The effect of cationic and anionic substitution on the $alpha;-(Al, Fe)2O3 lattice parameters

Wolska, E.; Szajda, W.

doi:10.1016/0167-2738(88)90379-7

Cited by 10 publications

(4 citation statements)

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“…Both corundum (α-Al 2 O 3 ) and hematite (α-Fe 2 O 3 ) belong to the same space group R3 c with the lattice parameters a = 4.760 Å, c = 12.993 Å [15] and a = 5.039 Å, c = 13.740 Å [16], [17], respectively and can form solid solutions in form of ( [18], [19] to be in the range of 9-11 mol%, which corresponds well to phase diagrams from [20], [21]. The presence and concentration of substitution atoms in solid solution of α-Al 2 O 3 has a strong influence on its optical properties [22], [23] and thus, depending on the laser parameters, even small differences in Fe amount in corundum can tremendously affect the interaction with the laser [13], [14].…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…Properties and applications of alumina containing different metal oxide additives have been studied since decades [16], [19], [24]- [26] and are still a topic of most recent research [27]- [31] due to the valuable properties of this ceramic material. Effect of adding small amounts of hematite on alumina properties was extensively studied by G.L.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

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Pre-processing of hematite-doped alumina granules for Selective Laser Melting

Makowska

Pfeiffer

Casati

et al. 2019

Ceramics International

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Structure and composition evolution of α-Fe 2 O 3 doped alumina granules during calcination is investigated by means of synchrotron X-ray powder diffraction. The α-Fe 2 O 3 nanoparticles are added to increase the absorption of laser light, however, they also play a significant role in transition kinetics of alumina. It is shown that calcination in air leads to implementation of Fe 3+ ions in corundum structure, while calcination in reducing atmosphere leads to creation of metallic iron.Moreover, it is demonstrated that for alumina granules consisting of a mixture of micron-size αalumina, submicron α-alumina and nano-size γ−/δ--alumina, it is possible to obtain a system composed of two corundum-type structures with different Fe doping levels and the ratio of these two phases can be controlled by calcination temperature.

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Section: Accepted Manuscriptmentioning

confidence: 99%

Section: Accepted Manuscriptmentioning

confidence: 99%

Pre-processing of hematite-doped alumina granules for Selective Laser Melting

Makowska

Pfeiffer

Casati

et al. 2019

Ceramics International

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“…Further support for structural OH was obtained by Wolska andSzajda (1985, 1988) from infrared (IR) spectra. They showed an additional absorption feature at --950 cm -L and a shoulder at -650 cm -1, which are both absent in hematite heated to 1000~ As A1 content increases, the band at 950 cm -1 moves to lower wave numbers and appears as a shoulder of the Fe-O vibrations (compare Figure la with lb in Wolska and Szajda, 1988). Furthermore, on heating, the feature at 650 cm -~ was stable to a higher temperature (>700~ in the aluminiferrous hematite than in the pure hematite.…”

Section: Properties Of Hematitementioning

confidence: 99%

The Effect of Al on Fe Oxides. XIX. Formation of Al-Substituted Hematite from Ferrihydrite at 25°C and pH 4 to 7

Schwertmann

2000

Clays and clay miner.

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Abstract--Iron oxides in surface environments generally form at temperatures of 25 • 10~ but synthesis experiments are usually done at higher temperatures to increase the rate of crystallization. To more closely simulate natural environments, the transformation of 2-line ferrihydrite to hematite and goethite at 25~ in the presence of different A1 concentrations and at pH values from 4 to 7 was studied in a long-term (16-20 y) experiment. Aluminum affects the hydrolysis and charging behavior of 2-line fenihydrite and retards crystallization. A1 also promotes the formation of hematite over goethite and leads to multidomainic discoidal and framboidal crystals instead of rhombohedral crystals. The strong hematite-promoting effect of A1 appears to be the result of a lower solubility of the Al-containing ferrihydrite precursor relative to pure ferrihydrite. Hematite incorporates A1 into its structure, as is shown by a decrease in the a and c-cell lengths and a decrease in magnetic hyperfine fields (M6ssbauer spectroscopy). With hematite formed at low-temperature, these decreases were, however, smaller for the cell length and greater for the magnetic field than for hematite produced at higher temperatures. Both phenomena are removed by heating the hematite at 200~ They are attributed to structural OH and/or structural defects. The relative content of AI in the structure is lower for hematite formed at 25~ than for hematites synthesized at higher temperatures (80 and 500~The maximum possible substitution of one sixth of the Fe positions was not achieved, similar to soil hematites. These results show that properties of widely distributed soil A1-containing hematites can reflect formation environment.

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“…In such processes of solid solution formation double substitution may occur, i.e. Fek cations are replaced by A13+ cations at the same time as 02anions are replaced by OH-groups (Wolska, 1981;Wolska and Szajda, 1988;Wolska and Schwertmann, 1989).…”

Section: Introductionmentioning

confidence: 99%

Synthetic solid solutions formed between goethite and diaspore

Wolska

Szajda

Piszora

1992

J Plant Nutrition & Soil

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The substitutional solid solutions of goethite (a‐FeOOH) and diaspore (α‐AlOOH) have been investigated by X‐ray powder diffraction and chemical analysis in order to establish the solubility limits of aluminium in the goethite structure. α‐Fe1‐xAIxOOH samples were obtained by ageing of coprecipitated amorphous (Fe,Al) hydroxides at pH 13 in NaOH and Na[Al(OH)4] solutions at 25°C (G25 series) and 70°C (G70 series), respectively. Chemical analysis reveals that the aluminium content of Al goethites is consistent with Al concentration in the coprecipitated hydroxides up to about 10 mol% Al. In Al goethites obtained from (Fe,Al) hydroxides with higher Al:Fe ratios, the relative Al content is considerably lower. It was found that pure ferrihydrite stored in the aluminate solution is also transformed into Al goethite. The X‐ray diffraction results show a significant divergence of the unitcell parameters from Vegard's law. This points out the limited ranges of the solid solution between goethite and diaspore and suggests the formation of defect, cation‐deficient structures.

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The effect of cationic and anionic substitution on the $alpha;-(Al, Fe)2O3 lattice parameters

Cited by 10 publications

References 11 publications

Pre-processing of hematite-doped alumina granules for Selective Laser Melting

Pre-processing of hematite-doped alumina granules for Selective Laser Melting

The Effect of Al on Fe Oxides. XIX. Formation of Al-Substituted Hematite from Ferrihydrite at 25°C and pH 4 to 7

Synthetic solid solutions formed between goethite and diaspore

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