Vacancy ordering in the structure of gamma-Al2O3

Defect structure of gamma-Al2O3 prepared by the thermal decomposition of we ll-crystallized, high purity boehmite (gamma-AlOOH) has been studied by HRE M. It was shown that the intrinsic feature of gamma-alumina structure is a presence of almost hexagonal closed loops formed due to the ordering of cat ion vacancies over octahedral positions on (110) and (111) planes. These de fects are relatively stable they are preserved, though being changed in sha pe, in the gamma-alumina sample upon its further calcination until the appe arance of traces of delta-alumina phase. (C) 2000 Elsevier Science Ltd. All rights reserved.