Systematic study of the influence of the K/Na ratio on the structure, microstructure, and electrical properties of (KxNa1−x)NbO3 lead-free ceramics

Optimization of the calcination and two-step sintering temperatures of (K0.48Na0.48Li0.04)(Nb0.95Sb0.05)O3 ceramics

“…As discussed above, the ceramic sample corresponding to the T 2 is 1050 °C, and the ceramic sample has a homogeneous microstructure, large grains, high density, and small grain boundaries of the ceramics. This result makes it easier to reverse ferroelastic domain walls leading to improved dielectric properties of ceramic samples [8]. This result is consistent with the results obtained by studying the microstructure and ceramic density as well as good crystallization of the structure at the optimum sintering temperature.…”

“…This result is consistent with the results obtained by studying the microstructure and ceramic density as well as good crystallization of the structure at the optimum sintering temperature. As reported by Tu et al [8], the large grain size, small grain boundaries and high density of KNLNS ceramic are favorable for getting enhanced piezoelectric properties. Wang et al [27] reported that the maximum density and the largest coefficient d 33 value were recorded when the 0.92(Na 0.535 K 0.48 )NbO 3 − 0.083LiNbO 3 samples were sintered at 950 °C.…”

“…KNN-based ceramics are characterized by high Curie temperature (T C = 420 °C) and improved piezoelectric response, and these properties can be attributed to the polymorphic phase transition process. These materials outperform other lead-free piezoelectric ceramics [8].…”

“…Furthermore, the increase in the Q m value can be attributed to the improvement in the dielectric loss and the microstructure of the ceramics. It is explained that the replacement of K + (1.38 Å) ions and Na + (1.32 Å) ions occupying the A sites of the perovskite lattice by Li + (0.92 Å) ions and the Nb 5+ (0.64 Å) ions occupying the B-site by Sb (0.62 Å) leading to good crystallization, which contributes to a decrease in the dielectric loss of the materials and the result is improved the mechanical quality coefficient [8].…”

“…It has been previously reported [6,7] that (Na 1/2 K 1/2 )NbO 3 prepared following the solid phase reaction method exhibits good piezoelectric properties (d 33 = 80 pC N −1 , k p = 36%-40%, Q m = 130, and ε r = 290). Tu et al [8] reported that K 0.41 Na 0.59 NbO 3 was characterized by the best physical properties (ε r = 470, k p = 0, 32, k t = 0, 5, d 33 = 120 pC N −1 , P r = 11, 6 μC cm −2 ). KNN-based ceramics are characterized by high Curie temperature (T C = 420 °C) and improved piezoelectric response, and these properties can be attributed to the polymorphic phase transition process.…”