Concentration-driving pinning effect in lead-free Mn-substituted BCZT ferroelectric ceramics

Domain wall motion in ferroelectrics, closely related to electric characteristics and amenable to tuning through doping, remains incompletely understood, particularly with regard to the pinning defect in the (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ (BCZT) system, which has attracted significant interest. Here, we investigate the defect dipole-assisted pinning effect in Mn-substituted BCZT (abbreviated as BCZT-xMn) ceramics with Mn concentrations ranging from x = 0 to 0.04. As x increases, we observe a gradual decrease in the maximum permittivity, accompanied by a leftward shift in temperature, leading to a diffuse phase transition. Analysis of the dielectric spectrum reveals a consistent trend in the activation energy within a specific concentration range, suggesting the incorporation of oxygen vacancies to maintain electric neutrality. The resulting oxygen vacancies, combined with Mn dopants, form defect dipoles Mn⁴⁺+e′− V_O ^⋅⋅ −Mn⁴⁺+e′, attaining sufficient concentration at x = 0.02, and enabling precise establishment of the pinning effect. This phenomenon is extensively documented by the observation of pinched polarization-electric field loops and double current peaks in the current-electric field curves, visually corroborated by experimental data and a 3D phase-field simulation model. Consequently, this study not only elucidates the concentration-driven pinning effect in the BCZT system but also provides valuable insights into doping effects in other lead-free ferroelectrics.