Phase formation, crystal chemistry, and properties in the system Bi2O3–Fe2O3–Nb2O5

Lufaso, Michael W.; Vanderah, Terrell A.; Pazos, Ileana M.; Levin, Igor; Roth, Robert; Nino, Juan C.; Provenzano, V.; Schenck, Peter K.

doi:10.1016/j.jssc.2006.08.036

Cited by 126 publications

(118 citation statements)

References 56 publications

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“…This indicates that in spite of the apparently single-phase X-ray diffractograms, the BiFeÜ3 phase was not synthesized as a puré product from these mixed-oxides experiments. Furthermore, repeated grinding-flring and/orprolonged annealing times were also tried but, as happened before to some other authors, 10 ' 25 no signiflcant changes in the phase distributions and fractions were observed. Therefore it seems that once the secondary phases are formed they are tricky to remove and attempts should be made to circumvent their formation.…”

Section: Resulte and Discussionmentioning

confidence: 95%

“…7 These secondary by-products have been interpreted as intermediates in the formation of the ferrite, 8 ' 9 but the fact is that their elimination through a simple mixed-oxides solid state reaction route has proven extremely difficult if not impossible. [10][11][12] Many alternative strategies have been (are being) attempted to prepare puré BiFeÜ3, from a rapid liquid-phase sintering, 13 ' 14 a microwave or spark-plasma assisted sintering, 15 ' 16 or even a mechanochemical high energy milling processing, 17 to different wet chemical methods [18][19][20][21][22][23][24] ; but even in those that have succeed, the precise reaction mechanisms have not been identified yet. Why the secondary phases are usually present in the system is source of discussion in the literature: the presence of trace impurities, 25 the formation of non-stoichiometric solid solutions 26 and/or a certain degree of thermodynamic metastability, 9 have been proposed to explain such an anomalous situation for a presumed BÍ203-Fe2Ü3 binary system.…”

Section: Introductionmentioning

confidence: 99%

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Reaction pathways in the solid state synthesis of multiferroic BiFeO3

Bernardo

Jardiel

Peiteado

et al. 2011

Journal of the European Ceramic Society

156

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The obtaining of multiferroic BiFe0 3 as a puré single-phase product is particularly complex since the formation of secondary phases seems to be unavoidable. The process by which these secondary impurities are formed is studied by analyzing the diffusion and solid state reactivity of the Bi 2 03-Fe 2 03 system. Experimental evidence is reported which indicates that the progressive diffusion of Bi 3+ ions into the Fe 2 0 3 particles governs the solid state synthesis of the perovskite BiFe0 3 phase. However a competition is established between the diffusion process which tends to complete the formation of BiFe0 3 , and the crystallization of stable Bi 2 Fe 4 0 9 mullite crystals, which tend to block that formation reaction.

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Section: Resulte and Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Reaction pathways in the solid state synthesis of multiferroic BiFeO3

Bernardo

Jardiel

Peiteado

et al. 2011

Journal of the European Ceramic Society

156

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“…The consistent observation of this reflection indicates that all Bi-Co-Nb-O pyrochlores exhibit positional displacements. Furthermore, the [29] Fe, [36] Mn [37] ), occurs at substantially lower Bi concentrations than conventional formulations placing only Bi on the A sites and the smaller M/Nb cations on the B sites. The pyrochlore field includes compositions with "excess" B cations that require mixing of some Co on the A sites with Bi 3+ , as found for Zn in all Bi-Zn-Nb-O pyrochlores.…”

Section: Phase Formationmentioning

confidence: 90%

Phase Formation and Properties in the System Bi₂O₃:2CoO_1+x:Nb₂O₅

Vanderah

Siegrist²,

Lufaso

et al. 2006

Eur J Inorg Chem

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Subsolidus phase relations have been determined for the Bi–Co–Nb–O system in air (750–925 °C). Ternary compound formation was limited to pyrochlore (A2B2O6O′), which formed a substantial solid solution region at Bi‐deficient stoichiometries (relative to Bi2Co2/3Nb4/3O7) suggesting that about 8 to 25 % of the A sites are occupied by Co. X‐ray powder diffraction data confirmed that all Bi–Co–Nb–O pyrochlores exhibit displacive behavior. A structural refinement of the pyrochlore Bi1.56Co0.96Nb1.48O7 using single‐crystal X‐ray diffraction data is reported with the A and O′ atoms displaced (0.34 Å and 0.45 Å, respectively) from ideal positions to96g sites and 32e sites, respectively [Fd3$\bar {S}$m (#227), a = 10.551(1) Å]. The displacive structural behavior is similar to that found in analogous Bi–M–Nb–O pyrochlores (M = Zn, Fe, Mn). Bi–Co–Nb–O pyrochlores exhibited overall paramagnetic behavior with negative Curie–Weiss temperature intercepts indicating weak antiferromagnetic interactions. At 250 K and 1 MHz the relative dielectric permittivity of the pyrochlore 0.4400:0.2100:0.3500 Bi2O3:2CoO1+x:Nb2O5 was ca. 115 with tan δ = 0.06; however, at lower frequencies the sample was conductive. Low‐temperature dielectric relaxation such as that observed for Bi1.5Zn0.92Nb1.5O6.92 and other bismuth‐based pyrochlores was not observed. Consideration of bond lengths, effective magnetic moments, and dielectric properties suggests that the average oxidation state of Co in the pyrochlore phases is close to but slightly higher than 2.0. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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“…1(b)]. Interestingly, the secondary phases typically monitored during the solid-state synthesis of Nb-doped BiFeO 3 materials, namely the Bi 2 Fe 4 O 9 mullite and/or the NbFeBiO pyrochlore, 25), 33) are not observed in the X-ray diffractograms of the mechanochemically synthesized powders.…”

Section: Resultsmentioning

confidence: 99%

Metastable nature of donor-doped BiFeO<sub>3</sub> obtained by mechanochemical synthesis

Bernardo

Jardiel

Peiteado

et al. 2016

J. Ceram. Soc. Japan

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Nb5+ or W 6+ donor-doped powders were synthesized by applying a mechanochemical synthesis route, in an attempt to improve the multiferroic properties of BiFeO 3 based materials. The as-synthesized samples evidence a highly efficient incorporation of Nb 5+ or W 6+ into the BiFeO 3 perovskite lattice, together with a low presence of secondary phases. The relatively high purity of the mechanosynthetized products is even more appealing when it is compared with the multiphase scenario obtained by a mixed oxides route for these compositions. This confirms this technique as a good alternative to conventional solid state processing; however the thermal evolution of the as-prepared powders also reveals a metastable nature of the synthesized phases which upon an external energy input leads to an unwelcome multiphase system.

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Phase formation, crystal chemistry, and properties in the system Bi2O3–Fe2O3–Nb2O5

Cited by 126 publications

References 56 publications

Reaction pathways in the solid state synthesis of multiferroic BiFeO3

Reaction pathways in the solid state synthesis of multiferroic BiFeO3

Phase Formation and Properties in the System Bi₂O₃:2CoO_1+x:Nb₂O₅

Metastable nature of donor-doped BiFeO<sub>3</sub> obtained by mechanochemical synthesis

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Phase formation, crystal chemistry, and properties in the system Bi2O3–Fe2O3–Nb2O5

Cited by 126 publications

References 56 publications

Reaction pathways in the solid state synthesis of multiferroic BiFeO3

Reaction pathways in the solid state synthesis of multiferroic BiFeO3

Phase Formation and Properties in the System Bi2O3:2CoO1+x:Nb2O5

Metastable nature of donor-doped BiFeO<sub>3</sub> obtained by mechanochemical synthesis

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Phase Formation and Properties in the System Bi₂O₃:2CoO_1+x:Nb₂O₅