Origin of Relaxor Behavior in K1/2Bi1/2TiO3–Bi(Mg1/2Ti1/2)O3 Investigated by Electrical Impedance Spectroscopy

Lead‐free binary K_1/2Bi_1/2TiO₃‐Bi(Mg_1/2Ti_1/2)O₃ (KBT‐BMT) ferroelectric ceramics with a morphology of dense and evenly sized grains have been prepared by conventional solid oxide reaction route. X‐ray diffraction analysis indicates that all the samples possess pure perovskite structure, and undergo a phase transformation from tetragonal to pseudocubic phase as BMT adds into KBT. Meanwhile, BMT addition brings in the enhancement of the relaxor behavior as revealed by temperature‐dependent dielectric profiles and the P–E loops. The impedance analysis reveals that the relaxation process existing in the ceramics belongs to a localized species. Further, in the frequency‐dependent M″(f) spectra, a shoulder response emerges accompanied by a bulk response as suitable amount of BMT is added, and its frequency dependence obeys Vogel–Fulcher relation f = f₀ exp[ ‐ E_b/k_B(T ‐ T_VF)]. The shoulder response is believed to be the evidence of the existence of the polar nanoregions, which dominate the relaxor behavior of KBT‐BMT ceramics.