Neodymium

What is neodymium?

Neodymium is a chemical element or rare earth metal in the periodic table with the symbol Nd and atomic number 60. It is a hard, silvery, slightly malleable f-block element that is the fourth member of the lanthanide series.

It is an important component of neodymium magnets that are obtained by alloying with iron and boron. The strong permanent magnets of rare earth metal neodymium are used widely in many electronic devices such as mobile phones, microphones, loudspeakers, electronic musical instruments, and wind turbines.

The rare earth metals praseodymium and neodymium were discovered in 1885 by the Austrian chemist Carl Auer von Welsbach. The name neodymium is obtained from the Greek words neos means new and didymos means twin. Commercially, neodymium compounds were used first for glass coloration.

Where is neodymium found?

It is the second most abundant of the rare-earth metals after lanthanum and cerium. It is almost the same abundant as that copper. Neodymium is found commercially in two main ores such as monazite and bastnasite.

The rare earth mineral monazite is chemically quite inert and mostly found in beach sands and river beds through weathering. The rare earth ore monazite is found mainly in China, USA, Brazil, India, South Africa, Sri Lanka, Australia, and Malaysia. Another ore bastnasite occurs mainly in USA and China.

Isotopes

The lanthanide neodymium has five stable naturally occurring isotopes like ¹⁴²Nd, ¹⁴³Nd, ¹⁴⁵Nd, ¹⁴⁶Nd, and ¹⁴⁸Nd. 33 other radioactive isotopes may be synthesized by various artificial nuclear reactions. The radioactive isotopes ¹⁴⁴Nd and ¹⁵⁰Nd have very long half-lives.

The half-lives of remaining radioactive isotopes have less than that of twelve days. The majority of radioactive Nd isotopes have half-lives shorter than 70 seconds.

¹⁴²Nd has been used for the production of short-lived thulium and ytterbium isotopes. ¹⁴⁶Nd has been used for the production of ¹⁴⁷Pm. Promethium-147 is used in luminous paint, atomic batteries, and thickness-measurement devices.

Neodymium in the periodic table

It is placed with lanthanides or f-block elements in the periodic table. Neodymium is a rare earth metal that lies between praseodymium and promethium.

Properties

It is the fourth member of the lanthanide series that form a bright, silvery metallic luster. It is an active metal that is highly malleable and ductile. Neodymium is alloyed with other metals like iron and boron to make stable and powerful magnets that are used in various commercial equipment.

Neodymium
Symbol	Nd
Discovery	Carl Auer von Welsbach in 1885
Name derived from	The Greek word neos didymos means new twin
Common isotope	60Nd142
Oxidation states	+3, +2, +4
CAS number	7440-00-8
Periodic properties
Atomic number	60
Relative atomic mass	144.242
Electron per cell	2, 8, 18, 22, 8, 2
Electronic Configuration	[Xe] 4f4 6s2
Block	f-block
Group	Lanthanides
Period	6
Physical properties
State at 20 °C	Solid
Melting point	1016 °C, 1289 K
Boiling point	3074 °C, 3347 K
Molar heat capacity	27.45 J mol−1 K−1
Crystal structure	hexagonal close-packed (hcp)
Density	7.01 g/cm3
Heat of fusion	7.14 kJ mol−1
Heat of vaporization	289 kJ mol−1
Atomic properties
Atomic radius (non-bonded)	2.39 Å
Covalent radius	1.88 Å
Electronegativity	1.14 (Pauling scale)
Electron affinity	Unknown
Ionization energy (kJ/mol)	1st	2nd	3rd
	533.08	1034.32	2132.30

Like other rare earth metals, neodymium may not serve any known biological function in the human body. It is not very toxic but neodymium dust and salts are very irritating to our eyes and mucous membranes, and moderately irritating to our skin.

Electron configuration

The 60 electrons of neodymium are arranged to show the electron configuration of [Xe] 4f⁴ 6s². Like other lanthanides, Nd commonly uses three valence electrons to show a +3 oxidation number or state. The reaming 4f electrons are strongly bound due to the greater stabilization of 4f orbitals in comparison to 5d or 6s.

Chemical properties

Neodymium is a highly electropositive and active metal. The electrode potential value of Nd is comparable to that of alkaline earth metals. Nd acts as a strong reducing agent.

The compact metal is quite stable to dry air at ordinary temperatures but rapidly dull in a humid atmosphere. Neodymium metal tarnishes slowly in the air by the formation of an oxide layer. Like praseodymium, it also burns in oxygen at 150 °C to form Nd (III) oxide.
4 Nd + 3 O₂ → 2 Nd₂O₃

Neodymium is attacked by acids like dilute sulfuric acid with the liberation of hydrogen gas. The acidic solutions contain Nd³⁺ ions that exist as [Nd(H₂O)₉]³⁺ complexes.
2 Nd + 3 H₂SO₄ → 2 Nd³⁺ + 3 SO₄⁻² + 3 H₂

Chemical compounds

Neodymium hydroxide

The rare earth metal neodymium dissolves slowly in cold water but more rapidly in warm water with the liberation of hydrogen. It forms Nd (III) hydroxide with water.
2 Nd + 6 H₂O → 2 Nd(OH)₃ + 3 H₂

Halides

Neodymium metal reacts with all the halogens like chlorine, fluorine, bromine, or iodine to form trihalides.

2 Nd + 3 F₂ → 2NdF₃ (violet)
2 Nd + 3 Cl₂ → 2NdCl₃ (mauve)
2 Nd + 3 Br₂ → 2NdBr₃ (violet)
2 Nd + 3 I₂ → 2NdI₃ (green)

Carbonate

Neodymium carbonate is a chemical compound with the chemical formula Nd₂(CO₃)₂. It may be prepared by passing carbon dioxide in an aqueous solution of Nd(OH)₃.

The carbonate is insoluble in water but dissolves in acids with the liberation of carbon dioxide.

Sulfate

It is a salt of the rare-earth metal neodymium with the chemical formula Nd₂(SO₄)₃. Neodymium sulfate is obtained by dissolving Nd (III) oxide in sulfuric acid.
Nd₂O₃ + 3 H₂SO₄ → Nd₂(SO₄)₃ + 3 H₂O

It forms multiple hydrates like octa-, penta-, and dihydrate but the octahydrate form is the most common. It is used in glass for making extremely powerful lasers.

Acetate

Neodymium acetate is a salt that contains one Nd⁺³ ion and three acetate anions with the chemical formula of Nd(CH₃COO)₃. Nd acetate is a purple solid that is soluble in water.

It can be formed when acetic acid reacts with neodymium oxide, hydroxide, or carbonate.
6 CH₃COOH + Nd₂O₃ → 2 Nd(CH₃COO)₃ + 3 H₂O
3 CH₃COOH + Nd(OH)₃ → Nd(CH₃COO)₃ + 3 H₂O

It may be used for making ultra-high purity compounds, catalysts, and nanoscale materials. Neodymium acetate is a substitute for uranyl acetate in electron microscopy. It may also be used in glass, crystal, capacitors, and lenses for welding goggles.

Uses of neodymium

Commercially, neodymium uses mainly for making powerful magnets, for coloration of glasses, making powerful lasers, making fertilizers, etc. The most common use of Nd metal is given below,

Neodymium magnets

A neodymium magnet is the most widely used commercial magnet of rare earth metals. It is a permanent magnet that is made from an alloy of neodymium, iron, and boron to form a tetragonal crystalline solid with the chemical formula Nd₂Fe₁₄B.

The strong permanent magnets of rare earth metal neodymium are used widely in many electronic devices such as

1. mobile phone speakers
2. computer hard disks
3. microphones and loudspeakers
4. electronic musical instruments
5. wind turbines

It is also used in mechanical e-cigarette firing switches, locks for doors, magnetic bearings and couplings, NMR spectrometers, etc.

Neodymium glass

Commercially, pure neodymium was used first in glass coloration. The color of the glasses changes under different lighting conditions. It shows reddish-purple under daylight or yellow incandescent light but blue under white fluorescent lighting or greenish under trichromatic lighting.

Neodymium glass is obtained by mixing neodymium oxide (Nd₂O₃) in the glass melt. The red color of glasses may be produced by combing gold or selenium. The most common use of these glasses may include,

• It is used widely for the production of natural light in incandescent light bulbs.
• It is also used in automobile rear-view mirrors to reduce glare at night.
• The Nd glass is used in astronomical work to produce sharp bands by which spectral lines may be calibrated.
• The rare earth metal neodymium can be used to remove the green color caused by iron contaminants from the glass.
• Didymium is a natural mixture of Pr and Nd. It is used for making protective glasses that absorbed ultraviolet radiation.
• Nd glass is used for glass blowing and welding work.

Neodymium lasers

They are liquid lasers obtained from certain transparent materials with a small concentration of neodymium ions. These layers are very powerful and offer many technical advantages.

• Nd:YAG (yttrium aluminium garnet): It is a crystalline solid that is used in solid-state lasers.
• Nd:YAP (yttrium aluminium perovskite): It is a laser that has various clinical applications.
• Nd:YLF (yttrium lithium fluoride): It is a lasing medium for arc lamp-pumped and diode-pumped solid-state lasers.
• Nd:YVO4 (yttrium orthovanadate): It is a crystalline material obtained by adding neodymium ions to yttrium orthovanadate.
• Nd:glass: It is a laser that is obtained by dipping Nd⁺³ in glasses.

In fertilizer

In agriculture, lanthanide compounds such as Pr and Nd compounds are used as insecto fungicides and trace elements in fertilizers. They are frequently used for making fertilizers in china.

In transmission electron microscopy

Uranyl acetate is a radioactive and toxic substance that has been used as a standard contrasting agent in transmission electron microscopy (TEM) for decades. It causes various health hazards or radioactive pollution.

Presently, neodymium acetate or platinum blue may be used as a standard contrasting agent instead of uranyl acetate in transmission electron microscopy.

Neodymium price

Neodymium is the second most abundant rare earth metal after lanthanum and cerium. The metal Nd is used widely for making magnets and coloration of glasses.

In 2020, the price of the rare earth metal oxide neodymium oxide was 49,763 US dollars per metric ton. The price of neodymium magnets is relatively high than that of other magnets due to the high price of rare earth metal Nd.