Synthesis of (K, Na) (Nb, Ta)O3 lead-free piezoelectric ceramic powders by high temperature mixing method under hydrothermal conditions

Sodium niobate particles with controlled morphology synthesized by hydrothermal method and their use as templates in KNN fibers

“…In the literature, NaNbO 3 was reported to grow with a rectangular [32] or rhomb-shaped morphology [33]. There are also other reports on synthesis of KNN through high temperature mixing under hydrothermal conditions reported in the literature [22,34], where this stepwise formation can be avoided and the perovskite phase can directly be obtained, similar to our results obtained at or above 160°C. The morphology of the particles in these studies was also cubic, as expected, and as observed in our study.…”

“…Hydrothermal synthesis is another method to grow single crystalline particles with anisometric morphology, such as nano-needles and nano-plates [20]. KNN powders have prepared by hydrothermal synthesis method and the structural and electrical properties of the bulk ceramic samples fabricated from these powders were also reported [21,22]. Sodium niobate (NN) templates with various morphologies, such as needle-like, plate-like and cubical forms have also been synthesized by hydrothermal method [23].…”

Enhanced ferroelectric and piezoelectric performance of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 lead-free ceramics upon Ce and Sb co-doping

“…In the past decade, tremendous efforts have been devoted to fabricating lead-free ceramic systems, such as K 0.5 Na 0.5 NbO 3 (KNN), Bi 0.5 Na 0.5 TiO 3 (BNT), BaTiO 3 (BT) and BiFeO 3 (BFO). [6][7][8][9][10] Among them, BT-based ceramics have received widespread attention due to their stable chemical properties, low preparation cost, large dielectric permittivity (3 r ) and low leakage current. 11,12 However, in actuality, the BT-based ceramics are not the ideal piezoelectric materials, and the low piezoelectric coefficient (d 33 ¼ $190 pC N À1 ) compromises the commercialization of their applications.…”

Compositional inhomogeneity and segregation in (K0.5Na0.5)NbO3 ceramics

“…It is well known that sintering of the ceramic green body can be affected by the characteristics of the powders that depend on the synthesis method and processing [7]. To date, it has been reported that KNN ceramic powders can be synthesized by chemical methods such as solid-state reaction (SSR) [8][9][10][11][12], hydrothermal [13][14][15], sol-gel [16][17][18], precipitation [19], and mechanochemical activation [20] [21]. The difference between the K + and Na + diffusion rates likely leads to local inhomogeneity in the KNN solid solution, which can, in principle, be diminished by increasing the calcination temperature [21].…”