Low‐temperature preparation of bismuth ferrite microcrystals by a sol‐gel‐hydrothermal method

Abstract

Well-crystallized pure perovskite bismuth ferrite (BiFeO 3 ) powders with various morphologies have been synthesized by a novel sol-gel-hydrothermal route for the first time, which combined the conventional sol-gel process and the hydrothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA) and ferroelectric test system. The results revealed that the compositions, morphological and dimensional changes in bismuth ferrite samples synthesized by sol-gel-hydrothermal method strongly depend on the concentrations of mineralizer. Ferroelectric hysteresis loops are displayed in the BiFeO 3 samples. The bismuth ferrites were hydrothermally synthesized at as low a temperature as 180 °C, which is comparatively lower than that synthesized by the normal sol-gel route. The formation mechanism of the bismuth ferrite crystalline was also discussed.

Low-temperature hydrothermal synthesis of BiFeO3 microcrystals and their visible-light photocatalytic activity

“…Previous studies [22][23][24][25][26][27][28][29][30][31][32] have suggested that the formation process of BFO phase under the hydrothermal condition can be described as the following reactions:…”

“…It is believed that the reaction temperature and concentration of OH À play the key roles in the hydrothermal formation of pure BFO materials. Earlier studies [22][23][24][25][26][27][28][29][30] have demonstrated that the pure BFO materials can be obtained by the hydrothermal process only when the temperature is above 150 8C or the concentration of mineralizer (such as KOH) is over 4 M. As for our case, the reaction temperature is kept at 120 8C. It is impossible to obtain pure BFO phase under such low temperature without any other addition even though the concentration of KOH is high as 10 M. However, when urea was added into the precursor solution, BFO phase dramatically appeared in the products even under such low temperature of 120 8C.…”

“…Typical techniques in this family are sol-gel [13][14][15][16], co-precipitation [17,18], microemulsion [19], autocombustion method [20,21] and hydrothermal process [22][23][24][25][26][27][28][29][30][31][32], respectively. Among these synthesis techniques, hydrothermal method for the synthesis of pure BFO phase has attracted more attention than others, because pure BFO materials can be achieved by hydrothermal treatment at a temperature of about 200 8C without a further calcination step.…”

Hydrothermal synthesis and mechanism and property study of La-doped BiFeO3 crystallites

“…''Dissolution-crystallization'' has been considered to be a basic mechanism to describe the hydrothermal process [23,24], in which the dissolution of the reactants is strongly dependent on a mineralizer and crystallization only occurring in the supersaturated fluid. Dissolution takes place when the reactants are loaded and heated in a hydrothermal system; then, more stable phases precipitate once the supersaturation for the phases is achieved.…”

Affinity‐tuned peroxidase‐like activity of hydrogel‐supported Fe3O4 nanozyme through alteration of crosslinking concentration

“…9 Fe 3 O 4 nanozyme has exhibited fascinating prospects principally in biomedical and environmental applications including H 2 O 2 and glucose detection, [10][11][12][13] and wastewater treatment. 14,15 It was reported that the peroxidase-like activity depended heavily on dispersion and content of Fe 3 O 4 nanozyme, [16][17][18][19] as well as affinity towards substrates. 20 Among the researches, affinity was usually improved by modifying the surface of Fe 3 O 4 nanoparticles with small molecules or linear polymers.…”