Central role of TiO2 anatase grain boundaries on resistivity of CaCu3Ti4O12-based materials probed by Raman spectroscopy

This study focuses on characterization and control of grain boundaries to enhance the properties of CaCu3Ti4O12 (CCTO) ceramics capacitors for industrial applications. A novel factor deals with TiO2 anatase revealed by Raman scattering in grain boundaries, found as a dominant parameter of largest sample resistivity, consistent with higher grain boundary resistivity and higher breakdown voltage. Four selected samples of CCTO-based compositions showing very different properties in terms of permittivity ranging from 1000 to 684 000 measured at 1 kHz, capacitance of grain boundaries ranging from 8 10−10 to 4.5 10−7 F cm−1, grain boundary resistivity ranging from 193 to 30,000,000 Ω cm and sample resistivity extending from 450 to 1011 Ω cm. The relationship between permittivity weighted by grain size and capacitance of grain boundaries confirms the internal barrier layer capacitance model over 5 orders of magnitude.