Microstructure and Dielectric Properties of BaTiO3 Ceramics: A Local Structural Disorder Perspective with Site-Specific Configurational Entropy

The continuous miniaturization of multilayer ceramic capacitors (MLCCs) leads to elevated electric fields, reducing the dielectric constant of BaTiO 3 -based ceramics under DC bias. While doping-induced polar nanoregions (PNRs) can enhance DC-bias stability, they often reduce dielectric constant due to the lack of precise control over local polarization structures. Here, a site-selective entropy engineering strategy is employed to systematically compare A-site and B-site substitutions using Ba 1-4x Sr x Ca x La x Na x TiO 3 and BaTi 1-4x Zr x Hf x Ta x Y x O 3 (x = 0.05–0.2). By maintaining comparable configurational entropy (ΔS config ), the distinct roles of A-site and B-site disorder are decoupled. The results reveal that A-site entropy preserves relatively large and correlated PNRs, enabling a higher dielectric constant with improved DC-bias stability. In contrast, B-site entropy introduces stronger local lattice disorder and more randomized PNRs, as evidenced by PFM and TEM observations, leading to suppressed polarization saturation and enhanced thermal and DC-bias stability, but at the expense of a reduced dielectric constant. These findings establish a site-dependent entropy regulation mechanism and provide a rational framework for designing high-performance BT-based dielectrics with optimized high-field reliability.