Relaxor-based ferroelectric single crystals Mn doped 0.72 Pb(Mg1/3Nb2/3)03-0.28PbTiO(3) (Mn-PMN-0.28PT) were grown by the modified Bridgman technique. The effects of nitrogen annealing on structural quality, defect and electrical properties of [111]-oriented Mn-PMN-0.28PT were systematically investigated. X-ray rocking curves (XRC) were used and the results indicated that the quality of single crystals could be significantly improved by appropriate annealing. X-ray photoelectron spectroscopy (XPS) was used to investigate the content and valence states of main elements in Mn-PMN-0.28PT, including oxygen vacancies. The conduction mechanisms at different temperature ranges were discussed. The dielectric loss of annealed samples decreased about 50% compared to the unannealed one, which should be attributed to the motion of domain walls pinned by defects. The pinning effect caused by oxygen vacancies on domain wall motion was enhanced through nitrogen annealing and the pyroelectric performances were optimized. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.