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Hot-press sintering K0.5Na0.5NbO3–0.5 mol%Al2O3 ceramics with enhanced ferroelectric and piezoelectric properties

Yu, Zi-de, Chen, Xiao-ming, Su, Yu-long, Lian, Han-li, Lu, Jiang-bo, Zhou, Jian-ping, Liu, Peng
Journal of materials science 2019 v.54 no.21 pp. 13457-13466
ambient temperature, annealing, ceramics, electric field, microstructure, thermal stability
Lead-free ceramics K₀.₅Na₀.₅NbO₃–0.5 mol%Al₂O₃ with simple composition were prepared via the hot-press sintering. The ceramics exhibit dense microstructure, fine grains, and pure orthorhombic structure. Via the hot-press sintering as well as adding 0.5 mol%Al₂O₃ into K₀.₅Na₀.₅NbO₃, piezoelectric and ferroelectric properties of the obtained ceramics were obviously enhanced. The ceramics exhibit high remnant polarization Pᵣ = 26.8 μC/cm² and piezoelectric constant d₃₃ = 137 pC/N. The maximum unipolar strain is 0.17%, and the converse piezoelectric coefficient d₃₃* is 212 pm/V under electric field E = 80 kV/cm. Under E = 50 kV/cm, the Pᵣ increases from 21.6 to 22.2 μC/cm², and the d₃₃* increases from 223 to 322 pm/V as the temperature increases from room temperature to 170 °C. The ex situ measurement result demonstrates that d₃₃ still keeps a high value of 97 pC/N as the annealing temperature increases to 380 °C, implying excellent thermal stability.