(1-x) (Bi 0.49 Na 0.49 Ca 0.02 TiO 3)-xCaHfO 3 (BCNTH-x, x = 0.01, 0.02, 0.03, 0.035, 0.04) systems were prepared by solid-state reaction method. Their microstructures, dielectric/piezoelectric/ferroelectric properties and impedance spectroscopy were investigated. All compositions demonstrated a single orthorhombic structure with Pbnm space group. Temperature-dependent permittivity curves displayed one anomaly, which shifts to low temperature from 278 to 208°C with increased CaHfO 3 content, because of the replacement of Hf 4? for Ti 4? at the B-site that reduced B-site cation ordering. Analysis of dielectric and ferroelectric properties indicated that a crossover from typical ferroelectrics to relaxor ferroelectrics occurred in BCNTH-0.03 and BCNTH-0.035 ceramics. The largest electrostrictive strain of 0.22% and the lowest coercive field of 37.7 kV/cm were achieved in BCNTH-0.035 and BCNTH-0.03 ceramics under 100 kV/cm, respectively. Ferroelectric domain and domain wall were fitted by impedance complexes, and the corresponding activation energy was 0.46 and 1.18 eV, which may be correlated to the combination of motion of the first ionization of oxygen vacancies and doubly ionized oxygen vacancies, respectively. 1 Introduction Piezoelectric ceramics are extensively investigated due to their wide-ranging applications in sensors, non-volatile memories, and pyroelectric detectors, among others [1]. Lead-based piezoelectric ceramics with high strain, such as Pb(Zr, Ti)O 3 [2], (Pb,La)(Zr, Ti)O 3 [3] etc. [4-6]. are commonly used. Lead-based piezoelectric materials almost dominate the market for piezoelectric materials by PZT. However, lead