Fe and Cr K-edges EXAFS Study of Double Perovskite (Sr2-xCax)FeMoO6(0 ≤ x ≤ 2.0) and Sr2CrMO6(M = Mo, W) Systems

The local structure of the double perovskite (Sr2-xCax)FeMoO6 (0 ≤ × ≤ 2.0) and Sr2CrMO6 (M = Mo, W) systems have been probed by extended X-ray absorption fine structure (EXAFS) spectroscopy at the Fe and Cr K-edges. We found Fe-O (ave) distance apparently decreases from 1.999 Å (x = 0) to 1.991 Å (x = 1.0) in (Sr2-xCax)FeMoO6 (tetragonal structure). When x is increased further from 1.5 to 2.0, the Fe-O bond distance decreased from 2.034 Å to 2.012 Å (monoclinic structure). In addition, Cr-O, Sr-Cr, and Cr-Mo bond distances in Sr2CrWO6 are all slightly larger than the bond distances of Sr2CrMoO6, which is due to the ionic radius of the W5+ (0.62 Å) which is larger than the ionic radius of Mo5+ (0.61 Å). The results are consistent with our XRD refinements data.