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.
Experiments and Observations on Electricity
Franklin's first experiments explained in this first set of letters to Collinson that the Leyden jar, a type of capacitor, had equal and opposite charges on the inner and outer conductors. This was shown in illustrations in his book. The significant Franklin theory introduced to Collinson in a letter dated April 29, 1747, was the concept of the "dissectible condenser." Today we call this distribution of charges in a device, a capacitor. He observed that a charge was built up on both sides between a piece of nonconducting material. In the case of the Leyden jar this was glass (nonconducting matter) and on each side of it was a metal material (conducting matter). These opposite metal layers had the exact opposite electric charges (positive and negative). He observed that when the wire on the inside of the jar was "electrised" positively by a certain amount, that the outer conductor simultaneously became "electrised" negatively in the same proportion.