A series of solid solutions have been prepared by co-crystallization of Al(acac)3 and Cr(acac)3 and studied by X-ray diffraction. The end members and seven isotopic members of the series Al1 - xCrx(acac)3, with x varying from 0.02 to 0.91, crystallize in the monoclinic space group P21/c with Z = 4. The unit cell parameters vary slightly with composition, and fall into the following ranges: a, 13.987-14.009; b, 7.534-7.553; c, 16.308-16.348 Å; β, 98.78-98.99°. The cell axes do not vary in a linear manner with the mole% Cr. The Al : Cr molar ratio in each crystal studied by X-ray diffraction was determined by wavelength dispersive spectroscopy (WDS) and compared with the refinement of the Al : Cr site occupancy, which was attempted by the following methods: (1) refinement based upon bulk sample analysis, (2) refinement of occupancy with common displacement parameters, (3) refinement of occupancy and displacement parameters, and (4) construction of a mixed atom type based on the results of all three methods. Results from methods 2 and 3 were found to agree with WDS data within experimental error for all crystals studied. Method 1 was the least successful, the refinement often being significantly problematic. A discussion of suitable methods for refinement of partial site occupancy in solid solutions for isomorphous structures is presented. The variance of crystal lattice parameters and the M-O and O-M-O structural parameters with Al : Cr ratio is investigated.
|Number of pages||5|
|Journal||Journal of the Chemical Society, Dalton Transactions|
|State||Published - 2001|