Large electrostrictive response via tailoring ergodic relaxor state in Bi1/2Na1/2TiO3-based ceramics with Bi(Mn1/2Ce1/2)O3 end-member

Lead-free Bi1/2Na1/2TiO3 (BNT)-based relaxor ferroelectric ceramics with superior electrostrictive coefficient features have recently gained a lot of attention due to their application in high-precision displacement actuators. In this work, we propose an effective approach to enhance the electrostrictive effect via tuning the phase transition temperature around ambient temperature in BNT-based ceramics. Herein, a novel Bi(Mn1/2Ce1/2)O3 (BMnCe) modifier was adopted as an activator into 0.935Bi1/2Na1/2TiO3-0.065BaTiO3 (0.935BNT-0.065BT) for modifying the phase boundary (TF-R) around the ambient temperature. The compositional and temperature-dependent dielectric, ferroelectric, and electrostrain were systematically investigated. All samples exhibit a pure perovskite structure. Rietveld refinement revealed that the 0.935BNT-0.065BT ceramic presents a coexistence of rhombohedral (R3c) and tetragonal (P4bm) phases. As the BMnCe content increases, the tetragonal (P4bm) phase becomes more prevalent and eventually shifts into a pseudocubic phase. It was found that the addition of BMnCe can effectively tune the TF-R below ambient temperature and enhance the relaxor behavior. The polarization and electrostrain analysis revealed that the ferroelectric long-range order decreases with increasing BMnCe; specifically, a unique region emerges where remnant polarization, quasistatic d33, and negative strain abruptly drop. As a result, a high electrostrain (S) of 0.43 % with a normalized strain (Smax/Emax) of 716 pm/V was achieved at the critical composition (0.01 M concentration of BMnCe). More importantly, (0.935-x)BNT-0.065BT-xBMnCe (x = 0.01) shows a large electrostrictive coefficient (Q33) of 0.032 m4/C2 with a giant normalized electrostrictive coefficient (Q33/E) of 5.33ｘ10−9 m5/C2V at room temperature. Furthermore, the Q33 and Q33/E values show temperature insensitivity up to 120 °C, rendering the compound suitable for actuation-based devices. These results offer an effective avenue for designing high-performance BNT-based materials with giant electrostrictive coefficients.