High dielectric permittivity and dielectric relaxation behavior in a Y2/3Cu3Ti4O12 ceramic prepared by a modified Sol−Gel route.

In this work, Y 2/3 Cu 3 Ti 4 O 12 ceramics were fabricated via a modified sol−gel route. Structural, dielectric, and electrical parameters were systematically investigated. The XRD results indicate that a CaCu 3 Ti 4 O 12 phase (JCPDS No. 75–2188) is present in every sintered sample. SEM images of Y 2/3 Cu 3 Ti 4 O 12 ceramics disclose a fine-grained ceramic microstructure. Interestingly, high dielectric permittivity, ∼6600–7600, with loss tangents of ∼0.918–1.086 were achieved in the sintered Y 2/3 Cu 3 Ti 4 O 12 samples. Density functional theory (DFT) calculations were used to investigate the most stable structure of the Y 2/3 Cu 3 Ti 4 O 12 ceramics. Our DFT results reveal that two calcium vacancies (V Ca) are isolated from each other. We also determined the lowest energy configuration of an oxygen vacancy (V O) in the Y 2/3 Cu 3 Ti 4 O 12 ceramics occurred during the sintering process. We found that the V O is trapped close to the Y atom in this structure. Both computational and experimental studies specify that the oxygen vacancy is located close to the Y atom in the Y 2/3 Cu 3 Ti 4 O 12 lattice and it might be a bivalent oxygen vacancy. As a result, due to charge balance, charge compensation of the transition ions, i.e. , Cu and Ti ions, might take place. The charge compensation mechanisms in the Y 2/3 Cu 3 Ti 4 O 12 lattice were verified using an XPS technique. Impedance spectroscopy confirms the presence of an inhomogeneous microstructure consisting of semiconducting grains and insulating grain boundaries in the sintered Y 2/3 Cu 3 Ti 4 O 12 ceramics. This electrical result is consistent with the computational analysis, showing that a charge compensation mechanism might be involved in generation of the grains' semiconductive region due to the presence of a V O. Consequently, high dielectric permittivity in Y 2/3 Cu 3 Ti 4 O 12 may have originated from an internal barrier layer capacitor (IBLC) effect. [ABSTRACT FROM AUTHOR]