BNT-based piezoelectric ceramics have garnered considerable attention owing to their potential to exhibit large electrostrain. However, irreversible phase transitions and domain structure alterations lead to limited effective strain and poor temperature stability, which restricts their application in high-precision displacement devices, representing a major bottleneck in current research. In this study, 0.82Bi 0.5 Na 0.5 TiO 3 –0.18Bi 0.5 K 0.5 TiO 3 (BNKT) was selected as the base composition, and an A/B-site co-doping strategy was employed to develop a (Ba 0.5 Sr 0.5 )HfO 3 (BSH) composite modification system. By precisely adjusting the BSH doping concentration ( x = 0–0.03), the ferroelectric – relaxor phase transition temperature ( T F-R ) was effectively shifted to below room temperature, thereby significantly lowering the field-induced phase transition energy barrier. Finally, the BNKT-0.02BSH ceramic exhibits a high piezoelectric strain coefficient ( d 33 ∗) of 648 pm/V under an electric field of 65 kV/cm, along with a strain response of 0.475 % at 80 kV/cm. Meanwhile, the strain stability remains above 85 % over the temperature range of 30–100 °C. Multi-scale characterization techniques, including X-ray diffraction and temperature-dependent Raman spectroscopy, confirmed that the improved performance enhancement is attributed to BSH modification, which increases local structural heterogeneity and significantly promotes electric field-induced reversible phase transitions between the relaxor to ferroelectric states. This study offers novel insights into the understanding of the composition-structure-property relationship.
The lead-free piezoelectric ceramics used in piezoelectric actuators have attracted extensive attention owing to their substantial electric-field-induced strain. In this study, The (1- x )Bi 0.5 (Na 0.41 K 0.09 )TiO 3 - x Sr(Hf 0.5 Sb 0.4 )O 3 (BNKT- x SHS) piezoelectric ceramics were synthesized using the conventional solid-state reaction method. The impact of SHS substitution on the microstructure and electrical properties was systematically explored. Among them, the BNKT-0.015SHS sample, featuring ergodic relaxor states, demonstrates a high piezoelectric strain coefficient ( d 33 *) of 785 p.m./V under a low electric field of 50 kV/cm(Strain = 0.392 %). It exhibits a repeatable strain value of 0.47 % under an 80 kV/cm electric field( d 33 * = 590 p.m./V). Moreover, the strain values remain around 0.4 % between room temperature and 100 °C, with variations within 90 %. The heightened repeatable strain response is considered to be linked to the electric field-induced reversible phase transition occurring within the ergodic relaxor state. The higher strain temperature stability is ascribed to the coexistence of quadrilateral polar nanoregions and rhombic polydomain nanoregions. This study provides an effective example for achieving significant strain responses, presenting a feasible candidate material for applications in piezoelectric actuators.
In recent years, lead-free Bi 0.5 Na 0.5 TiO 3 (BNT) based piezoelectric ceramics with excellent strain properties have gained widespread recognition for their application in high-precision displacement actuators. The (1- x )(0.82Bi 0.5 Na 0.5 TiO 3 -0.18K 0.5 Bi 0.5 TiO 3 )- x Ba(Fe 0.5 Sb 0.5 )O 3 ceramics were fabricated through the die-pressing method in this work. The effect of BFS introduction on the dielectric, ferroelectric and microstructure characteristics of BNKT ceramics was systematically investigated. Among these compositions, the BNKT-0.015BFS ceramics exhibited a piezoelectric strain coefficient ( d 33 *) of 658 pm/V at an electric field of 55 kV/cm, while achieving a strain response of 0.51 % at 85 kV/cm. The observed improvement in strain performance can be attributed to the evolution from non-ergodic relaxor state to ergodic relaxor state caused by BFS substitution. Furthermore, transmission electron microscopy (TEM) explicitly confirmed coexistence of rhombohedral and tetragonal phase and revealed the morphology of nanosized domains. This study adds to a deeper comprehension of the characteristics of strain response enhancement in BNT-based ceramics, opening up avenues for designing novel lead-free piezoelectric ceramics with outstanding electromechanical performance.
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