High-performance piezoelectric materials, whose displacement is sensitive to an external field and vice versa, are constantly required in electromechanical applications. Here, we introduce Nd³⁺ ions into 0.49Pb(Nb_2/3Ni_1/3)O₃-0.51Pb(Hf_0.3Ti_0.7)O₃ (PNN-PHT) ceramics via the solid-state method. By constructing a ferroelectric system in the morphotropic phase boundary region and exploiting the synergistic effect of polar nanoregions and an enhanced local structural heterogeneity, excellent piezoelectricity and dielectric properties are obtained. The optimized piezoelectric coefficient d₃₃, dielectric constant ε₃₃, electromechanical coupling factor k_p, and dielectric loss tanδ are 1125 pC/N, 8667, 0.66, and 1.94%, respectively. The Vogel-Fulcher law and relaxation analysis were adopted to understand the origin of the high piezoelectricity. The Rayleigh analysis method was used to study the intrinsic and extrinsic contributions to the piezoelectricity of the Nd-doped PNN-PHT ceramics, the extrinsic contribution was found to be up to 19% in the optimal region (PNN-PHT + 0.4 at% Nd₂O₃). Moreover, according to in-situ ferroelectric measurements and fatigue measurements, the PNN-PHT + 0.4 at% Nd₂O₃ ceramic exhibits excellent fatigue resistance and stable piezoelectric behavior at 60 ℃. This work provides an approach to realize high-performance piezoelectric ceramics with good electromechanical stability under external condition, which is expected to expand the range of application of piezoelectric materials, e.g., for transducers.