Abstract
Structure analysis using X-ray and neutron powder diffraction and elemental mapping has been used to demonstrate that nominal A-site deficient Sr(2-x)FeMoO(6-δ) (0 ≤x≤ 0.5) compositions form as Mo-rich Sr(2)Fe(1-y)Mo(1+y)O(6) (0 ≤y≤ 0.2) perovskites at high temperatures and under reducing atmospheres. These materials show a gradual transition from the Fe and Mo rock salt ordered double perovskite structure to a B-site disordered arrangement. Analysis of the fractions of B-O-B' linkages revealed a gradual increase in the number of Mo-O-Mo linkages at the expense of the ferrimagnetic (FIM) Fe-O-Mo linkages that dominate the y = 0 material. All samples contain about 10-15% antiferromagnetic (AF) Fe-O-Fe linkages, independent of the degree of B-site ordering. The magnetic susceptibility of the y = 0.2 sample is characteristic of a small domain ferrimagnet (T(c)∼ 250 K), while room temperature neutron powder diffraction demonstrated the presence of G-type AF ordering linked to the Fe-O-Fe linkages (m(Fe) = 1.25(7)μ(B)). The high temperature thermoelectric properties are characteristic of a metal with a linear temperature dependence of the Seebeck coefficient, S (for all y) and electrical resistivity ρ (y≥ 0.1). The largest thermoelectric power factor S(2)/ρ = 0.12 mW m(-1) K(-1) is observed for Sr(2)FeMoO(6) at 1000 K.
Highlights
Thermoelectric modules are widely considered as an important component for a sustainable energy future.[1,2] Traditionally these devices use p- and n-type semiconductors such as Bi2Te3, PbTe and Si1−xGex to convert heat into electricity
The energy dispersive X-ray (EDX) measurements were performed on three random spots of ca. 8 × 9 μm for each sample, and the average values of the atomic ratios were used in the composition calculations
Elemental and structure analysis demonstrates that the nominal A-site deficient Sr2−xFeMoO6−δ compositions form a series of Mo-rich non-A-site deficient Sr2Fe1−yMo1+yO6 perovskites under high-temperature (1350–1400 °C) and reducing conditions (5% H2 in N2)
Summary
Thermoelectric modules are widely considered as an important component for a sustainable energy future.[1,2] Traditionally these devices use p- and n-type semiconductors such as Bi2Te3, PbTe and Si1−xGex to convert heat into electricity. The observation of Fe-flakes on the surface of some of the pellets and in the diffraction patterns (see below) strongly suggested that the composition of our perovskite samples had changed during high-temperature reaction under 5% H2/N2 atmosphere.
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