Lattice distortion and room-temperature ferroelectric properties of (Sm, Cr) co-doped BiFeO3 thin films

Pure BiFeO₃ (BFO) and Bi_0.85Sm_0.15Fe_0.97Cr_0.03O₃ (BSFCO) thin films were prepared on FTO/glass (SnO₂: F) substrates by using a chemical solution deposition method. The effects of (Sm, Cr) co-doping on the microstructure and ferroelectric properties of the BSFCO thin films were studied. The X-ray diffraction and Raman scattering spectra proved that the co-doped BSFCO thin film has a lattice distortion compared with the pure BFO thin film. The remnant polarization (2P _r) of the BSFCO thin film was 153.67 μC/cm² at 1 kHz in the applied electric field of 1,270 kV/cm. At an applied electric field of 100 kV/cm, the leakage current density of the co-doped BSFCO thin film (2.12 × 10^?6 A/cm²) was 3 orders lower than that of the pure BFO thin film (3.8 × 10^?3 A/cm²). The improved properties of the co-doped thin film could be attributed to lattices distortion, more grain boundaries, higher binding energy of Sm–O and the mixed-valence states of Cr³⁺ and Cr ⁶⁺.