Structure and hyperfine interactions in Bi1−xNdxFeO3 solid solutions prepared by solid-state sintering

The series of polycrystalline ceramic powders, Bi1−xNdxFeO3 (x = 0.1−1) was successfully synthesized by mixed oxide method followed by pressureless sintering. X-ray diffraction and Mössbauer spectroscopy were used as complementary methods to study structure and hyperfine interactions of the samples. It was found that with an increase of Nd content, within the range of x = 0.2−0.3 a structural phase transition from rhombohedral to orthorhombic system occurs. The lattice parameters and unit-cell volume decrease with an increase of Nd concentration. The Mössbauer spectra registered for Bi1−xNdxFeO3 are characterized by sextets with slightly broadened lines and reveal distributions of hyperfine magnetic fields. It was found that the value of the hyperfine magnetic field induction monotonically increases with Nd content. The mean values of isomer shift are typical for Fe3+ ions in a high spin state and slightly decrease from 0.40 mm s−1 for x = 0.3 to 0.37 mm s−1 for x = 0.9. The small value of quadrupole shift confirms octahedral coordination of the iron ions. The structural transition is accompanied by an increase of isomer shift and a change of sign of quadrupole shift.