Lead-free (Na0.52K0.48−x)(Nb1−xySby)O3-xLiTaO3 (NKNS–LT) piezoelectric ceramics have been fabricated by ordinary sintering. A special attention was paid to the composition design through which the dielectric and piezoelectric properties of the (Li, Ta, Sb) modified NKN systems were significantly promoted. A property spectrum was generated with a particular discussion on the relationship between the Sb content, the LT content, the polymorphic phase transition, and the electrical properties and their temperature stability. Excellent and tunable electrical properties of d33=242–400 pC/N, kp=36%–54%, inline image, and Tc=230°–430°C demonstrate a tremendous potential of the compositions studied for device applications.