Niobium capacitor
The development of solid electrolyte tantalum capacitors began in the early 1950s as a miniaturized, more reliable low-voltage support capacitor to complement the newly invented transistor. The solution found by R. L. Taylor and H. E. Haring of the Bell Labs was based on experience with ceramics. They ground down tantalum to a powder, pressed this powder into a cylindrical form and then sintered the powder particles into a pellet (“slug”) at high temperatures, between 1500 and 2000 °C, under vacuum conditions. These first sintered tantalum capacitors used a non-solid electrolyte not consistent with the concept of solid state electronics. 1952 a targeted search in the Bell Labs for a solid electrolyte by D. A. McLean and F. S. Power led to the invention of manganese dioxide as a solid electrolyte for a sintered tantalum capacitor.
Film capacitor
The "film capacitors" were developed together with the growing market of broadcast and electronic equipment technology in the mid-20th century. These capacitors are standardized under the rules of IEC/EN 60384-1 “Capacitors for use in electronic equipment” and different "film materials" have their own sub standards, the IEC/EN 60384-"n" series. The "power capacitors" begin at a power handling capacity of approximately 200 volt-amps, such as for ballast capacitors in fluorescent lamps. The standardization of power capacitors follows the rules of IEC/EN 61071 and IEC/EN 60143-1, and have for various different applications their own sub standards, such as for railway applications.