Colossal permittivity and relaxation behavior in LiCuNb3O9-doped CaCu3Ti4O12 ceramics with larger electrical response inside grains
Copper calcium titanate (CaCu 3 Ti 4 O 12 , CCTO) ceramics with colossal permittivity have gained widespread concern because of their potential application in modern electronic devices with miniaturization and integration. However, the extent of grain and grain boundary contribution to the colossal permittivity of CCTO-based ceramics based on the internal barrier layer capacitor (IBLC) model is still in debate. This affects their electrical performance optimization and real-world applications. In this study, a series of novel lead-free colossal permittivity ceramics, x LiCuNb 3 O 9 –(1– x )CaCu 3 Ti 4 O 12 (LCNO-CCTO), were designed and prepared using a solid-phase reaction approach. The colossal permittivity response mechanism of LCNO-CCTO ceramics was further explored by performing the complex impedance spectrum and analyzing the activation energy from the grain and grain boundary contribution viewpoint. As a result, the LCNO-CCTO ceramics present the cubic perovskite structure with the space groups of \(Im \overline{3}\) . All the LCNO-CCTO ceramics exhibit the significantly enhanced colossal permittivity (10 5 ) response, and the ceramic with x = 0.15 shows the highest permittivity of about 4.64 × 10 5 (20 Hz, room temperature) accompanied by a lower grain resistance of 9.61 Ω and larger grain activation energy of 0.21 eV. The enhanced colossal permittivity response is primarily attributed to the great electrical response inside grains of LCNO-CCTO ceramics, resulting from a smaller grain resistance. Also importantly, the high-frequency dielectric relaxation characteristics are improved by incorporating the LCNO into CCTO ceramics as an ion form. Accordingly, the LCNO-CCTO ceramics show a suppressed high-frequency dielectric loss. These results can provide a thorough knowledge and useful optimization strategy for developing high-performance colossal permittivity materials. Graphical
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