Difference between revisions of "Tellurium" - New World Encyclopedia

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{{Elementbox_header | number=52 | symbol=Te | name=tellurium | left=[[antimony]] | right=[[iodine]] | above=[[selenium|Se]] | below=[[polonium|Po]] | color1=#cccc99 | color2=black }}
 
{{Elementbox_header | number=52 | symbol=Te | name=tellurium | left=[[antimony]] | right=[[iodine]] | above=[[selenium|Se]] | below=[[polonium|Po]] | color1=#cccc99 | color2=black }}
 
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'''Tellurium''' ([[International Phonetic Alphabet|IPA]]: {{IPA|/tiˈlʊəriəm, tɛ-/}}) (chemical symbol '''Te''', [[atomic number]]* 52) is a [[chemical element]] that is classified as a [[metalloid]]. A brittle silver-white in color, it looks like [[tin]]. Tellurium is chemically related to [[selenium]] and [[sulfur]]. This element is primarily used in [[alloy]]s and as a [[semiconductor]].
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'''Tellurium''' (chemical symbol '''Te''', [[atomic number]] 52) is a relatively rare [[chemical element]] that belongs to the group of [[metalloid]]s—its chemical properties are intermediate between those of [[metal]]s and [[nonmetal]]s. Silvery in color, it looks like [[tin]], but chemically it is more closely related to [[selenium]] and [[sulfur]].
 +
 
 +
This element is primarily used in [[alloy]]s. For instance, when added to [[lead]], it enhances the metal's strength and durability; when alloyed with [[stainless steel]] and [[copper]], it makes them more workable. When alloyed with both [[cadmium]] and [[mercury (element)|mercury]], it forms an [[infrared]]-sensitive [[semiconductor]]. In addition, it is used in [[ceramic]]s, [[glass]]es, and blasting caps. [[Bismuth]] telluride is useful for [[thermoelectric]] devices, and cadmium telluride has potential applications in photovoltaic cells for [[solar power]]. When [[zinc]] is added to cadmium telluride, the product is extremely well-suited for use in solid-state detectors for [[X ray]]s and [[gamma ray]]s.
 +
{{toc}}
 +
Yet, tellurium and its compounds should be considered [[toxic]] and need to be handled with care. Exposure to even small amounts of tellurium can generate a garlicky odor in one's breath, [[sweat]], and [[urine]]. Additional symptoms of exposure to the element or its compounds (at relatively high concentrations) include [[headache]], [[dyspnea]], weakness, skin rash, a [[metallic]] taste in the mouth, and blue-black markings on the [[finger]]s, [[neck]], [[face]], and [[gum]]s. Death may occur from [[pulmonary edema]]. A person exposed to tellurium compounds should be given medical attention.
 +
 
 +
== Occurrence and production ==
 +
 
 +
In [[nature]], tellurium is sometimes found in its elemental form, but it is more often found as the tellurides of [[gold]] and [[silver]], such as the minerals [[calaverite]], [[krennerite]], [[petzite]], and [[sylvanite]]. Tellurium compounds are the only chemical compounds of gold found in nature. Yet, unlike gold, tellurium itself is also found combined with other elements, forming metallic salts.
 +
 
 +
The principal source of tellurium is from [[electrolysis|anode]] sludges produced during the electrolytic refining of blister [[copper]]. In addition, it is a component of dusts from [[blast furnace]] refining of [[lead]]. Tellurium is produced mainly in the [[United States]], [[Canada]], [[Peru]], and [[Japan]].
 +
 
 +
Commercial-grade tellurium, which is not toxic if properly handled, is usually marketed as minus 200-mesh powder, but it is also available as slabs, ingots, sticks, and lumps.
 +
 
 +
== History ==
 +
 
 +
Tellurium (from the [[Latin]] word ''tellus'', meaning "earth") was discovered in 1782 by the Hungarian [[Franz-Joseph Müller von Reichenstein]] (Müller Ferenc) in [[Transylvania]]. Another Hungarian scientist, Pál Kitaibel, discovered the element independently in 1789, but he later gave the credit to Müller. It was named in 1798 by [[Martin Heinrich Klaproth]] who had isolated it earlier.
 +
 
 +
The 1960s brought growth in thermoelectric applications for tellurium, as well as its use in free-machining [[steel]], which became the dominant use.
  
 
== Notable characteristics ==
 
== Notable characteristics ==
[[Image:Tellurium crystal.jpg|thumb|left|Tellurium crystal]]
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[[Image:Tellurium crystal.jpg|thumb|left|Tellurium crystal.]]
Tellurium is a relatively rare element, in the same chemical family as [[oxygen]], [[sulfur]], [[selenium]], and [[polonium]] (the [[chalcogen]]s).
+
 
 +
In the [[periodic table]], tellurium is located in group 16 (formerly group 6A), between [[selenium]] and [[polonium]]. Along with [[sulfur]], [[selenium]], and [[polonium]], it is a member of the [[oxygen]] family of elements, also called the ''chalcogens''. In addition, it lies in period five, between [[antimony]] and [[iodine]].
 +
 
 +
In its pure and [[crystal]]line state, tellurium has a silvery-white color and a metallic luster. When the element is precipitated from a solution of tellurous acid (H<sub>2</sub>TeO<sub>3</sub>) or telluric acid (H<sub>6</sub>TeO<sub>6</sub>), it appears to have an amorphous form. There is, however, some debate whether this form is really amorphous or composed of minute crystals.
 +
 
 +
Tellurium is brittle and can be easily pulverized. When burned in air, it produces a greenish-blue flame and forms [[tellurium dioxide]]. In its molten state, the element is corrosive toward copper, [[iron]], and stainless [[steel]].
  
<!-- PLEASE MARK THIS PARAGRAPHS FOR REVIEW —>
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Chemically, tellurium is related to [[sulfur]] and [[selenium]] and forms similar compounds. Yet, while sulfur and selenium are nonmetals, tellurium (as well as polonium) is classified as a metalloid.
  
When [[crystal]]line, tellurium is silvery-white and when it is in its pure state it has a metallic luster. This is a brittle and easily pulverized metalloid. Amorphous tellurium is found by precipitating it from a solution of tellurous or telluric [[acid]] (Te(OH)<sub>6</sub>). However, there is some debate whether this form is really amorphous or made of minute crystals. Tellurium is a p-type [[semiconductor]] that shows a greater conductivity in certain directions which depends on [[atom]]ic alignment.
+
Tellurium is a P-type [[semiconductor]]. Its conductivity, which is higher in certain directions, increases slightly on exposure to light. It can be doped with various metals, including [[tin]], [[copper]], [[silver]], and [[gold]].
  
Chemically related to [[selenium]] and [[sulfur]], the conductivity of this element increases slightly when exposed to light. It can be doped with [[copper]], [[gold]], [[silver]], [[tin]], or other metals. Tellurium has a greenish-blue flame when burned in normal air and forms [[tellurium dioxide]] as a result. When in its molten state, tellurium is corrosive to copper, [[iron]], and [[stainless steel]].
+
=== Isotopes ===
  
== Applications ==
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There are 30 known [[isotope]]s of tellurium, with [[atomic mass]]es ranging from 108 to 137. Naturally occurring tellurium consists of eight isotopes (listed in the table on the right), three of which are radioactive. Among all its radioactive isotopes, <sup>128</sup>Te has the longest half-life (2.2&times;10<sup>24</sup> years).
It is mostly used in [[alloy]]s with other metals. It is added to [[lead]] to improve its strength, durability and to decrease the corrosive action of [[sulfuric acid]]. When added to [[stainless steel]] and [[copper]] it makes these metals more workable. Other uses:
 
* It is alloyed into [[cast iron]] for chill control.
 
* Used in [[ceramic]]s.
 
* It is used in [[chalcogenide glass]]es.
 
* [[Bismuth]] telluride ([[bismuth telluride|Bi<sub>2</sub>Te<sub>3</sub>]]) has found use in [[thermoelectric]] devices.
 
  
Tellurium is also used in [[blasting cap]]s, and has potential applications in [[cadmium telluride]] (CdTe) [[solar panel]]s. Some of the highest efficiencies for solar cell electric power generation have been obtained by using this material, but this application has not yet caused demand to increase significantly. If some of the cadmium in CdTe is replaced by [[zinc]] then [[CdZnTe]] is formed which is used in solid-state [[x-ray]] detectors.
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== Compounds ==
  
Alloyed with both cadmium and [[mercury (element)|mercury]], to form [[HgCdTe|mercury cadmium telluride]], an [[infrared]] sensitive [[semiconductor]] material is formed.
+
Tellurium can form a variety of [[chemical compound|compounds]]. Some examples are given below.
  
Organic tellurides have been employed as initiators for living radical polymerisation and electron-rich mono- and di-tellurides possess [[antioxidant]] activity.
+
* ''Bismuth(III) telluride'' (Bi<sub>2</sub>Te<sub>3</sub>): This compound is a [[semiconductor]] and an efficient [[Peltier effect|thermoelectric]] material for devices used in refrigeration or portable power generation. Although generally a low-risk material, it can be fatal if large doses are ingested. One should avoid breathing its dust. Also, its reaction with [[water]] may release toxic fumes.
  
== History ==
+
* ''Cadmium telluride'' (CdTe): This crystalline compound is a useful material for solar cells ([[photovoltaic]]s). It is used as an [[infrared]] optical material for [[optical window]]s and [[Lens (optics)|lenses]]. It can be alloyed with [[mercury (element)|mercury]] to make a versatile infrared detector material (HgCdTe). Alloyed with a small amount of [[zinc]], it makes an excellent solid-state [[X-ray]] and [[gamma ray]] detector (CdZnTe).
Tellurium ([[Latin]] ''tellus'' meaning "earth") was discovered in [[1782]] by the Hungarian [[Franz-Joseph Müller von Reichenstein]] (Müller Ferenc) in [[Transylvania]].  
 
In [[1789]] another Hungarian scientist, Pál Kitaibel, also discovered the element independently, but later he gave the credit to Müller. In [[1798]] it was named by [[Martin Heinrich Klaproth]] who earlier isolated it.
 
  
The [[1960s]] brought growth in thermoelectric applications for tellurium, as well as its use in free-machining [[steel]], which became the dominant use.
+
* ''Silver telluride'' (Ag<sub>2</sub>Te): It occurs in [[nature]] in the form of the [[mineral]]s [[hessite]] and [[empressite]]. It is a [[semiconductor]] that can be doped to have either n-type or p-type conductivity. On heating, [[silver]] is lost from the material.
  
== Occurrence ==
+
*''Telluric acid'' (H<sub>6</sub>TeO<sub>6</sub> or Te(OH)<sub>6</sub>): It is a weak [[acid]], forming ''tellurate'' [[salt]]s with strong [[base]]s.<ref>Holleman, A. F. and E. Wiberg. "Inorganic Chemistry." Academic Press: San Diego, 2001. ISBN 0-12-352651-5</ref> In addition, it is an oxidizing agent. It can be formed by the [[redox|oxidation]] of tellurium or tellurium dioxide with [[hydrogen peroxide]] or [[chromium trioxide]].
Tellurium is sometimes found in its native (elemental) form, but is more often found as the tellurides of [[gold]] ([[calaverite]], [[krennerite]], [[petzite]], [[sylvanite]], and others). Tellurium compounds are the only chemical compounds of gold found in nature, but tellurium itself (unlike gold) is also found combined with other elements (in metallic salts). The principal source of tellurium is from [[anode]] sludges produced during the electrolytic refining of blister [[copper]]. It is a component of dusts from [[blast furnace]] refining of [[lead]].  Tellurium is produced mainly in the US, [[Canada]], [[Peru]], and [[Japan]].
 
  
Commercial-grade tellurium, which is not toxic, is usually marketed as minus 200-mesh powder but is also available as slabs, ingots, sticks, or lumps. The yearend price for tellurium in [[2000]] was [[United States dollar|US$]] 14 per pound.
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* ''Tellurium dioxide'' (TeO<sub>2</sub> or paratellurite): This solid [[oxide]] is the main product of burning tellurium in air. It is highly [[insoluble]] in [[water]] and completely soluble in concentrated [[sulfuric acid]]. It is [[amphoteric]], which means that it can act as an acid or as a base, depending on the solution it is in. It is used as an [[acousto-optic]] material. It is also a conditional glass former, meaning that it will form a glass with small additions of a second compound such as an oxide or halide. TeO<sub>2</sub> glasses have high [[refractive indices]], transmit into the mid-[[infrared]] region of the [[electromagnetic spectrum]], and have properties useful for [[optical fiber]] amplification.
  
*See also: [[Telluride, Colorado]], [[:category:Telluride minerals]]
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* ''Tellurium hexafluoride'' (TeF<sub>6</sub>): It is a colorless, highly toxic gas with a foul smell. It is most commonly prepared by passing [[fluorine]] gas over tellurium metal at 150 °C. Below this temperature, a mixture of lower fluorides are formed, including [[tellurium tetrafluoride]] and [[ditellurium decafluoride]]. The physical properties of tellurium hexafluoride resemble those of the [[sulfur]] analog, but unlike the latter, it is not chemically [[inert]]. It is hydrolyzed in water to form telluric acid, and it reacts with Te below 200 °C.
  
== Compounds ==
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== Applications ==
Tellurium is in the same series as [[sulfur]] and [[selenium]] and forms similar compounds. A compound with metal or hydrogen and similar ions is called a [[telluride]]. [[Gold]] and [[silver]] tellurides are considered good ores. See also
 
[[Cadmium zinc telluride]] (CdZnTe),
 
[[Telluric acid]] (H<sub>6</sub>TeO<sub>6</sub>). Compounds with tellurate ions complexes TeO<sub>4</sub><sup>2-</sup> or TeO<sub>6</sub><sup>6-</sup> are known as [[tellurate]]s.
 
;See also: [[:Category:Tellurium compounds]]
 
  
== Isotopes ==
+
* Tellurium is mostly used in [[alloy]]s with other metals. Consider some examples.
There are 30 known isotopes of tellurium with [[atomic mass]]es that range from 108 to 137. Naturally found tellurium consists of eight isotopes (listed in the table to the right); three of them are observed to be radioactive. <sup>128</sup>Te has the longest known half-life time (2.2&times;10<sup>24</sup> years) among all radioactive isotopes.
+
** Alloyed with [[lead]], it improves the material's strength and durability, and decreases the corrosive action of [[sulfuric acid]].
 +
** When added to [[stainless steel]] or [[copper]], it makes these metals more workable.
 +
** It is alloyed with cast [[iron]] for chill control.
 +
** When alloyed with both cadmium and [[mercury (element)|mercury]], it forms [[HgCdTe|mercury cadmium telluride]], an [[infrared]]-sensitive [[semiconductor]].
 +
* Tellurium is also used in [[ceramic]]s and chalcogenide [[glass]]es.
 +
* It is used in [[blasting cap]]s.
 +
* [[Bismuth]] telluride (Bi<sub>2</sub>Te<sub>3</sub>) is used in [[thermoelectric]] devices for refrigeration or portable power generation.
 +
* [[Cadmium telluride]] (CdTe) has potential applications in [[solar panel]]s. Some of the highest efficiencies for solar cell electric power generation have been obtained by using this material. It is used as an [[infrared]] optical material for [[optical window]]s and [[Lens (optics)|lenses]].
 +
* If cadmium telluride is alloyed with some [[zinc]] to form [[CdZnTe]], this material is used in solid-state detectors for [[X ray]]s and [[gamma ray]]s.
  
 
== Precautions ==
 
== Precautions ==
Humans exposed to as little as 0.01 mg/m<sup>3</sup> or less in air develop "tellurium breath", which has a [[garlic]]-like odor. The garlic odour that is associated with human intake of tellurium compounds is caused from the tellurium being metabolized by the body. When the body metabolizes tellurium in any oxidation state, the tellurium gets converted into [[dimethyl telluride]]. Dimethyl telluride is volatile and produces the garlic-like smell.
 
  
Tellurium and tellurium compounds should be considered to be [[toxic]] and need to be handled with care.
+
Tellurium and its compounds should be considered [[toxic]] and need to be handled with care. A person exposed to as little as 0.01 milligrams (or less) of tellurium per cubic meter of air develops "tellurium breath," which has a garlicky odor. The same smell is also present in [[sweat]] and [[urine]]. The body metabolizes tellurium in any oxidation state, converting it to [[dimethyl telluride]]. This product is volatile and smells like garlic.
 +
 
 +
Exposure to tellurium or its compounds can also cause [[headache]], [[dyspnea]], weakness, skin rash, and a [[metallic]] taste in the mouth. In addition, it can produce bluish-black markings on the [[finger]]s, [[neck]], [[face]], and [[gum]]s. Death may occur from [[pulmonary edema]]. People exposed to tellurium compounds should receive medical attention.
 +
 
 +
==See also==
 +
 
 +
* [[Chemical element]]
 +
* [[Periodic table]]
 +
 
 +
== Notes ==
 +
<references/>
  
 
==References==
 
==References==
  
*[http://periodic.lanl.gov/elements/52.html Los Alamos National Laboratory &ndash; Tellurium]
+
*[http://periodic.lanl.gov/elements/52.html Los Alamos National Laboratory &ndash; Tellurium] Retrieved December 5, 2007.
  
 
== External links ==
 
== External links ==
 
+
All links retrieved February 26, 2023.
*[http://www.webelements.com/webelements/elements/text/Te/index.html WebElements.com &ndash; Tellurium]
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*[http://www.webelements.com/webelements/elements/text/Te/index.html WebElements.com &ndash; Tellurium]  
  
 
[[Category:Physical sciences]]
 
[[Category:Physical sciences]]
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[[Category:Chemical elements]]
 
[[Category:Chemical elements]]
  
{{credit|82395259}}
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{{credit7|Tellurium|82395259|Bismuth_telluride|60553348|Cadmium_telluride|75528991|Silver_telluride|78333050|Telluric_acid|70955870|Tellurium_dioxide|76611250|Tellurium_hexafluoride|63347557}}

Latest revision as of 05:35, 27 February 2023

52 antimonytelluriumiodine
Se

Te

Po
Te-TableImage.png
periodic table
General
Name, Symbol, Number tellurium, Te, 52
Chemical series metalloids
Group, Period, Block 16, 5, p
Appearance silvery lustrous gray
Te,52.jpg
Atomic mass 127.60(3) g/mol
Electron configuration [Kr] 4d10 5s2 5p4
Electrons per shell 2, 8, 18, 18, 6
Physical properties
Phase solid
Density (near r.t.) 6.24 g/cm³
Liquid density at m.p. 5.70 g/cm³
Melting point 722.66 K
(449.51 °C, 841.12 °F)
Boiling point 1261 K
(988 °C, 1810 °F)
Heat of fusion 17.49 kJ/mol
Heat of vaporization 114.1 kJ/mol
Heat capacity (25 °C) 25.73 J/(mol·K)
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K     (775) (888) 1042 1266
Atomic properties
Crystal structure hexagonal
Oxidation states ±2, 4, 6
(mildly acidic oxide)
Electronegativity 2.1 (Pauling scale)
Ionization energies
(more)
1st: 869.3 kJ/mol
2nd: 1790 kJ/mol
3rd: 2698 kJ/mol
Atomic radius 140 pm
Atomic radius (calc.) 123 pm
Covalent radius 135 pm
Van der Waals radius 206 pm
Miscellaneous
Magnetic ordering nonmagnetic
Thermal conductivity (300 K)
(1.97–3.38) W/(m·K)
Speed of sound (thin rod) (20 °C) 2610 m/s
Speed of sound (thin rod) (r.t.) 43 m/s
Shear modulus 16 GPa
Bulk modulus 65 GPa
Mohs hardness 2.25
Brinell hardness 180 MPa
CAS registry number 13494-80-9
Notable isotopes
Main article: Isotopes of tellurium
iso NA half-life DM DE (MeV) DP
120Te 0.096% Te is stable with 68 neutrons
122Te 2.603% Te is stable with 70 neutrons
123Te 0.908% >1.0×1013 y ε 0.051 123Sb
124Te 4.816% Te is stable with 72 neutrons
125Te 7.139% Te is stable with 73 neutrons
126Te 18.952% Te is stable with 74 neutrons
128Te 31.687% 2.2×1024 y ββ 0.867 128Xe
130Te 33.799% 7.9×1020 y ββ 2.528 130Xe

Tellurium (chemical symbol Te, atomic number 52) is a relatively rare chemical element that belongs to the group of metalloids—its chemical properties are intermediate between those of metals and nonmetals. Silvery in color, it looks like tin, but chemically it is more closely related to selenium and sulfur.

This element is primarily used in alloys. For instance, when added to lead, it enhances the metal's strength and durability; when alloyed with stainless steel and copper, it makes them more workable. When alloyed with both cadmium and mercury, it forms an infrared-sensitive semiconductor. In addition, it is used in ceramics, glasses, and blasting caps. Bismuth telluride is useful for thermoelectric devices, and cadmium telluride has potential applications in photovoltaic cells for solar power. When zinc is added to cadmium telluride, the product is extremely well-suited for use in solid-state detectors for X rays and gamma rays.

Yet, tellurium and its compounds should be considered toxic and need to be handled with care. Exposure to even small amounts of tellurium can generate a garlicky odor in one's breath, sweat, and urine. Additional symptoms of exposure to the element or its compounds (at relatively high concentrations) include headache, dyspnea, weakness, skin rash, a metallic taste in the mouth, and blue-black markings on the fingers, neck, face, and gums. Death may occur from pulmonary edema. A person exposed to tellurium compounds should be given medical attention.

Occurrence and production

In nature, tellurium is sometimes found in its elemental form, but it is more often found as the tellurides of gold and silver, such as the minerals calaverite, krennerite, petzite, and sylvanite. Tellurium compounds are the only chemical compounds of gold found in nature. Yet, unlike gold, tellurium itself is also found combined with other elements, forming metallic salts.

The principal source of tellurium is from anode sludges produced during the electrolytic refining of blister copper. In addition, it is a component of dusts from blast furnace refining of lead. Tellurium is produced mainly in the United States, Canada, Peru, and Japan.

Commercial-grade tellurium, which is not toxic if properly handled, is usually marketed as minus 200-mesh powder, but it is also available as slabs, ingots, sticks, and lumps.

History

Tellurium (from the Latin word tellus, meaning "earth") was discovered in 1782 by the Hungarian Franz-Joseph Müller von Reichenstein (Müller Ferenc) in Transylvania. Another Hungarian scientist, Pál Kitaibel, discovered the element independently in 1789, but he later gave the credit to Müller. It was named in 1798 by Martin Heinrich Klaproth who had isolated it earlier.

The 1960s brought growth in thermoelectric applications for tellurium, as well as its use in free-machining steel, which became the dominant use.

Notable characteristics

Tellurium crystal.

In the periodic table, tellurium is located in group 16 (formerly group 6A), between selenium and polonium. Along with sulfur, selenium, and polonium, it is a member of the oxygen family of elements, also called the chalcogens. In addition, it lies in period five, between antimony and iodine.

In its pure and crystalline state, tellurium has a silvery-white color and a metallic luster. When the element is precipitated from a solution of tellurous acid (H2TeO3) or telluric acid (H6TeO6), it appears to have an amorphous form. There is, however, some debate whether this form is really amorphous or composed of minute crystals.

Tellurium is brittle and can be easily pulverized. When burned in air, it produces a greenish-blue flame and forms tellurium dioxide. In its molten state, the element is corrosive toward copper, iron, and stainless steel.

Chemically, tellurium is related to sulfur and selenium and forms similar compounds. Yet, while sulfur and selenium are nonmetals, tellurium (as well as polonium) is classified as a metalloid.

Tellurium is a P-type semiconductor. Its conductivity, which is higher in certain directions, increases slightly on exposure to light. It can be doped with various metals, including tin, copper, silver, and gold.

Isotopes

There are 30 known isotopes of tellurium, with atomic masses ranging from 108 to 137. Naturally occurring tellurium consists of eight isotopes (listed in the table on the right), three of which are radioactive. Among all its radioactive isotopes, 128Te has the longest half-life (2.2×1024 years).

Compounds

Tellurium can form a variety of compounds. Some examples are given below.

  • Bismuth(III) telluride (Bi2Te3): This compound is a semiconductor and an efficient thermoelectric material for devices used in refrigeration or portable power generation. Although generally a low-risk material, it can be fatal if large doses are ingested. One should avoid breathing its dust. Also, its reaction with water may release toxic fumes.
  • Cadmium telluride (CdTe): This crystalline compound is a useful material for solar cells (photovoltaics). It is used as an infrared optical material for optical windows and lenses. It can be alloyed with mercury to make a versatile infrared detector material (HgCdTe). Alloyed with a small amount of zinc, it makes an excellent solid-state X-ray and gamma ray detector (CdZnTe).
  • Silver telluride (Ag2Te): It occurs in nature in the form of the minerals hessite and empressite. It is a semiconductor that can be doped to have either n-type or p-type conductivity. On heating, silver is lost from the material.
  • Telluric acid (H6TeO6 or Te(OH)6): It is a weak acid, forming tellurate salts with strong bases.[1] In addition, it is an oxidizing agent. It can be formed by the oxidation of tellurium or tellurium dioxide with hydrogen peroxide or chromium trioxide.
  • Tellurium dioxide (TeO2 or paratellurite): This solid oxide is the main product of burning tellurium in air. It is highly insoluble in water and completely soluble in concentrated sulfuric acid. It is amphoteric, which means that it can act as an acid or as a base, depending on the solution it is in. It is used as an acousto-optic material. It is also a conditional glass former, meaning that it will form a glass with small additions of a second compound such as an oxide or halide. TeO2 glasses have high refractive indices, transmit into the mid-infrared region of the electromagnetic spectrum, and have properties useful for optical fiber amplification.
  • Tellurium hexafluoride (TeF6): It is a colorless, highly toxic gas with a foul smell. It is most commonly prepared by passing fluorine gas over tellurium metal at 150 °C. Below this temperature, a mixture of lower fluorides are formed, including tellurium tetrafluoride and ditellurium decafluoride. The physical properties of tellurium hexafluoride resemble those of the sulfur analog, but unlike the latter, it is not chemically inert. It is hydrolyzed in water to form telluric acid, and it reacts with Te below 200 °C.

Applications

  • Tellurium is mostly used in alloys with other metals. Consider some examples.
    • Alloyed with lead, it improves the material's strength and durability, and decreases the corrosive action of sulfuric acid.
    • When added to stainless steel or copper, it makes these metals more workable.
    • It is alloyed with cast iron for chill control.
    • When alloyed with both cadmium and mercury, it forms mercury cadmium telluride, an infrared-sensitive semiconductor.
  • Tellurium is also used in ceramics and chalcogenide glasses.
  • It is used in blasting caps.
  • Bismuth telluride (Bi2Te3) is used in thermoelectric devices for refrigeration or portable power generation.
  • Cadmium telluride (CdTe) has potential applications in solar panels. Some of the highest efficiencies for solar cell electric power generation have been obtained by using this material. It is used as an infrared optical material for optical windows and lenses.
  • If cadmium telluride is alloyed with some zinc to form CdZnTe, this material is used in solid-state detectors for X rays and gamma rays.

Precautions

Tellurium and its compounds should be considered toxic and need to be handled with care. A person exposed to as little as 0.01 milligrams (or less) of tellurium per cubic meter of air develops "tellurium breath," which has a garlicky odor. The same smell is also present in sweat and urine. The body metabolizes tellurium in any oxidation state, converting it to dimethyl telluride. This product is volatile and smells like garlic.

Exposure to tellurium or its compounds can also cause headache, dyspnea, weakness, skin rash, and a metallic taste in the mouth. In addition, it can produce bluish-black markings on the fingers, neck, face, and gums. Death may occur from pulmonary edema. People exposed to tellurium compounds should receive medical attention.

See also

Notes

  1. Holleman, A. F. and E. Wiberg. "Inorganic Chemistry." Academic Press: San Diego, 2001. ISBN 0-12-352651-5

References
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External links

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