A double Schottky barrier model suitable for the description of the grain boundary resistivity of n-conducting BaTiO3 ceramics has been modified by taking account of frozen-in diffusion profiles of cation vacancies at the grain boundaries which are formed during the cooling process after sintering. The space charge model has been extended in order to predict the electrical properties of PTC ceramics (positive temperature coefficient of resistivity) under voltage load for maximum dc-bias values around 03 - 0.5 V/grain boundary. The effect of the voltage drop across the Schottky barrier on the concentration profiles of electrons in the depletion zone as well as the space charge potential has been elaborated in detail. (C) 2013 Elsevier B.V. All rights reserved.