Ca doped Y2/3Cu3Ti4O12: Structure and dielectric properties

Abstract

In this study, we systematically examined the structure and dielectric properties of Y2/3-xCa3x/2Cu3Ti4O12 (x = 0.0, 0.05, 0.10, 0.15, and 0.20). X-ray diffraction (XRD) analysis revealed that the structure of all ceramics conformed to the CaCu3Ti4O12 ceramics database, specifically with JCPDS No. 75–2188, and no impurity phases were detected. The conducted experiments revealed a notable rise in the dielectric constant at elevated concentrations of Ca doping, ranging from 104 to 105. Conversely, the loss tangent values, lower than those of Y2/3Cu3Ti4O12, exhibited a decrease from 0.533 to 0.333 as x increased from 0 to 0.20. Synchrotron radiation, based on X-ray photoelectron spectroscopy, was employed to investigate the valence states of Ti and Cu ions. This observation is directly linked to the presence of oxygen vacancies within the lattice. Impedance spectroscopy analysis unveiled two distinct electrical states within the Ca-doped Y2/3Cu3Ti4O12 system. The first part corresponds to the semiconductive nature exhibited by the grain, while the subsequent part pertains to the insulative characteristics observed at the grain boundary. The remarkable dielectric permittivity observed in Ca-doped Y2/3Cu3Ti4O12 system ceramics can be attributed to the existence of a heterogeneous microstructure comprising semiconducting grains and insulating grain boundaries. The presence of Cu+ and Ti3+ ions could potentially account for the semiconductive state observed within the grains of Y2/3Cu3Ti4O12 ceramics.