Brown spinel pigments based on zinc chromite, method of their production and use

US5254162A · kind A · utility

Assignee

• Degussa AG · DE

Inventors

• Dietrich Speer · Hanau, DE
• Akos Kiss · Alzenau, DE
• Jenny Horst · Gelnhausen, DE

Key dates

• Filing date: Sep 18, 1992
• Grant date: Oct 19, 1993
• Expiry date: Sep 18, 2012

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01P2002/32
• WIPO field: Basic materials chemistry
• WIPO sector: Chemistry

Abstract

Brown spinel pigments based on zinc chromite which are iron-free and exhibit an atomic ratio of chromium to zinc in a range of 1 to greater than 0.5 up to 2 are disclosed. Preferred pigments additionally contain manganese, in which instance the atomic ratio of Mn to Cr is a maximum of 0.2. The production of the pigments involves a firing process of a powder mixture consisting of the oxides the metals, or precursors thereof, contained in the pigment. Instead of previously known grayish-brown unattractive products, attractive brown pigments are obtained by means of the selected molar ratio and a baking temperature above 1200.degree. C. The novel pigments can be used in the presence of glass frits even at firing temperatures above 1200.degree. C. to 1500.degree. C. and are suitable for a common firing of ceramic carrier and decoration.