Pigments for producing purple-coloured ceramic decorations, process for producing them and their use

摘要

A pigment for producing crimson coloured ceramic decor fired at high temperature comprises the following components: (A) fine particulate carrier material(s) which is fireable, preferably a glass frit; (B) hydrated oxide(s) of aluminium, silicon, tin, lead, titanium, zirconium, niobium, tantalum, scandium, yttrium, lanthanum, cerium or zinc; and (C) water insoluble gold (I) or (III) compound(s), or colloidal gold. The weight ratio of (A) to (B), calculated as an oxide, is 10:0.1. The pigment contains 0.05-10 wt.% (C). The pigment is prepared by co-precipitation of (B) and (C) in the presence of (A) in an aqueous(-organic) phase and in the presence of a reducing agent for (C), using a solution containing soluble gold compound(s) or colloidal gold, soluble compound(s) containing the metal for (B) and precipitating agent(s). Water insoluble gold compounds in the co-precipitate can be converted into colloidal gold by carrying out a r eduction reaction by using a standard reducing agent or by carrying out thermal degradation at 100-300 degrees C. Also claimed is the preparation of a pigment by this method.