Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Patent
1995-12-28
1997-10-14
Ledynh, Bot L.
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
3613211, 3613215, 361322, H01G 406
Patent
active
056778252
ABSTRACT:
An improved ferroelectric capacitor exhibiting reduced imprint effects in comparison to prior art capacitors. A capacitor according to the present invention includes top and bottom electrodes and a ferroelectric layer sandwiched between the top and bottom electrodes, the ferroelectric layer comprising a perovskite structure of the chemical composition ABO.sub.3 wherein the B-site comprises first and second elements and a dopant element that has an oxidation state greater than +4. The concentration of the dopant is sufficient to reduce shifts in the coercive voltage of the capacitor with time. In the preferred embodiment of the present invention, the ferroelectric element comprises Pb in the A-site, and the first and second elements are Zr and Ti, respectively. The preferred dopant is chosen from the group consisting of Niobium, Tantalum, and Tungsten. In the preferred embodiment of the present invention, the dopant occupies between 1 and 8% of the B-sites.
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Dimos Duane B.
Evans, Jr. Joseph T.
Pike Gordon E.
Tuttle Bruce A.
Warren William L.
Ledynh Bot L.
Ward Calvin B.
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