Chromium(IV) oxide
chemical compound
Chromium dioxide or chromium(IV) oxide is an inorganic compound with the formula CrO2. It is a black, synthetic, magnetic solid. It once was widely used in magnetic tape emulsion. With the increase in popularity of CDs and DVDs and more recently digital media, the use of chromium(IV) oxide has declined. However, it is still used in data tape applications for enterprise-class storage systems. It is still considered by many oxide and tape manufacturers to have been one of the best magnetic recording particulates ever invented.
Preparation and basic properties
CrO2 was first prepared by Friedrich Wöhler by decomposition of chromyl chloride. Acicular chromium dioxide was first synthesized in 1956 by Norman L. Cox, a chemist at E.I. DuPont, by decomposing chromium trioxide in the presence of water at a temperature of 800 K (527 °C; 980 °F) and a pressure of 200 MPa. The balanced equation for the hydrothermal synthesis is:
3 CrO3 + Cr2O3 → 5 CrO2 + O2
The magnetic crystal that forms is a long, slender glass-like rod – useful as a magnetic pigment for recording tape. When commercialized in the late 1960s as a recording medium, DuPont assigned it the trade name of Magtrieve.
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