[en] The crystalline grain growth and the dielectric and the piezoelectric properties of Li- and Ta-modified (Na_0.05K_0.47Li_0.03)(Nb_0.8Ta_0.2)O₃ (NKLNT) ceramics were investigated for different sintering temperatures. The sintering temperature affected the grain growth, density, dielectric constant, and piezoelectric coefficient. The grain growth, density, dielectric constant, and piezoelectric coefficient were enhanced when the optimum sintering temperature T_s = 1080 °C was adopted. The sintering temperature impacts high performance because of a narrow temperature window in which the piezoelectric properties can be controlled. We investigated several aspects, including the optimum sintering, grain morphologies, dielectric behavior, and piezoelectric properties.