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Series of compositions Bi2(M′ x M 1−x )4O9 (M′, M=Al, Ga, Fe; 0≤x≤1) with mullite-type crystal structure: Synthesis, characterization and 18O/16O exchange experiment

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Title: Series of compositions Bi2(M′ x M 1−x )4O9 (M′, M=Al, Ga, Fe; 0≤x≤1) with mullite-type crystal structure: Synthesis, characterization and 18O/16O exchange experiment
Authors: Debnath, T.1 tapasnet@yahoo.com, Rüscher, C.H.1, Fielitz, P.2, Ohmann, S.2, Borchardt, G.2
Source: Journal of Solid State Chemistry. Nov2010, Vol. 183 Issue 11, p2582-2588. 7p.
Subjects: Bismuth compounds, Fourier transform infrared spectroscopy, X-ray diffraction, Absorption spectra, Infrared spectra, Polycrystals, Inorganic synthesis
Abstract: Abstract: Series of compositions Bi2(M′ x M 1−x )4O9 with x=0.0, 0.1,…, 1.0 and M′/M=Ga/Al, Fe/Al and Fe/Ga were synthesized by dissolving appropriate amounts of corresponding metal nitrate hydrates in glycerine, followed by gelation, calcination and final heating at 800°C for 24h. The new compositions with M′/M=Ga/Al form solid-solution series, which are isotypes to the two other series M′/M=Fe/Al and Fe/Ga. The XRD data analysis yielded in all cases a linear dependence of the lattice parameters related on x. Rietveld structure refinements of the XRD patterns of the new compounds, Bi2(Ga x Al1−x )4O9 reveal a preferential occupation of Ga in tetrahedral site (4h). The IR absorption spectra measured between 50 and 4000cm−1 of all systems show systematic shifts in peak positions related to the degree of substitution. Samples treated in 18O2 atmosphere (16h at 800°C, 200mbar, 95% 18O2) for 18O/16O isotope exchange experiments show a well-separated IR absorption peak related to the M–18Oc–M vibration, where Oc denotes the common oxygen of two tetrahedral type MO4 units. The intensity ratio of M–18Oc/M–16Oc IR absorption peaks and the average crystal sizes were used to estimate the tracer diffusion coefficients of polycrystalline Bi2Al4O9 (D=2×10−22 m2s−1), Bi2Fe4O9 (D=5×10−21 m2s−1), Bi2(Ga/Al)4O9 (D=2×10−21 m2s−1) and Bi2Ga4O9 (D=2×10−20 m2s−1). [Copyright &y& Elsevier]
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Abstract:Abstract: Series of compositions Bi2(M′ x M 1−x )4O9 with x=0.0, 0.1,…, 1.0 and M′/M=Ga/Al, Fe/Al and Fe/Ga were synthesized by dissolving appropriate amounts of corresponding metal nitrate hydrates in glycerine, followed by gelation, calcination and final heating at 800°C for 24h. The new compositions with M′/M=Ga/Al form solid-solution series, which are isotypes to the two other series M′/M=Fe/Al and Fe/Ga. The XRD data analysis yielded in all cases a linear dependence of the lattice parameters related on x. Rietveld structure refinements of the XRD patterns of the new compounds, Bi2(Ga x Al1−x )4O9 reveal a preferential occupation of Ga in tetrahedral site (4h). The IR absorption spectra measured between 50 and 4000cm−1 of all systems show systematic shifts in peak positions related to the degree of substitution. Samples treated in 18O2 atmosphere (16h at 800°C, 200mbar, 95% 18O2) for 18O/16O isotope exchange experiments show a well-separated IR absorption peak related to the M–18Oc–M vibration, where Oc denotes the common oxygen of two tetrahedral type MO4 units. The intensity ratio of M–18Oc/M–16Oc IR absorption peaks and the average crystal sizes were used to estimate the tracer diffusion coefficients of polycrystalline Bi2Al4O9 (D=2×10−22 m2s−1), Bi2Fe4O9 (D=5×10−21 m2s−1), Bi2(Ga/Al)4O9 (D=2×10−21 m2s−1) and Bi2Ga4O9 (D=2×10−20 m2s−1). [Copyright &y& Elsevier]
ISSN:00224596
DOI:10.1016/j.jssc.2010.07.019