Development of La2Ce2O7 electrolyte through an energy efficient flash sintering process for proton conducting solid oxide fuel cell

Abstract

Conventional sintering of La2Ce2O7 (LCO) is a highly energy-intensive process as it requires processing temperatures of 1400 degrees C for 5 h. In this work, we have done a comprehensive study of the flash sintering (FS) process in LCO ceramics and optimized FS parameters that resulted in its higher densification. The optimized flash sintering initiation temperature of 850 degrees C with a current density of 60 mA/mm(2) for 6 min of flash sintering, yielded a sintered density of 95.2 +/- 0.4 %. X-ray diffraction (XRD) analysis confirmed the phase-pure LCO, with no formation of secondary phases during FS, which was also confirmed by Raman spectroscopy. The F-type phase of LCO converted into the C-type phase post FS. Microstructural analysis revealed the variation in grain size across the thickness of the sample that can be attributed to the gradients in point defect concentration. The mean grain size near the cathode is lowest, followed by the anode, and it is highest for the mid-section. Impedance spectroscopy identified distinct resistance regions within the material, with ionic conductivity peaking at 2.1 x 10(-3) S cm(-1) at 650 degrees C and an activation energy of 1.42 eV. Distribution relaxation time (DRT) analysis indicated enhanced ionic mobility at higher temperatures. This study highlights the benefits of flash sintering as an energyefficient technique for processing LCO. The LCO ceramic sample is suitable for solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) for energy generation applications.