Dielectric Properties and Nonlinear Electrical Response of Nb⁵⁺/Cr³⁺-Codoped CaCu₃Ti₄O₁₂ Ceramics

High Resolution Image Download MS PowerPoint Slide Adding Nb 5+ /Cr 3+ codopants to CaCu 3 Ti 4 O 12 ceramics via a solid-state reaction can significantly reduce the low-frequency loss tangent (tan δ ≈0.043) compared to undoped and single-doped (either with Nb 5+ or Cr 3+ ) CaCu 3 Ti 4 O 12 ceramics. Interestingly, very high dielectric permittivities of 99,098 are obtained together with excellent dielectric-frequency stability. In comparison to single-doped ceramics, the grain boundary resistance ( R gb ∼5.0 × 10 6 Ω·cm) at room temperature has increased significantly. Based on density functional theory calculations, the Cr 3+ ion tends to remain distant from the Nb 5+ ion in this lattice. Furthermore, it was found that Cr 3+ can induce oxygen vacancies in the Nb 5+ /Cr 3+ -codoped CaCu 3 Ti 4 O 12 structure, resulting in an increase in the oxygen vacancy concentration within the grains of the samples containing Cr ions. Both experimental and computational results support the internal barrier layer capacitor model. This model highlights the grain boundary properties responsible for controlling the giant dielectric properties of the Nb 5+ /Cr 3+ -codoped CaCu 3 Ti 4 O 12 ceramics.