Structural, Magnetic, and Optical Properties of Complex Lead-Free Ferroelectric 0.97Bi0.5Na0.5TiO3 + 0.03AMnO3 (A = Mg, Ca, Sr, Ba) Materials

A series of alkaline-earth perovskite-type manganite AMnO3-δ (A = Mg, Ca, Sr and Ba)-modified lead-free ferroelectric Bi0.5Na0.5TiO3 materials were synthesized by a simple chemical method. The AMnO3-δ materials were found to well solid solution into the host Bi0.5Na0.5TiO3 crystals. The random distribution of alkaline-earth cations and Mn cations into the host Bi0.5Na0.5TiO3 induced complex magnetic properties. The optical bandgap of the pure Bi0.5Na0.5TiO3 material was obtained at around 3.08 eV, and reduced to 2.56 eV, 2.25 eV, 1.89 eV and 1.66 eV for MgMnO3-δ-, CaMnO3-δ-, SrMnO3-δ- and BaMnO3-δ-modified Bi0.5Na0.5TiO3 crystal, respectively. First principle theoretical calculations were performed for various incorporations of Mn cations at Bi-, Na-, Ti-sites, and Mn interstitials into the Bi0.5Na0.5TiO3 host lattice. Our results showed that the incorporation of Mn cations complexly contributed to the electronic bandgap of the host Bi0.5Na0.5TiO3 materials.