Neodymium(III) chloride
Encyclopedia
Neodymium chloride or neodymium trichloride is a chemical compound of neodymium
and chlorine
with the formula NdCl3. This anhydrous
compound is a mauve-colored solid that rapidly absorbs water on exposure to air to form a purple-colored hexahydrate
, NdCl3·6H2O. Neodymium(III) chloride is produced from minerals monazite
and bastnäsite
using a complex multistage extraction process. The chloride has several important applications as an intermediate chemical for production of neodymium metal and neodymium-based laser
s and optical fibers. Other applications include a catalyst in organic synthesis and in decomposition of waste water contamination, corrosion
protection of aluminium
and its alloys
, and fluorescent labeling of organic molecules (DNA
).
NdCl3 is a mauve colored hygroscopic solid whose color changes to purple upon absorption of atmospheric water. The resulting hydrate, like many other neodymium salt
s, has the interesting property that it instantly and reversibly turns light yellow under fluorescent light (see picture). The color change is likely due to the charge transfer
converting the Nd3+ ions into the Nd2+ state; the orange absorption band of Nd3+ decreases and the green Nd2+ absorption increases producing the yellowish color.
structure. This hexagonal
structure is common for many halogenated lanthanide
s and actinide
s such as LaCl3
, LaBr3
, SmCl3
, PrCl3
, EuCl3
, CeCl3
, CeBr3
, GdCl3
, AmCl3
and TbCl3
but not for YbCl3
and LuCl3
.
NdCl(H2O)72+. The coordination of neodymium is octahedral (8-fold) in all cases, but the ligand structure is different.
of 0.5 K. Its electrical conductivity is about 240 S/m and heat capacity
is ~100 J/(mol·K). NdCl3 is readily soluble in water and ethanol, but not in chloroform
or ether
. Reduction of NdCl3 with Nd metal at temperatures above 650 °C yields NdCl2:
Heating of NdCl3 with water vapors or silica produces neodymium oxochloride:
Reacting NdCl3 with hydrogen sulfide
at about 1100 °C produces neodymium sulfide:
Reactions with ammonia
and phosphine
at high temperatures yield neodymium nitride and phosphide, respectively:
Whereas the addition of hydrofluoric acid
produces neodymium fluoride:
NdCl3 is produced from minerals monazite and bastnäsite. The synthesis is complex because of the low abundance of neodymium in the Earth's crust (38 mg/kg) and because of difficulty of separating neodymium from other lanthanides. The process is however easier for neodymium than for other lanthanides because of its relatively high content in the mineral - up to 16% by weight, which is the third highest after cerium
and lanthanum
. Many synthesis varieties exist and one can be simplified as follows:
The crushed mineral is treated with hot concentrated sulfuric acid
to produce water-soluble sulfates of rare earths. The acidic filtrates are partially neutralized with sodium hydroxide to pH 3-4. Thorium
precipitates out of solution as hydroxide and is removed. After that the solution is treated with ammonium oxalate
to convert rare earths in to their insoluble oxalate
s. The oxalates are converted to oxides by annealing. The oxides are dissolved in nitric acid
that excludes the main components, cerium
, whose oxide is insoluble in HNO3. Neodymium oxide is separated from other rare-earth oxides by ion exchange
. In this process, rare-earth ions are adsorbed onto suitable resin by ion exchange with hydrogen, ammonium or cupric ions present in the resin. The rare earth ions are then selectively washed out by suitable complexing agent, such as ammonium citrate or nitrilotracetate.
This process normally yields Nd2O3
; the oxide is difficult to directly convert to elemental neodymium, which is often the goal of the whole technological procedure. Therefore the oxide is treated with hydrochloric acid
or ammonium chloride
to produce the less stable NdCl3:
The thus produced NdCl3 quickly absorbs water and converts to NdCl3·6H2O hydrate, which is stable for storage, and can be converted back into NdCl3 when necessary. Simple rapid heating of the hydrate is not practical for that purpose because it causes hydrolysis
with consequent production of Nd2O3. Therefore anhydrous
NdCl3 is prepared by dehydration of the hydrate either by slowly heating to 400 °C with 4-6 equivalents of ammonium chloride under high vacuum, or by heating with an excess of thionyl chloride
for several hours. The NdCl3 can alternatively be prepared by reacting neodymium metal with hydrogen chloride
or chlorine
, though this method is not economical due to the relatively high price of the metal and is used for research purposes only. After preparation, it is usually purified by high temperature sublimation under high vacuum.
Neodymium(III) chloride is the most common starting compound for production of neodymium metal. NdCl3 is heated with ammonium chloride
or ammonium fluoride
and hydrofluoric acid
or with alkali or alkaline earth metals in vacuum or argon atmosphere at 300-400 °C.
An alternative route is electrolysis
of molten mixture of anhydrous LaCl3 and NaCl or KCl at temperatures about 700 °C. The mixture does melt at those temperatures, even though they are lower than the melting points of NdCl3 and KCl (~770 °C).
, it serves as a source of Nd3+ ions for various light emitting materials. The latter include Nd-YAG lasers and Nd-doped optical fiber amplifiers
, which amplify light emitted by other lasers. The Nd-YAG laser emits infrared
light at 1.064 micrometres and is the most popular solid-state laser
(i.e. laser based on a solid medium). The reason for using NdCl3 rather than metallic neodymium or its oxide, in fabrication of fibers is easy decomposition of NdCl3 during the chemical vapor deposition
; the latter process is widely used for the fiber grows.
Neodymium(III) chloride is a dopant not only of traditional silica-based optical fibers, but of plastic fibers (dopedphotolime-gelatin, polyimide
, polyethylene
, etc.) as well. It is also used in as an additive into infrared organic light-emitting diode
s. Besides, neodymium doped organic films can not only act as LEDs, but also as color filters improving the LED emission spectrum.
Solubility of neodymium(III) chloride (and other rare-earth salts) is various solvents results in a new type of rare-earth laser, which uses not a solid but liquid as an active medium. The liquid containing Nd3+ ions is prepared in the following reactions:
where Nd3+ is in fact the solvated ion with several selenium oxychloride molecules coordinated in the first coordination sphere, that is [Nd(SeOCl2)m]3+. The laser liquids prepared by this technique emits at the same wavelength of 1.064 micrometres and possess properties, such as high gain and sharpness of the emission, that are more characteristic of crystalline than Nd-glass lasers. The quantum efficiency of those liquid lasers was about 0.75 relative to the traditional Nd:YAG laser.
and 2-propanol, it accelerates polymerization
of various diene
s. The products include such general purpose synthetic rubbers as polybutylene
, polybutadiene
, and polyisoprene.
Neodymium(III) chloride is also used to modify titanium dioxide
. The latter is one of the most popular inorganic photocatalyst for decomposition of phenol
, various dye
s and other waste water contaminants. The catalytic action of titanium oxide has to be activated by UV light, i.e. artificial illumination. However, modifying titanium oxide with neodymium(III) chloride allows catalysis under visible illumination, such as sun light. The modified catalyst is prepared by chemical coprecipitation–peptization method by ammonium hydroxide
from mixture of TiCl4 and NdCl3 in aqueous solution). This process is used commercially on large scale on 1000 liter reactor for using in photocatalytic self-cleaning paints.
using the same solution. In comparison with traditional chromium
based corrosion inhibitors, NdCl3 and other rare-earth salts are environment friendly and much less toxic to humans and animals.
The protective action of NdCl3 on aluminium alloys is based on formation of insoluble neodymium hydroxide. Being a chloride, NdCl3 itself is a corrosive agent, which is sometimes used for corrosion testing of ceramics.
and therefore are widely used as fluorescent labels. In particular, NdCl3 has been incorporated into organic molecules, such as DNA, which could be then easily traced using a fluorescence microscope
during various physical and chemical reactions.
on rabbits). Substances with LD50 above 2 g/kg are considered non-toxic.
Neodymium
Neodymium is a chemical element with the symbol Nd and atomic number 60. It is a soft silvery metal that tarnishes in air. Neodymium was discovered in 1885 by the Austrian chemist Carl Auer von Welsbach. It is present in significant quantities in the ore minerals monazite and bastnäsite...
and chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
with the formula NdCl3. This anhydrous
Anhydrous
As a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another...
compound is a mauve-colored solid that rapidly absorbs water on exposure to air to form a purple-colored hexahydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
, NdCl3·6H2O. Neodymium(III) chloride is produced from minerals monazite
Monazite
Monazite is a reddish-brown phosphate mineral containing rare earth metals. It occurs usually in small isolated crystals. There are actually at least four different kinds of monazite, depending on relative elemental composition of the mineral:...
and bastnäsite
Bastnasite
The mineral bastnäsite is one of a family of three carbonate-fluoride minerals, which includes bastnäsite- with a formula of CO3F, bastnäsite- with a formula of CO3F, and bastnäsite- with a formula of CO3F. Most bastnäsite is bastnäsite-, and cerium is by far the most common of the rare earths in...
using a complex multistage extraction process. The chloride has several important applications as an intermediate chemical for production of neodymium metal and neodymium-based laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
s and optical fibers. Other applications include a catalyst in organic synthesis and in decomposition of waste water contamination, corrosion
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
protection of aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
and its alloys
Aluminium alloy
Aluminium alloys are alloys in which aluminium is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories...
, and fluorescent labeling of organic molecules (DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
).
Appearance
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
s, has the interesting property that it instantly and reversibly turns light yellow under fluorescent light (see picture). The color change is likely due to the charge transfer
Charge transfer complex
A charge-transfer complex or electron-donor-acceptor complex is an association of two or more molecules, or of different parts of one very large molecule, in which a fraction of electronic charge is transferred between the molecular entities. The resulting electrostatic attraction provides a...
converting the Nd3+ ions into the Nd2+ state; the orange absorption band of Nd3+ decreases and the green Nd2+ absorption increases producing the yellowish color.
Solid
The anhydrous NdCl3 features Nd in a nine-coordinate tricapped trigonal prismatic geometry and crystallizes with the UCl3Uranium(III) chloride
Uranium chloride , UCl3, is a chemical compound that contains the earth metal uranium and chlorine. UCl3 is used mostly to reprocess spent nuclear fuel. Uranium chloride is synthesized various ways from uranium chloride; however, UCl3 is less stable than UCl4.-Preparation:There are two ways to...
structure. This hexagonal
Hexagonal crystal system
In crystallography, the hexagonal crystal system is one of the 7 crystal systems, the hexagonal lattice system is one of the 7 lattice systems, and the hexagonal crystal family is one of the 6 crystal families...
structure is common for many halogenated lanthanide
Lanthanide
The lanthanide or lanthanoid series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium...
s and actinide
Actinide
The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.The actinide series derives its name from the group 3 element actinium...
s such as LaCl3
Lanthanum(III) chloride
Lanthanum chloride is the inorganic compound with the formula LaCl3. It is a common salt but is mainly used in research. It is a white solid that is highly soluble in water and alcohols.-Structure:The La3+ centre is 9-coordinate in the trichloride...
, LaBr3
Lanthanum(III) bromide
Lanthanum bromide is an inorganic halide salt of lanthanum. When pure, it is a colorless white powder. The single crystals of LaBr3 are hexagonal crystals with melting point of 783°C. It is highly hygroscopic and water soluble. There are several hydrates, La3Br·X H2O, of the salt also known...
, SmCl3
Samarium(III) chloride
Samarium chloride , also known as samarium trichloride, is a compound of samarium and chlorine. It is a pale yellow solid which rapidly absorbs water on exposure to moist air to form a hexahydrate, SmCl3.6H2O. Simple rapid heating of the hydrate alone may cause small amounts of hydrolysis...
, PrCl3
Praseodymium(III) chloride
Praseodymium chloride is the inorganic compound with the formula PrCl3. It is a blue-green solid that rapidly absorbs water on exposure to moist air to form a light green heptahydrate.-Preparation:...
, EuCl3
Europium(III) chloride
Europium chloride is a compound of europium and chlorine with the formula EuCl3.-Properties:Europium trichloride is a yellow solid which begins to decompose at or below its melting point to give at least some EuCl2. Being hygroscopic it rapidly absorbs water on exposure to moist air to form a...
, CeCl3
Cerium(III) chloride
Cerium chloride , also known as cerous chloride or cerium trichloride, is a compound of cerium and chlorine. It is a white hygroscopic solid; It rapidly absorbs water on exposure to moist air to form a hydrate which appears to be of variable composition, though the heptahydrate CeCl3·7 H2O is known...
, CeBr3
Cerium(III) bromide
Cerium bromide is an inorganic compound with the formula CeBr3. This white hygroscopic solid is of interest as a component of scintillation counters.-Preparation and basic properties:...
, GdCl3
Gadolinium(III) chloride
Gadolinium chloride, also known as gadolinium trichloride, is GdCl3. It is a colorless, hygroscopic, water-soluble solid. The hexahydrate GdCl3∙6H2O is commonly encountered and is sometimes also called gadolinium trichloride. Gd3+ species are of special interest because the ion has the maximum...
, AmCl3
Americium(III) chloride
Americium chloride or americium trichloride is the chemical compound composed of americium and chlorine with the formula AmCl3. It forms pink hexagonal crystals....
and TbCl3
Terbium(III) chloride
Terbium chloride is a chemical compound. In the solid state TbCl3 has the YCl3 layer structure. Terbium chloride frequently forms a hexahydrate.-Hazards:Terbium chloride causes hyperemia of the iris....
but not for YbCl3
Ytterbium(III) chloride
Ytterbium chloride is an inorganic chemical compound.-History:Ytterbium, a Lanthanide series element, was discovered in 1878 by Marignac who named the element after a town in Sweden. The first synthesis of YbCl3 in the literature was that of Hoogschagen, in 1946...
and LuCl3
Lutetium(III) chloride
Lutetium chloride or lutetium trichloride is the chemical compound composed of lutetium and chlorine with the formula LuCl3. It forms hygroscopic white monoclinic crystals...
.
Solution
The structure of neodymium(III) chloride in solution crucially depends on the solvent: In water, the major species are Nd(H2O)83+, and this situation is common for most rare earth chlorides and bromides. In methanol, the species are NdCl2(CH3OH)6+ and in hydrochloric acidHydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
NdCl(H2O)72+. The coordination of neodymium is octahedral (8-fold) in all cases, but the ligand structure is different.
Properties
NdCl3 is a soft paramagnetic solid, which turns ferromagnetic at very low temperatureNéel temperature
The Néel temperature or magnetic ordering temperature , TN, is the temperature above which an antiferromagnetic material becomes paramagnetic—that is, the thermal energy becomes large enough to destroy the macroscopic magnetic ordering within the material....
of 0.5 K. Its electrical conductivity is about 240 S/m and heat capacity
Heat capacity
Heat capacity , or thermal capacity, is the measurable physical quantity that characterizes the amount of heat required to change a substance's temperature by a given amount...
is ~100 J/(mol·K). NdCl3 is readily soluble in water and ethanol, but not in chloroform
Chloroform
Chloroform is an organic compound with formula CHCl3. It is one of the four chloromethanes. The colorless, sweet-smelling, dense liquid is a trihalomethane, and is considered somewhat hazardous...
or ether
Diethyl ether
Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...
. Reduction of NdCl3 with Nd metal at temperatures above 650 °C yields NdCl2:
- 2 NdCl3 + Nd → 3 NdCl2
Heating of NdCl3 with water vapors or silica produces neodymium oxochloride:
- NdCl3 + H2O → NdOCl + 2 HCl
- 2 NdCl3 + SiO2O → 2 NdOCl + SiCl4
Reacting NdCl3 with hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
at about 1100 °C produces neodymium sulfide:
- 2 NdCl3 + 3 H2S → 2 Nd2S3 + 6 HCl
Reactions with ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
and phosphine
Phosphine
Phosphine is the compound with the chemical formula PH3. It is a colorless, flammable, toxic gas. Pure phosphine is odourless, but technical grade samples have a highly unpleasant odor like garlic or rotting fish, due to the presence of substituted phosphine and diphosphine...
at high temperatures yield neodymium nitride and phosphide, respectively:
- NdCl3 + NH3 → NdN + 3 HCl
- NdCl3 + PH3 → NdP + 3 HCl
Whereas the addition of hydrofluoric acid
Hydrofluoric acid
Hydrofluoric acid is a solution of hydrogen fluoride in water. It is a valued source of fluorine and is the precursor to numerous pharmaceuticals such as fluoxetine and diverse materials such as PTFE ....
produces neodymium fluoride:
- NdCl3 + 3 HF → NdF3 + 3 HCl
Preparation
Cerium
Cerium is a chemical element with the symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet . Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth's crust by weight...
and lanthanum
Lanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57.Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is the first element of the lanthanide series. It is found in some rare-earth minerals, usually in combination with cerium and...
. Many synthesis varieties exist and one can be simplified as follows:
The crushed mineral is treated with hot concentrated sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
to produce water-soluble sulfates of rare earths. The acidic filtrates are partially neutralized with sodium hydroxide to pH 3-4. Thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
precipitates out of solution as hydroxide and is removed. After that the solution is treated with ammonium oxalate
Ammonium oxalate
Ammonium oxalate, C2H8N2O4, is an oxalate salt with ammonia. It is a constituent of some types of kidney stone. Found also in guano....
to convert rare earths in to their insoluble oxalate
Oxalate
Oxalate , is the dianion with formula C2O42− also written 22−. Either name is often used for derivatives, such as disodium oxalate, 2C2O42−, or an ester of oxalic acid Oxalate (IUPAC: ethanedioate), is the dianion with formula C2O42− also written (COO)22−. Either...
s. The oxalates are converted to oxides by annealing. The oxides are dissolved in nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
that excludes the main components, cerium
Cerium
Cerium is a chemical element with the symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet . Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth's crust by weight...
, whose oxide is insoluble in HNO3. Neodymium oxide is separated from other rare-earth oxides by ion exchange
Ion exchange
Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex. In most cases the term is used to denote the processes of purification, separation, and decontamination of aqueous and other ion-containing solutions with solid polymeric or mineralic 'ion...
. In this process, rare-earth ions are adsorbed onto suitable resin by ion exchange with hydrogen, ammonium or cupric ions present in the resin. The rare earth ions are then selectively washed out by suitable complexing agent, such as ammonium citrate or nitrilotracetate.
This process normally yields Nd2O3
Neodymium(III) oxide
Neodymium oxide or neodymium sesquioxide is the chemical compound composed of neodymium and oxygen with the formula Nd2O3. It forms very light grayish blue hexagonal crystals...
; the oxide is difficult to directly convert to elemental neodymium, which is often the goal of the whole technological procedure. Therefore the oxide is treated with hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
or ammonium chloride
Ammonium chloride
Ammonium chloride NH4Cl is an inorganic compound with the formula NH4Cl. It is a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of natural, mineralogical form of ammonium chloride...
to produce the less stable NdCl3:
- Nd2O3 + 6 NH4Cl → 2 NdCl3 + 3 H2O + 6 NH3
The thus produced NdCl3 quickly absorbs water and converts to NdCl3·6H2O hydrate, which is stable for storage, and can be converted back into NdCl3 when necessary. Simple rapid heating of the hydrate is not practical for that purpose because it causes hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
with consequent production of Nd2O3. Therefore anhydrous
Anhydrous
As a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another...
NdCl3 is prepared by dehydration of the hydrate either by slowly heating to 400 °C with 4-6 equivalents of ammonium chloride under high vacuum, or by heating with an excess of thionyl chloride
Thionyl chloride
Thionyl chloride is an inorganic compound with the formula SOCl2. It is a reactive chemical reagent used in chlorination reactions. It is a colorless, distillable liquid at room temperature and pressure that decomposes above 140 °C. Thionyl chloride is sometimes confused with sulfuryl...
for several hours. The NdCl3 can alternatively be prepared by reacting neodymium metal with hydrogen chloride
Hydrogen chloride
The compound hydrogen chloride has the formula HCl. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric humidity. Hydrogen chloride gas and hydrochloric acid are important in technology and industry...
or chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
, though this method is not economical due to the relatively high price of the metal and is used for research purposes only. After preparation, it is usually purified by high temperature sublimation under high vacuum.
Production of neodymium metal
Ammonium chloride
Ammonium chloride NH4Cl is an inorganic compound with the formula NH4Cl. It is a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of natural, mineralogical form of ammonium chloride...
or ammonium fluoride
Ammonium fluoride
Ammonium fluoride is the inorganic compound with the formula NH4F. It crystallizes as small colourless prisms, having a sharp saline taste, and is exceedingly soluble in water.-Crystal structure:...
and hydrofluoric acid
Hydrofluoric acid
Hydrofluoric acid is a solution of hydrogen fluoride in water. It is a valued source of fluorine and is the precursor to numerous pharmaceuticals such as fluoxetine and diverse materials such as PTFE ....
or with alkali or alkaline earth metals in vacuum or argon atmosphere at 300-400 °C.
- LaCl3 + 3 Li → La + 3 LiCl
An alternative route is electrolysis
Electrolysis
In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...
of molten mixture of anhydrous LaCl3 and NaCl or KCl at temperatures about 700 °C. The mixture does melt at those temperatures, even though they are lower than the melting points of NdCl3 and KCl (~770 °C).
Lasers and fiber amplifiers
Although NdCl3 itself does not have strong luminescenceLuminescence
Luminescence is emission of light by a substance not resulting from heat; it is thus a form of cold body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which is light emitted by a...
, it serves as a source of Nd3+ ions for various light emitting materials. The latter include Nd-YAG lasers and Nd-doped optical fiber amplifiers
Optical amplifier
An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from the cavity is suppressed...
, which amplify light emitted by other lasers. The Nd-YAG laser emits infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
light at 1.064 micrometres and is the most popular solid-state laser
Solid-state laser
A solid-state laser is a laser that uses a gain medium that is a solid, rather than a liquid such as in dye lasers or a gas as in gas lasers. Semiconductor-based lasers are also in the solid state, but are generally considered as a separate class from solid-state lasers .-Solid-state...
(i.e. laser based on a solid medium). The reason for using NdCl3 rather than metallic neodymium or its oxide, in fabrication of fibers is easy decomposition of NdCl3 during the chemical vapor deposition
Chemical vapor deposition
Chemical vapor deposition is a chemical process used to produce high-purity, high-performance solid materials. The process is often used in the semiconductor industry to produce thin films. In a typical CVD process, the wafer is exposed to one or more volatile precursors, which react and/or...
; the latter process is widely used for the fiber grows.
Neodymium(III) chloride is a dopant not only of traditional silica-based optical fibers, but of plastic fibers (dopedphotolime-gelatin, polyimide
Polyimide
Polyimide is a polymer of imide monomers. The structure of imide is as shown. Polyimides have been in mass production since 1955...
, polyethylene
Polyethylene
Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...
, etc.) as well. It is also used in as an additive into infrared organic light-emitting diode
Organic light-emitting diode
An OLED is a light-emitting diode in which the emissive electroluminescent layer is a film of organic compounds which emit light in response to an electric current. This layer of organic semiconductor material is situated between two electrodes...
s. Besides, neodymium doped organic films can not only act as LEDs, but also as color filters improving the LED emission spectrum.
Solubility of neodymium(III) chloride (and other rare-earth salts) is various solvents results in a new type of rare-earth laser, which uses not a solid but liquid as an active medium. The liquid containing Nd3+ ions is prepared in the following reactions:
- SnCl4 + 2 SeOCl2 → SnCl62− + 2 SeOCl+
- SbCl5 + SeOCl2 → SbCl62− + SeOCl+
- 3 SeOCl+ + NdCl3 → Nd3+(solv) + 3 SeOCl2,
where Nd3+ is in fact the solvated ion with several selenium oxychloride molecules coordinated in the first coordination sphere, that is [Nd(SeOCl2)m]3+. The laser liquids prepared by this technique emits at the same wavelength of 1.064 micrometres and possess properties, such as high gain and sharpness of the emission, that are more characteristic of crystalline than Nd-glass lasers. The quantum efficiency of those liquid lasers was about 0.75 relative to the traditional Nd:YAG laser.
Catalysis
Another important application of NdCl3 is in catalysis—in combination with organic chemicals, such as triethylaluminiumTriethylaluminium
Triethylaluminium is an organoaluminium compound. This volatile, colorless liquid is highly pyrophoric, igniting immediately upon exposure to air. It is normally stored in stainless steel containers either as a pure liquid or as a solution in hydrocarbon solvents such as hexane, heptane, or ...
and 2-propanol, it accelerates polymerization
Polymerization
In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...
of various diene
Diene
In organic chemistry a diene or diolefin is a hydrocarbon that contains two carbon double bonds.Conjugated dienes are functional groups, with a general formula of CnH2n-2. Dienes and alkynes are functional isomers...
s. The products include such general purpose synthetic rubbers as polybutylene
Polybutylene
Polybutylene is a polyolefin or saturated polymer with the chemical formula n. It should not be confused with polybutene, a low molecular weight oligomer with a different repeat unit....
, polybutadiene
Polybutadiene
Polybutadiene is a synthetic rubber that is a polymer formed from the polymerization process of the monomer 1,3-butadiene.It has a high resistance to wear and is used especially in the manufacture of tires, which consumes about 70% of the production...
, and polyisoprene.
Neodymium(III) chloride is also used to modify titanium dioxide
Titanium dioxide
Titanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula . When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891. Generally it comes in two different forms, rutile and anatase. It has a wide range of...
. The latter is one of the most popular inorganic photocatalyst for decomposition of phenol
Phenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...
, various dye
Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....
s and other waste water contaminants. The catalytic action of titanium oxide has to be activated by UV light, i.e. artificial illumination. However, modifying titanium oxide with neodymium(III) chloride allows catalysis under visible illumination, such as sun light. The modified catalyst is prepared by chemical coprecipitation–peptization method by ammonium hydroxide
Ammonium hydroxide
Ammonia solution, also known as ammonium hydroxide, ammonia water, ammonical liquor, ammonia liquor, aqua ammonia, aqueous ammonia, or simply ammonia, is a solution of ammonia in water. It can be denoted by the symbols NH3...
from mixture of TiCl4 and NdCl3 in aqueous solution). This process is used commercially on large scale on 1000 liter reactor for using in photocatalytic self-cleaning paints.
Corrosion protection
Other applications are being developed. For example, it was reported that coating of aluminium or various aluminium alloys produces very corrosion-resistance surface, which then resisted immersion into concentrated aqueous solution of NaCl for two months without sign of pitting. The coating is produced either by immersion into aqueous solution of NdCl3 for a week or by electrolytic depositionElectroplating
Electroplating is a plating process in which metal ions in a solution are moved by an electric field to coat an electrode. The process uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal...
using the same solution. In comparison with traditional chromium
Chromium
Chromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
based corrosion inhibitors, NdCl3 and other rare-earth salts are environment friendly and much less toxic to humans and animals.
The protective action of NdCl3 on aluminium alloys is based on formation of insoluble neodymium hydroxide. Being a chloride, NdCl3 itself is a corrosive agent, which is sometimes used for corrosion testing of ceramics.
Labeling of organic molecules
Lanthanides, including neodymium are famous for their bright luminescenceLuminescence
Luminescence is emission of light by a substance not resulting from heat; it is thus a form of cold body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which is light emitted by a...
and therefore are widely used as fluorescent labels. In particular, NdCl3 has been incorporated into organic molecules, such as DNA, which could be then easily traced using a fluorescence microscope
Fluorescence microscope
A fluorescence microscope is an optical microscope used to study properties of organic or inorganic substances using the phenomena of fluorescence and phosphorescence instead of, or in addition to, reflection and absorption...
during various physical and chemical reactions.
Health issues
Neodymium(III) chloride does not seem toxic to humans and animals (approximately similar to table salt). The LD50 (dose at which there is 50% mortality) for animals is about 3.7 g per kg of body weight (mouse, oral), 0.15 g/kg (rabbit, intravenous injection). Mild irritation of skin occurs upon exposure with 500 mg during 24 hrs (Draize testDraize test
The Draize Test is an acute toxicity test devised in 1944 by Food and Drug Administration toxicologists John H. Draize and Jacob M. Spines...
on rabbits). Substances with LD50 above 2 g/kg are considered non-toxic.