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= Neodymium =
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Introduction
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Neodymium is a chemical element; it has symbol Nd and atomic number
60. It is the fourth member of the lanthanide series and is considered
to be one of the rare-earth metals. It is a hard, slightly malleable,
silvery metal that quickly tarnishes in air and moisture. When
oxidized, neodymium reacts quickly producing pink, purple/blue and
yellow compounds in the +2, +3 and +4 oxidation states. It is
generally regarded as having one of the most complex spectra of the
elements. Neodymium was discovered in 1885 by the Austrian chemist
Carl Auer von Welsbach, who also discovered praseodymium. Neodymium is
present in significant quantities in the minerals monazite and
bastnäsite. Neodymium is not found naturally in metallic form or
unmixed with other lanthanides, and it is usually refined for general
use. Neodymium is fairly common--about as common as cobalt, nickel, or
copper--and is widely distributed in the Earth's crust. Most of the
world's commercial neodymium is mined in China, as is the case with
many other rare-earth metals.
Neodymium compounds were first commercially used as glass dyes in 1927
and remain a popular additive. The color of neodymium compounds comes
from the Nd3+ ion and is often a reddish-purple. This color changes
with the type of lighting because of the interaction of the sharp
light absorption bands of neodymium with ambient light enriched with
the sharp visible emission bands of mercury, trivalent europium or
terbium. Glasses that have been doped with neodymium are used in
lasers that emit infrared with wavelengths between 1047 and 1062
nanometers. These lasers have been used in extremely high-power
applications, such as in inertial confinement fusion. Neodymium is
also used with various other substrate crystals, such as yttrium
aluminium garnet in the Nd:YAG laser.
Neodymium alloys are used to make high-strength neodymium magnets,
which are powerful permanent magnets. These magnets are widely used in
products like microphones, professional loudspeakers, in-ear
headphones, high-performance hobby DC electric motors, and computer
hard disks, where low magnet mass (or volume) or strong magnetic
fields are required. Larger neodymium magnets are used in electric
motors with a high power-to-weight ratio (e.g., in hybrid cars) and
generators (e.g., aircraft and wind turbine electric generators).
Physical properties
======================================================================
Metallic neodymium has a bright, silvery metallic luster. Neodymium
commonly exists in two allotropic forms, with a transformation from a
double hexagonal to a body-centered cubic structure taking place at
about 863 °C. Neodymium, like most of the lanthanides, is paramagnetic
at room temperature. It becomes an antiferromagnet upon cooling below
20 K. Below this transition temperature it exhibits a set of complex
magnetic phases that have long spin relaxation times and spin glass
behavior. Neodymium is a rare-earth metal that was present in the
classical mischmetal at a concentration of about 18%. To make
neodymium magnets it is alloyed with iron, which is a ferromagnet.
Electron configuration
========================
Neodymium is the fourth member of the lanthanide series. In the
periodic table, it appears between the lanthanides praseodymium to its
left and the radioactive element promethium to its right, and above
the actinide uranium. Its 60 electrons are arranged in the
configuration [Xe]4f46s2, of which the six 4f and 6s electrons are
valence. Like most other metals in the lanthanide series, neodymium
usually only uses three electrons as valence electrons, as afterwards
the remaining 4f electrons are strongly bound: this is because the 4f
orbitals penetrate the most through the inert xenon core of electrons
to the nucleus, followed by 5d and 6s, and this increases with higher
ionic charge. Neodymium can still lose a fourth electron because it
comes early in the lanthanides, where the nuclear charge is still low
enough and the 4f subshell energy high enough to allow the removal of
further valence electrons.
Chemical properties
======================================================================
Neodymium has a melting point of 1024 C and a boiling point of 3074 C.
Like other lanthanides, it usually has the oxidation state +3, but can
also form in the +2 and +4 oxidation states, and even, in very rare
conditions, +0. Neodymium metal quickly oxidizes at ambient
conditions, forming an oxide layer like iron rust that can spall off
and expose the metal to further oxidation; a centimeter-sized sample
of neodymium corrodes completely in about a year. Nd3+ is generally
soluble in water. Like its neighbor praseodymium, it readily burns at
about 150 °C to form neodymium(III) oxide; the oxide then peels off,
exposing the bulk metal to the further oxidation:
:
Neodymium is an electropositive element, and it reacts slowly with
cold water, or quickly with hot water, to form neodymium(III)
hydroxide:
:
Neodymium metal reacts vigorously with all the stable halogens:
: [a violet substance]
: [a mauve substance]
: [a violet substance]
: [a green substance]
Neodymium dissolves readily in dilute sulfuric acid to form solutions
that contain the lilac Nd(III) ion. These exist as a [Nd(OH2)9]3+
complexes:
:
Compounds
===========
: Neodymium(III) sulfateNeodymium acetate powder Neodymium(III)
hydroxide powder
Some of the most important neodymium compounds include:
* halides: NdF3; NdCl2; NdCl3; NdBr3; NdI2; NdI3
* oxides: neodymium(III) oxide
* hydroxide: neodymium(III) hydroxide
* carbonate: Nd2(CO3)3
* sulfate: neodymium(III) sulfate
* acetate: Nd(CH3COO)3
* neodymium magnets (Nd2Fe14B)
Some neodymium compounds vary in color under different types of
lighting.
File:Neodymium tl1.jpg|Neodymium compounds in fluorescent tube
light--from left to right, the sulfate, nitrate, and chloride
File:Neodymium fluorescent1.jpg|Neodymium compounds in compact
fluorescent lamp light
File:Neodymium daylight1.jpg|Neodymium compounds in normal daylight
Organoneodymium compounds
===========================
Organoneodymium compounds are compounds that have a neodymium-carbon
bond. These compounds are similar to those of the other lanthanides,
characterized by an inability to undergo π backbonding. They are thus
mostly restricted to the mostly ionic cyclopentadienides
(isostructural with those of lanthanum) and the σ-bonded simple alkyls
and aryls, some of which may be polymeric.
Isotopes
======================================================================
Naturally occurring neodymium (60Nd) is composed of five stable
isotopes--142Nd, 143Nd, 145Nd, 146Nd and 148Nd, with 142Nd being the
most abundant (27.2% of the natural abundance)--and two radioisotopes
with extremely long half-lives, 144Nd (alpha decay with a half-life
('t'1/2) of years) and 150Nd (double beta decay, 't'1/2 ≈ years). In
all, 35 radioisotopes of neodymium have been detected , with the most
stable radioisotopes being the naturally occurring ones: 144Nd and
150Nd. All of the remaining radioactive isotopes have half-lives that
are shorter than twelve days, and the majority of these have
half-lives that are shorter than 70 seconds; the most stable
artificial isotope is 147Nd with a half-life of 10.98 days.
Neodymium also has 15 known metastable isotopes, with the most stable
one being 139mNd ('t'1/2 = 5.5 hours), 135mNd ('t'1/2 = 5.5 minutes)
and 133m1Nd ('t'1/2 ~70 seconds). The primary decay modes before the
most abundant stable isotope, 142Nd, are electron capture and positron
decay, and the primary mode after is beta minus decay. The primary
decay products before 142Nd are praseodymium isotopes, and the primary
products after 142Nd are promethium isotopes. Four of the five stable
isotopes are only observationally stable, which means that they are
expected to undergo radioactive decay, though with half-lives long
enough to be considered stable for practical purposes. Additionally,
some observationally stable isotopes of samarium are predicted to
decay to isotopes of neodymium.
Neodymium isotopes are used in various scientific applications. 142Nd
has been used for the production of short-lived isotopes of thulium
and ytterbium. 146Nd has been suggested for the production of 147Pm,
which is a source of radioactive power. Several neodymium isotopes
have been used for the production of other promethium isotopes. The
decay from 147Sm ('t'1/2 = ) to the stable 143Nd allows for
samarium-neodymium dating. 150Nd has also been used to study double
beta decay.
History
======================================================================
In 1751, the Swedish mineralogist Axel Fredrik Cronstedt discovered a
heavy mineral from the mine at Bastnäs, later named cerite. Thirty
years later, fifteen-year-old Wilhelm Hisinger, a member of the family
owning the mine, sent a sample to Carl Scheele, who did not find any
new elements within. In 1803, after Hisinger had become an ironmaster,
he returned to the mineral with Jöns Jacob Berzelius and isolated a
new oxide, which they named 'ceria' after the dwarf planet Ceres,
which had been discovered two years earlier. Ceria was simultaneously
and independently isolated in Germany by Martin Heinrich Klaproth.
Between 1839 and 1843, ceria was shown to be a mixture of oxides by
the Swedish surgeon and chemist Carl Gustaf Mosander, who lived in the
same house as Berzelius; he separated out two other oxides, which he
named 'lanthana' and 'didymia'. He partially decomposed a sample of
cerium nitrate by roasting it in air and then treating the resulting
oxide with dilute nitric acid. The metals that formed these oxides
were thus named 'lanthanum' and 'didymium'.See:
* From p. 356: '"L'oxide de cérium, extrait de la cérite par la
procédé ordinaire, contient à peu près les deux cinquièmes de son
poids de l'oxide du nouveau métal qui ne change que peu les propriétés
du cérium, et qui s'y tient pour ainsi dire caché. Cette raison a
engagé M. Mosander à donner au nouveau métal le nom de 'Lantane'."'
(The oxide of cerium, extracted from cerite by the usual procedure,
contains almost two fifths of its weight in the oxide of the new
metal, which differs only slightly from the properties of cerium, and
which is held in it so to speak "hidden". This reason motivated Mr.
Mosander to give to the new metal the name 'Lantane').
* Didymium was later proven to not be a single element when it was
split into two elements, praseodymium and neodymium, by Carl Auer von
Welsbach in Vienna in 1885. Von Welsbach confirmed the separation by
spectroscopic analysis, but the products were of relatively low
purity. Pure neodymium was first isolated in 1925. The name neodymium
is derived from the Greek words 'neos' (νέος), new, and 'didymos'
(διδύμος), twin.
Double nitrate crystallization was the means of commercial neodymium
purification until the 1950s. Lindsay Chemical Division was the first
to commercialize large-scale ion-exchange purification of neodymium.
Starting in the 1950s, high purity (>99%) neodymium was primarily
obtained through an ion exchange process from monazite, a mineral rich
in rare-earth elements. The metal is obtained through electrolysis of
its halide salts. Currently, most neodymium is extracted from
bastnäsite and purified by solvent extraction. Ion-exchange
purification is used for the highest purities (typically >99.99%).
Since then, the glass technology has improved due to the improved
purity of commercially available neodymium oxide and the advancement
of glass technology in general. Early methods of separating the
lanthanides depended on fractional crystallization, which did not
allow for the isolation of high-purity neodymium until the
aforementioned ion exchange methods were developed after World War II.
Occurrence
============
Neodymium is rarely found in nature as a free element, instead
occurring in ores such as monazite and bastnäsite (which are mineral
groups rather than single minerals) that contain small amounts of all
rare-earth elements. Neodymium is rarely dominant in these minerals,
with exceptions such as monazite-(Nd) and kozoite-(Nd).
The main mining areas are in China, United States, Brazil, India, Sri
Lanka, and Australia.
The Nd3+ ion is similar in size to ions of the early lanthanides of
the cerium group (those from lanthanum to samarium and europium). As a
result, it tends to occur along with them in phosphate, silicate and
carbonate minerals, such as monazite (MIIIPO4) and bastnäsite
(MIIICO3F), where M refers to all the rare-earth metals except
scandium and the radioactive promethium (mostly Ce, La, and Y, with
somewhat less Pr and Nd). Bastnäsite is usually lacking in thorium and
the heavy lanthanides, and the purification of the light lanthanides
from it is less involved than from monazite. The ore, after being
crushed and ground, is first treated with hot concentrated sulfuric
acid, which liberates carbon dioxide, hydrogen fluoride, and silicon
tetrafluoride. The product is then dried and leached with water,
leaving the early lanthanide ions, including lanthanum, in solution.
Solar System abundances Atomic number Element Relative amount
42 Molybdenum |2.771
47 Silver |0.590
50 Tin |4.699
58 Cerium |1.205
59 Praseodymium |0.205 '60' 'Neodymium' |'1'
74 Tungsten |0.054
90 Thorium 0.054
92 Uranium 0.022
In space
==========
Neodymium's per-particle abundance in the Solar System is 0.083 ppb
(parts per billion). This figure is about two thirds of that of
platinum, but two and a half times more than mercury, and nearly five
times more than gold. The lanthanides are not usually found in space,
and are much more abundant in the Earth's crust.
In the Earth's crust
======================
Neodymium is classified as a lithophile under the Goldschmidt
classification, meaning that it is generally found combined with
oxygen. Although it belongs to the rare-earth metals, neodymium is not
rare at all. Its abundance in the Earth's crust is about 41 mg/kg. It
is similar in abundance to lanthanum.
Production
============
The world's production of neodymium was about 7,000 tons in 2004. The
bulk of current production is from China. Historically, the Chinese
government imposed strategic material controls on the element, causing
large fluctuations in prices. The uncertainty of pricing and
availability have caused companies (particularly Japanese ones) to
create permanent magnets and associated electric motors with fewer
rare-earth metals; however, so far they have been unable to eliminate
the need for neodymium. According to the US Geological Survey,
Greenland holds the largest reserves of undeveloped rare-earth
deposits, particularly neodymium. Mining interests clash with native
populations at those sites, due to the release of radioactive
substances, mainly thorium, during the mining process.
Neodymium is typically 10-18% of the rare-earth content of commercial
deposits of the light rare-earth-element minerals bastnäsite and
monazite. With neodymium compounds being the most strongly colored for
the trivalent lanthanides, it can occasionally dominate the coloration
of rare-earth minerals when competing chromophores are absent. It
usually gives a pink coloration. Outstanding examples of this include
monazite crystals from the tin deposits in Llallagua, Bolivia;
ancylite from Mont Saint-Hilaire, Quebec, Canada; or lanthanite from
Lower Saucon Township, Pennsylvania. As with neodymium glasses, such
minerals change their colors under the differing lighting conditions.
The absorption bands of neodymium interact with the visible emission
spectrum of mercury vapor, with the unfiltered shortwave UV light
causing neodymium-containing minerals to reflect a distinctive green
color. This can be observed with monazite-containing sands or
bastnäsite-containing ore.
The demand for mineral resources, such as rare-earth elements
(including neodymium) and other critical materials, has been rapidly
increasing owing to the growing human population and industrial
development. Recently, the requirement for a low-carbon society has
led to a significant demand for energy-saving technologies such as
batteries, high-efficiency motors, renewable energy sources, and fuel
cells. Among these technologies, permanent magnets are often used to
fabricate high-efficiency motors, with neodymium-iron-boron magnets
(Nd2Fe14B sintered and bonded magnets; hereinafter referred to as
NdFeB magnets) being the main type of permanent magnet in the market
since their invention. NdFeB magnets are used in hybrid electric
vehicles, plug-in hybrid electric vehicles, electric vehicles, fuel
cell vehicles, wind turbines, home appliances, computers, and many
small consumer electronic devices. Furthermore, they are indispensable
for energy savings. Toward achieving the objectives of the Paris
Agreement, the demand for NdFeB magnets is expected to increase
significantly in the future.
Magnets
=========
Neodymium magnets (an alloy, Nd2Fe14B) are the strongest permanent
magnets known. A neodymium magnet of a few tens of grams can lift a
thousand times its own weight, and can snap together with enough force
to break bones. These magnets are cheaper, lighter, and stronger than
samarium-cobalt magnets. However, they are not superior in every
aspect, as neodymium-based magnets lose their magnetism at lower
temperatures and tend to corrode, while samarium-cobalt magnets do
not.
Neodymium magnets appear in products such as microphones, professional
loudspeakers, headphones, guitar and bass guitar pick-ups, and
computer hard disks where low mass, small volume, or strong magnetic
fields are required. Neodymium is used in the electric motors of
hybrid and electric automobiles and in the electricity generators of
some designs of commercial wind turbines (only wind turbines with
"permanent magnet" generators use neodymium). For example, drive
electric motors of each Toyota Prius require 1 kg of neodymium per
vehicle. Neodymium magnets are also widely used in pure electric
vehicle motors, driving rapid growth in demand. Neodymium magnets are
used in medical devices such as MRI and treatments for chronic pain
and wound healing.
Glass
=======
Neodymium glass (Nd:glass) is produced by the inclusion of neodymium
oxide (Nd2O3) in the glass melt. In daylight or incandescent light
neodymium glass appears lavender, but it appears pale blue under
fluorescent lighting. Neodymium may be used to color glass in shades
ranging from pure violet through wine-red and warm gray.
The first commercial use of purified neodymium was in glass
coloration, starting with experiments by Leo Moser in November 1927.
The resulting "Alexandrite" glass remains a signature color of the
Moser glassworks to this day. Neodymium glass was widely emulated in
the early 1930s by American glasshouses, most notably Heisey, Fostoria
("wisteria"), Cambridge ("heatherbloom"), and Steuben ("wisteria"),
and elsewhere (e.g. Lalique, in France, or Murano). Tiffin's
"twilight" remained in production from about 1950 to 1980. Current
sources include glassmakers in the Czech Republic, the United States,
and China.
The sharp absorption bands of neodymium cause the glass color to
change under different lighting conditions, being reddish-purple under
daylight or yellow incandescent light, blue under white fluorescent
lighting, and greenish under trichromatic lighting. In combination
with gold or selenium, red colors are produced. Since neodymium
coloration depends upon "forbidden" f-f transitions deep within the
atom, there is relatively little influence on the color from the
chemical environment, so the color is impervious to the thermal
history of the glass. However, for the best color, iron-containing
impurities need to be minimized in the silica used to make the glass.
The same forbidden nature of the f-f transitions makes rare-earth
colorants less intense than those provided by most d-transition
elements, so more has to be used in a glass to achieve the desired
color intensity. The original Moser recipe used about 5% of neodymium
oxide in the glass melt, a sufficient quantity such that Moser
referred to these as being "rare-earth doped" glasses. Being a strong
base, that level of neodymium would have affected the melting
properties of the glass, and the lime content of the glass might have
needed adjustments.
Light transmitted through neodymium glasses shows unusually sharp
absorption bands; the glass is used in astronomical work to produce
sharp bands by which spectral lines may be calibrated. Another
application is the creation of selective astronomical filters to
reduce the effect of light pollution from sodium and fluorescent
lighting while passing other colours, especially dark red
hydrogen-alpha emission from nebulae. Neodymium is also used to remove
the green color caused by iron contaminants from glass.
Neodymium is a component of "didymium" (referring to mixture of salts
of neodymium and praseodymium) used for coloring glass to make
welder's and glass-blower's goggles; the sharp absorption bands
obliterate the strong sodium emission at 589 nm. The similar
absorption of the yellow mercury emission line at 578 nm is the
principal cause of the blue color observed for neodymium glass under
traditional white-fluorescent lighting. Neodymium and didymium glass
are used in color-enhancing filters in indoor photography,
particularly in filtering out the yellow hues from incandescent
lighting. Similarly, neodymium glass is becoming widely used more
directly in incandescent light bulbs. These lamps contain neodymium in
the glass to filter out yellow light, resulting in a whiter light
which is more like sunlight. During World War I, didymium mirrors were
reportedly used to transmit Morse code across battlefields. Similar to
its use in glasses, neodymium salts are used as a colorant for
enamels.
Lasers
========
Certain transparent materials with a small concentration of neodymium
ions can be used in lasers as gain media for infrared wavelengths
(1054-1064 nm), e.g. Nd:YAG (yttrium aluminium garnet), Nd:YAP
(yttrium aluminium perovskite), Nd:YLF (yttrium lithium fluoride),
Nd:YVO4 (yttrium orthovanadate), and Nd:glass. Neodymium-doped
crystals (typically Nd:YVO4) generate high-powered infrared laser
beams which are converted to green laser light in commercial DPSS
hand-held lasers and laser pointers.
Trivalent neodymium ion Nd3+ was the first lanthanide from rare-earth
elements used for the generation of laser radiation. The Nd:CaWO4
laser was developed in 1961. Historically, it was the third laser
which was put into operation (the first was ruby, the second the
U3+:CaF laser). Over the years the neodymium laser became one of the
most used lasers for application purposes. The success of the Nd3+ ion
lies in the structure of its energy levels and in the spectroscopic
properties suitable for the generation of laser radiation. In 1964
Geusic et al. demonstrated the operation of neodymium ion in YAG
matrix Y3Al5O12. It is a four-level laser with lower threshold and
with excellent mechanical and temperature properties. For optical
pumping of this material it is possible to use non-coherent flashlamp
radiation or a coherent diode beam.
The current laser at the UK Atomic Weapons Establishment (AWE), the
HELEN (High Energy Laser Embodying Neodymium) 1-terawatt
neodymium-glass laser, can access the midpoints of pressure and
temperature regions and is used to acquire data for modeling on how
density, temperature, and pressure interact inside warheads. HELEN can
create plasmas of around 106 K, from which opacity and transmission of
radiation are measured.
Neodymium glass solid-state lasers are used in extremely high power
(terawatt scale), high energy (megajoules) multiple beam systems for
inertial confinement fusion. Nd:glass lasers are usually frequency
tripled to the third harmonic at 351 nm in laser fusion devices.
Other
=======
Other applications of neodymium include:
* Neodymium has an unusually large specific heat capacity at
liquid-helium temperatures, so is useful in cryocoolers.
* Neodymium acetate can be used as a standard contrasting agent in
electron microscopy (a substitute for the radioactive and toxic uranyl
acetate).
* Probably because of similarities to Ca2+, Nd3+ has been reported to
promote plant growth. Rare-earth element compounds are frequently used
in China as fertilizer.
* Samarium-neodymium dating is useful for determining the age
relationships of rocks and meteorites.
*Neodymium isotopes recorded in marine sediments are used to
reconstruct changes in past ocean circulation.
Biological role and precautions
======================================================================
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The early lanthanides, including neodymium, as well as lanthanum,
cerium and praseodymium, have been found to be essential to some
methanotrophic bacteria living in volcanic mudpots, such as
'Methylacidiphilum fumariolicum'. Neodymium is not otherwise known to
have a biological role in any other organisms.
Neodymium metal dust is combustible and therefore an explosion hazard.
Neodymium compounds, as with all rare-earth metals, are of low to
moderate toxicity; however, its toxicity has not been thoroughly
investigated. Ingested neodymium salts are regarded as more toxic if
they are soluble than if they are insoluble. Neodymium dust and salts
are very irritating to the eyes and mucous membranes, and moderately
irritating to skin. Breathing the dust can cause lung embolisms, and
accumulated exposure damages the liver. Neodymium also acts as an
anticoagulant, especially when given intravenously.
Neodymium magnets have been tested for medical uses such as magnetic
braces and bone repair, but biocompatibility issues have prevented
widespread applications. Commercially available magnets made from
neodymium are exceptionally strong and can attract each other from
large distances. If not handled carefully, they come together very
quickly and forcefully, causing injuries. There is at least one
documented case of a person losing a fingertip when two magnets he was
using snapped together from 50 cm away.
Another risk of these powerful magnets is that if more than one magnet
is ingested, they can pinch soft tissues in the gastrointestinal
tract. This has led to an estimated 1,700 emergency room visits and
necessitated the recall of the Buckyballs line of toys, which were
construction sets of small neodymium magnets.
See also
======================================================================
*Neodymium compounds
*:Category:Neodymium compounds
*Lanthanides
*Period 6 elements
*Rare earth metals
Bibliography
======================================================================
*
*
* R. J. Callow, 'The Industrial Chemistry of the Lanthanons, Yttrium,
Thorium, and Uranium', Pergamon Press, 1967.
*
External links
======================================================================
* [
http://www.webelements.com/webelements/elements/text/Nd/index.html
WebElements.com--Neodymium]
* [
http://education.jlab.org/itselemental/ele060.html It's
Elemental--The element Neodymium]
* [
http://www.periodicvideos.com/videos/060.htm Neodymium] at 'The
Periodic Table of Videos' (University of Nottingham)
*[
http://environmentalchemistry.com/yogi/periodic/Nd.html
EnvironmentalChemistry.com – Neodymium]
*[
http://www.seltenerden.de?arg=zoom&element=Nd&art=121&seite=0&total=2#magnify&linkid=ewiki-Nd
Pictures and more details about Neodymium metal]
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=========
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Original Article:
http://en.wikipedia.org/wiki/Neodymium
