La-doped Ba₂In₂O₅ electrolyte: Pechini synthesis, microstructure, electrical conductivity, and application for CO gas sensing

Abstract

Dense (Ba_1-xLa_x)₂ In₂O_5+x electrolytes with different compositions (x=0.4,0.5, 0.6) were fabricated using powders obtained by the Pechini method. The formation of BLIO powders was investigated by using X-ray diffraction and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The calcination temperature and time were optimized. The sintered (Ba_1-xLa_x)₂ In₂O_5+x electrolytes showed a relative density greater than ∼97% , and the major phase of three electrolyte compositions was indexed as a cubic perovskite. The electrical conductivity of BLIO ceramics at elevated temperatures in air was measured by ac-impedance spectroscopy. The activation energies for conduction in BLIO were 102 kj mol^-1 between 473 and 666 K and 118 kj mol^-1 between 769 and 873 K, which are comparable to that for 8 mol % yttria-stabilized cubic zirconia. Mixed-potential gas sensors utilizing BLIO-based electrolytes exhibited good sensitivity to different CO concentrations from ∼100 to ∼500 ppm and excellent selectivity to methane at around 873 K.