Field-assisted sintering exposes samples in a graphite die to reducing conditions. Using TiO2 as a test case, this work shows that internal redox equlibria in the sample, rather than the graphite-CO-O-2 equilibrium, appear to control the oxygen fugacity. Samples sintered at 1160 degrees C for 20 min are homogeneous in oxygen content and have an average composition of TiO1.983 +/- 0.001. The oxygen fugacity during these sintering experiments is calculated to be about 10(-16) atm, which is higher than the value obtained from thermodynamic equilibrium of graphite-CO-O-2 at the given temperature. The oxygen fugacity is similar to that for the quasi-two-phase region, or hysteresis loop, representing the coexistence of reduced rutile with random crystallographic shear (CS) planes and the first ordered CS phase.