Abstract
Crystal structures of Ba2In2O5: (Ba1-xLax)(2)In2O5+x (x = 0.1, 0.2, 0.3, and 0.5), and Ba-2(In1-xGax)(2)O-5 (x = 0.1, 0.2 and 0.5) are analyzed by transmission electron microscopy and electron diffraction. Ba2In2O5 has an orthorhombic brownmillerite structure and belongs to space Croup Ibm2. (Ba1-xLax)(2)In2O5+x has a tetragonal brownmillerite structure while Ba-2(In1-xGax)(2)O-5 has an orthorhombic brownmillerite structure. These compounds consist of small domains that are at 90degrees orientation to each other. The domain size gets small with increasing La or Ga content. The oxygen vacancies are distributed randomly in the compounds with high La or Ga content, and consequently, the structure approximates as a cubic perovskite structure. (C) 2001 American Vacuum Society.