<p>Lead-free (Na, K, Li)(Nb, Ta, Sb)O₃-Bi_0.5Li_0.5ZrO₃ (NKLNTS-BLZ)/polyvinylidene fluoride (PVDF) composites with 0–3 connectivity were fabricated via a solution-casting method. The microstructure, phase evolution, and dielectric properties were systematically investigated as a function of filler content (0–40 vol%). SEM analysis revealed that fillers were well-dispersed at lower concentrations, significant agglomeration and micro-voids were observed at 40 vol%. The composites exhibited a giant dielectric constant, reaching a maximum of 250 (at 1&#xa0;kHz) with 40 vol% loading. However, this enhancement was accompanied by a critical trade-off in dielectric loss and breakdown strength. To elucidate the conduction mechanism, AC conductivity was analyzed using Jonscher’s power law. The results showed that the power-law exponent (<i>n</i>) increased from 0.38 (pure PVDF) to ~ 0.6 (10–30 vol%), indicating a dominant hopping conduction mechanism desirable for insulation. Conversely, at 40 vol%, the <i>n</i> value dropped sharply to 0.27, signaling the onset of percolation and leakage currents. Consequently, the 30 vol% composition was identified as the optimal loading, effectively balancing high permittivity with electrical stability. These findings demonstrate that NKLNTS-BLZ/PVDF composites are promising candidates for next-generation embedded capacitors, provided that the filler fraction is optimized to mitigate conduction losses.</p> Graphical abstract <p></p>