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edfas.org 25 ELECTRONIC DEV ICE FA I LURE ANALYSIS | VOLUME 23 NO . 2 sentativeO- K edge of the LSMphase (with a pre-edge peak indicated by an arrow) is observed for the first two EELS spectra acquired (from the bottom). With the acquisition gradually approaching the Zr-rich particles, the pre-edge peak begins to diminish and eventually disappears when the spectra are recordedonly fromthe Zr-richparticle. The resulting O- K edge is found to resemble the one reported for the LZO phase shown in Fig. 5b, suggesting that the O element inside these Zr-richphases exhibits the zirconate- like bonding structure. [16,17] Qualitative comparison of the Mn- L 2,3 edge between the bulk LSM phase and the Zr-rich phase is also conducted. General features, including the edge position and the L 3 / L 2 ratio, are observed to be essentially identical, indicating the same valence state is exhibitedby theMn ions fromboth the LSMand the Zr-rich phase (the results are not shown). The fact that theMn ions show the same valence state in the LSM and Zr-rich grains further sug- gests that the Zr-rich phase originates from the LSM grain. The obtained EELS results therefore suggest that theZr-richphase likely forms inside the LSM grain as a result of the Zr ions diffusing from YSZ into the LSM. Considering the possibility of overlap of two adjacent phases which might affect the EDS and EELS analysis, structural analysis on this unknown Zr-rich phase is also done by employing a line-scan nano-beam dif- fraction pattern (LSDP) technique. This LSDP technique is implemented through a customwritten scriptwithin theGatanDigital Micrograph software environment, which allows for a point-by-point control of the beam position, beammovement, and diffraction pattern recording on the CCD camera. The LSDP is performed on the same area as the STEM-EDS and STEM-EELS in Fig. 4. Figure6shows theresults. Figure6a is thebright-fieldimage of the LSM particle illustrating the position where the LSDP acquisition takes place. Figures 6b and c are the diffraction patterns taken from spot 1 and spot 2, which correspond to the bulk LSMphase and the Zr-rich phase, respectively. Figure 6d is the high-resolution TEM image of the LSM phase, whichwas taken fromthe spot 1 location in Fig. 6a. The LSMphase is found toexhibit apseudo-cubic structure as confirmed by the diffraction pattern in Fig. 6b and the HREM image in Fig. 6d. The lattice parameter is measured to be ~0.4 nm, which is in a good agreement with the Fig. 5 (a) STEM-EELS spectra acquired across the same areas inside an LSM particle as seen in Fig. 4. (b) The reference O- K edge spectra for LSM, YSZ, and LZO, [16] (air flow cell). Fig. 6 (a) TEMbright field image of LSMparticle superimposedwith the positions where nano-beamdiffraction (NBD) patterns are taken from. (b) NBDpattern of LSMparticle. (c) NBDpattern taken on Zr-rich grain. (d) HR-TEM image of LSMparticles. An IFFT image is also included for a better image, (air flow cell). (a) (b) (continued on page 28)