We propose to represent or document all the isothermal and nonisothermal mass/charge transport properties of mixed ionic electronic conductor compounds in terms of a simple Onsager transport coefficient matrix. To this end, the general equations of motion for mobile ions and electrons are formulated, complying with the irreversible thermodynamic rules, in terms of experimentally operable forces, and the measurement principles of the Onsager matrix are introduced on the basis of the chemical polarization in isothermal semi-blocking and nonisothermal complete-blocking conditions. (C) 2013 Elsevier B.V. All rights reserved.