(Zn2+ + Cd2+) co-doped CaCu3Ti4O12 ceramics with enhanced dielectric permittivity and reduced dielectric loss tangent

Abstract

The present study systematically investigated the structure, dielectric properties, and electrical response of Ca1-xCdxCu3-yZnyTi4O12 (x = y = 0, 0.025, 0.05, and 0.10). The XRD analysis indicates the presence of a CaCu3Ti4O12 phase in all the sintered ceramics, with no indications of impurity phases found. Achieving high dielectric permittivity and low loss tangent can be accomplished through codoping with Zn2+/Cd2+. At room temperature and 1 kHz, the Ca0.95Cd0.05Cu2.95Zn0.05Ti4O12 ceramic has a high dielectric constant of ∼1.61 × 105 and a low loss tangent of ∼0.03. In addition, codoping ions can enhance the stability of dielectric permittivity with respect to temperature variations. The utilization of impedance spectroscopy as a technique confirms the heterogeneous microstructure observed in sintered materials. The results of this investigation suggest a potential association between the internal barrier layer capacitor model and the underlying cause of the colossal dielectric characteristics observed in Ca1-xCdxCu3-yZnyTi4O12 materials. The analysis of X-ray photoelectron spectroscopy indicates the presence of Cu+ and Ti3+ species, which could potentially exert a significant impact on the development of n-type semiconducting grains in Ca1-xCdxCu3-yZnyTi4O12 ceramics. This influence is attributed to the existence of oxygen vacancies. Theoretical simulations revealed that a Zn atom is situated in proximity to a Cd atom within the CCTO structure. Furthermore, our findings indicate that the oxygen vacancy does not interact with the dopants. Our electron density analysis suggests that the presence of Cu+ and Ti3+ ions, as observed by XPS measurements, is a consequence of the existing oxygen vacancy.