SYNTHETIC CUBANITE CuFe2S3: PRESSURE-INDUCED TRANSFORMATION TO ISOCUBANITE

Abstract

Cubanite, the orthorhombic polymorph of CuFe 2 S 3 , is very sensitive to temperature, pressure and compositional variations. This sensitivity has prevented its successful synthesis in a controlled laboratory environment. We report here the first successful synthesis of cubanite and its high-pressure Mössbauer spectroscopic and electrical properties up to 7 GPa. We also compare the Mössbauer spectroscopic and electrical resistivity results on our synthetic cubanite with the behavior of naturally occurring cubanite under identical conditions. The magnetic hyperfine field, a sensitive Mössbauer parameter of the synthetic sample, corresponds to that of orthorhombic cubanite. We report here the pressure-induced transformation of the magnetic sextet (cubanite) to a paramagnetic doublet (isocubanite) at ~4 GPa at room temperature. This transformation has been confirmed independently by our electrical resistivity measurements up to 7 GPa. The present results could be useful in estimating the metamorphic pressure conditions of cubanite-bearing carbonaceous chondrites. soMMaiRe La cubanite, polymorphe orthorhombique de CuFe 2 S 3 , est très sensible aux variations en température, pression et composition. A cause de cette sensibilité, il a été jusqu'à maintenant impossible de la synthétiser au laboratoire sous conditions contrôlées. Nous avons réussi cette synthèse pour la première fois, et nous avons déterminé son spectre Mössbauer et ses propriétés électriques à pression élevée, jusqu'à 7 GPa. Aussi, nous comparons nos résultats avec le comportement de la cubanite naturelle à conditions identiques. Le champ magnétique hyperfin, un paramètre Mössbauer sensible de l'échantillon synthétique, correspond à celui de la cubanite. Nous avons découvert une transformation sensible à la pression du sextet magnétique (cubanite) au doublet paramagnétique (isocubanite) à ~4 GPa à température ambiante. Cette transformation a été confirmée de façon indépendante par nos mesures de la résistivité électrique jusqu'à 7 GPa. Nos résultats pourraient s'avérer utiles pour estimer la pression du métamorphisme des chondrites carbonacées porteuses de cubanite. (Traduit par la Rédaction)Mots-clés: cubanite, isocubanite, transition à haute pression, cellule à enclume de diamant, spectroscopie de Mössbauer, propriétés électriques. §

An experimental study of the formation of cubanite (CuFe2S3) in primitive meteorites

“…This short-lived phase was not structurally characterized, and moreover, these pH levels are inconsistent with predictions for pH levels of CI-chondrite parent-body fluids from mineral equilibria calculations (Dufresne and Anders 1962) and thermodynamic modeling of mineral assemblages (Zolensky et al 1989). More recent work has reported the synthesis of cubanite through radiative and microwave heating of copper, iron, and sulfur in evacuated silica tubes, a dry process (Pareek et al 2008;Chandra et al 2010Chandra et al , 2011. The experimentally formed CuFe 2 S 3 discussed herein is chemically and structurally consistent with orthorhombic cubanite, and is synthesized under aqueous conditions relevant to the CI-chondrite parent body at temperatures consistent with cubanite stability.…”

Facile synthesis of nano-sized CuFe2S3: morphology and diverse functional tuning and crystal growth mechanism exploring

“…However, in the previous reports, it has been proven that the CuFe 2 S 3 will transform to a cubic form at high temperature [ 19–21 ]. The crystal structure of this cubic CuFe 2 S 3 is based on a cubic close-packed matrix of sulfur atoms, wherein the metal atoms are located in the tetrahedral interstices, furthermore, the ferrous, iron and cuprous ions are randomly distributed on these cation sites [ 15 , 20 ]. This special structure endows cubic CuFe 2 S 3 with unique photoelectricity and magnetic properties, which play a crucial role in biological application.…”

Microwave Synthesis: a Physical Concept

“…In this direction, synthesis of this rarely found mineral, cubanite (CuFe 2 S 3 ) was successfully attempted using conventional as well as microwave heating. The rapid microwave heating seems to be advantageous over conventional technique showing a characteristic peak of cubanite at d= 3.22 Å (Pareek et al 2008, Chandra et al 2010,2011. It is reported that synthesis of orthorhombic cubanite depends not only on the preparatory conditions (controlled heating and cooling rate) but also on compositional variation.…”

“…Though x-ray diffraction pattern on conventionally synthesized sample does not indicate orthorhombic cubanite, Mössbauer spectroscopic studies confirm the presence of the phase through its sensitive parameters-magnetic hyperfine interaction and isomer shift. This is first ever study of successfully synthesized cubanite (Chandra et al 2010). The microwave dielectric heating effect originates from the natural ability of certain substances to efficiently absorb and to transform the electromagnetic energy into heat.…”