The Formation of Cr-Al Spinel under a Reductive Atmosphere

In the present work, for the first time, the possibility of formation of CrAl(2)O(4) was shown from the equimolar mixture of co-precipitated Al(2)O(3) and Cr(2)O(3) oxides under a reductive environment. The crystallographic properties of the formed compound were calculated using the DICVOL procedure. It was determined that it has a cubic crystal structure with space group Fd-3m and a unit cell parameter equal to 8.22(3) Å. The formed CrAl(2)O(4) is not stable under ambient conditions and easily undergoes oxidation to α-Al(2)O(3) and α-Cr(2)O(3). The overall sequence of the phase transformations of co-precipitated oxides leading to the formation of spinel structure is proposed.