Capacitor dielectric with inner blocking layers and method for producing the same

• US 4,131,903 A
• Filed: 07/14/1977
• Issued: 12/26/1978
• Est. Priority Date: 08/03/1976
• Status: Expired due to Term

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Schmelz, Helmut, Schwaen, Werner
• Primary Examiner(s): Edlow, Martin H.
• Application Number:
  US05/815,579
• Time in Patent Office: 530 Days
• Field of Search: 357/10, 357/61, 252/62.3 BT, 252/63.5
• US Class Current: 257/43
• CPC Class Codes: H01G 4/1281 with grain boundary layer

Abstract

A capacitor dielectric with inner blocking layers is disclosed wherein the portion of copper located in intermediate layers between the crystallites is enriched toward the crystallite surfaces. The dielectric is produced by a heating speed of 200 to 800° C/h towards a sinter temperature, and a cooling-off speed of 10 to 100° C/h to about 350° C below the sinter temperature.

Claims

1. A capacitor dielectric with inner blocking layers, comprising:

(a) a polycrystalline ceramic body made of a material with a perovskite structure on the basis of barium titanate having the general formula ##EQU2## with M^II selected from the group Ca, Sr, Pb and Mg and M^IV = Zr, Sn, with z assuming the values 1.005 to 1.05;

(b) said dielectric containing at least two different doping substances of which one selected from the group antimony, niobium, lanthanum and bismuth is inside crystallites of the crystalline body and causes predominantly n-type conduction, and the other selected from the group copper, cobalt, nickel, iron and manganese in the surface layer of the crystallites causes predominantly p-type conduction, the proportion of the doping substance causing the n-type condution being 1.5 to 2.5 times greater than a maximum doping amount (maximum solid state solubility) and the proportion of the substance causing the p-type conduction amounting to 0.01 to 0.15% by weight;

(c) a titanate intermediate phase disposed between grains of the crystallites which is rich in titanium dioxide and is at least partially recrystallized and contains the doping substance causing p-type conduction spread inhomogeneously such that this p-type doping substance is highly enriched towards the crystallite grain surfaces.

2. A capacitor dielectric as in claim 1, characterized in that the dielectric comprises BaO.1.025 (Ti₀.85 Sn₀.15)O₂ with 0.2% by weight of Sb₂ O₃ and 0.0535% by weight of CuO.

3. A capacitor dielectric as in claim 1, characterized in that the dielectric comprises BaO.1.03 TiO₂ with 0.15% by weight of Sb₂ O₃ and 0.04% by weight of CuO.