A capacitor is a passive electronic component that has the ability to store and release energy very quickly, making it essential in countless electronic circuits such as XXX. They consist of two conductive materials separated by an insulating material named dielectric. When a voltage is applied, electric charges accumulate on the conductive materials, storing energy.  

Several types of capacitors can be found on the market, typically classified by the dielectric material they use, such as film, ceramic, and electrolytic capacitors. Depending on the dielectric material, its thickness, and the available area, these capacitors can offer a wide range of capacitance values, voltage ratings and operating temperature ranges, allowing them to meet different requirements for various applications. Film and ceramic capacitors are nonpolar meaning there is no restriction on the polarity applied to their terminals X. In contrast, electrolytic capacitors are polar, meaning their positive terminal is predetermined and must be connected correctly. [J. Torki, C. Joubert, and A. Sari, “Electrolytic capacitor: Properties and operation,” J. Energy Storage, vol. 58, no. December 2022, p. 106330, 2023, doi: 10.1016/j.est.2022.106330]. Electrolytic capacitors are distinctive in that their dielectric is formed by growing an oxide surface layer on the surface of a metal foil, typically made of aluminum or tantalum. This oxide layer serves as a unidirectional insulator, responsible for the polarized nature of these capacitors. An electrolyte, either liquid, polymer, or solid  is used to interface with the rough oxide layer. This unique construction allows the electrolytic capacitors to achieve high capacitance values, making them ideal for applications where high energy storage in a compact size is required. [T .Won, Replacing Aluminum Electrolytic Capacitors with Tantalum or Ceramic Capacitors, Kyocera AVX Components Corporation, Technical Paper]

Among electrolytic capacitors we can find aluminum electrolytic capacitors (AECs), tantalum electrolytic capacitors and niobium electrolytic capacitors. AECs are considered the most cost-effective owing to the abundance of aluminum and well-established manufacturing processes. Moreover, they present good stability and long service life allowing working within this range of temperature. Tantalum capacitors, while more expensive, offer much higher capacitance/volume efficiency compared to AECs, with up to three times the capacitance per unit volume. This is due to the higher dielectric constant of tantalum pentoxide (Ta2O5) which is around 26, three times greater than aluminum oxide (Al2O3). [M. Mosier, Wet Electrolyte Tantalum Capacitors: An Introduction to the Basics, Vishay Technical Note, 2024] Additionally, the manufacturing process of tantalum capacitors allows for the deposition of an extremely thin layer of the dielectric, further enhancing the capacitance. As a result, tantalum capacitors are highly efficient, providing more capacitance in a smaller volume, making them ideal for applications requiring high energy density and compact sizes, qualities that are particularly advantageous for printed circuit boards (PCBs). Noubium electrolytic capacitors are made using passivated niobium metal or niobium monoxide, combined with a solid electrolyte such as manganese dioxide (MnO2) or conductive polymer. Niobium pentoxide Nb2O5 has a higher  dielectric constant (approximately 41) compared to Ta2O5  allowing similar energy storage capabilities, though at a lower voltage rating. The production process of niobium capacitors closely resembles that of tantalum capacitors, but niobium’s abundance makes these capacitors a more economical alternative to tantalum for certain applications.  [J. Torki, C. Joubert, and A. Sari, “Electrolytic capacitor: Properties and operation,” J. Energy Storage, vol. 58, no. December 2022, p. 106330, 2023, doi: 10.1016/j.est.2022.106330]