Preparation and characterization of GdSmZr₂O₇–(Li_0.52Na_0.48)₂CO₃ composite electrolyte for intermediate temperature solid oxide fuel cells

A novel GdSmZr₂O₇–(Li_0.52Na_0.48)₂CO₃ composite electrolyte material is successfully developed by pressureless-sintering for intermediate temperature solid oxide fuel cells. GdSmZr₂O₇ nanopowders are synthesized by a low cost chemical coprecipitation and calcination method. The phase structure and morphology as a function of the calcination temperature are investigated by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The resulting GdSmZr₂O₇ nanopowders after calcination at 800 °C for 5 h exhibit good crystallization and uniform particle morphology with an average size of 50 nm. The GdSmZr₂O₇–40 wt.% (Li_0.52Na_0.48)₂CO₃ composite sintered at 600 °C for 1 h has a high conductivity of 0.54 S cm⁻¹ at a temperature of 600 °C. From the Arrhenius curve of the composite, the activation energy has different temperature behaviors around the knee region of 480 °C, where the slope changes and separates the intrinsic oxygen vacancy conduction dominated region from the 'superionic highway’ region. For GdSmZr₂O₇–40 wt.% (Li_0.52Na_0.48)₂CO₃ composite at temperatures above 480 °C, there is good correlation between ionic diffusivity and conductivity. The introduction of (Li_0.52Na_0.48)₂CO₃ carbonate into GdSmZr₂O₇ ceramics significantly promotes the enhancement of its conductivity by one or two orders of magnitude at the intermediate temperatures, especially above 480 °C. A maximum power density of 221 mW cm⁻² at 650 °C was achieved for excellent performance of fuel cell based on GSZ–40LN composite electrolyte.