Difference between revisions of "Indium" - New World Encyclopedia
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− | '''Indium''' ( | + | '''Indium''' (chemical symbol '''In''', [[atomic number]]* 49) is a rare, soft, malleable and easily fusible [[metal]]. It is chemically similar to [[aluminum]] and [[gallium]], but it looks more like [[zinc]]. Zinc ores are also the primary source of this metal. Its current primary application is to form transparent electrodes from [[indium tin oxide]]* in [[liquid crystal displays]] (LCDs). It is also widely used in thin films, to form lubricated layers. During [[World War II]], it was widely used to coat bearings in high-performance [[aircraft]]. |
== Occurrence == | == Occurrence == | ||
[[Image:Indium wire.jpg|thumb|left|Ductile Indium wire]] | [[Image:Indium wire.jpg|thumb|left|Ductile Indium wire]] | ||
− | |||
− | + | Indium is produced mainly from residues generated during [[zinc]] [[ore]] processing, but it is also found in [[iron]], [[lead]], and [[copper]] ores. The amount of indium consumed is largely a function of worldwide LCD production. Increased manufacturing efficiency and recycling (especially in [[Japan]]) maintain a balance between demand and supply. Demand increased as the metal is used in [[LCD]]s and televisions, and supply decreased when a number of [[China|Chinese]] [[mining]] concerns stopped extracting indium from their [[zinc]] tailings. | |
+ | |||
+ | Up until 1924, there was only about one [[gram]]* of isolated indium on the planet. The Earth is estimated to contain about 0.1 parts per million (ppm) of indium. This means it is about as abundant as [[silver]], but indium is nearly three times more expensive by weight. Canada is a leading producer of indium. Worldwide production is typically over 300 tonnes per year, but demand has risen rapidly with the increased popularity of LCD computer monitors and television sets. | ||
== History == | == History == | ||
− | Indium | + | |
+ | Indium was discovered by [[Ferdinand Reich]]* and [[Hieronymous Theodor Richter]]* in 1863, when they were testing [[zinc]] ores with a [[spectrograph]]* in search of [[thallium]]. The element was named after the [[indigo]]* line in its [[atomic spectrum]]*. It is interesting to note that most elements were discovered while searching for other elements. Richter went on to isolate the metal in 1867. | ||
== Notable characteristics == | == Notable characteristics == | ||
− | |||
− | One unusual property of indium is that its most common [[isotope]] is | + | In the [[periodic table]], indium lies in group 13 (former group 3A), between [[gallium]] and [[thallium]], and in the same group as [[aluminum]]. Consequently, its properties resemble those of these three elements. In addition, it is situated in period 5, between [[cadmium]] and [[tin]]. |
+ | |||
+ | Indium is a very soft, silvery-[[white]]* [[metal]], with a bright [[Luster (mineralogy)|luster]]*. As a pure metal, it emits a high-pitched "cry" when bent. This element and [[gallium]] are able to wet [[glass]]. | ||
+ | |||
+ | === Isotopes === | ||
+ | |||
+ | One unusual property of indium is that its most common [[isotope]], <sup>115</sup>In, is slightly radioactive—it decays very slowly by [[beta emission]] to [[tin]]. The estimated abundance of <sup>115</sup>In is about 95.7%, while that of the stable isotope, <sup>113</sup>In, is 4.3%. | ||
+ | |||
+ | The radioactivity of <sup>115</sup>In is not considered hazardous, mainly because its decay rate is nearly 50,000 times slower than that of natural [[thorium]], with a half-life of 4{{e|14}} years. Also, indium is not a notorious [[cumulative poison]]*, like its neighbor [[cadmium]], and is relatively rare. | ||
+ | |||
+ | Numerous other radioactive isotopes of indium are known, but most of them are extremely short-lived. | ||
== Applications == | == Applications == | ||
+ | |||
The first large-scale application for indium was as a coating for [[bearing (mechanical)|bearing]]s in high-performance [[aircraft]] engines during [[World War II]]. Afterwards, production gradually increased as new uses were found in fusible [[alloy]]s, [[solder]]s, and [[electronics]]. In the middle and late [[1980s]], the development of indium phosphide [[semiconductor]]s and indium-[[tin]]-[[oxide]] thin films for [[liquid crystal display]]s (LCD) aroused much interest. By 1992, the thin-film application had become the largest end use. Other uses; | The first large-scale application for indium was as a coating for [[bearing (mechanical)|bearing]]s in high-performance [[aircraft]] engines during [[World War II]]. Afterwards, production gradually increased as new uses were found in fusible [[alloy]]s, [[solder]]s, and [[electronics]]. In the middle and late [[1980s]], the development of indium phosphide [[semiconductor]]s and indium-[[tin]]-[[oxide]] thin films for [[liquid crystal display]]s (LCD) aroused much interest. By 1992, the thin-film application had become the largest end use. Other uses; | ||
*Used in the manufacture of low-melting-temperature [[alloy]]s. An alloy consisting of 24% indium and 76% gallium is [[liquid]] at room temperature. | *Used in the manufacture of low-melting-temperature [[alloy]]s. An alloy consisting of 24% indium and 76% gallium is [[liquid]] at room temperature. |
Revision as of 14:55, 25 October 2006
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General | |||||||||||||||||||
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Name, Symbol, Number | indium, In, 49 | ||||||||||||||||||
Chemical series | poor metals | ||||||||||||||||||
Group, Period, Block | 13, 5, p | ||||||||||||||||||
Appearance | silvery lustrous gray | ||||||||||||||||||
Atomic mass | 114.818(3) g/mol | ||||||||||||||||||
Electron configuration | [Kr] 4d10 5s2 5p1 | ||||||||||||||||||
Electrons per shell | 2, 8, 18, 18, 3 | ||||||||||||||||||
Physical properties | |||||||||||||||||||
Phase | solid | ||||||||||||||||||
Density (near r.t.) | 7.31 g/cm³ | ||||||||||||||||||
Liquid density at m.p. | 7.02 g/cm³ | ||||||||||||||||||
Melting point | 429.75 K (156.60 °C, 313.88 °F) | ||||||||||||||||||
Boiling point | 2345 K (2072 °C, 3762 °F) | ||||||||||||||||||
Heat of fusion | 3.281 kJ/mol | ||||||||||||||||||
Heat of vaporization | 231.8 kJ/mol | ||||||||||||||||||
Heat capacity | (25 °C) 26.74 J/(mol·K) | ||||||||||||||||||
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Atomic properties | |||||||||||||||||||
Crystal structure | tetragonal | ||||||||||||||||||
Oxidation states | 3 (amphoteric oxide) | ||||||||||||||||||
Electronegativity | 1.78 (Pauling scale) | ||||||||||||||||||
Ionization energies (more) |
1st: 558.3 kJ/mol | ||||||||||||||||||
2nd: 1820.7 kJ/mol | |||||||||||||||||||
3rd: 2704 kJ/mol | |||||||||||||||||||
Atomic radius | 155 pm | ||||||||||||||||||
Atomic radius (calc.) | 156 pm | ||||||||||||||||||
Covalent radius | 144 pm | ||||||||||||||||||
Van der Waals radius | 193 pm | ||||||||||||||||||
Miscellaneous | |||||||||||||||||||
Magnetic ordering | no data | ||||||||||||||||||
Electrical resistivity | (20 °C) 83.7 nΩ·m | ||||||||||||||||||
Thermal conductivity | (300 K) 81.8 W/(m·K) | ||||||||||||||||||
Thermal expansion | (25 °C) 32.1 µm/(m·K) | ||||||||||||||||||
Speed of sound (thin rod) | (20 °C) 1215 m/s | ||||||||||||||||||
Speed of sound (thin rod) | (r.t.) 11 m/s | ||||||||||||||||||
Mohs hardness | 1.2 | ||||||||||||||||||
Brinell hardness | 8.83 MPa | ||||||||||||||||||
CAS registry number | 7440-74-6 | ||||||||||||||||||
Notable isotopes | |||||||||||||||||||
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Indium (chemical symbol In, atomic number 49) is a rare, soft, malleable and easily fusible metal. It is chemically similar to aluminum and gallium, but it looks more like zinc. Zinc ores are also the primary source of this metal. Its current primary application is to form transparent electrodes from indium tin oxide in liquid crystal displays (LCDs). It is also widely used in thin films, to form lubricated layers. During World War II, it was widely used to coat bearings in high-performance aircraft.
Occurrence
Indium is produced mainly from residues generated during zinc ore processing, but it is also found in iron, lead, and copper ores. The amount of indium consumed is largely a function of worldwide LCD production. Increased manufacturing efficiency and recycling (especially in Japan) maintain a balance between demand and supply. Demand increased as the metal is used in LCDs and televisions, and supply decreased when a number of Chinese mining concerns stopped extracting indium from their zinc tailings.
Up until 1924, there was only about one gram of isolated indium on the planet. The Earth is estimated to contain about 0.1 parts per million (ppm) of indium. This means it is about as abundant as silver, but indium is nearly three times more expensive by weight. Canada is a leading producer of indium. Worldwide production is typically over 300 tonnes per year, but demand has risen rapidly with the increased popularity of LCD computer monitors and television sets.
History
Indium was discovered by Ferdinand Reich and Hieronymous Theodor Richter in 1863, when they were testing zinc ores with a spectrograph in search of thallium. The element was named after the indigo line in its atomic spectrum. It is interesting to note that most elements were discovered while searching for other elements. Richter went on to isolate the metal in 1867.
Notable characteristics
In the periodic table, indium lies in group 13 (former group 3A), between gallium and thallium, and in the same group as aluminum. Consequently, its properties resemble those of these three elements. In addition, it is situated in period 5, between cadmium and tin.
Indium is a very soft, silvery-white metal, with a bright luster. As a pure metal, it emits a high-pitched "cry" when bent. This element and gallium are able to wet glass.
Isotopes
One unusual property of indium is that its most common isotope, 115In, is slightly radioactive—it decays very slowly by beta emission to tin. The estimated abundance of 115In is about 95.7%, while that of the stable isotope, 113In, is 4.3%.
The radioactivity of 115In is not considered hazardous, mainly because its decay rate is nearly 50,000 times slower than that of natural thorium, with a half-life of 4×1014 years. Also, indium is not a notorious cumulative poison, like its neighbor cadmium, and is relatively rare.
Numerous other radioactive isotopes of indium are known, but most of them are extremely short-lived.
Applications
The first large-scale application for indium was as a coating for bearings in high-performance aircraft engines during World War II. Afterwards, production gradually increased as new uses were found in fusible alloys, solders, and electronics. 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. Other uses;
- Used in the manufacture of low-melting-temperature alloys. An alloy consisting of 24% indium and 76% gallium is liquid at room temperature.
- Some indium compounds such as indium antimonide, indium phosphide, and indium nitride are semiconductors with useful properties
- Used as a semiconductor dopant
- Can also be plated onto metals and evaporated onto glass which forms a mirror which is as good as those made with silver but has higher corrosion resistance.
- Its oxide is used in the making of electroluminescent panels.
- Used as a light filter in Low pressure sodium vapor lamps
- Indium's freezing point of 429.7485 K (156.5985 °C) is a defining fixed point on the international temperature scale ITS-90.
- Sometimes used as a component of nuclear control rods.
- Very small amounts used in aluminium alloy sacrificial anodes (for salt water applications) to prevent passivation of the aluminium
Precautions
Pure indium in metal form is considered non-toxic by most sources. This may not be the case with indium compounds: there is some unconfirmed evidence that suggests that indium has a low level of toxicity. However, in the welding and semiconductor industries, where indium exposure is relatively high, there have been no reports of any toxic side-effects. Other sources are more definite about indium compounds' toxicity - for example, the WebElements website states that "All indium compounds should be regarded as highly toxic. Indium compounds damage the heart, kidney, and liver, and may be teratogenic." For example, indium trichloride anhydrous (InCl3) is quite toxic, while indium phosphide (InP) is both toxic and a suspected carcinogen.
See also
ReferencesISBN links support NWE through referral fees
External links
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