Oxonitrides of the formula LnTaOn.sub.2 with enhanced brightness and a process for their production and use

US5439660A · kind A · utility

Assignee

• Cerdec Aktiengesellschaft Keramische Farben · DE

Inventors

• Martin Jansen · Bonn, DE
• Hans-Peter Letschert · Bonn, DE
• Dietrich Speer · Hanau, DE

Key dates

• Filing date: Mar 16, 1994
• Grant date: Aug 8, 1995
• Expiry date: Mar 16, 2014

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01P2006/60
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

Oxonitrides with a perovskite of the general formula LnTaON.sub.2, where Ln is a rare-earth element, and which exhibit an enhanced brightness, are produced by annealing a powder mixture consisting of a Ta (V) compound and a Ln compound in a reducing atmosphere that contains ammonia. Added to the powder mixture being annealed is a mineralizing agent from the series of alkali metal or alkaline earth halides, Na.sub.3 AlF.sub.6, Na.sub.2 SiF.sub.6, AlF.sub.3 or of the ammonia salts of carbonic acid or a mono- or dicarboxylic acid with 1 to 4 C atoms in a quantity of 0.1 to 10 parts by weight, relative to 1 part by weight of the mixture of the Ta and Ln compounds. Such oxonitrides can be used as pigments that are yellow-orange to reddish brown in color.