Oxygen vacancy related defect dipoles in CaCu3Ti4O12: Detected by electron paramagnetic resonance spectroscopy

摘要

Oxygen vacancy associate defects were studied by electron paramagnetic resonance (EPR) for the perovskite oxide CaCu3Ti4O12 (CCTO), which have a colossal dielectric constant. It is found that the EPR line width of the Cu2+-host signal of CCTO correlates with its permittivity. A new signal was found in the second differential of the Cu2+-host signal, which we think is associated with a specific copper oxygen vacancy defect. This signal shows a negative g factor shift with temperature, suggesting a contribution to the conduction. Assuming solid state reactions between the various defects and using the mass action law, we offer a more specific relation between permittivity, the content of oxygen vacancy and the new signal, which might be useful for an indirect but fast oxygen vacancy content determination. (C) 2015 Elsevier Ltd. All rights reserved.