Comparison of the structure–property relationships between sillenite and perovskite phases of Bi0.9Dy0.1FeO3 nanostructures

Abstract

We explored a comprehensive comparison of the structure–property relationships between sillenite and perovskite phases of Bi_0.9Dy_0.1FeO₃ (BDFO) nanostructures synthesized by hydrothermal (HT) and sol–gel (SG) techniques. The role of sillenite/perovskite phases as well as oxygen vacancies in the magnetic and catalytic properties was analyzed and compared, which to our knowledge, is the first of its kind at the nanometer scale. XRD results revealed the formation of a sillenite dominating phase through the HT synthesis at 160 °C, whereas, the SG method resulted in perovskite bismuth ferrite after calcination at an elevated temperature of 600 °C. Both scanning and transmission electron microscopy imaging demonstrated a mixed nanopowder and rod-like morphology of the materials synthesized by the HT technique, however, semi-spherical particles with a particle size of ∼100 nm were produced via the SG technique. The XPS analysis revealed that the number of oxygen vacancies was higher in the HT-synthesized BDFO compared to that of the SG-synthesized BDFO. A sharp transition of the HT-synthesized BDFO materials was observed at 43 K, whereas, the SG-synthesized materials revealed a gradual increase in the magnetization with the decrement of temperature from 400 to 5 K without any phase transition. The HT-synthesized BDFO demonstrated a better photocatalytic performance to degrade rhodamine B and colorless antibiotic ciprofloxacin compared to the SG-synthesized BDFO photocatalyst. This comprehensive analysis of the phase-structure, morphology, chemical states, and oxygen vacancies of BDFO materials synthesized under the standard synthesis conditions of two commonly used synthesis techniques might be helpful for researchers to understand the physico-chemical properties of analogous nanostructures for desired applications.