Tantalum pentoxide

Antireflection coatings are used over the silicon surface which, without the coating, reflects ca 35% of incident sunlight. A typical coating consists of a single layer of a transparent dielectric material with a refractive index of ca 2, which is between the index of siUcon and ait or cover material. Materials such as titanium dioxide, tantalum pentoxide, Ta20, or siUcon nitride, Si N, ca 0.08-p.m thick are common. The coating and a physically textured... 

Tantalum pentoxide [1314-61 -0] Ta20, is prepared by calcining tantaUc acid or hydrated tantalum oxide [75397-94-3] Ta20 at... 

Tantalum. Numerous methods developed to extract tantalum metal from compounds included the reduction of the oxide with carbon or calcium the reduction of the pentachloride with magnesium, sodium, or hydrogen and the thermal dissociation of the pentachloride (30). The only processes that ever achieved commercial significance are the electrochemical reduction of tantalum pentoxide in molten K TaF /KF/KCl mixtures and the reduction of K TaF with sodium. 

Interior of capacitive element containing tantalum, tantalum pentoxide (dielectric), manganese dioxide (solid electroyte)... 

Tantalum Oxides. Tantalum pentoxide [1314-61 -0] Ta20, (mp = 1880°C, density = 8.73 g/cm ) is a white powder existing in two thermodynamically stable modifications. The orthorombic P-phase changes at 1360°C into the tetragonal a-modiftcation. The existence of an S-modiftcation has also been reported (70). Tantalum pentoxide reacts slowly with hot hydrofluoric acid but is insoluble in water and in most solutions of acids and alkalies. For analytical purposes, it can be dissolved by fusion with alkali hydroxides, alkali carbonates, and potassium pyrosulfate. 

Hazards of Tantalum Compounds. The toxicity of tantalum compounds depends on then solubihty. Tantalum pentoxide is poorly absorbed and nontoxic perorahy. The pentachloride, on the other hand, shows an LD q of 985 mg/Kg adrninistered peroraHy. 

Brown et al. [494] developed a method for the production of hydrated niobium or tantalum pentoxide from fluoride-containing solutions. The essence of the method is that the fluorotantalic or oxyfluoroniobic acid solution is mixed in stages with aqueous ammonia at controlled pH, temperature, and precipitation time. The above conditions enable to produce tantalum or niobium hydroxides with a narrow particle size distribution. The precipitated hydroxides are calcinated at temperatures above 790°C, yielding tantalum oxide powder that is characterized by a pack density of approximately 3 g/cm3. Niobium oxide is obtained by thermal treatment of niobium hydroxide at temperatures above 650°C. The product obtained has a pack density of approximately 1.8 g/cm3. The specific surface area of tantalum oxide and niobium oxide is nominally about 3 or 2 m2/g, respectively. 

Table 1.16 Niobium and tantalum pentoxide contents in tin slags from various countries.

The principles of tantalum metal formation by the carbothermic reduction of tantalum pentoxide and the technology of tantalum metal production by this method are similar to those pertaining to niobium metal production by carbothermy. 

The industrial practice for the production of tantalum consists of two steps. In the first, the carbide is made by charging a graphite crucible with an intimate, pelletized mixture of lamp black and tantalum pentoxide and heating it in a high-frequency furnace under a dynamic vacuum (10 torr). In the next step, the ground carbide and the requisite amount of tantalum pentoxide are mixed, palletized, and fed to a reduction furnace where the reduction to the metal occurs. The formation of tantalum carbide as well as the reduction to the metal occur at about 2000 °C. The product leaving the reduction furnace is in the form of pellets or roundels (small cylinders) of porous metal, usually sintered together. 

Aluminium oxide, arsenic trioxide, bismuth trioxide, calcium oxide, chromic oxide, lanthanum oxide, lead dioxide, magnesium oxide, manganese dioxide, molybdenum trioxide, phosphorus pentoxide, stannic oxide, sulfur dioxide (explodes), tantalum pentoxide, tungsten trioxide, vanadium pentoxide. 

The other platform is dielectrics, for example, silicon dioxide, silicon nitride, silicon oxynitride, tantalum pentoxide, and titanium dioxide. They can be deposited by various methods, such as plasma-enhanced chemical vapor deposition, thermal evaporation, electron-beam evaporation, and sputtering. There are a number of dielectrics with refractive indices ranging from 1.45 to 2.4, facilitating diverse waveguide designs to satisfy different specification. Dielectrics have two other... 

Tantalum oxide film, 24 314 Tantalum oxides, 24 322, 334 Tantalum pentachloride, 24 335 Tantalum pentafluoride, 24 334-335 Tantalum pentoxide, electrochemical reduction of, 24 322 Tantalum powder, 24 323, 324-325 capacitor-grade, 24 326 safety of, 24 333-334 Tantalum products, world shipments of, 24 331t... 

Tantalum pentoxide is representative of tantalums stable oxidation state of+5 2Ta + 50 — TafDy Tantalum oxide is used to make optical glass for lenses and in electronic circuits. 

Tantalum pentoxide (Ta O ) is used to make special optical glass, for lasers, and in electronic circuits. 

Tantalum pentachloride is hydrolyzed by water to form hydrous tantalum pentoxide, Ta205 uH20 and hydrochloric acid ... 

Tantalum pentoxide is used in making high refractive index optical glass as a dielectric film on tantalum for its use as a capacitor component and rectifier and for preparing tantalum metal, its carbide, and many other tantalum compounds. 

Tantalum pentoxide is obtained as an intermediate in extracting tantalum from the columbite-tantalite series of minerals. Also, the oxide can be made by heating Ta metal in oxygen or air at elevated temperatures. 

Tantalum pentoxide [1314-61-0], Ta is prepared by calcining tantaUc acid or hydrated tantalum oxide [75397-94-3], Ta2Os H20, at temperatures between 800 and 1100°C. This oxide hydrate is produced by adding gaseous or aqueous ammonia to the solvent extraction produced aqueous tantalum solution in a continuous (29) or batch process. 

Vanadium pentoxide can be reduced to the metal by the action of hydrogen at high temperatures and pressures niobium pentoxide is more stable, and yields the trivalent oxide Nb203, whereas tantalum pentoxide has not hitherto been reduced by hydrogen. 

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