The effect of the preparation method and grain morphology on the physical properties of A2FeMoO6 (A = Sr, Ba)

The effect of the preparation route and the grain morphology on the physical properties of A(2)FeMoO(6) (AFMO) has been studied. Samples were prepared by solid-state reaction using the usual method but with an intermediate step in air at high temperature. Unlike previous work, we find that there is no sample degradation even after 75 days. Scanning electron microscope measurements show that the double perovskites can be formed with various grain morphologies. The electrical resistance varies by four orders of magnitude but there is no significant change in the thermoelectric power. The saturation magnetization (3.5 mu(B)/formula unit) and (101) XRD peak intensity are identical which show that there is no difference in the Fe/Mo anti-site disorder. The results imply that the charge transport is limited by electron tunnelling between the grains and therefore directly related to the grain morphology. (c) 2005 Elsevier B.V. All rights reserved.