2.1. Sample preparation
Measurement of electrical conductivity required densified sintered pellets through fully mixed with a few drops of polyvinyl alcohol (PVA) solution, followed by dry pressing at 40 MPa and then isostatic cool pressing under 270 MPa, then fired at 1100 °C (950 °C for M = Cu) for 24 h at ramping rate of 1 °C min−1. The relative density of sintered pellets could achieve ~95%, which were determined by Archimedes method. The measured conductivity can be corrected with the equation below :equation(1)σcorr=σapp2(drel/100−0.5)Where σcorrσcorr, dreldrel and σappσapp are the porosity-corrected conductivity, the relative density and the measured apparent conductivity, respectively.
Symmetrical CX-5461 with LaM0.25Mn0.75O3-δ SDC LaM0.25Mn0.75O3−δ configuration were fabricated by screen-printing technique, and then used for electrochemical testing. Dense SDC pellets (15 mm in diameter, 500 μm in thickness) were prepared by pressing the powders under 40 MPa, and then followed by isostatic cool pressing under 270 MPa, finally sintered at 1400 °C for 10 h. LaM0.25Mn0.75O3−δ cathode slurries were made by mixing the powders with binder (α-terpineol and ethylene cellulose) and coated on both surfaces of SDC by screen-printing, and then fired at 1100 °C (950 °C for M = Cu) in air for 2 h. The resulting electrode had an effective area of 0.25 cm2. Silver paste was attached to both sides as a current collector, which was heated to 600 °C for 30 min in air.