Indium is a chemical element with symbol In and atomic number 49. It is a post-transition metal that makes up 0.21 parts per million of the Earth's crust. Very soft and malleable, indium has a melting point higher than sodium and gallium, but lower than lithium and tin. Chemically, indium is similar to gallium and thallium, and it is largely intermediate between the two in terms of its properties. Indium was discovered in 1863 by Ferdinand Reich and Hieronymous Theodor Richter by spectroscopic methods. They named it for the indigo blue line in its spectrum. Indium was isolated the next year.
|Appearance||silvery lustrous gray|
|Standard atomic weight (Ar, standard)||114.818(1)|
|Indium in the periodic table|
|Atomic number (Z)||49|
|Group||group 13 (boron group)|
|Element category||post-transition metal|
|Electron configuration||[Kr] 4d10 5s2 5p1|
Electrons per shell
|2, 8, 18, 18, 3|
|Phase at STP||solid|
|Melting point||429.7485 K (156.5985 °C, 313.8773 °F)|
|Boiling point||2345 K (2072 °C, 3762 °F)|
|Density (near r.t.)||7.31 g/cm3|
|when liquid (at m.p.)||7.02 g/cm3|
|Triple point||429.7445 K, ~1 kPa|
|Heat of fusion||3.281 kJ/mol|
|Heat of vaporization||231.8 kJ/mol|
|Molar heat capacity||26.74 J/(mol·K)|
|Oxidation states||3, 2, 1, −1, −2, −5
|Electronegativity||Pauling scale: 1.78|
|Atomic radius||empirical: 167 pm|
|Covalent radius||142±5 pm|
|Van der Waals radius||193 pm|
|Speed of sound thin rod||1215 m/s (at 20 °C)|
|Thermal expansion||32.1 µm/(m·K) (at 25 °C)|
|Thermal conductivity||81.8 W/(m·K)|
|Electrical resistivity||83.7 nΩ·m (at 20 °C)|
|Magnetic susceptibility||−64.0·10−6 cm3/mol (298 K)|
|Young's modulus||11 GPa|
|Brinell hardness||8.8–10.0 MPa|
|Discovery||Ferdinand Reich and Hieronymous Theodor Richter (1863)|
|First isolation||Hieronymous Theodor Richter (1864)|
|Main isotopes of indium|
Indium is a minor component in zinc sulfide ores and is produced as a byproduct of zinc refinement. It is most notably used in the semiconductor industry, in low-melting-point metal alloys such as solders, in soft-metal high-vacuum seals, and in the production of transparent conductive coatings of indium tin oxide (ITO) on glass.
Indium has no biological role, though its compounds are somewhat toxic when injected into the bloodstream. Most occupational exposure is through ingestion, from which indium compounds are not absorbed well, and inhalation, from which they are moderately absorbed.
Indium is a silvery-white, highly ductile post-transition metal with a bright luster. It is so soft (Mohs hardness 1.2) that like sodium, it can be cut with a knife. It also leaves a visible line on paper. It is a member of group 13 on the periodic table and its properties are mostly intermediate between its vertical neighbours gallium and thallium. Like tin, a high-pitched cry is heard when indium is bent – a crackling sound due to crystal twinning. Like gallium, indium is able to wet glass. Like both, indium has a low melting point, 156.60 °C (313.88 °F); higher than its lighter homologue, gallium, but lower than its heavier homologue, thallium, and lower than tin. The boiling point is 2072 °C (3762 °F), higher than that of thallium, but lower than gallium, conversely to the general trend of melting points, but similarly to the trends down the other post-transition metal groups because of the weakness of the metallic bonding with few electrons delocalized.
The density of indium, 7.31 g/cm3, is also greater than gallium, but lower than thallium. Below the critical temperature, 3.41 K, indium becomes a superconductor. At standard temperature and pressure, indium crystallizes in the face-centered tetragonal crystal system in the space group I4/mmm (lattice parameters: a = 325 pm, c = 495 pm): this is a slightly distorted face-centered cubic structure, where each indium atom has four neighbours at 324 pm distance and eight neighbours slightly further (336 pm). Indium displays a ductile viscoplastic response, found to be size-independent in tension and compression. However it does have a size effect in bending and indentation, associated to a length-scale of order 50–100 µm, significantly large when compared with other metals.
Indium has 49 electrons, with an electronic configuration of [Kr]4d105s25p1. In compounds, indium most commonly donates the three outermost electrons to become indium(III), In3+. In some cases, the pair of 5s-electrons are not donated, resulting in indium(I), In+. The stabilization of the monovalent state is attributed to the inert pair effect, in which relativistic effects stabilize the 5s-orbital, observed in heavier elements. Thallium (indium's heavier homolog) shows an even stronger effect, causing oxidation to thallium(I) to be more probable than to thallium(III), whereas gallium (indium's lighter homolog) commonly shows only the +3 oxidation state. Thus, although thallium(III) is a moderately strong oxidizing agent, indium(III) is not, and many indium(I) compounds are powerful reducing agents. While the energy required to include the s-electrons in chemical bonding is lowest for indium among the group 13 metals, bond energies decrease down the group so that by indium, the energy released in forming two additional bonds and attaining the +3 state is not always enough to outweigh the energy needed to involve the 5s-electrons. Indium(I) oxide and hydroxide are more basic and indium(III) oxide and hydroxide are more acidic.
|−0.40||In2+ + e−||↔ In+|
|−0.49||In3+ + e−||↔ In2+|
|−0.443||In3+ + 2 e−||↔ In+|
|−0.3382||In3+ + 3 e−||↔ In|
|−0.14||In+ + e−||↔ In|
Indium metal does not react with water, but it is oxidized by stronger oxidizing agents such as halogens to give indium(III) compounds. It does not form a boride, silicide, or carbide, and the hydride InH3 has at best a transitory existence in ethereal solutions at low temperatures, being unstable enough to spontaneously polymerize without coordination. Indium is rather basic in aqueous solution, showing only slight amphoteric characteristics, and unlike its lighter homologs aluminium and gallium, it is insoluble in aqueous alkaline solutions.
Indium has 39 known isotopes, ranging in mass number from 97 to 135. Only two isotopes occur naturally as primordial nuclides: indium-113, the only stable isotope, and indium-115, which has a half-life of 4.41×1014 years, four orders of magnitude greater than the age of the universe and nearly 30,000 times greater than that of natural thorium. The half-life of 115In is very long because the beta decay to 115Sn is spin-forbidden. Indium-115 makes up 95.7% of all indium. Indium is one of three known elements (the others being tellurium and rhenium) of which the stable isotope is less abundant in nature than the long-lived primordial radioisotopes.
The stablest artificial isotope is indium-111, with a half-life of approximately 2.8 days. All other isotopes have half-lives shorter than 5 hours. Indium also has 47 meta states, among which indium-114m1 (half-life about 49.51 days) is the most stable, more stable than the ground state of any indium isotope other than the primordial. All decay by isomeric transition. The indium isotopes lighter than 115In predominantly decay through electron capture or positron emission to form cadmium isotopes, while the other indium isotopes from 115In and greater predominantly decay through beta-minus decay to form tin isotopes.
Indium(III) oxide, In2O3, forms when indium metal is burned in air or when the hydroxide or nitrate is heated. In2O3 adopts a structure like alumina and is amphoteric, that is able to react with both acids and bases. Indium reacts with water to reproduce soluble indium(III) hydroxide, which is also amphoteric; with alkalis to produce indates(III); and with acids to produce indium(III) salts:
- In(OH)3 + 3 HCl → InCl3 + 3 H2O
The analogous sesquichalcogenides with sulfur, selenium, and tellurium are also known. Indium forms the expected trihalides. Chlorination, bromination, and iodination of In produce colorless InCl3, InBr3, and yellow InI3. The compounds are Lewis acids, somewhat akin to the better known aluminium trihalides. Again like the related aluminium compound, InF3 is polymeric.
Direct reaction of indium with the pnictogens produces the gray or semimetallic III–V semiconductors. Many of them slowly decompose in moist air, necessitating careful storage of semiconductor compounds to prevent contact with the atmosphere. Indium nitride is readily attacked by acids and alkalis.
Indium(I) compounds are not common. The chloride, bromide, and iodide are deeply colored, unlike the parent trihalides from which they are prepared. The fluoride is known only as an unstable gaseous compound. Indium(I) oxide black powder is produced when indium(III) oxide decomposes upon heating to 700 °C.
Other oxidation statesEdit
Less frequently, indium forms compounds in oxidation state +2 and even fractional oxidation states. Usually such materials feature In–In bonding, most notably in the halides In2X4 and [In2X6]2−, and various subchalcogenides such as In4Se3. Several other compounds are known to combine indium(I) and indium(III), such as InI6(InIIICl6)Cl3, InI5(InIIIBr4)2(InIIIBr6), InIInIIIBr4.
Organoindium compounds feature In–C bonds. Most are In(III) derivatives, but cyclopentadienylindium(I) is an exception. It was the first known organoindium(I) compound, and is polymeric, consisting of zigzag chains of alternating indium atoms and cyclopentadienyl complexes. Perhaps the best-known organoindium compound is trimethylindium, In(CH3)3, used to prepare certain semiconducting materials.
In 1863, the German chemists Ferdinand Reich and Hieronymous Theodor Richter were testing ores from the mines around Freiberg, Saxony. They dissolved the minerals pyrite, arsenopyrite, galena and sphalerite in hydrochloric acid and distilled raw zinc chloride. Reich, who was color-blind, employed Richter as an assistant for detecting the colored spectral lines. Knowing that ores from that region sometimes contain thallium, they searched for the green thallium emission spectrum lines. Instead, they found a bright blue line. Because that blue line did not match any known element, they hypothesized a new element was present in the minerals. They named the element indium, from the indigo color seen in its spectrum, after the Latin indicum, meaning 'of India'.
Richter went on to isolate the metal in 1864. An ingot of 0.5 kg (1.1 lb) was presented at the World Fair 1867. Reich and Richter later fell out when the latter claimed to be the sole discoverer.
Indium is created by the long-lasting (up to thousands of years) s-process (slow neutron capture) in low-to-medium-mass stars (which range in mass between 0.6 and 10 solar masses). When a silver-109 atom (the isotope that comprises approximately half of all silver in existence) catches a neutron, it undergoes a beta decay to become cadmium-110. Capturing further neutrons, it becomes cadmium-115, which decays to indium-115 by another beta decay. This explains why the radioactive isotope is more abundant than the stable one. The stable indium isotope, indium-113, is one of the p-nuclei, the origin of which is not fully understood; although indium-113 is known to be made directly in the s- and r-processes (rapid neutron capture), and also as the daughter of very long-lived cadmium-113, which has a half-life of about eight quadrillion years, this cannot account for all indium-113.
Indium is the 68th most abundant element in Earth's crust at approximately 50 ppb. This is similar to the crustal abundance of silver, bismuth and mercury. It very rarely forms its own minerals, or occurs in elemental form. Fewer than 10 indium minerals such as roquesite (CuInS2) are known, and none occur at sufficient concentrations for economic extraction. Instead, indium is usually a trace constituent of more common ore minerals, such as sphalerite and chalcopyrite. From these, it can be extracted as a by-product during smelting. While the enrichment of indium in these deposits is high relative to its crustal abundance, it is insufficient, at current prices, to support extraction of indium as the main product.
Different estimates exist of the amounts of indium contained within the ores of other metals. However, these amounts are not extractable without mining of the host materials (see Production and availability). Thus, the availability of indium is fundamentally determined by the rate at which these ores are extracted, and not their absolute amount. This is an aspect that is often forgotten in the current debate, e.g. by the Graedel group at Yale in their criticality assessments, explaining the paradoxically low depletion times some studies cite.
Production and availabilityEdit
Indium is produced exclusively as a by-product during the processing of the ores of other metals. Its main source material are sulfidic zinc ores, where it is mostly hosted by sphalerite. Minor amounts are probably also extracted from sulfidic copper ores. During the roast-leach-electrowinning process of zinc smelting, indium accumulates in the iron-rich residues. From these, it can be extracted in different ways. It may also be recovered directly from the process solutions. Further purification is done by electrolysis. The exact process varies with the mode of operation of the smelter.
Its by-product status means that indium production is constrained by the amount of sulfidic zinc (and copper) ores extracted each year. Therefore, its availability needs to be discussed in terms of supply potential. The supply potential of a by-product is defined as that amount which is economically extractable from its host materials per year under current market conditions (i.e. technology and price). Reserves and resources are not relevant for by-products, since they cannot be extracted independently from the main-products. Recent estimates put the supply potential of indium at a minimum of 1,300 t/yr from sulfidic zinc ores and 20 t/yr from sulfidic copper ores. These figures are significantly greater than current production (655 t in 2016). Thus, major future increases in the by-product production of indium will be possible without significant increases in production costs or price. The average indium price in 2016 was $US240/kg, down from $US705/kg in 2014.
China is a leading producer of indium (290 tonnes in 2016), followed by South Korea (195 t), Japan (70 t) and Canada (65 t). The Teck Resources refinery in Trail, British Columbia, is a large single-source indium producer, with an output of 32.5 tonnes in 2005, 41.8 tonnes in 2004 and 36.1 tonnes in 2003.
The primary consumption of indium worldwide is LCD production. Demand rose rapidly from the late 1990s to 2010 with the popularity of LCD computer monitors and television sets, which now account for 50% of indium consumption. Increased manufacturing efficiency and recycling (especially in Japan) maintain a balance between demand and supply. According to the UNEP, indium's end-of-life recycling rate is less than 1%.
In 1924, indium was found to have a valued property of stabilizing non-ferrous metals, and that became the first significant use for the element. The first large-scale application for indium was coating bearings in high-performance aircraft engines during World War II, to protect against damage and corrosion; this is no longer a major use of the element. New uses were found in fusible alloys, solders, and electronics. In the 1950s, tiny beads of indium were used for the emitters and collectors of PNP alloy-junction transistors. In the middle and late 1980s, the development of indium phosphide semiconductors and indium tin oxide thin films for liquid-crystal displays (LCD) aroused much interest. By 1992, the thin-film application had become the largest end use.
Indium(III) oxide and indium tin oxide (ITO) are used as a transparent conductive coating on glass substrates in electroluminescent panels. Indium tin oxide is used as a light filter in low-pressure sodium-vapor lamps. The infrared radiation is reflected back into the lamp, which increases the temperature within the tube and improves the performance of the lamp.
Indium has many semiconductor-related applications. Some indium compounds, such as indium antimonide and indium phosphide, are semiconductors with useful properties: one precursor is usually trimethylindium (TMI), which is also used as the semiconductor dopant in II–VI compound semiconductors. InAs and InSb are used for low-temperature transistors and InP for high-temperature transistors. The compound semiconductors InGaN and InGaP are used in light-emitting diodes (LEDs) and laser diodes. Indium is used in photovoltaics as the semiconductor copper indium gallium selenide (CIGS), also called CIGS solar cells, a type of second-generation thin-film solar cell. Indium is used in PNP bipolar junction transistors with germanium: when soldered at low temperature, indium does not stress the germanium.
Indium wire is used as a vacuum seal and a thermal conductor in cryogenics and ultra-high-vacuum applications, in such manufacturing applications as gaskets that deform to fill gaps. Indium is an ingredient in the gallium–indium–tin alloy galinstan, which is liquid at room temperature and replaces mercury in some thermometers. Other alloys of indium with bismuth, cadmium, lead, and tin, which have higher but still low melting points (between 50 and 100 °C), are used in fire sprinkler systems and heat regulators.
Indium is one of many substitutes for mercury in alkaline batteries to prevent the zinc from corroding and releasing hydrogen gas. Indium is added to some dental amalgam alloys to decrease the surface tension of the mercury and allow for less mercury and easier amalgamation.
Indium's high neutron-capture cross-section for thermal neutrons makes it suitable for use in control rods for nuclear reactors, typically in an alloy of 80% silver, 15% indium, and 5% cadmium. In nuclear engineering, the (n,n') reactions of 113In and 115In are used to determine magnitudes of neutron fluxes.
Biological role and precautionsEdit
Indium has no metabolic role in any organism. In a similar way to aluminium salts, indium(III) ions can be toxic to the kidney when given by injection. Indium tin oxide and indium phosphide harm the pulmonary and immune systems, predominantly through ionic indium, though hydrated indium oxide is more than forty times as toxic when injected, measured by the quantity of indium introduced. Radioactive indium-111 (in very small amounts on a chemical basis) is used in nuclear medicine tests, as a radiotracer to follow the movement of labeled proteins and white blood cells in the body. Indium compounds are mostly not absorbed upon ingestion and are only moderately absorbed on inhalation; they tend to be stored temporarily in the muscles, skin, and bones before being excreted, and the biological half-life of indium is about two weeks in humans.
People can be exposed to indium in the workplace by inhalation, ingestion, skin contact, and eye contact. The National Institute for Occupational Safety and Health has set a recommended exposure limit (REL) of 0.1 mg/m3 over an 8-hour workday.
- Meija, J.; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
- Mangum, B. W. (1989). "Determination of the Indium Freezing-point and Triple-point Temperatures". Metrologia. 26 (4): 211. Bibcode:1989Metro..26..211M. doi:10.1088/0026-1394/26/4/001.
- Guloy, A. M.; Corbett, J. D. (1996). "Synthesis, Structure, and Bonding of Two Lanthanum Indium Germanides with Novel Structures and Properties". Inorganic Chemistry. 35 (9): 2616–22. doi:10.1021/ic951378e.
- Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
- Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
- W. M. Haynes (2010). David R. Lide, ed. CRC Handbook of Chemistry and Physics: A Ready-reference Book of Chemical and Physical Data. CRC Press. ISBN 978-1-4398-2077-3.
- Alfantazi, A. M.; Moskalyk, R. R. (2003). "Processing of indium: a review". Minerals Engineering. 16 (8): 687–694. doi:10.1016/S0892-6875(03)00168-7.
- Binder, Harry H. (1999). Lexicon der chemischen Elemente (in German). S. Hirzel Verlag. ISBN 3-7776-0736-3.
- Dean, John A. (523). Lange's handbook of chemistry (Fifteenth edition). McGraw-Hill, Inc. ISBN 0-07-016190-9.
- Greenwood and Earnshaw, p. 222
- Greenwood and Earnshaw, p. 252
- Iliev, S. P.; Chen, X.; Pathan, M. V.; Tagarielli, V. L. (2017-01-23). "Measurements of the mechanical response of Indium and of its size dependence in bending and indentation". Materials Science and Engineering: A. 683: 244–251. doi:10.1016/j.msea.2016.12.017. hdl:10044/1/43082.
- Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1985). "Thallium". Lehrbuch der Anorganischen Chemie (in German) (91–100 ed.). Walter de Gruyter. pp. 892–893. ISBN 3-11-007511-3.
- Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.
- Greenwood and Earnshaw, p. 256
- Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 8.20. ISBN 1439855110.
- Greenwood and Earnshaw, p. 255
- Audi, Georges; Bersillon, O.; Blachot, J.; Wapstra, A. H. (2003). "The NUBASE Evaluation of Nuclear and Decay Properties". Nuclear Physics A. Atomic Mass Data Center. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
- Dvornický, R.; Šimkovic, F. (13–16 June 2011). "Second unique forbidden β decay of 115In and neutrino mass". AIP Conf. Proc. 1417 (33). doi:10.1063/1.3671032.
- "IUPAC Periodic Table of the Isotopes" (PDF). ciaaw.org. IUPAC. 1 October 2013. Retrieved 21 June 2016.
- Anthony John Downs (1993). Chemistry of aluminium, gallium, indium, and thallium. Springer. ISBN 0-7514-0103-X.
- Greenwood and Earnshaw, p. 286
- Greenwood and Earnshaw, pp. 263–7
- Greenwood and Earnshaw, p. 288
- Greenwood and Earnshaw, pp. 270–1
- Sinclair, Ian; Worrall, Ian J. (1982). "Neutral complexes of the indium dihalides". Canadian Journal of Chemistry. 60 (6): 695–698. doi:10.1139/v82-102.
- Greenwood and Earnshaw, p. 287
- Beck, Horst Philipp; Wilhelm, Doris (1991). "In7Cl9—A New"Old" Compound in the System In-Cl". Angewandte Chemie International Edition in English. 30 (7): 824–825. doi:10.1002/anie.199108241.
- Dronskowski, Richard (1995). "Synthesis, Structure, and Decay of In4Br7". Angewandte Chemie International Edition in English. 34 (10): 1126–1128. doi:10.1002/anie.199511261.
- Fischer, E. O.; Hofmann, H. P. (1957). "Metall-cyclopentadienyle des Indiums". Angewandte Chemie (in German). 69 (20): 639–640. doi:10.1002/ange.19570692008.
- Beachley O. T.; Pazik J. C.; Glassman T. E.; Churchill M. R.; Fettinger J.C.; Blom R. (1988). "Synthesis, characterization and structural studies of In(C5H4Me) by x-ray diffraction and electron diffraction techniques and a reinvestigation of the crystalline state of In(C5H5) by x-ray diffraction studies". Organometallics. 7 (5): 1051–1059. doi:10.1021/om00095a007.
- Shenai, Deo V.; Timmons, Michael L.; Dicarlo, Ronald L.; Lemnah, Gregory K.; Stennick, Robert S. (2003). "Correlation of vapor pressure equation and film properties with trimethylindium purity for the MOVPE grown III–V compounds". Journal of Crystal Growth. 248: 91–98. Bibcode:2003JCrGr.248...91S. doi:10.1016/S0022-0248(02)01854-7.
- Shenai, Deodatta V.; Timmons, Michael L.; Dicarlo, Ronald L.; Marsman, Charles J. (2004). "Correlation of film properties and reduced impurity concentrations in sources for III/V-MOVPE using high-purity trimethylindium and tertiarybutylphosphine". Journal of Crystal Growth. 272: 603–608. Bibcode:2004JCrGr.272..603S. doi:10.1016/j.jcrysgro.2004.09.006.
- Reich, F.; Richter, T. (1863). "Ueber das Indium". Journal für Praktische Chemie (in German). 90 (1): 172–176. doi:10.1002/prac.18630900122.
- Venetskii, S. (1971). "Indium". Metallurgist. 15 (2): 148–150. doi:10.1007/BF01088126.
- Greenwood and Earnshaw, p. 244
- Weeks, Mary Elvira (1932). "The Discovery of the Elements: XIII. Some Spectroscopic Studies". Journal of Chemical Education. 9 (8): 1413–1434. Bibcode:1932JChEd...9.1413W. doi:10.1021/ed009p1413.[permanent dead link]
- Reich, F.; Richter, T. (1864). "Ueber das Indium". Journal für Praktische Chemie (in German). 92 (1): 480–485. doi:10.1002/prac.18640920180.
- Schwarz-Schampera, Ulrich; Herzig, Peter M. (2002). Indium: Geology, Mineralogy, and Economics. Springer. ISBN 978-3-540-43135-0.
- Boothroyd, A. I. (2006). "Heavy elements in stars". Science. 314 (5806): 1690–1691. doi:10.1126/science.1136842. PMID 17170281.
- C. Arlandini, F. Käppeler, K. Wisshak, R. Gallino, M. Lugaro, M. Busso, O. Straniero: Neutron Capture in Low-Mass Asymptotic Giant Branch Stars: Cross Sections and Abundance Signatures. In: The Astrophysical Journal, Vol. 525, 1999, p. 886–900. ( doi:10.1086/307938)
- Zs. Nemeth, F. Käppeler, C. Theis, T. Belgya, S. W. Yates: Nucleosynthesis in the Cd-In-Sn region. In: The Astrophysical Journal, Vol. 426, 1994, p. 357–365. ( doi:10.1086/174071)
- "The distribution of gallium, germanium and indium in conventional and non-conventional resources - Implications for global availability (PDF Download Available)". ResearchGate. doi:10.13140/rg.2.2.20956.18564. Retrieved 2017-06-02.
- Frenzel, Max; Hirsch, Tamino; Gutzmer, Jens (July 2016). "Gallium, germanium, indium, and other trace and minor elements in sphalerite as a function of deposit type — A meta-analysis". Ore Geology Reviews. 76: 52–78. doi:10.1016/j.oregeorev.2015.12.017.
- Bachmann, Kai; Frenzel, Max; Krause, Joachim; Gutzmer, Jens (June 2017). "Advanced Identification and Quantification of In-Bearing Minerals by Scanning Electron Microscope-Based Image Analysis". Microscopy and Microanalysis. 23 (3): 527–537. Bibcode:2017MiMic..23..527B. doi:10.1017/S1431927617000460. ISSN 1431-9276.
- Frenzel, Max; Mikolajczak, Claire; Reuter, Markus A.; Gutzmer, Jens (June 2017). "Quantifying the relative availability of high-tech by-product metals – The cases of gallium, germanium and indium". Resources Policy. 52: 327–335. doi:10.1016/j.resourpol.2017.04.008.
- "Mineral Commodities Summary 2007: Indium" (PDF). United States Geological Survey. Retrieved 2007-12-26.
- Werner, T. T.; Mudd, G. M.; Jowitt, S. M. (2015-10-02). "Indium: key issues in assessing mineral resources and long-term supply from recycling". Applied Earth Science. 124 (4): 213–226. doi:10.1179/1743275815Y.0000000007. ISSN 0371-7453.
- Graedel, T. E.; Barr, Rachel; Chandler, Chelsea; Chase, Thomas; Choi, Joanne; Christoffersen, Lee; Friedlander, Elizabeth; Henly, Claire; Jun, Christine (2012-01-17). "Methodology of Metal Criticality Determination". Environmental Science & Technology. 46 (2): 1063–1070. Bibcode:2012EnST...46.1063G. doi:10.1021/es203534z. ISSN 0013-936X.
- Harper, E. M.; Kavlak, Goksin; Burmeister, Lara; Eckelman, Matthew J.; Erbis, Serkan; Sebastian Espinoza, Vicente; Nuss, Philip; Graedel, T. E. (2015-08-01). "Criticality of the Geological Zinc, Tin, and Lead Family". Journal of Industrial Ecology. 19 (4): 628–644. doi:10.1111/jiec.12213. ISSN 1530-9290.
- U.S. Geological Survey – Historical Statistics for Mineral and Material Commodities in the United States; INDIUM STATISTICS // USGS, April 1, 2014
- Greenwood and Earnshaw, p. 247
- Frenzel, Max; Tolosana-Delgado, Raimon; Gutzmer, Jens (December 2015). "Assessing the supply potential of high-tech metals – A general method". Resources Policy. 46, Part 2: 45–58. doi:10.1016/j.resourpol.2015.08.002.
- Indium - in: USGS Mineral Commodity Summaries (PDF). United States Geological Survey. 2017.
- Kelly, TD; Matos, GR (2015). "Historical Statistics for Mineral and Material Commodities in the United States". Retrieved 06-02-2017. Check date values in:
- "Indium Price Supported by LCD Demand and New Uses for the Metal" (PDF). Geology.com. Retrieved 2007-12-26.
- "USGS Mineral Commodity Summaries 2011" (PDF). USGS and USDI. Retrieved August 2, 2011.
- French, Sidney J. (1934). "A story of indium". Journal of Chemical Education. 11 (5): 270. Bibcode:1934JChEd..11..270F. doi:10.1021/ed011p270.
- Tolcin, Amy C. "Mineral Yearbook 2007: Indium" (PDF). United States Geological Survey.
- Downs, Anthony John (1993). Chemistry of Aluminium, Gallium, Indium, and Thallium. Springer. pp. 89 and 106. ISBN 978-0-7514-0103-5.
- "The Electroluminescent Light Sabre". Nanotechnology News Archive. Azonano. June 2, 2005. Archived from the original on October 12, 2007. Retrieved 2007-08-29.
- Bachmann, K. J. (1981). "Properties, Preparation, and Device Applications of Indium Phosphide". Annual Review of Materials Science. 11: 441–484. Bibcode:1981AnRMS..11..441B. doi:10.1146/annurev.ms.11.080181.002301.
- Shenai, Deodatta V.; Timmons, Michael L.; DiCarlo Jr., Ronald L.; Marsman, Charles J. (2004). "Correlation of film properties and reduced impurity concentrations in sources for III/V-MOVPE using high-purity trimethylindium and tertiarybutylphosphine". Journal of Crystal Growth. 272 (1–4): 603–608. Bibcode:2004JCrGr.272..603S. doi:10.1016/j.jcrysgro.2004.09.006.
- Schubert, E. Fred (2003). Light-Emitting Diodes. Cambridge University Press. p. 16. ISBN 0-521-53351-1.
- Powalla, M.; Dimmler, B. (2000). "Scaling up issues of CIGS solar cells". Thin Solid Films. 361–362: 540–546. Bibcode:2000TSF...361..540P. doi:10.1016/S0040-6090(99)00849-4.
- Weissler, G. L., ed. (1990). "Vacuum physics and technology". San Diego: Acad. Press: 296. ISBN 978-0-12-475914-5.
- Surmann, P; Zeyat, H (Nov 2005). "Voltammetric analysis using a self-renewable non-mercury electrode". Analytical and Bioanalytical Chemistry. 383 (6): 1009–13. doi:10.1007/s00216-005-0069-7. PMID 16228199.
- Geological Survey (U.S.) (2010). Minerals Yearbook, 2008, V. 1, Metals and Minerals. Government Printing Office. pp. 35–2. ISBN 978-1-4113-3015-3.
- Powell L. V., Johnson G. H., Bales D. J. (1989). "Effect of Admixed Indium on Mercury Vapor Release from Dental Amalgam" (PDF). Journal of Dental Research. 68 (8): 1231–3. doi:10.1177/00220345890680080301. PMID 2632609.
- Scoullos, Michael J. (2001-12-31). "Other types of cadmium alloys". Mercury, cadmium, lead: handbook for sustainable heavy metals policy and regulation. p. 222. ISBN 978-1-4020-0224-3.
- Berger, Harold; National Bureau Of Standards, United States; Committee E-7 On Nondestructive Testing, American Society for Testing and Materials (1976). "Image Detectors for Other Neutron Energies". Practical applications of neutron radiography and gaging: a symposium. pp. 50–51.
- Castronovo, F. P.; Wagner, H. N. (October 1971). "Factors Affecting the Toxicity of the Element Indium". British Journal of Experimental Pathology. 52 (5): 543–559. PMC . PMID 5125268.
- Gwinn, W. M.; Qu, W.; Bousquet, R. W.; Price, H.; Shines, C. J.; Taylor, G. J.; Waalkes, M. P.; Morgan, D. L. (2014). "Macrophage Solubilization and Cytotoxicity of Indium-Containing Particles as in vitro Correlates to Pulmonary Toxicity in vivo". Toxicological Sciences. 144 (1): 17–26. doi:10.1093/toxsci/kfu273. PMC . PMID 25527823.
- "IN-111 FACT SHEET" (PDF). Nordion(Canada), Inc. Archived from the original (PDF) on 3 December 2011. Retrieved 23 September 2012.
- Van Nostrand, D.; Abreu, S. H.; Callaghan, J. J.; Atkins, F. B.; Stoops, H. C.; Savory, C. G. (May 1988). "In-111-labeled white blood cell uptake in noninfected closed fracture in humans: prospective study". Radiology. 167 (2): 495–498. doi:10.1148/radiology.167.2.3357961. PMID 3357961.
- Nordberg, Gunnar F.; Fowler, Bruce A.; Nordberg, Monica (7 August 2014). Handbook on the Toxicology of Metals (4th ed.). Academic Press. p. 845. ISBN 978-0-12-397339-9.
- "CDC – NIOSH Pocket Guide to Chemical Hazards – Indium". www.cdc.gov. Retrieved 2015-11-06.