Significantly reduced the low-loss tangent in A2/3Cu3Ti4O12 (A = Gd and Sm) ceramics through a double-step calcination process

Abstract

This study employs a method, integrating a double calcination process with a solid-state reaction, to diminish the loss tangent of Gd2/3Cu3Ti4O12 and Sm2/3Cu3Ti4O12 ceramics. Fine-grained microstructures can be detected in sintered Gd2/3Cu3Ti4O12 and Sm2/3Cu3Ti4O12 ceramics. The dielectric constants of Gd2/3Cu3Ti4O12 and Sm2/3Cu3Ti4O12 ceramics vary within the range of 4.14 × 103 to 6.82 × 103 at room temperature and 1 kHz. Additionally, Sm2/3Cu3Ti4O12 displays an impressively low loss tangent, ranging from 0.017 to 0.019. X-ray photoelectron spectroscopy can detect the presence of both Cu+/Cu2+ and Ti3+/Ti4+ states, which may be influenced by oxygen vacancies within the lattice. Theoretical calculations using density functional theory have demonstrated that both Sm and Gd ions can increase oxygen vacancy concentrations, leading to a reduction in the loss tangent of these ceramics. Moreover, electron density analysis revealed that the presence of oxygen vacancies in this structure is responsible for the Cu+ and Ti3+ states observed in our XPS experiments. Lastly, the observed dielectric response in both Gd2/3Cu3Ti4O12 and Sm2/3Cu3Ti4O12 ceramics is probably attributed to a heterogeneous microstructure and the cumulative effects arising from both the grain and grain boundaries.