This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.
 

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Gamma (γ)-alumina has essentially a defective spinel structure with cation-site vacancies. The Al atoms occupy both tetrahedral and octahedral coordinated sites. Researchers have presented various γ-alumina crystal structures. The proportion of tetrahedral:octahedral Al coordinates are different in different γ-aluminas, for instance, η-alumina has 36:51 and θ-alumina 50:50.