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SUMMARY:Cluster expansion and Monte Carlo simulation of the Ga-doped Ba2In
 2O5 fast anionic conductor - Riza Dervisoglu (University of Cambridge)
DTSTART:20110127T131000Z
DTEND:20110127T140000Z
UID:TALK29374@talks.cam.ac.uk
CONTACT:Dr Per Ola Kristensson
DESCRIPTION:The local structure and phase transformations of Ga-doped Ba2I
 n2O5 are studied by cluster expansion (CE) calculations based upon density
  functional theory (DFT)\, and Monte Carlo (MC) simulations based upon CE.
  Further\, we conducted x-ray diffraction experiments which confirmed our 
 theoretical results. Our results show that Ba2In2O5 (BIO) has two phase tr
 ansformations with increasing temperature\, from an orthorhombic (ortho) p
 hase to tetragonal (tet) and finally to a disordered cubic (cub) form\, al
 l of which is consistent with the results of Speakman et al. High oxygen i
 on conductivity occurs in tet and cub phases therefore these phases should
  be stabilized at lower temperatures for applicability in solid oxide fuel
  cells. We show with MC that increasing the Ga doping amount in Ba2(In1-xG
 ax)2O5 (BIGO) results in a progressive reduction in the low- and high-temp
 erature phase transformation temperatures. The ortho-tet phase transformat
 ion is even completely suppressed for BIGO at x>0.2 within quenched sample
 s\, as also experimentally shown by Yao et al. However\, the present theor
 etical and experimental studies indicate phase separation of Ga-rich and -
 poor regimes for BIGO prepared at equilibrium conditions.
LOCATION:Entertaining Room\, Darwin College
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