Тантал пентоксиді: қасиеттері, құрылымы және қолданылуы

Tantalum pentoxide, also known as tantalum(V) oxide, is the inorganic compound with the formula It is a white solid that is insoluble in all solvents but is attacked by strong bases and hydrofluoric acid. is an inert material with a high refractive index and low absorption (i. e. colourless), which makes it useful for coatings. It is also extensively used in the production of capacitors, due to its high dielectric constant.

Tantalum occurs in the minerals tantalite and columbite (columbium being an archaic name for niobium), which occur in pegmatites, an igneous rock formation. Mixtures of columbite and tantalite are called coltan. Tantalite was discovered by Anders Gustaf Ekeberg at Ytterby, Sweden, and Kimoto, Finland. The minerals microlite and pyrochlore contain approximately 70% and 10% Ta, respectively.

The crystal structure of tantalum pentoxide has been the matter of some debate. The bulk material is disordered, being either amorphous or polycrystalline; with single crystals being difficult to grow. As such Xray crystallography has largely been limited to powder diffraction, which provides less structural information. At least 2 polymorphs are known to exist. A low temperature form, known as L or β Ta2O5, and the high temperature form known as H or α Ta2O5. The transition between these two forms is slow and reversible; taking place between 1000 and 1360 °C, with a mixture of structures existing at intermediate temperatures. The overall crystal system is orthorhombic in both cases, with the space group of β Ta2O5 being identified as Pna2 by single crystal X ray diffraction. A high pressure form (Z Ta2O5) has also been reported, in which the Ta atoms adopt a 7 coordinate geometry to give a monoclinic structure (space group C2). Purely amorphous tantalum pentoxide has a similar local structure to the crystalline polymorphs, built from TaO6 and TaO7 polyhedra, while the molten liquid phase has a distinct structure based on lower coordination polyhedra, mainly TaO5 and TaO6. The difficulty in forming material with a uniform structure has led to variations in its reported properties. Like many metal oxides Ta2O5 is an insulator and its band gap has variously been reported as being between 3.8 and 5.3 eV, depending on the method of manufacture. In general the more amorphous the material the greater its observed band gap. These observed values are significantly higher than those predicted by computational chemistry (2.3 3.8 eV). Its dielectric constant is typically about 25 although values of over 50 have been reported. In general tantalum pentoxide is considered to be a high k dielectric material.

Owing to its high band gap and dielectric constant, tantalum pentoxide has found a variety of uses in electronics, particularly in tantalum capacitors. These are used in automotive electronics, cell phones, and pagers, electronic circuitry; thin film components; and high speed tools. In the 1990s, interest grew in the use of tantalum oxide as a high k dielectric for DRAM capacitor applications. It is used in on chip metal insulator metal capacitors for high frequency CMOS integrated circuits. Tantalum oxide may have applications as the charge trapping layer for non volatile memories. There are applications of tantalum oxide in resistive switching memories.

Due to its high refractive index, Ta2O5 has been utilized in the fabrication of the glass of photographic lenses. It can also be deposited as an optical coating with typical applications being antireflection and multilayer filter coatings in near UV to near infrared. Ta2O5 has also been found to have a high nonlinear refractive index, on the order of three times that of silicon nitiride, which has led to interest in the utilization of Ta2O5 in photonic integrated circuits. Ta2O5 has been recently utilized as the material platform for the generation of supercontinuum and Kerr frequency combs