Synthesis of BiFeO₃ by Wet Chemical Methods

Abstract

The synthesis of phase-pure BiFeO 3 has been demonstrated by a chemical synthesis route as well as the solid-state method at 8251C. Polymeric BiFeO 3 precursors were obtained from aqueous solutions of nitrate salts and carboxylic acids with and without ethylene glycol added as a polymerization agent. The polymeric precursors were shown to decompose above 2001C with successive nucleation and growth of BiFeO 3 above 4001C. The phase purity of the product was shown to depend on the type of carboxylic acid used, and tartaric, malic, and maleic acids resulted in nanocrystalline phase-pure BiFeO 3 . The unit cell and Ne´el temperature of the bulk materials obtained by the two methods were in accord with previous reports.

Reaction pathways in the solid state synthesis of multiferroic BiFeO3

“…In this sense one presumed possibility is to go straightly to the temperatures at which the 1:1 perovskite phase is stable with regards to the other two phases of the systems; according to previous reports by Selbach et al this may be achieved by rapid heating and fast cooling the BÍ20 3 -Fe 2 0 3 mixture at T> 161 °C. 9 ' 30 Another plausible option would involve the increase in the system reactivity: this can be done by applying a more reactive wet chemical synthesis method, something recurrently used in the literature and that also reduces the probability of impurity contamination. Accordingly, we designed some fast flring and co-precipitation experiments whose major features are described in Section 2, and with the obtained powders we ran the corresponding calcination treatments.…”

Modified Pechini Synthesis of Oxide Powders and Thin Films

“…By this polymer-complex solution method, less amount of organics is used and for the synthesis of CaAl2O4 a phase pure material was prepared with a higher amount of cations than the number of functional groups in the polymer (Gülgün et al 1999) For some specific cations it has more recently been observed that complexing agents with -OH groups like ethylene glycol and polyvinyl alcohol (PVA) are better compounds to promote homogeneity of the final oxide than carboxylic acids. This has empirically been found to be of great advantage for amphoteric cations like In 3+ , Sn 4+ and Bi 3+ in the preparation of indium tin oxide (Kundu and Biswas 2008;Sunde et al 2012) and BiFeO3 (Selbach et al 2007;Liu et al 2010). An amino carboxylic acid, e.g.…”

“…This gives a very high degree of homogeneity, which is beneficial for the preparation of these compounds. The size of the polybasic acid as well as the ratio between the acid and cations have shown to be of importance as more organics has to be burned off, influencing on the local temperature as well as the partial pressure of oxygen (Selbach et al 2007). In a synthesis protocol closely related to the modified Pechini synthesis, a polymer (PVA or PEG) is used to physically stabilize the cations by a proposed entanglement around the cations.…”

“…in much larger quantities than when it is only added in smaller amounts as a polymerization agent to an aqueous solution. The majority of works use nitrates of bismuth and iron as cation precursors (Selbach et al 2007)). The choice of precursors and amount of organic additives can be important.…”

“…Several modified Pechini-related synthesis routes have been used, with different polybasic carboxylic acids as complexing agents with and without the addition of EG as polymerization agent (Selbach et al 2007). Here, phase-pure BiFeO3 was obtained by tartaric and malic acid, with and without EG, and maleic acid with EG.…”