Ionic conductivity behavior by activated hopping conductivity (AHC) of barium aluminoborosilicate glass-ceramic system designed for SOFC sealing

Non-conducting BaO-B2O3-Al2O3-SiO2 parent glasses designed for solid oxide fuel cell (SOFC) sealing applications were prepared using the melt-quenching technique. The glass formation region was determined according to phase equilibrium relations and was found to be in the composition range 70BaO-(x)Al2O3-(10-x)B2O3-20SiO(2) where 3.0 < x < 6.0 wt%. The conductivity values obtained conductivity ranged from 10(-5) to 10(-10) S/cm at temperatures between 600 and 850 degrees C. The batch compositions presented a threshold of dc conductivity near 70BaO wt% with a quasi linear behavior with the decrease of the BaO content. Different values of conduction activation energy were observed at temperatures above the glass transition temperature (T-g) (up to 700 degrees C), which were attributed to the thermal bond-breaking of non-bridging oxygen (NBO) defects. The experimental results of the electrochemical characterization by impedance spectroscopy of glass-ceramic interfaces with yttria-stabilized zirconia (YSZ) acting as solid ionic conductor electrolyte are presented and discussed.