SYNTHESIS OF A ZIRCON-CADMIUM SULPHO SELENIDE PIGMENT BY A SOL-GEL TECHNIQUE

The preparation of fire red cadmium sulpho-selenide pigments based on zircon via solid-state reactions encountered some difficulties. Undesirable reactivity and inadequate homogeneity of components were two important problems, which counteracted complete covering of colouring agents by zircon and hence stable production of these materials. By using a sol-gel method, the above-mentioned problem can be eliminated and a desirable colour shade can be obtained. In the sol-gel process, at first a precipitant was prepared by mixing Se (dissolved in sodium sulphide solution) and a cadmium sulphate-zirconium acetate solution. Gelation occurred by adding a diluted sodium silicate solution into the washed and dried precipitate. A lithium fluoride mineraliser was added to the washed/dried gel. Calcination of the latter compound was carried out at about 950 C. The experiments showed that the relative volume of zircon to cadmium sulpho-selenide had an important role on a complete encapsulation of colorants and so on the quality of the pigment. According to the experiment, the optimum relative volume of colorant agent to zircon was determined to be about 40/60. 15 refs.