Rare earth (La) and metal ion (Pb) substitution induced structural and multiferroic properties of bismuth ferrite

In this study, bulk samples of multiferroic with compositional formula, BiFeO3 and Bi(0.825)A(0.175)FeO(3) (A = La, Pb), were synthesized by solid state reaction route. X-ray diffraction (XRD) along with the Rietveld refinement revealed the distorted rhombohedral (R3c) structure for pristine BiFeO3 and Bi0.825La0.175FeO3 and tetragonal (P4/mmm) for Bi0.825Pb0.175FeO3 ceramic. To support the structural results, bond length between atoms for both of the compounds was calculated. A change in Raman mode position in BiFeO3 (BFO) has been observed with La and Pb substitution from Raman scattering measurements and also recommended a structural change with rare earth and metal ion substitution at Bi site. From the frequency dependent dielectric constant and dielectric loss plots, a decrease in dielectric values with increase in frequency was observed for both of the samples. For microelectronic devices, porous ceramics with lower value of dielectric constant are most useful. Thus, further studies are also needed to carefully tune the magnetoelectric properties and structural distortion after La/Pb substitution in BFO.