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Author Efimov, K.; Xu, Q.; Feldhoff, A. pdf  doi
openurl 
  Title Transmission electron microscopy study of BA0.5Sr0.5CO0.8Fe0.2O3-\delta Perovskite decomposition at intermediate temperatures Type A1 Journal article
  Year (down) 2010 Publication Chemistry of materials Abbreviated Journal Chem Mater  
  Volume 22 Issue 21 Pages 5866-5875  
  Keywords A1 Journal article; Electron microscopy for materials research (EMAT)  
  Abstract The cubic perovskite Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-delta) (denoted BSCF) is the state-of-the-art ceramic membrane material used for oxygen separation technologies above 1150 K. BSCF is a mixed oxygen-ion and electron conductor (MIEC) and exhibits one of the highest oxygen permeabilities reported so far for dense oxides. Additionally, it has excellent phase stability above 1150 K. In the intermediate temperature range (750-1100 K), however, BSCF suffers from a slow decomposition of the cubic perovskite into variants with hexagonal stacking that are barriers to oxygen transport. To elucidate details of the decomposition process, both sintered BSCF ceramic and powder were annealed for 180-240 h in ambient air at temperatures below 1123 K and analyzed by different transmission electron microscopy techniques. Aside from hexagonal perovskite Ba(0.5)Sr(0.5)CoO(3-delta) , the formation of lamellar noncubic phases was observed in the quenched samples. The structure of the lamellae with the previously unknown composition Ba(1-x)Sr(x)Co(2-y)Fe(y)O(5-delta) was found to be related to the 15R hexagonal perovskite polytype. The valence and spin-state transition of cobalt leading to a considerable diminution of its ionic radius can be considered a reason for BSCF's inherent phase instability at intermediate temperatures.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Washington, D.C. Editor  
  Language Wos 000283623700010 Publication Date 2010-10-13  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0897-4756;1520-5002; ISBN Additional Links UA library record; WoS full record; WoS citing articles  
  Impact Factor 9.466 Times cited 117 Open Access  
  Notes Esteem 026019 Approved Most recent IF: 9.466; 2010 IF: 6.400  
  Call Number UA @ lucian @ c:irua:95546 Serial 3720  
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