The crystal growth process of YBCO superconductive oxide under an external electric field has been investigated by means of in situ observations and differential thermal analysis. The effects of an external electric field on the growth processes via the peritectic reaction of 123 (YBa2Cu3O7-x) crystals from liquid +211 (Y2BaCuO5). including (1) dissolution of the 211 phase into solution, (2) transportation process of the solute, Y (Y2O3), in the liquid, and (3) kinetic attachment of the solute to the growth front, were analyzed in detail based on the coupling equation. An external electric field of 600 V/cm resulted in the generation of an electric double layer either at the interface between the solution and the ambient atmosphere or at the interface of the solution and the 211 grains; however, almost no electric field could be generated in the bulk liquid due to it being electrically conductive. The external electric field enhanced dissolution of the 211 gains slightly, but had almost no effective electric field operated on the transportation process of the solute, and little effect was observed on the attachment kinetics. On the other hand, the external electric field increased the Gibbs energy for the nucleation of the 123 grains, which retarded the nucleation of the 123 grains. (c) 2007 Elsevier B.V. All rights reserved.