Degussa Aktiengesellschaft

Degussa Akteingesellschaft

Gangolf Kriechbaum

Peter K Kleinschmit

Doris Peuckert

Hans Strack

Crystalline zirconium oxide powder with a BET surface of less than 30 m.sup.2 /g, preferably 10 to 20 m.sup.2 /g, a primary particle size of 0.1 to 0.5 .mu.m, a monoclinic crystal structure and, optionally, a content of Y.sub.2 O.sub.3 of 1 to 10% by weight and/or of 1 to 10% by wt. MgO. It is produced by adding an aqueous zirconium salt solution optionally containing yttrium ions and/or magnesium ions under agitation into a vessel which contains an aqueous base solution such as e.g. sodium hydroxide solution with a content of NaOH which corresponds to an excess of at least 0.5 mole/l NaOH. The mixture obtained in this manner is then treated hydrothermally at a temperature of 200.degree. to 400.degree. C., the product obtained is separated by filtration, washed chloride-free with water and dried at 100.degree. to 120.degree. C. The zirconium oxide powder can be used to produce sintered ceramics.

Zirconium oxide powder, process for its preparation and its use

Zirconium oxide powder, process for its preparation and use

Precipitated silica is mixed with a solution of caustic soda, water and sodium aluminate to form a mixture of the composition:

Process for the production of a seed mixture for the synthesis of

Crystalline zirconium oxide powder with a BET surface of less than 30 m.sup.2 /g, preferably 10 to 20 m.sup.2 /g, a primary particle size of 0.1 to 0.5 .mu.m, a monoclinic crystal structure and, optionally, a content of Y.sub.2 O.sub.3 of 1 to 10% by weight and/or of 1 to 10 % by wt. MgO. It is produced by adding an aqueous zirconium salt solution optionally containing yttrium ions and/or magnesium ions under agitation into a vessel which contains an aqueous base solution such as e.g. sodium hydroxide solution with a content of NaOH which corresponds to an excess of at least 0.5 mole/1 NaOH. The mixture obtained in this manner is then treated hydrothermally at a temperature of 200.degree. to 400.degree. C., the product obtained is separated by filtration, washed chloride-free with water and dried at 100.degree. to 200.degree. C. The zirconium oxide power can be used to produce sintered ceramics.

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Gangolf Kriechbaum