Nanostructured dielectric materials for high energy density multi layer ceramic capacitors
View Patent ↗A high energy density multilayer ceramic capacitor, having at least two electrode layers and at least one substantially dense polycrystalline dielectric layer positioned therebetween. The at polycrystalline dielectric layer has an average grain size of less than about 300 nanometers, a particle size distribution of between about 150 nanometers and about 3 micrometers, and a maximum porosity of about 1 percent. The dielectric layer is selected from the group including TiO 2 , BaTiO 3 , Al 2 O 3 , ZrO 2 , lead zirconium titanate, and combinations thereof and has a breakdown strength of at least about 1100 kV per centimeter.
1. A method for producing a polycrystalline ceramic material, comprising:
pressing a predetermined amount of substantially pure substantially fine precursor powder to yield a generally dense green body;
sintering the green body in an oxidizing atmosphere at sufficient firing temperature for sufficient soak time to yield a substantially densified sintered body; and
cooling the substantially densified body at a substantially slow rate of about 3° C./min;
wherein the substantially densified sintered body has a maximum porosity of less than about 1 percent; and
wherein the substantially densified sintered body has an average grain size of less than about 300 nm.
2. The method of claim 1 wherein the substantially densified sintered body has an average grain size of less than about 100 nm.
3. The method of claim 1 wherein the precursor powder is selected from the group including TiO 2 , BaTiO 3 , Al 2 O 3 , ZrO 2 , lead zirconium titanate, and combinations thereof.
4. The method of claim 1 wherein the substantially slow rate is no greater than 1 degrees Celsius per minute.
5. The method of claim 1 wherein the substantially densified sintered body has a maximum porosity of less than about 0.1 percent.
6. The method of claim 1 wherein the substantially densified sintered body has a maximum porosity of less than about 0.01 percent.
7. The method of claim 1 wherein the average grain size is between about 150 nanometers and about 3 micrometers in diameter.
8. The method of claim 1 wherein the firing temperature is between about 750 degrees Celsius and about 1200 degrees Celsius and wherein the soak time is between about 120 minutes and about 850 minutes.
9. The method of claim 1 wherein the firing temperature is about 750 degrees Celsius and wherein the soak time is about 850 minutes.
10. The method of claim 1 wherein the firing temperature is about 1200 degrees Celsius and wherein the soak time is about 120 minutes.
11. A method for producing a dielectric substrate, comprising:
pressing substantially pure substantially fine precursor powder to yield a dense green body;
sintering the green body in an oxidizing atmosphere to yield a densified sintered body; and
cooling the densified sintered body at a predetermined rate;
wherein the densified sintered body has a maximum porosity of less than about 1 percent; and
wherein the substantially densified sintered body has an average grain size of less than about 200 nm.
12. The method of claim 11 wherein the densified sintered body has an average grain size of less than about 150 nm.
13. The method of claim 11 wherein the precursor powder is selected from the group including TiO 2 , BaTiO 3 , Al 2 O 3 , ZrO 2 , lead zirconium titanate, and combinations thereof.
14. The method of claim 11 wherein the predetermined rate is no greater than 3 degrees Celsius per minute.
15. The method of claim 11 wherein the substantially slow rate is no greater than 1 degrees Celsius per minute.
16. The method of claim 11 wherein the densified sintered body has a maximum porosity of less than about 0.1 percent.
17. The method of claim 11 wherein the densified sintered body has a maximum porosity of less than about 0.01 percent.
18. The method of claim 11 wherein the average grain size is between about 150 nanometers and about 3 micrometers in diameter.
19. The method of claim 11 wherein the green body is sintered at a temperature between about 750 degrees Celsius and about 1200 degrees Celsius for a time between about 120 minutes and about 850 minutes.
20. The method of claim 19 wherein the temperature is about 750 degrees Celsius and wherein the time is about 850 minutes.
21. The method of claim 19 wherein the temperature is about 1200 degrees Celsius and wherein the time is about 120 minutes.
22. The method of claim 19 wherein the oxidizing atmosphere is oxygen.
23. A method for producing a dielectric substrate, comprising:
pressing a predetermined amount of substantially fine powder of predetermined composition to yield a green body;
sintering the green body in an oxidizing atmosphere at a firing temperature from about 750 degrees Celsius to about 1200 degrees Celsius for a time from about 120 minutes to about 850 minutes to yield a sintered body; and
cooling the sintered body at a rate not greater than 1 degree Celsius per minute;
wherein the substantially densified sintered body has a maximum porosity of less than about 0.1 percent; and
wherein the substantially densified sintered body has an average grain size of less than about 100 nm.
24. The method of claim 1 wherein the substantially slow cooling rate is about 1° C./min.