Bismuth-based lead-free incipient piezoceramics have potential in piezoactuators owing to their large strain response. However, a substantial strain hysteresis and poor temperature/frequency stability heavily restrict their practical applications. Herein, we designed a compositional inhomogeneity and constructed quenched random fields to enhance the relaxor dynamics by introducing a classical relaxor material, Ba(Zr0.2Ti0.8)O-3, into a nonergodic material, (Na0.5Bi0.5)TiO3-0.15SrTiO(3). Intriguingly, we obtained a large piezoelectric d33* coefficient of 602 pm/V and a narrow hysteresis of 32% at the x = 0.04 (BZT4) composition. The strain properties present a robust frequency (~2%, 1-20 Hz) and temperature stability (~13%, 25-150 degrees C). The excellent actuating properties of BZT4 were due to a field-induced reversible ergodic relaxor-ferroelectric transformation, and the narrow hysteresis can be attributed to quick switching of the dynamic relaxor phase to external stimuli. The origin of the structural transition and salient strain performance was systematically investigated. This study provides a novel route for designing lead-free incipient perovskite with a large strain, narrow hysteresis and high stability for eco-friendly actuators.