The crystal chemistry and electrical properties of Fe doped Ca₁₂Al₁₄O₃₃ (Mayenite)

Abstract

X-ray and neutron powder diffraction have been used to study the crystal chemistry of Fe doped mayenite (Ca₁₂Al_14-xFe_xO₃₃). Solid- state synthesis was used to prepare Ca₁₂Al_14-xFe_xO₃₃ where x = 0, 0.1, 0.2, 0.5 and 0.6 and the citrate gel route was used to prepare Ca₁₂Al_14-xFe_xO₃₃ where x = 0, 0.05, 0.1, 0.2, 0.3 and 0.4. X-ray powder diffraction data indicate that samples with the same composition but synthesized by the citrate gel route were more likely to be phase pure than samples obtained by traditional solid-state synthesis. The refined lattice parameters were observed to increase with increasing Fe concentration, irrespective of the synthesis method. Refined neutron powder data confirm that Fe is going into Al site rather than Ca site. A 2-point probe was used to measure the electrical properties of the Fe doped citrate gel synthesized samples and showed that the resistivity increases for the Fe doped samples compared to the undoped mayenite.