Tantalum pentoxide, also known as tantalum (V) oxide, is the inorganic compound with the formula Ta2O5. It is a white solid that is insoluble in all solvents but is attacked by strong bases and hydrofluoric acid. Ta2O5 is an inert material with has a high refractive index and low absorption (i.e. colorless), which makes it useful for coatings. It is also extensively used in the production of capacitors, due to its high dielectric constant.
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.
Due to its high refractive index, Ta2O5 has been utilized in the fabrication of the glass of photographic lenses.