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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