Enhanced dielectric and optical properties in Zn 2+ and Zr 4+ co-doping BiFeO 3 ceramic

This work focuses on a new BiFeO 3 (BFO)-based ceramic prepared by co-doping of Zn 2+ and Zr 4+ at the Fe-site under low concentration (2%). BiFe 0.98 (Zn 1/2 Zr 1/2 ) 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 (Bi 25 FeO 39 and Bi 2 Fe 4 O 9 ). 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 ( ε ′ r ) and loss tangent (tan δ ) in BFZZ-02 were ∼734 and ∼0.035, respectively. The weak value in tan δ at room temperature, suggested a decrease in leakage current density compared to BFO owing to the reduction of oxygen vacancies and the formation of Fe 2+ . The nonexistence of Fe 2+ was confirmed by Mossbauer spectroscopy. Eventually, the optical bandgap of BFZZ-02 ( E g ≈ 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.