Structure transition and enhanced ferroelectric properties of (Mn, Cr) co-doped BiFeO₃ thin films

Pure BiFeO₃ (BFO) and (Mn, Cr) co-doped BiFe_0.96−yMn_0.04Cr_yO₃ thin films were prepared on FTO/glass (SnO₂:F) substrates by using a sol–gel method. The effects of (Mn, Cr) co-doped on the microstructure and electric properties of the BiFeO₃ thin films were studied. The result indicates that the co-doped BiFe_0.94Mn_0.04Cr_0.02O₃ (BFMCO) thin film has a structure transition and better ferroelectric properties compared with the pure BFO thin film. The Rietveld refined XRD patterns of BFO and BFMCO thin films conform the trigonal (R3c:H) and the biphasic (R3c:H + R3m:R) structure, respectively. The co-existence of two phases and the mixed valences of Cr^3+/6+ and Mn^2+/3+, which apparently improves the electric properties of the (Mn, Cr) co-doped BFMCO thin films. The remnant polarization (P _r) of the BFMCO thin film was 93.58 μC/cm² at 1 kHz in the applied electric field of 636 kV/cm. At an applied electric field of 100 kV/cm, the leakage current density of (Mn, Cr) co-doped BFMCO thin film is 6.2 × 10⁻⁶ A/cm². It is about three orders much lower than that of the BFO thin film (1.43 × 10⁻³ A/cm²).