Transition and transport behavior in spinel oxide MgTi2O4 and its La-doped counterparts

• La doped MgTi2O4 was synthesized by spark plasma sintering.
• Metal behavior above Tt and a dual conducting mechanism behavior below Tt.
• The lowering of dimerization extent of Ti3+ in MgTi2O4 due to La doping.

Spinel oxides Mg1−xLaxTi2O4 (x = 0, 0.005, 0.01, and 0.015) were synthesized by spark plasma sintering. The temperature dependences of resistances were measured and investigated in details. It shows that the transition of MgTi2O4 occurs at Tt ∼258 K, while the transition is weakening, and the transition temperature Tt decreases with La3+ doping. The fit of resistances versus temperature curves demonstrate that Mg1−x LaxTi2O4 displays metal behavior above Tt, while a dual conducting mechanism, the Mott-insulator like variable range hopping (VRH) and normal activated conduction, should be responsible for the transport behavior of Mg1−x LaxTi2O4 below Tt.