Measurements of electrical resistivity versus temperature are reported for single-crystal specimens of the ${\mathrm{Fe}}_{3\mathrm{-}\mathit{y}}$${\mathrm{Ti}}_{\mathit{y}}$${\mathrm{O}}_4$ system in the composition range 0<y<0.9 and are compared to similar studies on ${\mathrm{Fe}}_{3\mathrm{-}\mathit{x}}$${\mathrm{Zn}}_{\mathit{x}}$${\mathrm{O}}_4$. These resistivity data are fitted to an Arrhenius law; various trends are briefly described. For y≥0.2, beyond which ${\mathrm{Fe}}^{2+}$ ions are increasingly present on tetrahedral interstices, the variation of the preexponential factor with y can be described on the basis of a small polaron model, assuming that the octahedral sites occupied by ${\mathrm{Ti}}^{4+}$ ions are not accessible to charge carriers. For y<0.2 this model fails; a possible explanation is offered in terms of changes in lattice properties in the concentration range where only ${\mathrm{Fe}}^{3+}$ ions are present on tetrahedral interstices.

• Received 20 November 1992

DOI:https://doi.org/10.1103/PhysRevB.48.2057