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X-ray photoelectron diffraction studies of lepidolite

Published online by Cambridge University Press:  09 July 2018

S. Evans  and
E. Raftery
S. Evans
Affiliation:
Edward Davies Chemical Laboratories, University College of Wales, Aberystwyth, Dyfed SY23 1NE, UK
E. Raftery
Affiliation:
Edward Davies Chemical Laboratories, University College of Wales, Aberystwyth, Dyfed SY23 1NE, UK
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Abstract

X-ray photoelectron diffraction data for three cleavage surfaces from a crystal of a Norwegian lepidolite containing 2·3% Rb and 3% Mn are reported and interpreted. Rubidium is shown to occupy anhydrous interlayer sites equivalent to those of potassium, and to be distributed uniformly throughout the crystals. Cleavage occurs in Mn-rich regions in which the manganese(II) is located in octahedral sites essentially equivalent to those of lithium. The octahedral Al sites can readily be distinguished from the Li,Mn sites and it is concluded that Al occupies predominantly M(2), cis sites while Li and Mn(II) prefer M(1), trans sites. Photoelectron diffraction data also indicate that 40 ± 5% of the Al is tetrahedrally coordinated, compared with a figure of ∼34% deduced independently from a surface analysis.

Resume

Resume

On décrit et interprète les résultats de diffraction de photo-électrons X pour trois surfaces de clivage d'un cristal d'une l'épidolite norvégienne contenant 2·3% Rb et 3% Mn. On démontre que le rubidium occupe des sites inter-feuillets anhydres équivalents à ceux du potassium et qu'il est distribué uniformément à travers le cristal. Les clivages apparaissent dans les régions riches en Mn où le manganèse (II) se trouve en sites octaédriques, essentiellement équivalents à ceux du lithium. On distingue facilement les sites octaédriques Al de ceux des sites Li, Mn et on conclut que Al occupe essentiellement des sites M(2), cis, alors que Li et Mn(II) préfèrent le site M(1), trans. Les données de diffraction photoélectronique indiquent aussi que 40 ± 5% d'Al sont coordonnés tétraédriquement, résultat que l'on peut comparer aux 34% déduits indépendamment par une analyse de surface.

Kurzreferat

Kurzreferat

Eine Auswertung von Röntgen-Photoelektronen-Beugungsdiagrammen dreier Spaltflächen eines norwegischen Lepidolits (2·3% Rb, 3% Mn) ergab, daß Rb ähnlich dem Kalium wasserfreie zwischenpositionen einnimmt und gleichmäßig im Kristall verteilt ist. Spaltbarkeit tritt in Mn-reichen Bereichen auf, in denen das Mn(II) ähnlich dem Li auf oktaedrischen Plätzen sitzt. Die oktaedrischen Al-Positionen können leicht von den (Li,Mn)-Positionen unterschieden werden, und es wird gefolgert, daß Al hauptsächlich M(2), cis-Positionen, Li und Mn(II) dagegen M(1), trans-Positionen besetzen. Die Ergebnisse zeigen weiterhin, daß 40 ± 5% des Al tetraedrisch koordiniert sind; aus Oberflächenanalysen wird hierfür ein Betrag von etwa 34% abgeleitet.

Resumen

Resumen

Se presentan e interpretan datos de difracción de fotoelectrones-X para tres superficies de exfoliación de un cristal de Lepidolita noruega conteniendo 2·3% de Rb y 3% de Mn. Se demuestra que el rubidio ocupa posiciones interlaminares anhidras equivalentes alas del potasio, y que está distribuido uniformemente en el cristal. La exfoliación tiene lugar en zonas ricas en manganeso, en las cuales el Mn+2 se localiza en las posiciones octaédricas esencialmente equivalentes a las del litio. Las posiciones octaédricas ocupadas por Al se diferencian de las ocupadas por Li, Mn, pudiéndose concluir que el Al ocupa predominantemente las posiciones M(2)cis, mientras que el Li y el Mn+2 prefieren las M(1)trans. Los datos de difracción de fotoelectrones indican asimismo que el 40 ± 5% del aluminio está tetraédricamente coordinado, compradao con el 34% deducido independientemente de un análisis de superficie.

Type
Research Article
Information
Clay Minerals , Volume 17 , Issue 4 , December 1982 , pp. 443 - 452
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1982

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