Mixed-conducting BiVO4-5, 7, 10, 12 wt % V2O5 liquid-channel grain-boundary structures were studied with respect to their electrochemical properties. The electrical conductivity and oxygen-ion transference number, measured by the four-probe dc and volumetric measurements of the faradaic efficiency techniques in the temperature range of 640-660 degrees C, vary from 5x10(-3) to 3x10(-2) Omega(-1) cm(-1) and from 0.68 to 0.85, respectively. The apparent conductivity activation energy decreases from 0.86 to 0.56 eV with increasing content of V2O5. (c) 2008 The Electrochemical Society. [DOI: 10.1149/1.2990701] All rights reserved.