Title: Zirconium Silicate
CAS Registry Number: 10101-52-7
Additional Names: Zirconium orthosilicate
Molecular Formula: O4SiZr
Molecular Weight: 183.31
Percent Composition: O 34.91%, Si 15.32%, Zr 49.76%
Line Formula: ZrSiO4
Literature References: Occurs in nature as the mineral zircon. Widely scattered in all kinds of rocks and in beach sand (South Carolina, Northeast Florida). Usually separated from sand by electrostatic and electromagnetic elutriation, yielding 99% pure ZrSiO4. Prepn from SiO2 and ZrO2 in an arc furnace: Curtis, Sowman, J. Am. Ceram. Soc. 36, 195 (1953); can also be made from solns of zirconium salts and sodium silicate.
Properties: Tetragonal, bipyramidal crystals. Should be colorless. Colors are from impurities and radioactive bombardment, often removable by calcination. Dissociates to ZrO2 and SiO2 when heated above 1540°. Recombines when cooled slowly, but forms a mixture of monoclinic ZrO2 and vitreous SiO2 when rapidly quenched. Undissociated (a-form) ZrSiO4 has a high sp gr, 4.7, and a high birefringence; the dissociated, g-form has a lower sp gr, 3.9-4.0, and a low birefringence. Hardness of a-form about the same as that of quartz (6-7.5). Very inert chemically. Unaffected by aq reagents.
Use: In refractories, ceramics, glazes, cements, coatings for casting molds, polishing materials, gem stones, catalyst in alkyl and alkenyl hydrocarbon manuf, in fritted glass filters, as stabilizer in silicone rubbers. In Europe in cosmetic creams and powders. |