Preparation and characterization of GdSmZr2O7-(Li0.52Na0.48)2CO3 composite electrolyte for intermediate temperature solid oxide fuel cells

A novel GdSmZr2O7-(Li0.52Na0.48)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.% (Li0.52Na0.48)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.% (Li0.52Na0.48)2CO3 composite at temperatures above 480 °C, there is good correlation between ionic diffusivity and conductivity. The introduction of (Li0.52Na0.48)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.