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Lanthanum strontium cobalt iron oxide (LSCF) is commonly used as a cathode in solid oxide fuel cells (SOFCs), because it is a mixed ionic-electronic conductor with reasonable oxygen ion conductivity and high electronic conductivity. Yttria stabilized zirconia (YSZ) is used as an electrolyte in SOFCs with good oxygen ion conductivity. AC techniques are used to test the performance of SOFCs. But electrode processes at the cathode and the anode cannot be studied separately using 2-probe electrical impedance spectroscopy (EIS). To overcome this problem, 2-probe EIS with three probes and DC tests were conducted. An LSCF/8YSZ/LSCF symmetrical bar-shaped cell was made, and platinum strip electrodes were applied as probes for EIS and DC measurements. Impedance spectra across the cathode and the platinum strip electrode and across the anode and the platinum strip electrode were measured separately. The sum was evaluated to see if it matches the EIS spectra across the cathode and the anode. The polarity was switched to study how it affects the electrode processes. The polarization resistances of the electrodes were also measured by a DC method separately. EIS and DC measurements are in good agreement. Results indicate the two electrodes need not be identical. 

Garnet type LLZTO ceramic oxide is a promising solid-state electrolyte for use in Li-ion batteries because it has good chemical stability, adequate mechanical strength. However, lithium dendrite growth still needs to be addressed. The opacity of the solid electrolyte hinders in-situ investigation of dendrite growth. Therefore, semi-transparent LLZTO with high-density is needed. The traditional fabrication process for the garnet type LLZTO is cumbersome, and dense LLZTO disks with high transparency are difficult to fabricate. In this work, Al-LLZTO powder was made by solid-state reaction. A wet ceramic processing method, pressure filtration followed by sintering, was developed to make dense LLZTO with high ionic conductivity (1.47×10-4 S/cm) and adequate transmittance (17–23%) to visible light from 500 to 800 nm to observe and monitor dendrite growth.