Giant dielectric behavior of monovalent cation/anion (Li⁺, F⁻) co‐doped CaCu₃Ti₄O₁₂ ceramics

Abstract

Giant dielectric behavior and electrical properties of monovalent cation/anion (Li+, F−) co‐doped CaCu3Ti4O12 ceramics prepared by a solid‐state reaction route were systematically investigated. Substitution of Li+ and F− led to a significantly enlarged mean grain size. A reduced loss tangent (tanδ ~0.06) with the retainment of an ultra‐high dielectric permittivity (ε′ ~7.7‐8.8 × 104) was achieved in the co‐doped ceramics, while the breakdown electric field and nonlinear coefficient of CaCu3Ti4O12 ceramics were increased by co‐doping with (Li+, F−). The variations in nonlinear electrical properties and giant dielectric response, as well as the dielectric relaxation, were well explained by the Maxwell‐Wagner polarization model for an electrically heterogeneous microstructure, in which a Schottky barrier height at the grain boundaries (GBs) was formed. ε′ was closely correlated to the GB capacitance. Significantly decreased tanδ value and enhanced nonlinear properties were related to a significant increase in the GB resistance, which was attributed to the significantly increased potential barrier height and conduction activation energy at the GBs. The semiconducting nature of the grains was also studied using X‐ray photoelectron spectroscopy and found to originate from the presence of Cu+ and Ti3+ ions.

Significantly improved non-ohmic and giant dielectric response in CaCu3Ti4O12 ceramics by incorporating Portland cement

“…This result confirmed that this phase was not in the CCTO grain. Thus, this area can be considered a Cu-rich phase, as has been reported in the literature [7,27]. Other elements were dispersed in both the CCTO and secondary phase grains.…”

Colossal dielectric permittivity, reduced loss tangent and the microstructure of Ca1−xCdxCu3Ti4O12−2yF2y ceramics

“…A great increase in grain size due to doping was also reported in earlier published papers. [6][7][8]27 This vastly increased grain size of the doped samples, compared to CCTO ceramic, might have been caused by liquid-phase sintering mechanisms. Generally, a liquidphase can form at junctions between particles or GBs, resulting in a much increased diffusion rate.…”

“…In advanced ceramics, essential raw materials for producing electronic components have been widely researched in this important eld. Focusing on capacitor applications, the colossal dielectric properties of polycrystalline ceramics, such as the codoped TiO 2 , 1,2,17,[20][21][22] codoped SnO 2 , 3 and ACu 3 Ti 4 O 12 (A ¼ Ca, [4][5][6][7][8][9]24 Cd, [10][11][12] Sm 2/3 , 13 Y 2/3 , 14 Na 1/2 Y 1/2 , 15 Na 1/2 Sm 1/2 , 25 Na 1/3 Cd 1/3 Y 1/3 16 ceramics have been developed and reported in the literature. Preserving high 3 0 values in these ceramics is the primary objective, followed by reducing loss tangents (tan d) and enhancing temperature/frequency stability.…”

“…Reports related to CaCu 3 Ti 4 O 12 (CCTO) based ceramics have been continuously published. [4][5][6][7][8][9][26][27][28][29] Due to its high 3 0 , numerous researchers have proposed an internal barrier layer capacitor (IBLC) structure, consisting of semiconducting grains and insulating grain boundaries (GBs). This was the rst model used to explain the colossal dielectric response in ACu 3 Ti 4 O 12 ceramics.…”

“…30 The most severe problem of CCTO for capacitor applications is its rather high tan d. Currently, modication of the preparation process and substitution of ions into the CCTO structure are frequently used to improve its dielectric and non-ohmic properties. [4][5][6][7][8][26][27][28][29] Additionally, modication of the A site of ACu 3 Ti 4 O 12 ceramics has also been a popular approach. [10][11][12][14][15][16]25 As previously reported by Yang et al, showed that doping Li + , Zn 2+ , Mg 2+ , and Zr 4+ into the CdCu 3 -Ti 4 O 12 structure can result in high 3 0 values of $1.0-5.0 Â 10 4 with low tan d values of $0.03-0.10.…”