Composition-dependent structural, dielectric and ferroelectric responses of lead-free Bi_0.5Na_0.5TiO₃-SrZrO₃ ceramics

The influence of SrZrO₃ (SZ) addition on the crystal structure, piezoelectric and the dielectric properties of lead-free Bi_0.5Na_0.5TiO₃ (BNT−SZ100x, with x = 0 − 0.10) ceramics was systematically investigated. A significant reduction in the grain size was observed with SZ substitution. The X-ray diffraction analysis of the sintered BNT−SZ ceramics revealed a single perovskite phase with a pseudocubic symmetry; however, electric poling indicated a non-cubic distortion in the poled BNT−SZ ceramics. With increase in the SZ content, the temperature of maximum dielectric constant (T_m) shifted towards lower temperatures, and the curves became more diffuse. Enhanced piezoelectric constant (d₃₃ = 102 pC/N) and polarization response were observed for the BNT−SZ5 ceramics. The results indicated that SZ substitution induced a transition from a ferroelectric to relaxor state with a field-induced strain of 0.24% for BNT−SZ9 corresponding to a normalized strain of 340 pm/V.