2, IUAC, New Delhi, , India
Ferroelectric ceramics are of technological promise because of their wide range of applications in dynamic random access memories (DRAMS), non-volatile memories, pyroelectric detectors and electro-optic devices, etc. Barium strontium titanate (Ba1-xSrxTiO3, hereafter denoted as BST) being ecofriendly material, is considered as one of the most promising candidate for ferroelectric devices due to its excellent properties of high dielectric constant, low leakage current and adjustable Curie temperature (TC). The doping of magnetic ion ‘Fe’ at ‘Ti’ site not only reduces the dielectric loss but also induces magnetism in it. However, very less is known about the magnetic properties and the electronic structures of the Fe-doped BST solid solutions. X-ray absorption spectroscopy especially X-ray absorption near-edge structure (XANES) when invited with Fe doped BST can provide information about the change in the valency of Fe and Ti ions and chemical bonding information. Present investigation focuses on the structural, magnetic and electronic properties of Fe doped BST ceramics . Bulk samples with composition Ba0.7Sr0.3FexTi1-xO3 where x =0, 0.1, 0.2, 0.3 were synthesized via conventional solid state reaction route. X-ray diffraction patterns of all the samples clearly show phase formation with the absence of impurity peaks. The Rietveld refinement confirmed the coexistence of the tetragonal and cubic phase for samples with Fe content x= 0, 0.1 and pure cubic phase for x > 0.1. The M–H hysteresis curves for samples with composition x = 0.1 and 0.2 exhibit paramagnetic behaviour even at low temperatures and the composition with x = 0.3 shows the nature of weak ferro- and ferri-magnetic orderings at about 2K. It is inevitable that presence of Fe2+ state is responsible for paramagnetism. However, with increasing Fe content mixed valency seem to be setting in. This strange magnetic behavior is due to the presence of mixed valence states and in particular Fe2+ state in the samples, as observed from Fe L3-edge XANES spectra. The Ti L3,2-edges at the XANES spectra confirmed that the doping of Fe in ABO3 structure leads to the lattice distortion. This doping induced distortion is also evidenced by the Fe K-edge XAS. The Fe L3-edge XANES spectra revealed that with increasing the Fe concentration, the mixed valence states and presence of Fe2+ are observed. The XANES spectra of the Ba L3-edge and Sr L3-edge spectra confirmed that the local structure around Ba2+ and Sr2+ respectively does not show any influence from the dopants in the BST system.
1. “Structural, Magnetic and Electronic Properties of Iron Doped Barium Strontium Titanate” ; Kaur.A et.al RSC Adv., 2016, 6, 112363