In this study, the effects of a sintering aid CuTa2O6 (CT) on (Na0.5K0.5)NbO3 (NKN) ceramics were investigated. The diffracted angles in XRD profiles decreased because the Nb-sites were replaced by Cu and Ta ions, causing the expansion of lattice volume. SEM images showed smaller grain sizes at a low concentration of CuTa2O6, and grain sizes increased as the concentration of CuTa2O6 doping increased because of a liquid phase formed. When CuTa2O6 dopants were doped into NKN ceramics, the TO-T and T-c phase transitions decreased because the replacement of Ta5+ ions in the B-site. A high bulk density (4.595 g/cm(3)) and electromechanical coupling factor (k(p), k(r)) were enhanced when CT dopants were doped into NKN ceramics. Moreover, the mechanical quality factor (Q(m)) also increased from 67 to 1550. NKN ceramics with sintering aid CuTa2O6 doping showed excellent piezoelectric properties: k(p): 42.5%; k(r): 49.1%; Q(m): 1550; and d(33): 96 pC/N. (C) 2012 Elsevier Ltd. All rights reserved.