Structural, ferroelectric and magnetic properties of BiFeO3 synthesized by hydro-evaporation and sonochemically assisted hydrothermal methods

Abstract

Multiferroic bismuth ferrite (BiFeO3) powders were synthesized using hydroevaporation (HE) and sonochemically assisted hydrothermal (HT) method to investigate how different synthesis methods affect the properties of the powders and sintered samples. The structural and microstructural analyses revealed that all the samples contain secondary phases, Bi25FeO40 and Bi2Fe4O9, but their contribution depends on conditions of thermal treatment (calcination and sintering). The densest (88% and 95 % of theoretical density for HE and HT sample, respectively) ceramics were obtained after pressing of powders at 9 t/cm2 followed by sintering at 820 °C for 2 h. Ferroelectric properties of sintered samples were correlated with grain size and density, while the presence of charge defects indicated distortion of crystal lattice. Magnetic measurements of M(H) for both sintered samples showed small deviation from linearity. The sample sintered from HT powder exhibited greater remnant electric polarization as well as greater value of magnetization as a function of temperature. Also, after cooling in magnetic field this sample indicated the asymmetric magnetic hysteresis loop (exchange bias effect). Although both samples showed weak electric (Pr ≤ 1 μC/cm2 ) and magnetic polarization (M ≤ 0.01 emu/g) at room temperature, ceramics obtained from HT powder was overall superior with respect to multiferroic properties.