Enhanced dielectric and optical properties in Zn2+ and Zr4+ co-doping BiFeO3 ceramic

This work focuses on a new BiFeO3 (BFO)-based ceramic prepared by co-doping of Zn2+ and Zr4+ at the Fe-site under low concentration (2%). BiFe0.98(Zn1/2Zr1/2)(0.02)O-3 ceramic (BFZZ-02) was synthesized by the solid-state reaction method. X-ray diffraction revealed the good crystalline nature with the formation of impurities (Bi25FeO39 and Bi2Fe4O9). A rhombohedral R3c structure of BFZZ-02 was elucidated using Rietveld refinement. Raman spectroscopy confirmed also the rhombohedrally distorted perovskite structure and displayed the existence of spin-two-phonon interaction at a higher wavenumber range. BFZZ-02 exhibited a significant improvement in dielectric properties compared to pure BFO. A very high dielectric constant value up to approximately 10000 (at 1 kHz) was reached at Neel temperature (T-N = 544 K). The room temperature dielectric constant (epsilon '(r)) and loss tangent (tan delta) in BFZZ-02 were similar to 734 and similar to 0.035, respectively. The weak value in tan delta at room temperature, suggested a decrease in leakage current density compared to BFO owing to the reduction of oxygen vacancies and the formation of Fe2+. The nonexistence of Fe2+ was confirmed by Mossbauer spectroscopy. Eventually, the optical bandgap of BFZZ-02 (E-g approximate to 1.87 eV) was found to be reduced compared to BFO and possible reasons were thus evaluated. Such result suggests a strong absorption of visible light suitable for photocatalytic and solar cell applications.