Terry J. Mazanec

Publications (2)4.54 Total impact

• Article: Atomic Resolution Analysis of the Defect Chemistry and Microdomain Structure of Brownmillerite‐Type Strontium Cobaltite

  Yasuo Ito, Robert F. Klie, Nigel D. Browning, Terry J. Mazanec
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  ABSTRACT: To investigate the fundamental aspects of vacancy ordering in oxygen-transporting ceramic membranes, we have performed atomic resolution analysis of individual domains in brownmillerite-type SrCoO3−δ. Electron energy loss spectroscopy indicates that the Co valence state in adjacent planes can be 2+ and 4+. This charge localization is accompanied by oxygen deficiency and the formation of ordered octahedral and tetrahedral coordinated Co sites. At microdomain boundaries, Z-contrast images reveal a structural relaxation of the octahedral site with the reduction of the Co valence state from 4+ to 3+ and the incorporation of extra oxygen vacancies.
  Journal of the American Ceramic Society 12/2004; 85(4):969 - 976. · 2.27 Impact Factor
• Article: Segregation Effects at Grain Boundaries in Fluorite‐Structured Ceramics

  Yuanyuan Lei, Yasuo Ito, Nigel D. Browning, Terry J. Mazanec
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  ABSTRACT: The atomic-scale structure, composition, and chemistry of grain boundaries in two fluorite-structured ceramic materials were characterized by a combination of Z-contrast imaging and electron energy-loss spectroscopy (EELS). In the case of a symmetric 24° [001] tilt bicrystal of yttria-stabilized-zirconia (YSZ), a shift in the zirconium M-edge onset and a change in the yttrium and zirconium M-edge ratios at the boundary indicate an increase in the number of electrons in the boundary plane. A detailed study of the structure and composition indicates that this is caused by an increase in the number of oxygen vacancies in the grain boundary core that is partially compensated by yttrium segregation. Studies of grain boundaries in an industrial Gd-doped ceria ceramic reveals similar changes in vacancy/dopant profiles indicating that these effects may be generic to grain boundaries in fluorite-structured materials.
  Journal of the American Ceramic Society 08/2002; 85(9):2359 - 2363. · 2.27 Impact Factor