Lead-free Na0.5K0.5NbO3 piezoelectric ceramics fabricated by spark plasma sintering: Annealing effect on electrical properties

Abstract

Niobate ceramics such as NaNbO 3 and KNbO 3 have been studied as promising Pb-free piezoelectric ceramics, but their sintering densification is fairly difficult. In the present study, highly dense Na 0.5 K 0.5 NbO 3 ceramics with submicron grains were prepared using SPS, whose density was raised to 4.47 g/cm 3 (>99% of the theoretical density) at 920°C. Reasonably good ferroelectric and piezoelectric properties were obtained in the SPSed Na 0.5 K 0.5 NbO 3 ceramics after annealing in air. The effect of annealing time on the electrical properties was investigated to determine optimal processing condition. The piezoelectric parameter (d 33 ) of the Na 0.5 K 0.5 NbO 3 ceramics annealed properly reached 148 pC/N.

Piezoelectric properties of (K0.5Na0.5)NbO3-BaTiO3lead-free ceramics prepared by spark plasma sintering

“…19,20 To address these issues, pressure-assisted sintering processes, such as spark plasma sintering (SPS) and hot-pressing, were used in the sintering of KNN-based ceramics. [21][22][23] SPS has the advantages of short soaking time and lower sintering temperature, yielding higher mechanical properties and restraining the volatilization of alkaline elements in KNN-based ceramics, compared with the conventional sintering approaches. Park 26 but it has no significant positive effect on more complex compositions, e.g., 0.95(Na 0:49 K 0:49 Li 0:02 Þ-(Nb 0:8 Ta 0:2 ÞO 3 -0.05CaZrO 3 (CZ5), 27 is possibly attributed to the severe compositional segregation.…”

(K,Na)NbO3-based Lead-free Piezoelectric Materials: An Encounter with Scanning Probe Microscopy

“…Recently, spark plasma sintering (SPS) has been increasingly used instead of conventional hot pressing because of its advantages of a rapid heating rate and short soaking time. Our group has done a series of systematic studies on SPS of KNN-based ceramics, with special emphasis on property enhancement [78][79][80][81][82][83].…”

Influence of the A/B Stoichiometry on Defect Structure, Sintering, and Microstructure in Undoped and Cu-Doped KNN

“…These procedures, when carried out with carbon equipment, cause strong reduction of the KNN ceramics which involves electrical conductivity from oxygen vacancies. The vacancies have to be eliminated by means of a subsequent oxidizing treatment [84]. Moreover, the small grain size at the low SPS sintering temperatures may not be favorable with respect to piezoelectric properties.…”