<p>Environmental concerns about the effects of the continued use of Pb-based ferroelectric single crystals are encouraging research on alternative lead-free compositions. Among the lead-free materials, (K, Na)NbO₃-based ferroelectric single crystals are one of the most promising candidates for the substitution of Pb-based ones. In this work, it was investigated the structural, chemical, and dielectric properties of lead-free Li, Ta, and Sb-modified (K, Na)NbO₃ (KNN–LTS) single crystals grown by vertical Bridgman–Stockbarger method. The polycrystalline X-ray diffraction characterization of the crushed KNN–LTS crystals showed a single perovskite phase of the as-grown KNN-LTS boule, thus revealing the success of the growing process. The compositional segregation observed in the crystals was similar to that reported in the literature. The temperature and frequency dependence of the dielectric permittivity were characterized for the [100]_c, [001]_c, and [111]_c crystallographic directions. The results revealed that the domain configuration related to the different measured crystallographic directions played an important role in the dielectric permittivity from room temperature to near the T_O–T transition. Higher dielectric permittivity was observed for the [001]_c and [100]_c directions, due to the contribution of 60° and 90° domain walls. On the other hand, at higher temperatures, it was seen that the compositional variations of Ta⁵⁺ content presented a more important influence on the dielectric properties. Similarly, observed in bulk ceramics, it was verified that the higher the Ta⁵⁺ amount in the ferroelectric crystals, the lower the dielectric constant near the Curie temperature.</p>