Effect of Crystallinity and Al Substitution on the Applied‐Field Mössbauer Spectra of Iron Oxides and Oxyhydroxides

Applied-field Mossbauer spectra are reported for selected synthetic samples of α-Fe1-xAlxOOH, γ-Fe1-xAlxOOH, δ-FeOOH, α-(Fe1-xAlx)2O3 and γ-Fe2O3. Field strengths of up to 90 kOe were used at temperatures of mostly 4.2 K. The effects of the Al substitution and/or the crystallinity are discussed. Specific characteristics of the spectra are enlightened which might serve as complimentary sources of information for the characterization of soil oxides and oxyhydroxides. It is pointed out that several questions remain unanswered to date and that further systematic research is justified. Einflus der Kristallinitat und Al-Substitution auf die Mossbauerspektren von Eisenoxiden und -oxyhydroxiden An ausgewahlten synthetischen Proben von α-Fe1-xAlxOOH, γ-Fe1-xAlxOOH, δ-FeOOH, α-(Fe1-xAlx)2O3 und γ-Fe2O3 wurden Mossbauerspektren unter externen Magnetfeldern aufgenommen. Die Messungen wurden unter Magnetfeldern von bis zu 90 kOe, meist bei einer Temperatur von 4,2 K, vorgenommen. Die Auswirkungen der Al-Substitution und/oder Kristallinitat werden diskutiert. Jene Kennzeichen der Spektren werden hervorgehoben, die als eine zusatzliche Informations-quelle zur Kennzeichnung von Eisenoxiden und -oxyhydroxiden in Boden dienen konnen. Es wird darauf hingewiesen, das einige Fragen bislang offen bleiben, und das weitere systematische Untersuchungen gerechtfertigt sind.

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