Real structure and catalytic activity of La1-xSrxCoO3 perovskites

Mechanoceramical synthesis of La1-xSrxCoO3 (0 less than or equal tox less t han or equal to1) perovskites was made from simple oxides. Samples calcined at 900 and 1100 degreesC for 4 h are nearly monophase and well crystallize d. Sr adding was found to cause a structure rearrangement from the hexagona l (at x less than or equal to0.4) to the cubic one (at 0.8>x>0.4) and back to the hexagonal at x>0.8. There are two maxima of the catalytic activity v ersus chemical composition: at x=0.3 and at x=0.8. TEM data for these sampl es were obtained and disordered surface layers were detected. There is a co rrelation between the catalytic activity and surface layers microstructure. (C) 2001 Elsevier Science Ltd. All rights reserved.