The conduction mechanism of lithium-germanium ferrites

The de conductivity of the spinel structure compositions Li0.5+0.5xGexFe2.5-1.5xO4, where x = 0, 0.2, 0.3, 0.5, is studied. This study shows the existence of two transition points. The first one is due to the Curie temperature T-C which is 795, 508, 480, and 448 K for x = 0, 0.2, 0.3, and 0.5, respectively. The second point is related to the order-disorder transition T-D which is 1012, 615, 595 K for x = 0, 0.2, 0.3, respectively. The latter point T-D disappears for x = 0.5. The conduction mechanism is discussed through the two-band model for x = O and through the spin polaron model for the other samples. It is found that the increase of the Ge4+ ion concentration leads to a decrease in both T-C and T-D.