Unusual relaxor–normal ferroelectric crossover in Cu-doped BiFeO3–BaTiO3 ceramics

The structural origin of relaxor behavior in perovskite ferroelectrics has remained elusive for decades. In this study, we observed a unique thermally driven normal to ferroelectric phase transition and Cu-doping induced relaxor to normal ferroelectric transition in 0.70BiFeO3–0.30BaTiO3 + x wt%CuO (x = 0.1, 0.2, 0.4, 0.6 and 0.8) ceramics. The XRD results show that Cu-doping induces a structural transition from pseudo-cubic phase to rhombohedral phase, associated with the domain switch from nanodomains to macrodomains, might be the origin of the relaxor–normal ferroelectric phase transition.