Structural and thermoelectric properties of hydrothermal-processed Ag-doped Fe2O3

Fe2-xAgxO3 (0 ≤ x ≤ 0.04) nanopowders with various Ag contents were synthesized at different hydrothermal reaction temperatures (150 °C and 180 °C). Their structural properties were fully investigated through an X-ray diffraction, a Fourier transform infrared spectroscopy, and an X-ray photoelectron spectroscopy. The hydrothermal reaction temperature, time, and Ag content remarkably affected the morphological characteristics and crystal structure of the synthesized powders. The Fe2-xAgxO3 (0 ≤ x ≤ 0.04) powders synthesized at 150 °C for 6 h and the Fe2-xAgxO3 (0.02 ≤ x ≤ 0.04) powders synthesized at 180 °C for 12 h formed the orthorhombic α-FeOOH phase with a rod-like morphology, whereas the Fe2-xAgxO3 (0 ≤ x ≤ 0.01) powders synthesized at 180 °C for 12 h formed the rhombohedral α-Fe2O3 phase with a spherical-like morphology. The Fe1.98Ag0.02O3 fabricated by utilizing Fe1.98Ag0.02O3 powders synthesized at 180 °C showed the largest power factor (0.64 ×10−5 Wm−1 K−2) and dimensionless figure-of-merit (0.0036) at 800 °C.