Potential barrier engineered colossal permittivity CaCu₃Ti₄O₁₂ ceramics with largely reduced dielectric loss

CaCu₃Ti₄O₁₂ (CCTO) ceramics exhibit a colossal permittivity response and good stability across wide temperature and frequency ranges, and play an indispensable role in microelectronic devices and energy storage applications. However, the advancements of CCTO-based ceramics are still impeded by a large dielectric loss. In this work, a potential barrier engineering was employed to fabricate the Sr²⁺ and Co²⁺ doped CCTO ceramics with improved dielectric properties via a solid-state method. The phase structure, microstructure and dielectric properties of the doped samples were systematically investigated. As anticipated, all the doped CCTO ceramics present a significant colossal permittivity characteristic and a reduced dielectric loss. Especially, the Ca_0.9Sr_0.1Cu_2.9Co_0.1Ti₄O₁₂ ceramic presents a significantly reduced dielectric loss of about 0.05, while maintaining a notably giant permittivity characteristic of about 3.24 × 10⁴ at a frequency of 10³ Hz. This ceramic is also characterized by a relatively dense microstructure, and the corresponding average grain size of about 15.31 μm. The pinning effect imposed by these defects on free charge carriers limits their mobility, thereby intensifying local polarization and reducing oxygen vacancies in this Sr²⁺/Co²⁺ co-doped CCTO ceramics. This phenomenon contributes to an increased barrier height of about 0.61 eV, which amplifies the grain boundary response and ultimately leads to reduced dielectric loss. This finding signifies that the potential barrier engineering is an effective strategy for designing giant permittivity materials with low dielectric loss.