Determination of Cation Distribution in ZnFe2O4, NiFe2O4 and NiAl2O4 Spinels by An In-house Anomalous X-ray Scattering Method.

Abstract

An in-house anomalous X-ray scatterig (AXS) method has been done for determiningcation distribution in ZnFe2O4, NiFe2O4 and NiAl2O4 spinels using the anomalous dispersion effect near the K absorption edges of Zn and Ni. When introduced the ratio (x) of the number of divalent cations of M element, MA, residing in the tetrahedral A-site to the total number of M element, x=MA/Mtotal, the measured intensity ratios of three reflection peaks with two energies close to the K edge of Zn or Ni can be quantitatively explained only by assigning the case where ZnFe2O4 is the normal type (x=1.0) and NiFe2O4 is the inverse type (x=0.0) spinel structure. On the other hand, the results for NiAl2O4 suggests that 15% of Ni2+ cations occupy the tetrahedral A-site (x=0.15) and the rest are octahedrally coordinated. The usefulness of the in-house AXS method is rather surprisingly well-recognized, particularly for obtaining the cation distribution in crystalline materials containing two elements of nearly the same atomic number.