Abstract:
The nominal compositions of BiFe1-xGdxO3 (x = 0.00, 0.05) nanoparticles were
synthesized using sol-gel method to investigate their structural, electrical, magnetic and
optical properties. The investigated properties were compared between undoped and Gddoped
BiFeO3 nanoparticles. The X-ray diffraction (XRD) patterns revealed that the
substitution of Gd in the place of Fe in BiFeO3 induces a tendency of phase transition
from rhombohedral to orthorhombic. The field emission scanning electron microscopy
images and their respective histograms demonstrated that due to the substitution of Gd,
the average particle size was reduced with a narrow size distribution. Particularly, for 5 %
Gd doped BiFeO3 annealed at 600 oC the average particle size was reduced up to around
~35 nm which is much smaller than that of undoped BiFeO3. From leakage current
density vs. electric field graphs it was observed that the leaky behavior of the synthesized
nanoparticles was suppressed due to Gd substitution and increasing annealing
temperature. The suppression of leakage current density improved the ferroelectric
behavior of the synthesized nanoparticles deduced from polarization vs. electric field
hysteresis loops. The dielectric properties of the synthesized nanoparticles follow exactly
the same trend of ferroelectric behavior and reduced leakage current density. The
magnetization versus magnetic field hysteresis loops were carried out using a
Superconducting Quantum Interface Device (SQUID) magnetometer at room
temperature. The SQUID analysis demonstrated that, due to the Gd substitution in
BiFeO3 nanoparticles the room temperature magnetic parameters such as saturation
magnetization (Ms) and remanent magnetization (Mr) decreased gradually with increasing
annealing temperature, however, the values of Ms and Mr are many folds higher than their
bulk counterparts. The magnetization parameters decreased may be due to the reduction
of leakage current and oxygen vacancy related defects and also possibly some structural
distortion due to Gd substitution. The band gap energy of the synthesized nanoparticles
was determined which indicates that, it is possible to reduce band gap of multiferroic
BiFeO3 nanoparticles by doping Gd in the place of Fe.
