Neodymium

properties
[ Xe ] 4 f 4 6 s 2 60 Nd Periodic table
General
Name , symbol , atomic number	Neodymium, Nd, 60
Element category	Lanthanoids
Group , period , block	La , 6 , f
Appearance	silvery white, yellowish hue
CAS number	7440-00-8
EC number	231-109-3
ECHA InfoCard	100.028.281
Mass fraction of the earth's envelope	22 ppm
Atomic
Atomic mass	144,242 (3) et al
Atomic radius (calculated)	185 (206) pm
Covalent radius	201 pm
Electron configuration	[ Xe ] 4 f 4 6 s 2
1. Ionization energy	5.5250 (6) eV ≈ 533.08 kJ / mol
2. Ionization energy	10.783 (20) eV ≈ 1 040.4 kJ / mol
3. Ionization energy	22nd.09 (4) eV ≈ 2 130 kJ / mol
4. Ionization energy	40.60 (4) eV ≈ 3 920 kJ / mol
5. Ionization energy	60.0 (3) eV ≈ 5 790 kJ / mol
Physically
Physical state	firmly
Crystal structure	hexagonal
density	7.003 g / cm 3 (25 ° C )
magnetism	paramagnetic ( Χ m = 3.6 10 −3 )
Melting point	1297 K (1024 ° C)
boiling point	3303 K (3030 ° C)
Molar volume	20.59 · 10 −6 m 3 · mol −1
Heat of evaporation	289 kJ / mol
Heat of fusion	7.1 kJ mol −1
Speed ​​of sound	2330 m s −1 at 293.15 K.
Specific heat capacity	190 J kg −1 K −1
Electric conductivity	1.56 · 10 6 A · V −1 · m −1
Thermal conductivity	17 W m −1 K −1
Chemically
Oxidation states	2, 3 , 4
Normal potential	−2.32 V (Nd 3+ + 3 e - → Nd)
Electronegativity	1.14 ( Pauling scale )
Isotopes
isotope NH t 1/2 ZA ZE (M eV ) ZP 142 Nd 27.13  % Stable 143 Nd 12.18% Stable 144 Nd 23.8% 2.29 x 10 15 a α 1.905 140 Ce 145 Nd 8.3% Stable 146 Nd 17.19% Stable 147 Nd {syn.} 10.98 d β - 0.896 147 pm 148 Nd 5.76% Stable 149 Nd {syn.} 1.728 h β - 1.691 149 pm 150 nd 5.64% 1.1 · 10 19 a β - β - 3.367 150 sm
For other isotopes see list of isotopes
NMR properties
Spin quantum number I γ in rad · T −1 · s −1 E r  ( 1 H) f L at B = 4.7 T in MHz 143 Nd 7/2 −1.457 10 7 5.45 145 Nd 7/2 −0.898 10 7 3.36
safety instructions
GHS labeling of hazardous substances powder danger H and P phrases H: 228-260 P: 210-231 + 232-280-370 + 378-402 + 404-501
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Neodymium (nomenclature recommendation was temporarily neodymium ) is a chemical element with the element symbol Nd and the atomic number 60. In the periodic table it is in the group of lanthanides and is therefore also one of the rare earth metals . The element name is derived from the Greek words νέος neos 'new' and δίδυμος didymos 'twin' (as a twin of lanthanum ). The metal is used in the form of the alloy neodymium-iron-boron for strong permanent magnets .

history

Neodymium

In 1841 Carl Gustav Mosander extracted the rare earth Didym from cerite earth . In 1874 Per Teodor Cleve noticed that Didym actually consisted of two elements. In 1879 Lecoq de Boisbaudran isolated samarium from Didym, which he extracted from the mineral samarskite . In 1885 Carl Auer von Welsbach succeeded in separating didymium into praseodymium and neodymium, which form salts of different colors. Pure metallic neodymium was not presented until 1925.

Occurrence

Neodymium occurs naturally only in chemical compounds associated with other lanthanoids , preferably minerals:

Monazite (Ce, La, Th, Nd, Y) PO 4 Bastnesite ((Ce, La, Th, Nd, Y) (CO 3 ) F) Misch metal contains up to 18% neodymium.

The most important supplier with 91% of world production is China . This leads to considerable environmental problems there. “When the neodymium is separated from the extracted rock, toxic waste products are created, and radioactive uranium and thorium are also released during the mining process. At least some of these substances get into the groundwater, contaminate fauna and flora considerably and are classified as harmful to human health ”. Other economically exploitable deposits can be found in Australia , especially in the Northern Territory, which is exploited by Arafura Resources .

Extraction and manufacture

As with all lanthanoids , the ores are first enriched by flotation , then the metals are converted into their halides and separated by fractional crystallization , ion exchange or extraction .

After a complex separation of the neodymium components, the oxide can be converted to neodymium (III) fluoride with hydrogen fluoride and then reduced to neodymium with calcium to form calcium fluoride . Calcium residues and impurities are separated off by remelting in a vacuum.

${\displaystyle \mathrm {2\ NdF_{3}\ +\ 3\ Ca\ \longrightarrow \ 2\ Nd\ +\ 3\ CaF_{2}} }$

This process was replaced in China around 1984 by fused-salt electrolysis of a mixture of neodymium fluoride, neodymium oxide and lithium fluoride. Formally, this process corresponds to the Hall-Héroult process, but the elementary neodymium is deposited on a perpendicular tungsten cathode, which is surrounded by an annular graphite anode. The molten neodymium is caught in a molybdenum tank, from which it is manually poured into an ingot mold. Each such electrolysis cell is operated as a single-chamber electrolysis cell. No verifiable information is known about the actual operation of the cells in the Chinese factories.

The Chinese government has announced that it will introduce stricter environmental regulations and take stronger action against illegal mines. At the beginning of June 2011 this intention appears to have been implemented for the first time. According to reports in the Financial Times, the state-owned producer (Baotou Steel Rare Earth) has a monopoly on mining and processing rare earths. 35 licensed businesses will be closed and compensated, nine more unlicensed businesses will be closed and not compensated. In the United States , the Mountain Pass mine in California and the Mount Weld mine in Australia are being reactivated. Both mines are operated by the Öko-Institut e. V. certifies acceptable environmental protection systems. However, there are also projects for the combined mining of rare earths in Greenland, in which the toxic residues are to be dumped into lakes .

Price development of neodymium oxide (source: Sachwerte purchase group, as of March 10, 2014)

The annual production in 2012 was estimated at 21,000 t, 91% of which comes from China. According to USGS , the price of 1 kg of neodymium in 2001 below 10 USD . The price rose to USD 80 by 2010 and peaked in 2011 at USD 244 per kg. Then it went down again and in 2013 was USD 65 per kg.

properties

Crystal structure of neodymium

Physical Properties

The shiny silver-white metal is one of the lanthanides and rare earth metals . It is somewhat more corrosion-resistant in air than europium , lanthanum , cerium or praseodymium , but easily forms a pink-violet oxide layer that can flake off in air.

Chemical properties

At high temperatures, neodymium burns to form sesquioxide Nd ₂ O ₃ . It reacts with water to form neodymium hydroxide Nd (OH) ₃ , forming hydrogen . With hydrogen it reacts to the hydride NdH ₂ . In addition to the main value / oxidation number 3, the oxidation numbers 2 and 4 also occur under special conditions.

use

• Neodymium-iron-boron compounds for the production of strongest magnets . They are used for magnetic resonance tomographs , micromotors and hard drives (positioning of the read / write heads), permanent magnet rotors (e.g. stepper and servo motors), efficient permanent magnet synchronous machines e.g. B. in some types of wind turbines (around one sixth), to drive electric and hybrid vehicles and as model-making drives , linear motors for positioning axes (e.g. CNC machines), high-quality loudspeakers and headphones . Compared to samarium-cobalt magnets they are stronger and much cheaper, but also much more sensitive to heat.
• Neodymium salts for coloring enamel
• Blue porcelain color
• Neodymium (III) oxide for coloring glass. It produces very warm purple to wine red and gray tones. Such glasses have sharp absorption bands and are used in astronomy for calibration .
• Discoloration of ferrous glass
• UV- absorbing glasses (sun protection glass)
• Part of the industrially widespread neodymium YAG laser
• Neodymium oxide-doped barium titanate for capacitor dielectrics
• Because of its pyrophoric properties as an alloy partner with cerium in flint stones
• For the production of neodymium-catalyzed polybutadiene rubber (Nd-PBR)

links

Oxides

• Neodymium (III) oxide (Nd ₂ O ₃ )

Halides

• Neodymium (II) fluoride (NdF ₂ )
• Neodymium (II) chloride (NdCl ₂ )
• Neodymium (II) bromide (NdBr ₂ ), only anhydrous
• Neodymium (II) iodide , (NdI ₂ )

• Neodymium (II, III) bromide (Nd ₄ Br ₉ ), only anhydrous

• Neodymium (III) fluoride (NdF ₃ )
• Neodymium (III) chloride (NdCl ₃ ), anhydrous
• Neodymium (III) bromide (NdBr ₃ ), anhydrous, two modifications
• Neodymium (III) iodide (NdI ₃ ), anhydrous

Other connections

• Neodymium (III) acetate (Nd (C ₂ H ₃ O ₂ ) ₃ )
• Neodymium carbide (NdC ₂ )
• Neodymium (III) nitrate (Nd (NO ₃ ) ₃  6 H ₂ O)
• Neodymium (III) sulfate (Nd ₂ (SO ₄ ) ₃  · 8 H ₂ O)
• Neodymium (III) sulfide (Nd ₂ S ₃ )

• 

  Neodymium (III) sulfate octahydrate

• 

  Neodymium (III) chloride

• 

  Neodymium (III) sulfate, nitrate and chloride in solution

Other substances

Neodymium-iron-boron (Nd ₂ Fe ₁₄ B) is the material from which the strongest permanent magnets can currently be made. They achieve a remanence of up to 1.4 Tesla . The coercive field strength H _cJ fluctuates in the range from 870 to 2750 kA / m.

Web links

Commons : Neodymium  - collection of pictures, videos and audio files

Wiktionary: Neodymium  - explanations of meanings, word origins, synonyms, translations

• Entry to neodymium. In: Römpp Online . Georg Thieme Verlag, accessed on January 3, 2015.
• metallic bright neodymium

Individual evidence

1. ^ Harry H. Binder: Lexicon of the chemical elements. S. Hirzel Verlag, Stuttgart 1999, ISBN 3-7776-0736-3 .
2. ↑ The values ​​for the properties (info box) are taken from www.webelements.com (neodymium) , unless otherwise stated .
3. ↑ CIAAW, Standard Atomic Weights Revised 2013 .
4. ↑ ^{a b c d e} Entry on neodymium in Kramida, A., Ralchenko, Yu., Reader, J. and NIST ASD Team (2019): NIST Atomic Spectra Database (ver. 5.7.1) . Ed .: NIST , Gaithersburg, MD. doi : 10.18434 / T4W30F ( https://physics.nist.gov/asd ). Retrieved June 11, 2020.
5. ↑ ^{a b c d e} Entry on neodymium at WebElements, https://www.webelements.com , accessed on June 11, 2020.
6. ^ NN Greenwood, A. Earnshaw: Chemistry of the elements. 1st edition. VCH, Weinheim 1988, ISBN 3-527-26169-9 , p. 1579.
7. ↑ Robert C. Weast (Ed.): CRC Handbook of Chemistry and Physics . CRC (Chemical Rubber Publishing Company), Boca Raton 1990, ISBN 0-8493-0470-9 , pp. E-129 to E-145. Values ​​there are based on g / mol and given in cgs units. The value specified here is the SI value calculated from it, without a unit of measure.
8. ↑ ^{a b} Yiming Zhang, Julian RG Evans, Shoufeng Yang: Corrected Values ​​for Boiling Points and Enthalpies of Vaporization of Elements in Handbooks. In: Journal of Chemical & Engineering Data . 56, 2011, pp. 328-337; doi: 10.1021 / je1011086 .
9. ↑ ^{a b} Entry on neodymium, powder in the GESTIS substance database of the IFA , accessed on April 26, 2017(JavaScript required) .
10. ↑ Carl Auer v. Welsbach: The decomposition of the Didym into its elements. In: Monthly magazine for chemistry . 6 (1), 1885, pp. 477-491; doi: 10.1007 / BF01554643 .
11. ^ Justin Rowlatt: Neither rare, nor earths . March 23, 2014 ( bbc.com [accessed June 8, 2019]).
12. ↑ ^{a b} neodymium. (No longer available online.) Setis.ec.europa.eu, archived from the original on March 5, 2016 ; accessed on August 26, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.   
13. ↑ The dirty secret of clean wind turbines. In: Panorama. April 28, 2011.
14. ↑ Michelle Röttger: China is cleaning up the market for rare earths. (Study) In: Financial Times. June 9, 2011, p. 2 , archived from the original on June 11, 2011 ; Retrieved June 26, 2011 . 
15. ↑ ^{a b} Mandy Schossig: Rare earths - data & facts. Öko-Institut e. V., Berlin, January 2011.
16. ↑ Scientific Investigations Report 2012–5188 - Metal Prices in the United States Through 2010. (PDF 2.4 MB, p. 143 (137) Figure 6.) USGS , accessed on August 26, 2015 (English).  
17. ^ Congressional Research Service - Rare Earth Elements: The Global Supply Chain. (PDF 603 kB, p. 11 (7) Figure 3) www.fas.org, December 16, 2013, accessed on August 26, 2015 (English).  
18. ↑ Approx. 2 t neodymium are needed for each wind turbine : "Around two tonnes of neodymium are needed for each wind turbine" .