Temperature Dependent Piezoelectric Properties of Lead-Free (1-x)K0.6Na0.4NbO3–xBiFeO3 Ceramics

Abstract

K 0.4 Na 0.6 NbO 3 -xBiFeO 3 lead-free piezoelectric ceramics were successfully prepared in a single perovskite phase using the conventional solid-state synthesis. Relative permittivity (ε r ) as a function of temperature indicated that small additions of BiFeO 3 not only broadened and lowered the cubic to tetragonal phase transition (T C ) but also shifted the tetragonal to orthorhombic phase transition (T O-T ) toward room temperature (RT). Ceramics with x = 1 mol.% showed optimum properties with small and large signal piezoelectric coefficient, d 33 = 182 pC/N and d * 33 = 250 pm/V, respectively, electromechanical coupling coefficient, k p = 50%, and T C = 355 • C. k p varied by ∼5% from RT to 90 • C, while d * 33 showed a variation of ∼15% from RT to 75 • C, indicating that piezoelectric properties were stable with temperature in the orthorhombic phase field. However, above the onset of T O-T , the properties monotonically degraded in the tetragonal phase field as T C was approached.

Thermally stable piezoelectric performance in low-temperature sintered Pb0.95Ba0.01Sr0.04(Zr0.53Ti0.47)O3 ceramics with a low loss factor

“…The variation curves are shown in Figure 4(f). The change of d 33 * is <14%, which is close to the PZT-systems reported recently [3], and better than some lead-free systems, such us KNN-based [22], BNT-based [23], and BT-based [24]. Hence the ceramics are demonstrated to be promising materials for actuator and transformer devices.…”

Processing, microstructure, electrical properties and cytotoxic behaviour of lead-free 0.99K0.5Na0.5NbO3-0.01BiFeO3 piezoceramics prepared using Spark Plasma Sintering (SPS)

“…The best fit was obtained using the orthorhombic Amm2 and the tetragonal P4mm phases in percentage by weight respectively of 68 and 32%, in agreement with other works. [19]. From a comparison of the ionic radius, it is reasonable to expect that Bi 3+ (103 pm) occupies the Na + (102 pm) and K + (138 pm) sites while Fe 3+ (64.5 pm) occupies the Nb 5+ (64 pm) sites.…”