Aerosol Jet® Printing of functionally graded SOFC anode interlayer and microstructural investigation by low voltage scanning electron microscopy

Yttria-stabilized zirconia (YSZ) electrolyte and functionally graded anode interlayers with compositional variation were deposited by Aerosol Jet (R) Printing (AJP) using ink suspensions of NiO and YSZ. The AJP system's dual atomizer configuration that allows on-demand material mixing was used to deposit the graded composite anode interlayer. These layers together with an LSM (strontium doped lanthanum manganite) based pasted cathode layer were integrated in an anode supported SOFC button cell. Cells with graded anode interlayers performed better than cells with a non-graded anode interlayer. The enhancement in electrochemical performance can be attributed to the compositional gradation. The current printing method of fabricating SOFC layers shows clear advantages of high reproducibility. In routine SEM (scanning electron microscopy) evaluation of microstructures, acceleration voltages typically used are 10-20 kV. Due to the similar backscattering coefficients of YSZ and Ni, it is difficult to clearly distinguish between the two phases in the image. In this work, low accelerating voltages (<5 kV) were used to introduce a divergence of the YSZ and Ni backscatter coefficients to investigate the composite layers printed. The backscattering mechanism for image contrast was confirmed and clarified by specially designed SEM experiments that isolated BSE (back scattered electrons) from SE (secondary electrons). (C) 2012 Elsevier B.V. All rights reserved.