Engineering grain orientation and local heterogeneous enable further breakthroughs in piezoelectricity for NaNbO3-based piezoelectric oxides

Eco-friendly NaNbO 3 (NN)-based relaxor ferroelectric ceramics with high dielectric constants cannot meet the high piezoelectric activity quality factors (FOMs: d 33  ×  g 33 ) requirements of electromechanically coupled devices. To solve this issue, we successfully improved the piezoelectricity of NN-based relaxor piezoceramics while reducing the dielectric constant based on microstructural tuning by virtue of the chemical design and texturing engineering. Mainly affected by the highly <001> c orientation and relaxor MPB, the obtained novel 88.5NaNbO 3 –10Ba(Ti 0.7 Sn 0.3 )O 3 –1.5NaSbO 3 texture ceramics enjoys an ultrahigh piezoelectric coefficient ( d 33  = 423 pC/N), reaching a record high in NaNbO 3 -based lead-free ceramics. Meanwhile, a large FOMs value ( d 33  ×  g 33  = 13.3·10 −12 m 2 /N) is successfully realized due to the suppression of the dielectric constant. More importantly, the stable phase/domain evolution also encourages excellent temperature stability for piezoelectricity and FOMs. Especially for the piezoelectricity, when the annealing temperature is < 140 °C, the d 33 of the 1.5T ceramics can be stabilized ∼ 400 pC/N. Such excellent electrical temperature stability shows more competition in the reported NN-based piezoceramics. This work not only provides a design paradigm for high-performance piezoelectric materials , but also facilitates their development in electromechanical coupling devices.