Sn2-2xSbxFexO4 solid solutions as possible inert anode materials in aluminum electrolysis

Single-phase samples of the Sn2-2xSbxFexO4 solid solution were prepared by solid-state reaction in air at 1300 °C for 0.26 ≤ x ≤ 0.66. The crystal structure of the Sn2-2xSbxFexO4 phases was studied by electron diffraction and X-ray powder diffraction. The compounds crystallize with the rutile type structure with a disordered arrangement of cations (P42/mnm space group, a = 4.7127(6) A, c = 3.1595(4) A, RI = 0.020, RP = 0.019 for Sn1.48Sb0.26Fe0.26O4 and a = 4.6682(8) A, c = 3.1147(6) A, RI = 0.030, RP = 0.022 for Sn0.68Sb0.66Fe0.66O4). The valence state of cations in the Sn1.48Sb0.26Fe0.26O4 and Sn0.68Sb0.66Fe0.66O4 samples was determined by means of 119Sn, 121Sb, and 57Fe Mossbauer spectroscopy. The presence of Sn(II), Sb(III), or Fe(II) low valent state species was not detected in the samples. Resistivity vs temperature measurements revealed a semiconducting behavior from room temperature up to 900 °C with about four orders in magnitude decrease of the resistivity. Solubility tests in the cryolite-alumi...