Introducing a large polar tetragonal distortion into Ba-doped BiFeO3 by low-temperature fluorination

Area of Science:

• Materials Science
• Solid State Chemistry
• Crystallography

Background:

• Bismuth ferrite (BiFeO3) is a multiferroic material with potential applications in various electronic devices.
• Doping with elements like barium (Ba) can modify its structural and magnetic properties.
• Fluorination offers a route to tune the properties of perovskite oxides.

Purpose of the Study:

• To synthesize and characterize barium-doped BiFeO3 oxide and oxyfluoride compounds.
• To investigate the crystallographic and magnetic structures of these materials.
• To understand the effect of fluorination on the properties of Ba-doped BiFeO3.

Main Methods:

• Synthesis of Bi(1-x)Ba(x)FeO(3-x/2) and Bi(1-x)Ba(x)FeO(3-x)F(x) compounds (x = 0.2, 0.3) via low-temperature fluorination of oxide precursors using polyvinylidenedifluoride.
• X-ray diffraction for crystallographic analysis.
• Neutron diffraction for magnetic structure determination.

Main Results:

• Oxide compounds showed cubic (x=0.2) and slightly tetragonal (x=0.3) perovskite structures.
• Oxyfluoride compounds exhibited large tetragonal polar distortion (c/a ≈ 1.08 for x=0.2, c/a ≈ 1.05 for x=0.3), isostructural to PbTiO3.
• Remanent magnetization correlated with BaFe12O19 impurity, detectable by neutron diffraction.
• Oxyfluoride compounds displayed G-type antiferromagnetic ordering with magnetic moments in the a/b plane.

Conclusions:

• Fluorination induces significant tetragonal distortion in Ba-doped BiFeO3, leading to oxyfluoride compounds with distinct structural and magnetic properties.
• The magnetic behavior is influenced by the presence of BaFe12O19, highlighting the importance of impurity analysis.
• These findings contribute to the understanding of structure-property relationships in doped and fluorinated perovskite materials.