Enhanced dielectric properties with a significantly reduced loss tangent in (Mg2+, Al3+) co-doped CaCu3Ti4O12 ceramics: DFT and experimental investigations

Abstract

CaCu₃Ti₄O₁₂ and CaCu_2.95Mg_0.05Ti_3.95Al_0.05O₁₂ ceramics were fabricated via a solid-state reaction method. A single-phase of CaCu₃Ti₄O₁₂ was found in these two ceramics. Very great grain size expansion was produced by co-doping with Mg²⁺ and Al³⁺. DFT results indicate that both Mg and Al atoms preferentially occupy Cu sites, creating liquid-phase sintering decomposition at grain boundary layers. Very high dielectric permittivity of ∼58 397 and low loss tangent of about 0.047 were achieved in a CaCu_2.95Mg_0.05Ti_3.95Al_0.05O₁₂ ceramic. Additionally, the temperature stability of the dielectric response was improved. Better dielectric properties in the co-doped ceramic have possible origins from enhanced grain boundary responses, especially from the influences of metastable phases and oxygen enrichment at the grain boundaries. Experimental and computational results indicate that the colossal dielectric properties in CaCu₃Ti₄O₁₂ ceramics might be correlated with an internal barrier layer capacitor structure.