Holmium (Ho)

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Holmium 67Ho164.930

1978 von P.T. Cleve in Uppsala, Schweden, entdeckt und unabhängig davon von M. Delafontaine und J.L. Soret in Genf, Schweiz.

[Lateinisch: Holmia = Schweden]

  French: holmium
  English: holmium
  Italian: olmio
  Spanish: holmio

Beschreibung: Silberfarbenes Lanthanoid. Wird von Sauerstoff und Wasser angegriffen, löst sich in Säuren. Seine Legierungen werden zur Herstellung starker Magnete verwendet.

Holmium single crystal properties

 

State: Single crystal
Crystal structure: hexagonal
Production method: Floating zone
Standard size: diameter 7-8mm
thickness 1mm
Orientation: (0001)
Orientation accuracy: <2°, <1°, <0.4° or <0.1°
Polishing: as cut, one or two sides polished
Roughness of surface: <0.03 µm
Purity: 99.99%

 

 

Further Materials properties

 

Crystal structure: (cell dimensions/pm), space group
a-Ho h.c.p. (a=357.73, c=561.58), P63/mmc
b-Ho b.c.c. (a=396), Im3m
T(a -> a)= just below melting point
High pressure form: (a=334, c=2410), R3m
X-ray diffractions mass absorption coefficients: CuKa 128 (µ/r) / cm2g-1
MoKa 73.9 (µ/r) / cm2g-1
Neutron scattering length: 0.808 b/10-12 cm
Thermal neutron capture cross-section: 65 sa / barns
Density: 8.8 kg/m-3 [293 K]; 2390 [liquid at m.p.]
Melting point: 1473.85 °C / 1747 °K
Boiling point: 2694.85 °C / 2968 °K
Molar volume: 18.75 cm3
Thermal conductivity: 16.2 [300 K] Wm-1K-1
Coefficient of linear thermal expansion: 9.5 x 10-6 K-1
Electrical resistivity: 87.0 x 10-8 [293 K] Wm
Mass magnetic susceptibility: +5.49 x 10-6(s) kg-1m3
Young's modulus: 64.8 GPa
Rigidity modulus: 26.3 GPa
Bulk modulus: 40.2 GPa
Poisson's ratio: 0.231 GPa
Radi: Ho3+ 89; atomic 177; covalent 158
Electronegativity: 1.23 (Pauling); 1.10 (Allred); £3.3 eV (absolute)
Effective nuclear charge: 2.85 (Slater); 8.44 (Clementi); 11.60 (Froese-Fischer)
Number of Isotopes (incl. nuclear isomers): 39
Isotope mass range: 148 -> 170

 

 

Biological data

 

Biological role: none, but acts to stimulate metabolism
Toxicity  
Toxic intake: n.a.
Lethal intake: LD50 (chloride, oral, mouse)=7200 mg kg-1
Hazards: Holmium is mildly toxic by ingestion
Level in humans  
Organs: n.a., but low
Daily dietary intake: n.a.
Total mass of element in average
[70 kg] person:		 n.a.

 

Geological data

 

Minerals:Many minerals are known, and aluminium is present in many other minerals
MineralFormulaDensityHardnessCrystal apperance
Bastnäsite  (Ce, La etc.) Co3F  4.9  4 - 4.5  hex., vit./greasy yellow
Monazite  (Ce, La, Nd, Th etc.) PO4  5.20  5 - 5.5  mon., waxy/vit., yellow-brown

 

Chief ore: monazite, bastnäsite
World production: c. 10 tonnes/year
Main mining areas: USA, Brazil, India, Sri Lanka, Australia, China
Reserves: 4 x 105 tonnes
Specimen: available as ingots or granules. Safe.

 

Abundances  
Sun: n.a.
Earth's crust: 1.4 ppm
Seawater:  
Atlantic surface: 2.4 x 10-7 ppm
Atlantic deep: 2.9 x 10-7 ppm
Pacific surface: 1.6 x 10-7 ppm
Pacific deep: 5.8 x 10-7 ppm
Residence time: n.a.
Classification: recycled
Oxidation state: III

 

Other sizes and specifications on request


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