Hydrothermal synthesis of perovskite bismuth ferrite crystallites with the help of NH<inf>4</inf>Cl

Abstract

Summary form only given. Multiferroics have attracted considerable attention recently because of their fascinating physical behaviors and potential applications. BiFeO3 is one of the well-known multiferroic compounds displaying coexistence of ferroelectricity and antiferromagnetism [1]. The BiFeO3 properties in nanosize were especially helpful for understanding the foundational ferroelectric and magnetic mechanism [2]-[4]. Recently, only a few approaches by the hydrothermal method were reported about the pure BiFeO3 with irregular shapes [5],[6]. The bismuth ferrite powders in these works were synthesized by using [Bi(NO3)3-5H2O] and [Fe(NO3)3-9H2O] as start materials, which reacted to produce pure BiFeO3 phase in a limited experimental range. In this paper, pure BiFeO3 crystallites were synthesized by using FeCl3-6H2O and BiCl3 as start materials and NH4CI as an addition in wide hydrothermal conditions. Bismuth ferrite powders were prepared via a hydrothermal process using a stoichiometric mixture of FeCl3-6H2O and BiCl3 as metal precursors and NaOH as a mineralizer. FeCl3-6H2O and BiCl3 kept the resultant concentration 0.05 M were dissolved in distilled water under a mechanical stirring. NaOH solution was slowly added to the above solution, followed by adding 1.29 g (1 M) NH4CI to part samples. Finally, the brown suspension was transferred into a 29 mL Teflon vessel filled at 4/5 of its volume. The hydrothermal treatment was performed with different reaction temperatures and holding times. After cooling down to room temperature, the products were washed several times and dried in an oven at 70 °C. X-ray diffraction (XRD) analysis was performed to determine the powder phases. Scanning electron microscopy (SEM Quan200) was employed to investigate the particle sizes and morphologies of the products. The magnetic properties of part samples were measured with an LDJ9600 type of vibrating sample magnetometer (VSM). The pure BiFeO3 phase can be synthesized at wide NaOH concentration and wide temperature range with the help of NH4Cl solvent as shown in Fig. 1 and 2. The BiFeO3 morphologies change from agglomerate and irregular particles to regular and dispersive cubic particles, and more morphologies were obtained with the help of NH4CI solvent as shown in Fig. 3 and 4. BiFeO3 sample with more compact particles shows relative higher saturation magnetization. The details will be reported in the full manuscript.