Structure transition and enhanced ferroelectric properties of (Mn, Cr) co-doped BiFeO_3 thin films

摘要

Pure BiFeO_3 (BFO) and (Mn, Cr) co-doped BiFe_(0.96-y)Mn_(0.04)Cr_yO_3 thin films were prepared on FTO/ glass (SnO_2:F) substrates by using a sol-gel method. The effects of (Mn, Cr) co-doped on the microstructure and electric properties of the BiFeO_3 thin films were studied. The result indicates that the co-doped BiFe_(0.94)Mn_(0.04) Cr_(0.02)O_3 (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 coexistence 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/cm~2 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/cm~2. It is about three orders much lower than that of the BFO thin film (1.43 × 10~(-3) A/cm~2).