Delafossite

Last updated
Delafossite
Cuprite-Delafossite-133433.jpg
Discrete, wine-red cuprite crystals on matrix covered by brightly reflective delafossite microcrystals
General
Category Oxide minerals
Formula
(repeating unit)		CuFeO2
IMA symbol Del [1]
Strunz classification 4.AB.15
Crystal system Trigonal
Crystal class Hexagonal scalenohedral (3m)
H-M symbol: (3 2/m)
Space group R3m
Unit cell a = 3.04, c = 17.12 [Å]; Z = 3
Identification
ColorBlack
Crystal habit Tabular to equant crystals; botryoidal crusts, spherulitic, powdery, massive
Twinning Contact twins on {0001}
Cleavage Imperfect on {1011}
Tenacity Brittle
Mohs scale hardness5.5
Luster Metallic
Streak Black
Diaphaneity Opaque
Specific gravity 5.41
Optical propertiesUniaxial
Pleochroism Distinct; O = pale golden brown; E = rose-brown
Other characteristicsWeakly magnetic
References [2] [3] [4]

Delafossite is a copper iron oxide mineral with formula CuFeO2 or Cu1+Fe3+O2. It is a member of the delafossite mineral group, which has the general formula ABO2, a group characterized by sheets of linearly coordinated A cations stacked between edge-shared octahedral layers (BO6). [5] Delafossite, along with other minerals of the ABO2 group, is known for its wide range of electrical properties, its conductivity varying from insulating to metallic. [5] Delafossite is usually a secondary mineral that crystallizes in association with oxidized copper and rarely occurs as a primary mineral. [5]

Contents

Composition

The chemical formula for delafossite is CuFeO2, which was first determined through chemical analysis of the pure mineral by G. S. Bohart. [6] The ratio he determined was very close to Cu:Fe:O=1:1:2, with slightly more iron than copper. Rogers. [6] attributed this fact to a small amount of hematite in the sample. In order to determine the composition of delafossite Rogers used the Ziervogel process. The Ziervogel process is used to test for the presence of cuprous oxides by looking for the "spangle reaction" which produces thin flakes of metallic silver when cuprous oxide is mixed with silver sulfate. When Rogers heated powdered delafossite with silver sulfate solution, the spangle reaction occurred. The only oxides possibilities to consider for delafossite are cuprous copper and ferrous iron. Rogers concluded that the iron was combining with the oxygen as a radical and that it only acted as a radical. This indicated that the copper in delafossite was in the cuprous rather than the cupric form. Hence he concluded that the composition of delafossite was probably cuprous metaferrite, CuFe3+O2. This composition was later confirmed by Pabst by the determination of interionic distances in the crystal lattice. [7]

Structure

The atomic structure of delafossite and the delafossite group consists of a sheet of linearly coordinated A cations stacked between edge-shared octahedral layers (BO6). In the delafossite atomic structure there are two alternating planar layers. The two layers consist of one layer triangular-patterned A cations and a layer of edge-sharing BO6 octahedra compacted with respect to the c axis. The delafossite structure can have two polytypes according to the orientation of the planar layer stacking. Hexagonal 2H types that have a space group of P63/mmc are formed when two A layers are stacked with each layer rotated 180° in relation to one another. Alternatively, when the layers are stacked each layer in the same direction in relation to one another, it makes a rhombohedral 3R type with a space group of R3m. [5]

Physical properties

The color of delafossite is black, with a hardness of 5.5, and imperfect cleavage in the {1011} direction. [2] Pabst [8] calculated the density of delafossite to be 5.52. Contact twinning has been observed in the {0001} direction. [2] The unit cell parameters were calculated to be a = 3.0351 Å, c = 17.166 Å, V = 136.94 Å3. [9] Delafossite is tabular to equidimensional in habit and has a black streak and a metallic luster. [6] Delafossite has hexagonal symmetry that can have the space groups R3m or P63/mmc depending on the stacking of A cation layers. Delafossite compounds can have magnetic properties when magnetic ions are in the B cation position. [5] Delafossite compounds also have properties dealing with electric conductivity such as insulation and/or metallic conduction. Delafossite compounds can exhibit p- or n-type conductivity based on their composition. [5]

Rhombohedral (3R), CuFeO2 properties:

Hexagonal (2H), CuFeO2 properties:

Synthesis

3R CuFeO2 is often synthesized by solid state reactions, sol gel methods, vapor deposition, and hydrothermal synthesis.

Pure 2H CuFeO2 and other 2H delafossite-type oxides are difficult to synthesize. The only pure 2H CuFeO2 crystals were pure 2H CuFeO2 nanoplates with a thickness of about 100 nm which were synthesized at temperatures as low as 100 °C from CuI and FeCl3·6H2O. [10]

Application

Solar cells: 2H CuFeO2 has a band gap of 1.33 eV and a high absorption coefficient of 3.8×104 cm−1 near the band gap edge at 700 nm. It demonstrated a photovoltaic effect when placed into thin film structures composed of ITO/ZnO/2H CuFeO2/graphite/carbon black. [10]

Other applications: CuFeO2 is made of earth abundant elements and has good stability in aqueous environments, and as such was investigated as photocathodes for photoelectrochemical reduction of CO2, solar water reduction, and as a cathode material in lithium batteries. Whereas the 3R phase was somewhat characterized, only X-ray diffraction and theoretical calculation of eg and t2g occupancies of the Fe3+ are available for 2H CuFeO2. [10]

Geologic occurrence

In 1873, delafossite was discovered by Charles Friedel in a region of Ekaterinbug, Siberia. [11] Since its discovery it has been identified as a fairly common mineral found in such places as the copper mines of Bisbee, Arizona. [6] Delafossite is usually a secondary mineral often found in oxidized areas of copper deposits although it can be a primary mineral as well. [2] [5] Delafossite can be found as massive, relatively distinct crystals on hematite. [6] Delafossite has since been found in mines around the world from Germany to Chile. [2]

Origin of the name

Delafossite was first noted by Charles Friedel in 1873 and given the composition Cu2O·Fe2O3. [6] The mineral was given the name delafossite in honor of the French mineralogist and crystallographer Gabriel Delafosse (1796–1878). [5] Delafosse is known for noting the close relationship between crystal symmetry and physical properties. [12]

See also

Related Research Articles

<span class="mw-page-title-main">Mineral</span> Crystalline chemical element or compound formed by geologic processes

In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.

<span class="mw-page-title-main">High-temperature superconductivity</span> Superconductive behavior at temperatures much higher than absolute zero

High-temperature superconductors are defined as materials with critical temperature above 77 K, the boiling point of liquid nitrogen. They are only "high-temperature" relative to previously known superconductors, which function at even colder temperatures, close to absolute zero. The "high temperatures" are still far below ambient, and therefore require cooling. The first breakthrough of high-temperature superconductor was discovered in 1986 by IBM researchers Georg Bednorz and K. Alex Müller. Although the critical temperature is around 35.1 K, this new type of superconductor was readily modified by Ching-Wu Chu to make the first high-temperature superconductor with critical temperature 93 K. Bednorz and Müller were awarded the Nobel Prize in Physics in 1987 "for their important break-through in the discovery of superconductivity in ceramic materials". Most high-Tc materials are type-II superconductors.

<span class="mw-page-title-main">Chalcopyrite</span> Copper iron sulfide mineral

Chalcopyrite ( KAL-kə-PY-ryte, -⁠koh-) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green-tinged black.

<span class="mw-page-title-main">Yttrium barium copper oxide</span> Chemical compound

Yttrium barium copper oxide (YBCO) is a family of crystalline chemical compounds that display high-temperature superconductivity; it includes the first material ever discovered to become superconducting above the boiling point of liquid nitrogen [77 K ] at about 93 K.

<span class="mw-page-title-main">Copper(I) oxide</span> Chemical compound – an oxide of copper with formula Cu2O

Copper(I) oxide or cuprous oxide is the inorganic compound with the formula Cu2O. It is one of the principal oxides of copper, the other being copper(II) oxide or cupric oxide (CuO). Cuprous oxide is a red-coloured solid and is a component of some antifouling paints. The compound can appear either yellow or red, depending on the size of the particles. Copper(I) oxide is found as the reddish mineral cuprite.

<span class="mw-page-title-main">Covellite</span> Sulfide mineral

Covellite is a rare copper sulfide mineral with the formula CuS. This indigo blue mineral is commonly a secondary mineral in limited abundance and although it is not an important ore of copper itself, it is well known to mineral collectors.

<span class="mw-page-title-main">Sperrylite</span>

Sperrylite is a platinum arsenide mineral with the chemical formula PtAs2 and is an opaque metallic tin white mineral which crystallizes in the isometric system with the pyrite group structure. It forms cubic, octahedral or pyritohedral crystals in addition to massive and reniform habits. It has a Mohs hardness of 6–7 and a very high specific gravity of 10.6.

<span class="mw-page-title-main">Todorokite</span> Hydrous manganese oxide mineral

Todorokite is a complex hydrous manganese oxide mineral with generic chemical formula (Na,Ca,K,Ba,Sr)
1-x(Mn,Mg,Al)
6O
12·3-4H
2O. It was named in 1934 for the type locality, the Todoroki mine, Hokkaido, Japan. It belongs to the prismatic class 2/m of the monoclinic crystal system, but the angle β between the a and c axes is close to 90°, making it seem orthorhombic. It is a brown to black mineral which occurs in massive or tuberose forms. It is quite soft with a Mohs hardness of 1.5, and a specific gravity of 3.49 – 3.82. It is a component of deep ocean basin manganese nodules.

<span class="mw-page-title-main">Copper monosulfide</span> Chemical compound

Copper monosulfide is a chemical compound of copper and sulfur. It was initially thought to occur in nature as the dark indigo blue mineral covellite. However, it was later shown to be rather a cuprous compound, formula Cu+3S(S2). CuS is a moderate conductor of electricity. A black colloidal precipitate of CuS is formed when hydrogen sulfide, H2S, is bubbled through solutions of Cu(II) salts. It is one of a number of binary compounds of copper and sulfur (see copper sulfide for an overview of this subject), and has attracted interest because of its potential uses in catalysis and photovoltaics.

<span class="mw-page-title-main">Birnessite</span> Manganese hydroxide mineral

Birnessite (nominally MnO2·nH2O), also known as δ-MnO2, is a hydrous manganese dioxide mineral with a chemical formula of Na0.7Ca0.3Mn7O14·2.8H2O. It is the main manganese mineral species at the Earth's surface, and commonly occurs as fine-grained, poorly crystallized aggregates in soils, sediments, grain and rock coatings (e.g., desert varnish), and marine ferromanganese nodules and crusts. It was discovered at Birness, Aberdeenshire, Scotland.

<span class="mw-page-title-main">Layered double hydroxides</span> Class of ionic solids characterized by a layered structure

Layered double hydroxides (LDH) are a class of ionic solids characterized by a layered structure with the generic layer sequence [AcB Z AcB]n, where c represents layers of metal cations, A and B are layers of hydroxide anions, and Z are layers of other anions and neutral molecules. Lateral offsets between the layers may result in longer repeating periods.

<span class="mw-page-title-main">Arthurite</span> Arsenate mineral

Arthurite is a mineral composed of divalent copper and iron ions in combination with trivalent arsenate, phosphate and sulfate ions with hydrogen and oxygen. Initially discovered by Sir Arthur Russell in 1954 at Hingston Down Consols mine in Calstock, Cornwall, England, arthurite is formed as a resultant mineral in the oxidation region of some copper deposits by the variation of enargite or arsenopyrite. The chemical formula of Arthurite is CuFe23+(AsO4,PO4,SO4)2(O,OH)2·4H2O.

Copper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both minerals and synthetic materials comprise these compounds. Some copper sulfides are economically important ores.

<span class="mw-page-title-main">Copper(I) sulfide</span> Chemical compound

Copper(I) sulfide is a copper sulfide, a chemical compound of copper and sulfur. It has the chemical compound Cu2S. It is found in nature as the mineral chalcocite. It has a narrow range of stoichiometry ranging from Cu1.997S to Cu2.000S. Samples are typically black.

Cuprospinel is a mineral. Cuprospinel is an inverse spinel with the chemical formula CuFe2O4, where copper substitutes some of the iron cations in the structure. Its structure is similar to that of magnetite, Fe3O4, yet with slightly different chemical and physical properties due to the presence of copper.

<span class="mw-page-title-main">Green rust</span> Generic name for various green iron layered double hydroxide

Green rust is a generic name for various green crystalline chemical compounds containing iron(II) and iron(III) cations, the hydroxide (OH−
) anion, and another anion such as carbonate (CO2−
3), chloride (Cl−
), or sulfate (SO2−
4), in a layered double hydroxide (LDH) structure. The most studied varieties are the following:

<span class="mw-page-title-main">Calcium copper titanate</span> Chemical compound

Calcium copper titanate (also abbreviated CCTO, for calcium copper titanium oxide) is an inorganic compound with the formula CaCu3Ti4O12. It is noteworthy for its extremely large dielectric constant (effective relative permittivity) of over 10,000 at room temperature.

<span class="mw-page-title-main">Copper(I) thiocyanate</span> Chemical compound

Copper(I) thiocyanate is a coordination polymer with formula CuSCN. It is an air-stable, white solid used as a precursor for the preparation of other thiocyanate salts.

Buserite is a hydrated layered manganese-oxide mineral with nominal chemical formula MnO2·nH2O. It was named after Swiss chemist professor W. Buser, who first identified it in 1952 in deep-sea manganese nodules. Buser named it 10 Å manganate because the periodicity in the layer stacking direction was 10 Å. It was renamed buserite in 1970 by the nomenclature commission of the International Mineralogical Association (IMA).

Robert Day Shannon is a retired research chemist formerly at DuPont de Nemours, Inc.

References

  1. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
  2. 1 2 3 4 5 Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (1997). "Delafossite". Handbook of Mineralogy (PDF). Vol. III (Halides, Hydroxides, Oxides). Chantilly, VA, US: Mineralogical Society of America. ISBN   0962209724.
  3. ↑ Delafossite. Mindat.org
  4. ↑ Delafossite. Webmineral
  5. 1 2 3 4 5 6 7 8 Marquardt, M. A.; Ashmore, N. A.; Cann, D. P. (2006). "Crystal chemistry and electrical properties of the delafossite structure". Thin Solid Films. 496 (1): 146–156. Bibcode:2006TSF...496..146M. doi:10.1016/j.tsf.2005.08.316.
  6. 1 2 3 4 5 6 Rogers, A. (1913). "Delafossite, a Cuprous Metaferrite from Bisbee, Arizona". American Journal of Science. 35 (207): 290–294. Bibcode:1913AmJS...35..290R. doi:10.2475/ajs.s4-35.207.290.
  7. ↑ Pabst, A. (1946). "Notes on the Structure of Delafossite" (PDF). American Mineralogist. 23 (539–546).
  8. ↑ Pabst, Adolf (1938). "Crystal Structure and Density of Delafossite". American Mineralogist. 20: 175–176.
  9. ↑ Shannon, R. D.; Rogers, D. B.; Prewitt, C. T. (1971). "Chemistry of noble metal oxides. I. Syntheses and properties of ABO2 delafossite compounds". Inorganic Chemistry. 10 (4): 713. doi:10.1021/ic50098a011.
  10. 1 2 3 4 Jin, Yi; Chuamanov, George (2016). "Solution Synthesis of Pure 2H CuFeO2 at Low Temperatures". RSC Advances. 6 (31): 26392–26397. Bibcode:2016RSCAd...626392J. doi:10.1039/C6RA01901C.
  11. ↑ Rogers, A. (1922). "Delafossite from Kimberly, Nevada" (PDF). American Mineralogist. 7: 102–104.
  12. ↑ 1839: Gabriel Delafosse et Alfred Des Cloizeaux Archived 2012-04-26 at the Wayback Machine . Institut de minéralogie et de physique des milieus condensés, 19 March 2009.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.