Tantalum pentoxide
- Tantalum pentoxide
- Ditantalpentaoxid
White odorless solid
Fixed
8.2 g · cm -3
1872 ° C
Practically insoluble in water
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Tantalum (V ) oxide, Ta2O5, is a chemical compound of tantalum and oxygen, and in addition to tantalum ( II) oxide and tantalum ( IV) oxide of the known oxides of tantalum. It is optically transparent.
Occurrence
Tantalum ( V) oxide is present in the mineral columbite.
Production and representation
Tantalum ( V) oxide can be obtained by chemical transport reactions of tantalum ( V) chloride, chlorine, hydrogen chloride or sulfur.
Properties
The refractive index of tantalum ( V) oxide as the optical thin film is 500 nm, depending on the coating method used, between 2.1 to 2.15 ( electron beam ) and about 2.2 ( ion beam sputtering ). The material is of about 350 nm to about 8 microns wavelength transparent.
Tantalum ( V) oxide is a colorless solid which occurs in two modifications, the low-temperature form T-shaped reversible transitions at 1360 ° C in the above said temperature stable H- modification. The T -form having a T- niobium (V ) oxide, related to the crystal structure of orthorhombic subcell, which is by its chemical (impurities with oxides of other metals ) and structural variability very complicated. It is insoluble in acids except hydrofluoric acid.
Use
An important application is in optical coating technology (PVD ) method, where it is used as a high-index material.
In the semiconductor technology, tantalum ( V) oxide is used as a so-called high-k dielectric, for on-chip capacitors. In contrast to the conventionally used silicon oxide ( SiO2), which has a relative permittivity of 3.9, the relative permittivity of tantalum, 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 of the process is the volatile tantalum complex pentakis (dimethylamino ) tantalum (Ta [N ( CH3) 2] 5), which is about tantalum pentachloride ( TaCl5 ), an important intermediate in the manufacture of tantalum, accessible.