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Growth of Cr2O3 crystals by the decomposition of a K2Cr2O7 melt

1979; Elsevier BV; Volume: 46; Issue: 3 Linguagem: Inglês

10.1016/0022-0248(79)90090-3

1873-5002

T. Sekiya, Hiroshi Okuda,

X-ray Diffraction in Crystallography

Potassium dichromate (K2Cr2O7) melts congruently at 400°C and decomposes to form Cr2O3 crystals at 780°C or higher by the following reaction: K2Cr2O7(1) = K2CrO4(1) + 0.5 Cr2O3(s) + 0.75 O2(g). In this decomposition reaction, the precipitated Cr2O3 crystals in the melt are gradually grown with increase of heating time, but the decomposition rate is too rapid to grow the crystals of good quality. The decomposition rate can be slowed by adding K2CrO4 to K2Cr2O7, and thus crystals of larger size and higher quality can be obtained. Most of the grown crystals take the shape of plates with the basal plane c(0001) and the side faces n (224¯3) and r (101¯1).