Synthesis, electrical properties and thermal analysis of transition metal-doped Mg2TiO4 spinels
The synthesis and characterization of Mg 2 TiO 4 doped with different transition elements (Mn, Fe, Co) are reported. Three different series of cubic spinel titanate are obtained by substitution of only one cation (Mg 2 x M x TiO 4 , Mg 2 Ti 1 x M x O 4 ) or both cations (Mg 2 t/2 Ti 1 x/2 M x O 4 ) for x = 0.1 and their electrical properties have been compared. AC conductivity data have been measured in air between 500 and 1000°C, showing for all the samples an Arrhenius dependence. Activation energy and conductivity are similar to Mg 2 TiO 4 (E a = 0.28 eV, σ ∼ 10 -3 S m 1 ) for M = Fe, Co, although conductivity is slightly higher for M = Mn. The DC conductivity was recorded over a wide range of oxygen partial pressures (10 19 to 1 atm.) at 930°C. The Co and Fe compounds show a n-type behaviour whereas the Mn compounds show a pseudo p-type behaviour at high Po 2 and n-type at low Po 2 . Conductivity at very low Po 2 is in the region 10 1 -10 -1 S m ' for all the samples investigated.