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 _0.7Sn _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.