Unraveling the discrepancy of temperature- and composition-dependent strain regulation in Bi0.5Na0.5TiO3 ceramics

Abstract

For Bi0.5Na0.5TiO3 (BNT)-based materials, regulating temperature and composition could both induce giant electro-strain under the critical condition. Nevertheless, only the temperature-dependent regulation method achieved low hysteresis and maintained a high strain under high ergodic condition simultaneously. Herein, we investigated the origin of this discrepancy by means of matrix with close strain level. These two regulation methods exhibited different regulation mechanisms, especially for the microscopic structure (i.e., the discrepant lattice structure and polar entities). The A-site and BO6 octahedral-dependent vibration modes exhibited obvious discrepancies under the highly ergodic condition, while the shift was relatively small around relaxor/ferroelectric crossover. Additionally, polar entities also exhibited discrepant morphology (e.g., composition-regulated one exhibited striped domains, and temperature-regulated one possessed fuzzy signals with partial nanosized domains under the critical condition) and kinetic behaviors (e.g., under highly ergodic condition, temperature-regulated polar entities rebounded slowly at the initial unloading stage). In a word, relatively small structural discrepancies leaded to similar strain performance under the critical condition, while the increasing ergodicity accompanied by increasing structural discrepancies, which finally induced different strain performance under the high ergodic condition. This insight for designing the BNT-based materials with giant electro-strain and low hysteresis was useful to accelerate the industrialization of eco-friendly actuators.

Large electrostrain achieved in BNKT‐based ceramics by the adjustment of phase boundary with Ba(Sn0.70Nb0.24)O3 addition

“…The Raman spectra of BNKT-xBSN ceramics over 100-1000 cm −1 at ambient temperature were also carried out in order to elucidate the impact of BSN doping on the structure of BNKT matrix ceramics, and the detailed test results are illustrated in Figure 2B. The Raman spectrum is categorized into four intervals, representing four vibrational modes [32][33][34] : (1) wavenumbers below ∼200 cm −1 correspond to the A vibration mode in the perovskite structure, including Bi 3+ , Na + , K + , Ba 2+ , etc; (2) wavenumbers in the range of 200-400 cm −1 predominantly represent the vibrational modes of B-O bonds; (3) wavenumbers spanning 400-700 cm −1 correspond to the vibrational modes of B-O 6 octahedra; (4) wavenumbers above ∼700 cm −1 are linked to the overlapping bands of A1 and E1 (longitudinal optics) types. 35 Furthermore, the Raman patterns of the ceramic samples underwent Gauss-Lorentz convolution, yielding eight characteristic peaks.…”