Enhanced Curie temperature and superior temperature stability by site selected doping in BCZT based lead-free ceramics

In this work, Bi³⁺ doped Ba_0.98-3x/2Bi_xCa_0.02Zr_0.02Ti_0.976Cu_0.008O₃ 0 ≤ x ≤ 0.03] lead free ceramics, to be employed for structural, dielectric and ferroelectric studies, have been synthesized via conventional solid state reaction method. Rietveld refinement of the X-ray diffraction (XRD) data evidences the existence of a pure perovskite phase with tetragonal symmetry for all ceramics. The Scanning Electron Microscopy (SEM) reveals that the grain size, which is 16.14 μm for x = 0 reduced to 2.11 μm for x = 0.03. Dielectric studies demonstrate excellent dielectric behavior with high Curie temperature (T_C ～159 °C), high dielectric constant (ε_r ～834, ε_max ～ 3146), and a low dielectric loss (tanδ ～ 0.019), for an optimum value of x = 0.02. The analysis of temperature coefficient of the dielectric permittivity indicates the applicability of these materials in multilayer ceramic capacitors. Impedance studies, conducted to understand the underlying physical mechanisms, are found to be in good agreement with the results of structural and dielectric studies. Furthermore, the ferroelectric measurement confirms the ferroelectric nature for all samples with an energy storage efficiency (η) of ～42% for x = 0.02 composition.