Mechanothermal effects on the defect structure in ZnO powders subjected to hydrostatic pressure

Abstract

Using electron paramagnetic resonance (EPR) spectroscopy method the mechanism of defect formation has been studied in ZnO powders, put to a bottoming (a hydrostatic pressing) up to P=8 GPa. The initiation of 6 paramagnetic centers by a pressing has been shown (V Zn- : Zn io - I, V Zn- - II, (V Zn-) 2- - III, V o+ -IV, SDS (shallow donor states) - V and SDS imp (SDS associated with impurities) - VI). The dependence of the signal intensity (I) on pressure P has been studied. The maxima on curves I =f (P) for EPR signals from centres I and II are attributed to the development of mechanothermal processes promoting an annealing of the created defects during pressing. Comparison with the data on anealing of paramagnetic centers has allowed to construct the dependence of an average sample temperature as a function of hydrostatic pressure, and to propose the model diagram of the development of mechanothermal processes under pressure.