Electric conductivity of Fe2SiO4-Fe3O4 spinel solid solutions

The spinel solid solution was found to exist in the whole range between Fe3 O4 and gamma -Fe2SiO4 at over 10 GPa. The resistivity of Fe3-xSixO4 (0.0 < x < 0.288) was measured in the temperature range of 80 similar to 300 K by the AC impedance method, Electron hopping between Fe3+ and Fe2+ in the octa hedral site of iron-rich phases gives a large electric conductivity at room temperature. The activation energy of the electron hopping becomes larger with increasing gamma -Fe2SiO4 component. A nonlinear change in electric co nductivity is not simply caused by the statistical probability of Fe3+-Fe2 electron hopping with increasing the total Si content. This is probably be cause a large number of Si4+ ions occupies the octahedral site and the adja cent Fe2+ keeping the local electric neutrality around Si4+ makes a cluster , which generates a local deformation by Si substitution. The temperature dependence of the conductivity of solid solutions indicates the Verwey transition temperature, which decreases from 124(+/-2) K at x = 0 (Fe3O4) to 102(+/-5) K at x = 0.288, and the electric conductivity gap a t the transition temperature decreases with Si4+ substitution.