A contribution to the crystal chemistry of the voltaite group: solid solutions, Mössbauer and infrared spectra, and anomalous anisotropy

Juraj Majzlan; Hannes Schlicht; Maria Wierzbicka-Wieczorek; Gerald Giester; Herbert Pöllmann; Beatrix Brömme; Stephen Doyle; Gernot Buth; Christian Bender Koch

doi:10.1007/s00710-012-0254-2

A contribution to the crystal chemistry of the voltaite group: solid solutions, Mössbauer and infrared spectra, and anomalous anisotropy

Juraj Majzlan, Hannes Schlicht, Maria Wierzbicka-Wieczorek, Gerald Giester, Herbert Pöllmann, Beatrix Brömme, Stephen Doyle, Gernot Buth, Christian Bender Koch

Kemisk Institut

10 Citationer (Scopus)

Abstract

Voltaite is a mineral of fumaroles, solfatares, coal-fire gas vents, and acid-mine drainage systems. The nominal composition is K₂Fe₅²⁺Fe₃³⁺Al(SO₄)₁₂·18H₂O and the nominal symmetry is cubic, Fd̄3c. The tetragonal (I4₁/acd) superstructure of voltaite is known as the mineral pertlikite. In this study, we investigated 22 synthetic voltaite samples in which Fe²⁺ was partially or completely replaced by Mg, Zn, Mn, or Cd, by single-crystal and powder X-ray diffraction (both in-house and synchrotron). Two samples contained NH₄⁺ instead of K⁺. The structure of voltaite is based on a framework defined by kröhnkite-like heteropolyhedral chains which host both M³⁺ and M²⁺ in octahedral coordination. Unit cell dimensions of the end-members scale almost linearly with the size of M²⁺. In the Fe²⁺-Mg-Zn solid solutions, the Fe²⁺-Mg and Fe²⁺-Zn solutions are linear (ideal) in terms of their lattice-parameter variations. The Mg-Zn solid solution, however, is strongly non-ideal. A detailed analysis of the topology of the chains showed that this behavior originates in expansion and contraction of individual M²⁺-O bonds within the chains. In the Mg-Zn solid solution, some of the M²⁺-O bonds expand while none contract. In the other solid solutions, expansion of some M²⁺-O bonds is always compensated by contraction of the other ones. Parts of the nominally cubic crystals are optically anisotropic and their symmetry is found to be tetragonal by single crystal X-ray diffraction measurements. The coexistence of cubic and tetragonal sectors within a single crystal without any detectable difference in their chemical composition is difficult to explain in terms of growth of such composite crystals. Mössbauer and infrared spectra collected on our synthetic crystals conform with previously published data.

Originalsprog	Engelsk
Tidsskrift	Mineralogy and Petrology
Vol/bind	107
Udgave nummer	2
Sider (fra-til)	221-233
Antal sider	13
ISSN	0930-0708
DOI	https://doi.org/10.1007/s00710-012-0254-2
Status	Udgivet - apr. 2013

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10.1007/s00710-012-0254-2

Citationsformater

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title = "A contribution to the crystal chemistry of the voltaite group: solid solutions, M{\"o}ssbauer and infrared spectra, and anomalous anisotropy",

abstract = "Voltaite is a mineral of fumaroles, solfatares, coal-fire gas vents, and acid-mine drainage systems. The nominal composition is K2Fe52+Fe33+Al(SO4)12·18H2O and the nominal symmetry is cubic, F{\=d}3c. The tetragonal (I41/acd) superstructure of voltaite is known as the mineral pertlikite. In this study, we investigated 22 synthetic voltaite samples in which Fe2+ was partially or completely replaced by Mg, Zn, Mn, or Cd, by single-crystal and powder X-ray diffraction (both in-house and synchrotron). Two samples contained NH4+ instead of K+. The structure of voltaite is based on a framework defined by kr{\"o}hnkite-like heteropolyhedral chains which host both M3+ and M2+ in octahedral coordination. Unit cell dimensions of the end-members scale almost linearly with the size of M2+. In the Fe2+-Mg-Zn solid solutions, the Fe2+-Mg and Fe2+-Zn solutions are linear (ideal) in terms of their lattice-parameter variations. The Mg-Zn solid solution, however, is strongly non-ideal. A detailed analysis of the topology of the chains showed that this behavior originates in expansion and contraction of individual M2+-O bonds within the chains. In the Mg-Zn solid solution, some of the M2+-O bonds expand while none contract. In the other solid solutions, expansion of some M2+-O bonds is always compensated by contraction of the other ones. Parts of the nominally cubic crystals are optically anisotropic and their symmetry is found to be tetragonal by single crystal X-ray diffraction measurements. The coexistence of cubic and tetragonal sectors within a single crystal without any detectable difference in their chemical composition is difficult to explain in terms of growth of such composite crystals. M{\"o}ssbauer and infrared spectra collected on our synthetic crystals conform with previously published data.",

author = "Juraj Majzlan and Hannes Schlicht and Maria Wierzbicka-Wieczorek and Gerald Giester and Herbert P{\"o}llmann and Beatrix Br{\"o}mme and Stephen Doyle and Gernot Buth and {Bender Koch}, Christian",

year = "2013",

month = apr,

doi = "10.1007/s00710-012-0254-2",

language = "English",

volume = "107",

pages = "221--233",

journal = "Mineralogy and Petrology",

issn = "0930-0708",

publisher = "Springer Wien",

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TY - JOUR

T1 - A contribution to the crystal chemistry of the voltaite group

T2 - solid solutions, Mössbauer and infrared spectra, and anomalous anisotropy

AU - Majzlan, Juraj

AU - Schlicht, Hannes

AU - Wierzbicka-Wieczorek, Maria

AU - Giester, Gerald

AU - Pöllmann, Herbert

AU - Brömme, Beatrix

AU - Doyle, Stephen

AU - Buth, Gernot

AU - Bender Koch, Christian

PY - 2013/4

Y1 - 2013/4

N2 - Voltaite is a mineral of fumaroles, solfatares, coal-fire gas vents, and acid-mine drainage systems. The nominal composition is K2Fe52+Fe33+Al(SO4)12·18H2O and the nominal symmetry is cubic, Fd̄3c. The tetragonal (I41/acd) superstructure of voltaite is known as the mineral pertlikite. In this study, we investigated 22 synthetic voltaite samples in which Fe2+ was partially or completely replaced by Mg, Zn, Mn, or Cd, by single-crystal and powder X-ray diffraction (both in-house and synchrotron). Two samples contained NH4+ instead of K+. The structure of voltaite is based on a framework defined by kröhnkite-like heteropolyhedral chains which host both M3+ and M2+ in octahedral coordination. Unit cell dimensions of the end-members scale almost linearly with the size of M2+. In the Fe2+-Mg-Zn solid solutions, the Fe2+-Mg and Fe2+-Zn solutions are linear (ideal) in terms of their lattice-parameter variations. The Mg-Zn solid solution, however, is strongly non-ideal. A detailed analysis of the topology of the chains showed that this behavior originates in expansion and contraction of individual M2+-O bonds within the chains. In the Mg-Zn solid solution, some of the M2+-O bonds expand while none contract. In the other solid solutions, expansion of some M2+-O bonds is always compensated by contraction of the other ones. Parts of the nominally cubic crystals are optically anisotropic and their symmetry is found to be tetragonal by single crystal X-ray diffraction measurements. The coexistence of cubic and tetragonal sectors within a single crystal without any detectable difference in their chemical composition is difficult to explain in terms of growth of such composite crystals. Mössbauer and infrared spectra collected on our synthetic crystals conform with previously published data.

AB - Voltaite is a mineral of fumaroles, solfatares, coal-fire gas vents, and acid-mine drainage systems. The nominal composition is K2Fe52+Fe33+Al(SO4)12·18H2O and the nominal symmetry is cubic, Fd̄3c. The tetragonal (I41/acd) superstructure of voltaite is known as the mineral pertlikite. In this study, we investigated 22 synthetic voltaite samples in which Fe2+ was partially or completely replaced by Mg, Zn, Mn, or Cd, by single-crystal and powder X-ray diffraction (both in-house and synchrotron). Two samples contained NH4+ instead of K+. The structure of voltaite is based on a framework defined by kröhnkite-like heteropolyhedral chains which host both M3+ and M2+ in octahedral coordination. Unit cell dimensions of the end-members scale almost linearly with the size of M2+. In the Fe2+-Mg-Zn solid solutions, the Fe2+-Mg and Fe2+-Zn solutions are linear (ideal) in terms of their lattice-parameter variations. The Mg-Zn solid solution, however, is strongly non-ideal. A detailed analysis of the topology of the chains showed that this behavior originates in expansion and contraction of individual M2+-O bonds within the chains. In the Mg-Zn solid solution, some of the M2+-O bonds expand while none contract. In the other solid solutions, expansion of some M2+-O bonds is always compensated by contraction of the other ones. Parts of the nominally cubic crystals are optically anisotropic and their symmetry is found to be tetragonal by single crystal X-ray diffraction measurements. The coexistence of cubic and tetragonal sectors within a single crystal without any detectable difference in their chemical composition is difficult to explain in terms of growth of such composite crystals. Mössbauer and infrared spectra collected on our synthetic crystals conform with previously published data.

U2 - 10.1007/s00710-012-0254-2

DO - 10.1007/s00710-012-0254-2

M3 - Journal article

SN - 0930-0708

VL - 107

SP - 221

EP - 233

JO - Mineralogy and Petrology

JF - Mineralogy and Petrology

IS - 2

ER -

A contribution to the crystal chemistry of the voltaite group: solid solutions, Mössbauer and infrared spectra, and anomalous anisotropy

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