Microstructural,dielectric, and nonlinear properties of Ca1–xCdxCu3Ti4O12 thin films

The effects of the A-site transition from Ca²⁺ to Cd²⁺ on the microstructure, morphology, and electrical properties of Ca_1–xCd_xCu₃Ti₄O₁₂ thin films were studied. The film surfaces are smooth, compact, and without cracks. The CaCu₃Ti₄O₁₂ and CdCu₃Ti₄O₁₂ films had similar morphologies and electrical properties. The grain size initially increased and subsequently decreased with the transition from Ca²⁺ to Cd²⁺ at the A site. The change in Ca sites has an obvious effect on Cu sites. The film with more copper-rich phases at the grain boundaries had the largest grain size when Ca²⁺ and Cd²⁺ equally occupied the A sites. The dielectric constant of Ca_1–xCd_xCu₃Ti₄O₁₂ was closely related to the copper oxide secondary phase. The dielectric loss tangent and nonlinearity coefficient were associated with the compact structure, copper oxide secondary phase, copper vacancies and improved grain boundary response. The simultaneous occupancy of the A sites by Ca²⁺ and Cd²⁺ improves the dielectric and nonlinear properties of Ca_1–xCd_xCu₃Ti₄O₁₂. Optimal dielectric properties (?_r = 5238 and tan δ = 0.009 at 1 kHz) and an enhanced nonlinearity coefficient (～4.22) were simultaneously obtained for the Ca_0.5Cd_0.5Cu₃Ti₄O₁₂ thin film. This study demonstrates that the extrinsic mechanism is the main origin of the high dielectric constant values in Ca_1–xCd_xCu₃Ti₄O₁₂ films. The resulting films are suitable for applications in capacitors.