is Ta<sub>2</sub>O<sub>5</sub>, also known as tantalum
(V) oxide. Both orthorhombic
phases are known. Ta<sub>2</sub>O<sub>5</sub> is a high refractive index
, low absorption material useful for coatings in the near-UV
spectra regions; it decomposes only at temperatures >1470 °C.
The metal oxide discovered by Anders Gustaf Ekeberg
was obtained from minerals taken from pegmatite
(an igneous rock associated with tantalite
) at Ytterby
, Sweden, and Kimoto, Finland
. The microlite-pyrochlore mineral series
is also a source of tantalum oxide. Microlite
contains approximately 70% of tantalum oxide, and pyrochlore
contains approximately 10%.
There are several methods available for the synthesis of tantalum oxide. One method involves isolating tantalum pentoxide by crushing a concentrate of the mineral columbite-tantalite and fusing the powdered mineral with sodium hydroxide
to give a slurry of mixed insoluble niobic
and tantalic acids
. The mixed acids are dissolved by passing anhydrous hydrofluoric acid
into the slurry and adding the stoichiometric quantity of potassium fluoride
to yield a salt. The salts can be separated by a liquid-liquid extraction process, using various ketones
as the liquids.
- (FeMn)(NbTa)<sub>2</sub>O<sub>6</sub> + 6NaOH → Ta<sub>2</sub>O<sub>5</sub>·7H<sub>2</sub>O......