °C for 5 h) solid state reaction, after high energy milling to enhance the mechano-chemical interaction of precursor oxides (CeO2 and Yb2O3). Single phase formation was confirmed by powder X-ray diffraction. Impedance spectroscopy data obtained under wide temperature (300–800 °C) and oxygen partial pressure (0.21 to about 10−25 atm) ranges indicates that this material exhibits predominant oxide-ion conductivity under oxidizing conditions while n-type electronic conductivity prevails at low oxygen partial pressure. The mixed oxide shows modest ionic conductivity (1.1 × 10−3 S cm−1 at 800 °C) with activation energy of 1.3 eV in the 600–800 °C temperature range. When combined with molten carbonates (Li2CO3 + Na2CO3, 1:1 molar ratio) to produce composite electrolytes, Ce0.5Yb0.5O1.75 slightly decomposed. However, the composite electrical performance is still acceptable and closely matches the conductivity of similar materials (>0.1 S cm−1 immediately above 500 °C).

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