Tantalum (V) oxide

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Crystal structure
Crystal structure of tantalum (V) oxide
__ Ta 5+      __ O 2−
General
Surname Tantalum (V) oxide
other names
  • Tantalum pentoxide
  • Ditantalum pentoxide
Ratio formula Ta 2 O 5
Brief description

white odorless solid

External identifiers / databases
CAS number 1314-61-0
EC number 215-238-2
ECHA InfoCard 100,013,854
PubChem 62157
ChemSpider 55987
Wikidata Q425103
properties
Molar mass 441.89 g mol −1
Physical state

firmly

density

8.2 g cm −3

Melting point

1872 ° C

solubility

practically insoluble in water (<0.005 mg l −1 )

safety instructions
GHS labeling of hazardous substances
no GHS pictograms
H and P phrases H: no H-phrases
P: no P-phrases
Toxicological data

8000 mg kg −1 ( LD 50ratoral )

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Tantalum (V) oxide , Ta 2 O 5 , is a chemical compound of tantalum and oxygen and, along with tantalum (II) oxide and tantalum (IV) oxide, is one of the well-known oxides of tantalum. It is optically transparent.

Occurrence

Tantalum (V) oxide occurs in the mineral columbite .

Extraction and presentation

Tantalum (V) oxide can be obtained through chemical transport reactions with tantalum (V) chloride , chlorine , hydrogen chloride or sulfur .

properties

The refractive index of tantalum (V) oxide as an optical thin film at a wavelength of 500 nm is between 2.1 and 2.15 ( electron beam evaporation ) and about 2.2 (ion beam sputtering ), depending on the coating process used . The material is transparent from about 350 nm to about 8 µm wavelength.

Tantalum (V) oxide is a colorless solid that occurs in two modifications, whereby the low-temperature T-form reversibly changes at 1360 ° C into the H-modification, which is stable above this temperature. The T modification has a crystal structure related to T niobium (V) oxide with the orthorhombic sub-cell, which is very complicated due to its chemical (contamination with oxides of other metals) and structural variability. It is insoluble in acids other than hydrofluoric acid .

use

An important application is in optical coating technology ( PVD process ), where it is used as a highly refractive material.

In semiconductor technology , tantalum (V) oxide is used as a so-called high-k dielectric for on-chip capacitors. In contrast to the commonly used silica (SiO 2 ) having a relative permittivity has from 3.9, the relative permittivity of tantalum pentoxide is, depending on the manufacturing process 24 to 28 The oxide deposition is carried out by means of atomic layer deposition ( Atomic Layer Deposition , ALD) or Chemical Vapor Deposition ( Chemical Vapor Deposition , CVD). The preferred base material for the process is the volatile tantalum complex pentakis (dimethylamino) tantalum (Ta [HN (CH 3 ) 2 ] 5 ), which is accessible via tantalum pentachloride (TaCl 5 ), an important intermediate product in tantalum production.

See also

Individual evidence

  1. Entry on tantalum compounds. In: Römpp Online . Georg Thieme Verlag, accessed on July 14, 2014.
  2. Tantalum (V) oxide at webelements.com
  3. a b c d Entry on tantalum (V) oxide in the GESTIS substance database of the IFA , accessed on December 19, 2019 (JavaScript required)
  4. a b Georg Brauer (Ed.) U. a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume III, Ferdinand Enke, Stuttgart 1981, ISBN 3-432-87823-0 , p. 1466.
  5. SP Murarka, Moshe Eizenberg, AK Sinha: interlayer dielectrics for semiconductor technologies . Academic Press, 2003, ISBN 0-12-511221-1 , pp. 339 .