Formation of a solid solution of ZnO : Mn 2+ during mechanical treatment of oxides mixture

Abstract

Electron paramagnetic-resonance measurements were carried out to study the structure of paramagnetic centres in ZnO+1% MnO 2 powder mixtures, processed by a ball-milling technique during different treatment times, t MT . Initiation of five different types of paramagnetic centres, I– V, was revealed. The electron-hole centres I (V Zn −:Zn i 0), II (V Zn −), and III ((V Zn −) 2 −) in ZnO first appear and then disappear with the mechanical treatment (different times t MT for different centres). It indicates that the formation of vacancies and other defects in ZnO have various reaction energies and that on annealing at higher temperatures, T MT , the defects having smaller activation energies are not stable. The formation of intermediate IV type centre is associated with diffusion of Mn 2+ ions into a superficial Zn(OH) 2 environment. The subsequent formation of spectrum V associated with the solid solution ZnO:Mn 2+, begins at t M T > 90 min .