Synthesis and electrical characterisation of different doped magnesium titanates

The synthesis and characterization are reported for the cubic spinel titanate Mg_(2−x)Ni_xTiO₄ (x≤0.25) and Mg_(2−x)Mn_xTiO₄ (x≤1). Single phase samples were observed for Mg_(2−x)Ni_xTiO₄ and with x≤0.4 for Mg_(2−x)Mn_xTiO₄. AC measurements were carried out on four different compositions (x=0.01, 0.03, 0.04 and 0.15) in the Mg_(2−x)Ni_xTiO₄ series and for Mg_1.9Mn_0.1TiO₄. For all these compounds, increasing conductivity with temperature and Arrhenius conductivity dependence are observed, the activation energy is around 0.28 eV for the Ni compounds and is 0.184 eV for Mg_1.9Mn_0.1TiO₄. The DC conductivity was recorded over a range of oxygen partial pressures (10⁻¹⁹ to 1 atm) at 930 °C. The Mg_(2−x)Ni_xTiO₄ compounds show a n-type behaviour whereas the Mg_(2−x)Mn_xTiO₄ show a p-type behaviour at high p(O₂) and n-type at low p(O₂). The stability under reduced conditions was checked and discussed for the different synthesized compounds. Paper presented at the 5th Euroconference onSolid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998.