Since they were first synthesized, the efforts devoted to the development of zircon pigments have been intense and continuous because the strong crystal lattice of zircon – ZrSiО4 is exceptionally favorable for the development of new colors.
Pure zircon is colorless. It can be found in nature (e.g. in the sands of the eastern coast of Australia) and it is the main source for preparation of zirconium compounds, mainly ZrО2. The zircon crystal lattice – acceptor incorporates the coloring ion at the expense of the defects to become colored zircon where the chromophore ion is protected by the strong lattice.
Zircon pigments are synthesized by heating a mixture of ZrО2, SiО2, chromophore ion and mineralizer. The mineralizers play an important role in the decreasing of the temperature of the process. Actually, the synthesis is carried out at 800-980°С while pure zircon is synthesized at 1600°С.
Beside the well known zircon pigments with vanadium, iron, praseodymium, attemts have been made to prepare pigments containing other elements like chromium, manganese, copper, etc..
A number of researchers focused their efforts on the mechanism of the formation of zircon pigments, the role of the mineralizers, as well as the possibility to use various raw materials in the process. The selenites of the rare earth elements turned out to be quite suitable for synthesis of zircon pigments.
The first zircon pigment synthesized was blue and contained vanadium. It was obtained by Seabright in 1948. In 1952, yellow colored praseodymium doped zircon pigments were developed in Japan. Seabright synthesized pink zircon pigments containing iron in 1960. During the second half of XX century, the interest towards this type os pigments increased and as a result a broad color palette of zircon pigments were created, their intensity was increased, the technology was improved, new mineralizers were found and new sources of raw materials were developed.
The blue zircon pigments are syntehsized by doping with vanadium in oxidizing medium. The V4+ ions are introduced in the crystal lattice of zircon with the process being facilitated by mineralizers.
The idea of our research is to obtain zircon pigments containing some d- and f- elements, as well as by their introduction in the lattice through their selenites.
1. Technology of Ceramic Products and Materials, ISBN: 9549841154, Publisher: Saraswati, 2003, edited by Prof. Bachvarov