Effect of Cr and La doping on the physical properties of Aurivillius Bi₅Ti₃FeO₁₅

Lead-based materials are the most used piezoelectric ceramics due to their high efficiency. Unfortunately, lead is toxic to humans and other living beings. Thus, there is significant interest in layered lead-free ceramics which show large piezoelectric effect at room temperature. This project studies layered Aurivillius perovskites of the form Bi₄Bi_n-3Ti₃Fe_n-3O_3n+3 where n = 4, specifically, the compounds Bi₅Ti₃FeO₁₅, Bi₄LaTi­₃FeO₁₅, and Bi₅Ti₃Fe_0.5Cr_0.5O₁₅ to understand the effect of doping the Bi-site with La and the Fe-site with Cr. We have prepared our samples using solid-state method and studied the crystal structure using synchrotron X-ray diffraction, thereby determining the space group of A21am for all three compositions. Further, we present the local crystal structure features using pair distribution function analysis. Our Raman scattering experiments reveal the vibrational modes and contrast the three compounds. The X-ray photoelectron spectroscopy results confirm the nominal valence of cationic species in the three compounds. All the three compounds show an antiferromagnetic nature of the magnetic ground state and are characterized using magnetometry and specific heat. We observe that the bulk properties of the three compounds are resilient to doping induced changes while only observable changes are to the local structure.