Abstract: Utilizing conventional solid-phase synthesis technology, (K_0.44Na_0.52Li_0.04)(Nb_0.9Ta_0.06Sb_0.04)O₃ lead-free piezoelectric ceramics with high density and superior electrical properties were successfully fabricated at sintering temperatures ranging from 1055 to 1070 ℃. The impact of various crystal structures of niobium pentoxide on the sintering behavior, phase composition, microstructure, and electrical characteristics of potassium sodium niobate-based piezoelectric ceramics was investigated. Experimental results demonstrate that Nb₂O₅, which exists in both orthorhombic and monoclinic phases, exhibits enhanced sintering performance and excellent electrical properties:piezoelectric constant d₃₃=211 pC/N, electromechanical coupling coefficient k_p=44%, and dielectric loss tanδ=0.0324. This suggests that incorporating a minor amount of monoclinic Nb₂O₅ can optimize the diffusion kinetics and phase boundary control of Nb⁵⁺, thereby significantly improving the overall performance of the ceramics. This research provides a critical foundation for the selection of raw materials and structural design of high-performance lead-free piezoelectric ceramics.