The de conductivity of the spinel structure compositions Li0.5+0.5xGex
Fe2.5-1.5xO4, 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 C
urie 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 conduc
tion mechanism is discussed through the two-band model for x = O and t
hrough 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.