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= Yttrium =
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Introduction
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Yttrium is a chemical element; it has symbol Y and atomic number 39.
It is a silvery-metallic transition metal chemically similar to the
lanthanides and has often been classified as a "rare-earth element".
Yttrium is almost always found in combination with lanthanide elements
in rare-earth minerals and is never found in nature as a free element.
89Y is the only stable isotope and the only isotope found in the
Earth's crust.
The most important present-day use of yttrium is as a component of
phosphors, especially those used in LEDs. Historically, it was once
widely used in the red phosphors in television set cathode ray tube
displays. Yttrium is also used in the production of electrodes,
electrolytes, electronic filters, lasers, superconductors, various
medical applications, and tracing various materials to enhance their
properties.
Yttrium has no known biological role. Exposure to yttrium compounds
can cause lung disease in humans.
Etymology
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The element is named after 'ytterbite', a mineral first identified in
1787 by the chemist Carl Axel Arrhenius. He named the mineral after
the village of Ytterby, in Sweden, where it had been discovered. When
one of the chemicals in ytterbite was later found to be a previously
unidentified element, the element was then named yttrium after the
mineral.
Properties
============
Yttrium is a soft, silver-metallic, lustrous and highly crystalline
transition metal in group 3. As expected by periodic trends, it is
less electronegative than its predecessor in the group, scandium, and
less electronegative than the next member of period 5, zirconium.
However, due to the lanthanide contraction, it is also less
electronegative than its successor in the group, lutetium. Yttrium is
the first d-block element in the fifth period.
The pure element is relatively stable in air in bulk form, due to
passivation of a protective oxide () film that forms on the surface.
This film can reach a thickness of 10 μm when yttrium is heated to 750
°C in water vapor. When finely divided, however, yttrium is very
unstable in air; shavings or turnings of the metal can ignite in air
at temperatures exceeding 400 °C. Yttrium nitride (YN) is formed when
the metal is heated to 1000 °C in nitrogen.
Similarity to the lanthanides
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The similarities of yttrium to the lanthanides are so strong that the
element has been grouped with them as a rare-earth element, and is
always found in nature together with them in rare-earth minerals.
Chemically, yttrium resembles those elements more closely than its
neighbor in the periodic table, scandium, and if physical properties
were plotted against atomic number, it would have an apparent number
of 64.5 to 67.5, placing it between the lanthanides gadolinium and
erbium.
It often also falls in the same range for reaction order, resembling
terbium and dysprosium in its chemical reactivity. Yttrium is so close
in size to the so-called 'yttrium group' of heavy lanthanide ions that
in solution, it behaves as if it were one of them. Even though the
lanthanides are one row farther down the periodic table than yttrium,
the similarity in atomic radius may be attributed to the lanthanide
contraction.
One of the few notable differences between the chemistry of yttrium
and that of the lanthanides is that yttrium is almost exclusively
trivalent, whereas about half the lanthanides can have valences other
than three; nevertheless, only for four of the fifteen lanthanides are
these other valences important in aqueous solution (Ce(IV), Sm(II),
Eu(II), and Yb(II)).
Compounds and reactions
=========================
As a trivalent transition metal, yttrium forms various inorganic
compounds, generally in the +3 oxidation state, by giving up all three
of its valence electrons. A good example is yttrium(III) oxide (),
also known as yttria, a six-coordinate white solid.
Yttrium forms a water-insoluble fluoride, hydroxide, and oxalate, but
its bromide, chloride, iodide, nitrate and sulfate are all soluble in
water. The Y(3+) ion is colorless in solution due to the absence of
electrons in the d and f electron shells.
Water readily reacts with yttrium and its compounds to form .
Concentrated nitric and hydrofluoric acids do not rapidly attack
yttrium, but other strong acids do.
With halogens, yttrium forms trihalides such as yttrium(III) fluoride
(), yttrium(III) chloride (), and yttrium(III) bromide () at
temperatures above roughly 200 °C. Similarly, carbon, phosphorus,
selenium, silicon and sulfur all form binary compounds with yttrium at
elevated temperatures.
Organoyttrium chemistry is the study of compounds containing
carbon-yttrium bonds. A few of these are known to have yttrium in the
oxidation state 0. (The +2 state has been observed in chloride melts,
and +1 in oxide clusters in the gas phase.) Some trimerization
reactions were generated with organoyttrium compounds as catalysts.
These syntheses use as a starting material, obtained from and
concentrated hydrochloric acid and ammonium chloride.
Hapticity is a term to describe the coordination of a group of
contiguous atoms of a ligand bound to the central atom; it is
indicated by the Greek letter eta, η. Yttrium complexes were the first
examples of complexes where carboranyl ligands were bound to a
d(0)-metal center through a η(7)-hapticity. Vaporization of the
graphite intercalation compounds graphite-Y or graphite- leads to the
formation of endohedral fullerenes such as Y@C. Electron spin
resonance studies indicated the formation of Y(3+) and (C)(3−) ion
pairs. The carbides YC, YC, and YC can be hydrolyzed to form
hydrocarbons.
Isotopes and nucleosynthesis
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Yttrium in the Solar System was created by stellar nucleosynthesis,
mostly by the s-process (≈72%), but also the r-process (≈28%). The
r-process consists of rapid neutron capture by lighter elements during
supernova explosions. The s-process is a slow neutron capture of
lighter elements inside pulsating red giant stars.
Yttrium isotopes are among the most common products of the nuclear
fission of uranium in nuclear explosions and nuclear reactors. In the
context of nuclear waste management, the most important isotopes of
yttrium are (91)Y and (90)Y, with half-lives of 58.51 days and 64
hours, respectively. Though (90)Y has a short half-life, it exists in
secular equilibrium with its long-lived parent isotope, strontium-90
((90)Sr) (half-life 29 years).
All group 3 elements have an odd atomic number, and therefore few
stable isotopes. Scandium has one stable isotope, and yttrium itself
has only one stable isotope, (89)Y, which is also the only isotope
that occurs naturally. However, the lanthanide rare earths contain
elements of even atomic number and many stable isotopes. Yttrium-89 is
thought to be more abundant than it otherwise would be, due in part to
the s-process, which allows enough time for isotopes created by other
processes to decay by electron emission (neutron → proton).
Such a slow process tends to favor isotopes with atomic mass numbers
(A = protons + neutrons) around 90, 138 and 208, which have unusually
stable atomic nuclei with 50, 82, and 126 neutrons, respectively. This
stability is thought to result from their very low neutron-capture
cross-section. Electron emission of isotopes with those mass numbers
is simply less prevalent due to this stability, resulting in them
having a higher abundance. 89Y has a mass number close to 90 and has
50 neutrons in its nucleus.
At least 32 synthetic isotopes of yttrium have been observed, and
these range in atomic mass number from 76 to 108. The least stable of
these is (109)Y with a half-life of 25 ms and the most stable is (88)Y
with half-life 106.629 days. Apart from (91)Y, (87)Y, and (90)Y, with
half-lives of 58.51 days, 79.8 hours, and 64 hours, respectively; all
other isotopes have half-lives of less than a day and most of less
than an hour.
Yttrium isotopes with mass numbers at or below 88 decay mainly by
positron emission (proton → neutron) to form strontium (Z = 38)
isotopes. Yttrium isotopes with mass numbers at or above 90 decay
mainly by electron emission (neutron → proton) to form zirconium (Z =
40) isotopes. Isotopes with mass numbers at or above 97 are also known
to have minor decay paths of β(−) delayed neutron emission.
Yttrium has at least 20 metastable ("excited") isomers ranging in mass
number from 78 to 102. Multiple excitation states have been observed
for (80)Y and (97)Y. While most yttrium isomers are expected to be
less stable than their ground state; (78m, 84m, 85m, 96m, 98m1, 100m,
102m)Y have longer half-lives than their ground states, as these
isomers decay by beta decay rather than isomeric transition.
History
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In 1787, part-time chemist Carl Axel Arrhenius found a heavy black
rock in an old quarry near the Swedish village of Ytterby (now part of
the Stockholm Archipelago). Thinking it was an unknown mineral
containing the newly discovered element tungsten, he named it
'ytterbite' and sent samples to various chemists for analysis.
Johan Gadolin at the Royal Academy of Åbo (Turku) identified a new
oxide (or "earth") in Arrhenius' sample in 1789, and published his
completed analysis in 1794. Anders Gustaf Ekeberg confirmed the
identification in 1797 and named the new oxide 'yttria'. In the
decades after Antoine Lavoisier developed the first modern definition
of chemical elements, it was believed that earths could be reduced to
their elements, meaning that the discovery of a new earth was
equivalent to the discovery of the element within, which in this case
would have been 'yttrium'.
Friedrich Wöhler is credited with first isolating the metal in 1828 by
reacting a volatile chloride that he believed to be yttrium chloride
with potassium.
In 1843, Carl Gustaf Mosander found that samples of yttria contained
three oxides: white yttrium oxide (yttria), yellow terbium oxide
(confusingly, this was called 'erbia' at the time) and rose-colored
erbium oxide (called 'terbia' at the time). A fourth oxide, ytterbium
oxide, was isolated in 1878 by Jean Charles Galissard de Marignac. New
elements were later isolated from each of those oxides, and each
element was named, in some fashion, after Ytterby, the village near
the quarry where they were found (see ytterbium, terbium, and erbium).
In the following decades, seven other new metals were discovered in
"Gadolin's yttria". Since yttria was found to be a mineral and not an
oxide, Martin Heinrich Klaproth renamed it gadolinite in honor of
Gadolin.
Until the early 1920s, the chemical symbol Yt was used for the
element, after which Y came into common use.
In 1987, yttrium barium copper oxide was found to achieve
high-temperature superconductivity. It was only the second material
known to exhibit this property, and it was the first-known material to
achieve superconductivity above the (economically important) boiling
point of nitrogen.
Abundance
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Yttrium is found in most rare-earth minerals, and some uranium ores,
but never in the Earth's crust as a free element. About 31 ppm of the
Earth's crust is yttrium, making it the 43rd most abundant element.
Yttrium is found in soil in concentrations between 10 and 150 ppm (dry
weight average of 23 ppm) and in sea water at 9 ppt. Lunar rock
samples collected during the American Apollo Project have a relatively
high content of yttrium.
Yttrium is not considered a "bone-seeker" like strontium and lead.
Normally, as little as 0.5 mg is found in the entire human body; human
breast milk contains 4 ppm. Yttrium can be found in edible plants in
concentrations between 20 ppm and 100 ppm (fresh weight), with cabbage
having the largest amount. With as much as 700 ppm, the seeds of woody
plants have the highest known concentrations.
there are reports of the discovery of very large reserves of
rare-earth elements in the deep seabed several hundred kilometers from
the tiny Japanese island of Minami-Torishima Island, also known as
Marcus Island. This location is described as having "tremendous
potential" for rare-earth elements and yttrium (REY), according to a
study published in 'Scientific Reports'. "This REY-rich mud has great
potential as a rare-earth metal resource because of the enormous
amount available and its advantageous mineralogical features," the
study reads. The study shows that more than 16 e6ST of rare-earth
elements could be "exploited in the near future." As well as yttrium
(Y), which is used in products like camera lenses and mobile phone
screens, the rare-earth elements found are europium (Eu), terbium
(Tb), and dysprosium (Dy).
Production
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As yttrium is chemically similar to lanthanides, it occurs in the same
ores (rare-earth minerals) and is extracted by the same refinement
processes. A slight distinction is recognized between the light (LREE)
and the heavy rare-earth elements (HREE), but the distinction is not
perfect. Yttrium is concentrated in the HREE group due to its ion
size, though it has a lower atomic mass.
Rare-earth elements (REEs) come mainly from four sources:
* Carbonate and fluoride containing ores such as the LREE bastnäsite
((Ce, La, etc.)(CO)F) contain on average 0.1% yttrium compared to the
99.9% for the 16 other REEs. The main source of bastnäsite from the
1960s to the 1990s was the Mountain Pass rare earth mine in
California, making the United States the largest producer of REEs
during that period. The name "bastnäsite" is actually a group name,
and the Levinson suffix is used in the correct mineral names, e.g.,
bästnasite-(Y) has Y as a prevailing element.
* Monazite ((Ce, La, etc.)PO), which is mostly phosphate, is a placer
deposit of sand created by the transportation and gravitational
separation of eroded granite. Monazite as a LREE ore contains 2% (or
3%) yttrium. The largest deposits were found in India and Brazil in
the early 20th century, making those two countries the largest
producers of yttrium in the first half of that century. Of the
monazite group, the Ce-dominant member, monazite-(Ce), is the most
common one.
* Xenotime, a REE phosphate, is the main HREE ore containing as much
as 60% yttrium as yttrium phosphate (YPO). This applies to
xenotime-(Y). The largest mine is the Bayan Obo deposit in China,
making China the largest exporter for HREE since the closure of the
Mountain Pass mine in the 1990s.
* Ion absorption clays or Longnan clays are the weathering products of
granite and contain only 1% of REEs. The final ore concentrate can
contain as much as 8% yttrium. Ion absorption clays are mostly in
southern China. Yttrium is also found in samarskite and fergusonite
(which also stand for group names).
One method for obtaining pure yttrium from the mixed oxide ores is to
dissolve the oxide in sulfuric acid and fractionate it by ion exchange
chromatography. With the addition of oxalic acid, the yttrium oxalate
precipitates. The oxalate is converted into the oxide by heating under
oxygen. By reacting the resulting yttrium oxide with hydrogen
fluoride, yttrium fluoride is obtained. When quaternary ammonium salts
are used as extractants, most yttrium will remain in the aqueous
phase. When the counter-ion is nitrate, the light lanthanides are
removed, and when the counter-ion is thiocyanate, the heavy
lanthanides are removed. In this way, yttrium salts of 99.999% purity
are obtained. In the usual situation, where yttrium is in a mixture
that is two-thirds heavy-lanthanide, yttrium should be removed as soon
as possible to facilitate the separation of the remaining elements.
Annual world production of yttrium oxide had reached 600 t by 2001; by
2014 it had increased to 7,000 ST. Global reserves of yttrium oxide
were estimated in 2014 to be more than 500,000 ST. The leading
countries for these reserves included Australia, Brazil, China, India,
and the United States. Only a few tonnes of yttrium metal are produced
each year by reducing yttrium fluoride to a metal sponge with calcium
magnesium alloy. The temperature of an arc furnace, in excess of 1,600
°C, is sufficient to melt the yttrium.
Consumer
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The red component of color television cathode ray tubes is typically
emitted from an yttria () or yttrium oxide sulfide () host lattice
doped with europium (III) cation (Eu(3+)) phosphors. The red color
itself is emitted from the europium while the yttrium collects energy
from the electron gun and passes it to the phosphor. Yttrium compounds
can serve as host lattices for doping with different lanthanide
cations. Tb(3+) can be used as a doping agent to produce green
luminescence. As such yttrium compounds such as yttrium aluminium
garnet (YAG) are useful for phosphors and are an important component
of white LEDs.
Yttria is used as a sintering additive in the production of porous
silicon nitride.
Yttrium compounds are used as a catalyst for ethylene polymerization.
As a metal, yttrium is used on the electrodes of some high-performance
spark plugs. Yttrium is used in gas mantles for propane lanterns as a
replacement for thorium, which is radioactive.
Garnets
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Yttrium is used in the production of a large variety of synthetic
garnets, and yttria is used to make yttrium iron garnets (, "YIG"),
which are very effective microwave filters which were recently shown
to have magnetic interactions more complex and longer-ranged than
understood over the previous four decades. Yttrium, iron, aluminium,
and gadolinium garnets (e.g. and ) have important magnetic
properties. YIG is also very efficient as an acoustic energy
transmitter and transducer. Yttrium aluminium garnet ( or YAG) has a
hardness of 8.5 and is also used as a gemstone in jewelry (simulated
diamond). Cerium-doped yttrium aluminium garnet (YAG:Ce) crystals are
used as phosphors to make white LEDs.
YAG, yttria, yttrium lithium fluoride (LiYF), and yttrium
orthovanadate (YVO) are used in combination with dopants such as
neodymium, erbium, ytterbium in near-infrared lasers. YAG lasers can
operate at high power and are used for drilling and cutting metal. The
single crystals of doped YAG are normally produced by the Czochralski
process.
Material enhancer
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Small amounts of yttrium (0.1 to 0.2%) have been used to reduce the
grain sizes of chromium, molybdenum, titanium, and zirconium. Yttrium
is used to increase the strength of aluminium and magnesium alloys.
The addition of yttrium to alloys generally improves workability, adds
resistance to high-temperature recrystallization, and significantly
enhances resistance to high-temperature oxidation (see graphite nodule
discussion below).
Yttrium can be used to deoxidize vanadium and other non-ferrous
metals. Yttria stabilizes the cubic form of zirconia in jewelry.
Yttrium has been studied as a nodulizer in ductile cast iron, forming
the graphite into compact nodules instead of flakes to increase
ductility and fatigue resistance. Having a high melting point, yttrium
oxide is used in some ceramic and glass to impart shock resistance and
low thermal expansion properties. Those same properties make such
glass useful in camera lenses.
Medical
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The radioisotope yttrium-90 ((90)Y) is used to label drugs such as
edotreotide and ibritumomab tiuxetan for the treatment of various
cancers, including lymphoma, leukemia, liver, ovarian, colorectal,
pancreatic and bone cancers. It works by adhering to monoclonal
antibodies, which in turn bind to cancer cells and kill them via
intense β-radiation from the (90)Y (see monoclonal antibody therapy).
A technique called radioembolization is used to treat hepatocellular
carcinoma and liver metastasis. Radioembolization is a low toxicity,
targeted liver cancer therapy that uses millions of tiny beads made of
glass or resin containing (90)Y. The radioactive microspheres are
delivered directly to the blood vessels feeding specific liver
tumors/segments or lobes. It is minimally invasive and patients can
usually be discharged after a few hours. This procedure may not
eliminate all tumors throughout the entire liver, but works on one
segment or one lobe at a time and may require multiple procedures.
Also see radioembolization in the case of combined cirrhosis and
hepatocellular carcinoma.
Needles made of (90)Y, which can cut more precisely than scalpels,
have been used to sever pain-transmitting nerves in the spinal cord,
and (90)Y is also used to carry out radionuclide synovectomy in the
treatment of inflamed joints, especially knees, in people with
conditions such as rheumatoid arthritis.
A neodymium-doped yttrium-aluminium-garnet laser has been used in an
experimental, robot-assisted radical prostatectomy in canines in an
attempt to reduce collateral nerve and tissue damage, and erbium-doped
lasers are coming into use for cosmetic skin resurfacing.
Superconductors
=================
Yttrium is a key ingredient in the yttrium barium copper oxide
(YBaCuO, aka 'YBCO' or '1-2-3') superconductor developed at the
University of Alabama in Huntsville and the University of Houston in
1987. This superconductor is notable because the operating
superconductivity temperature is above liquid nitrogen's boiling point
(77.1 K). Since liquid nitrogen is less expensive than the liquid
helium required for metallic superconductors, the operating costs for
applications would be less.
The actual superconducting material is often written as YBa2Cu3O7-'d',
where 'd' must be less than 0.7 for superconductivity. The reason for
this is still not clear, but it is known that the vacancies occur only
in certain places in the crystal, the copper oxide planes, and chains,
giving rise to a peculiar oxidation state of the copper atoms, which
somehow leads to the superconducting behavior.
The theory of low temperature superconductivity has been well
understood since the BCS theory of 1957. It is based on a peculiarity
of the interaction between two electrons in a crystal lattice.
However, the BCS theory does not explain high temperature
superconductivity, and its precise mechanism is still a mystery. What
is known is that the composition of the copper-oxide materials must be
precisely controlled for superconductivity to occur.
This superconductor is a black and green, multi-crystal, multi-phase
mineral. Researchers are studying a class of materials known as
perovskites that are alternative combinations of these elements,
hoping to develop a practical high-temperature superconductor.
Lithium batteries
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Yttrium is used in small quantities in the cathodes of some Lithium
iron phosphate battery (LFP), which are then commonly called LiFeYPO
chemistry, or LYP. Similar to LFP, LYP batteries offer high energy
density, good safety and long life. But LYP offers higher cathode
stability, and prolongs the life of the battery, by protecting the
physical structure of the cathode, especially at higher temperatures
and higher charging / discharge current. LYP batteries find use in
stationary applications (off-grid solar systems), electric vehicles
(some cars), as well other applications (submarines, ships), similar
to LFP batteries, but often at improved safety and cycle life time.
LYP cells have essentially the same nominal voltage as LFP, 3.25V, but
the maximum charging voltage is 4.0V, and the charging and discharge
characteristics are very similar.
Other applications
====================
In 2009, Professor Mas Subramanian and associates at Oregon State
University discovered that yttrium can be combined with indium and
manganese to form an intensely blue, non-toxic, inert, fade-resistant
pigment, YInMn blue, the first new blue pigment discovered in 200
years.
Precautions
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Yttrium can be highly toxic to humans, animals and plants.
Water-soluble compounds of yttrium are considered mildly toxic, while
its insoluble compounds are non-toxic. In experiments on animals,
yttrium and its compounds caused lung and liver damage, though
toxicity varies with different yttrium compounds. In rats, inhalation
of yttrium citrate caused pulmonary edema and dyspnea, while
inhalation of yttrium chloride caused liver edema, pleural effusions,
and pulmonary hyperemia.
Exposure to yttrium compounds in humans may cause lung disease.
Workers exposed to airborne yttrium europium vanadate dust experienced
mild eye, skin, and upper respiratory tract irritation--though this
may be caused by the vanadium content rather than the yttrium. Acute
exposure to yttrium compounds can cause shortness of breath, coughing,
chest pain, and cyanosis. The Occupational Safety and Health
Administration (OSHA) limits exposure to yttrium in the workplace to
over an 8-hour workday. The National Institute for Occupational Safety
and Health (NIOSH) recommended exposure limit (REL) is over an 8-hour
workday. At levels of , yttrium is immediately dangerous to life and
health. Yttrium dust is highly flammable.
External links
======================================================================
* [
http://pubsapp.acs.org/cen/80th/yttrium.html Yttrium by Paul C.W.
Chu at acs.org]
* [
http://www.periodicvideos.com/videos/039.htm Yttrium] at 'The
Periodic Table of Videos' (University of Nottingham)
*
*
[
https://link.springer.com/referenceworkentry/10.1007%2F978-3-319-39193-9_145-1
Encyclopedia of Geochemistry - Yttrium]
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=========
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Original Article:
http://en.wikipedia.org/wiki/Yttrium
