MICROCOMPOSITE PARTICLES SR3TI2O7-SRTIO3 WITH AN EPITAXIAL CORESHELL STRUCTURE

Microcomposite particles Sr3Ti2O7-SrTiO3 with an epitaxial core-shell structure were prepared by the hydrothermal treatment of Sr3Ti2O7 core particles. The Sr3Ti2O7 core particles synthesized in a fused salt ha d a plate-like morphology with a well developed {001} plane of the Rud dlesden-Popper type crystal structure. The particles after hydrotherma l treatment have an anisotropic morphology and a core-shell microcompo site structure: the plate-like Sr3Ti2O7 particles covered with SrTiO3 fine particulates and thin layers. TEM analysis revealed that the SrTi O3 shell on a Sr3Ti2O7 core particle had an epitaxial relationship wit h the core such that {100} SrTiO3//{001} Sr3Ti2O7 and [010] SrTiO3//[0 10] Sr3Ti2O7. The possible formation mechanisms of the SrTiO3 phase we re through solution-precipitation and the extraction of Sr-O layers fr om the Sr3Ti2O7 structure under the hydrothermal conditions. The proce ssing method will be extended to the other type of microcomposite with an anisotropic morphology and an functional surface phase. (C) 1998 E lsevier Science B.V. All rights reserved.