Process for forming sintered ceramic bodies having improved properties

Patent metadata

Field	Value
Publication number	US-11148979-B2
Application number	US-201816176768-A
Country	US
Kind code	B2
Filing date	Oct 31, 2018
Priority date	Oct 31, 2017
Publication date	Oct 19, 2021
Grant date	Oct 19, 2021

Abstract

A method is provided for making ceramic bodies having improved properties, such as optical and/or strength properties in which the ceramic bodies are densified by new sintering processes. The sintering profiles may have shorter run times than conventional sintering processes. Ceramic bodies made by these methods are suitable for use in dental applications, for example, as crowns.

First claim

We claim:

1. A method for forming a sintered ceramic body comprising
heating a bisque stage ceramic body in a heating chamber of a sintering oven, comprising
i. in a first heating stage, heating the sintering oven containing the bisque stage ceramic body to a first temperature that is from 1300° C. to 1700° C. for an optional first dwell time between 0 minutes and 10 minutes, and lowering the first temperature at least 25° C. to a second temperature;
ii. in a second heating stage wherein the second temperature is from 1000° C. to 1500° C., holding the second temperature for a second dwell time of at least 2 minutes; and
iii. in a third heating stage, increasing the second temperature at least 25° C. to a third temperature from 1400° C. to 1700° C. for an optional third dwell time between 0 minutes and 20 minutes before cooling in a cooling stage.

2. The method of claim 1 , wherein heating to the first temperature comprises a ramp rate of 0.5° C./minute to 60° C./minutes.

3. The method of claim 1 , comprising a preliminary heating stage that precedes the first heating stage, having a preliminary heating temperature that is from 1000° C. to 1350° C., and that is lower than the first temperature.

4. The method of claim 1 , comprising a ramp rate of 1° C./minute and 60° C./minutes from the second temperature and the third temperature.

5. The method of claim 1 , wherein the second dwell time is from 2 minutes to 120 minutes.

6. The method of claim 1 , wherein the first and third temperatures are 50° C. to 450° C. higher than the second temperature.

7. The method of claim 1 , wherein the first temperature is lower than the third temperature by 0° C. to 400° C.

8. The method of claim 1 , wherein
i. the first temperature is from 1350° C. to 1550° C.,
ii. the second temperature is from 1000° C. to 1400° C., and
iii. the third temperature is from 1500° C. to 1650° C.

9. The method of claim 1 , wherein
i. the first temperature is from 1350° C. to 1550° C. and the first dwell time is from 0 minutes to 5 minutes,
ii. the second temperature is from 1150° C. to 1250° C. and the second dwell time is from 60 minutes to 120 minutes, and
iii. the third temperature is from 1530° C. to 1650° C. and the third dwell time is from 0 minutes to 15 minutes.

10. The method of claim 1 , wherein the heating program is less than 3 hours between starting the first heating stage and completing a final dwell time of a final heating stage.

11. The method of claim 1 , wherein the ceramic body comprises yttria-stabilized zirconia stabilized comprising from 2 mol % to 8 mol % yttria.

Assignees

• Glidewell James R Dental Ceramics Inc

Inventors

• Balasubramanian Sreeram
• Yang Yan
• Akash

Classifications

• B28B11/243 Primary

  Setting, e.g. drying, dehydrating or firing ceramic articles (B28B11/242 takes precedence) · CPC title

• A61C13/0022

  Blanks or green, unfinished dental restoration parts · CPC title

• C04B2235/608

  Green bodies or pre-forms with well-defined density · CPC title

• C04B2235/6027

  Slip casting · CPC title

• C04B2235/96

  Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance · CPC title