Previously we have shown by simulations that I-V curve hysteresis and crossing can be obtained in devices based on mixed-ionic-electronic-conductors, with mobile donors and conduction electrons (or acceptors and holes), under an asymmetry in the device or in the applied voltage. We here investigate the role of the applied signal frequency and amplitude, ion mobility and the length of device on the crossing of the I-V curve. The results show that the I-V curve crossing is obtained in asymmetrical devices under certain conditions only. This result may be of importance for the design of memristive devices based on non-stoichiometric materials with mobile ionic defects. The I-V curve crossing does not occur at the origin, I = 0 and V = 0. (C) 2013 Elsevier B.V. All rights reserved.