Formation of a solid solution of ZnO:Mn2+ during mechanical treatment of oxides mixture

Electron paramagnetic-resonance measurements were carried out to study the structure of paramagnetic centres in ZnO + 1 % MnO2 powder mixtures, processed by a ball-milling technique during different treatment times, tMT. 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 tMT 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, (MT)-M-T, the defects having smaller activation energies are not stable. The formation of intermediate IV type centre is associated with diffusion of Mn2+ ions into a superficial Zn(OH)(2) environment. The subsequent formation of spectrum V associated with the solid solution ZnO:Mn2+, begins at (MT)-M-t > 90 min. (c) 2007 Elsevier Ltd. All rights reserved.