Large piezoelectric responses of Bi(Fe,Mg,Ti)O3-BaTiO3 lead-free piezoceramics near the morphotropic phase boundary

- The MPB was detected in the (1-x)Bi1+y(Fe0.96Mg0.02Ti0.02)O3-xBaTiO3 system.
- The excellent d33 = 198 pC/N and kp = 30.9% were achieved in the B1+yFMT-xBT system.
- High TC = 497 °C was also achieved in the B1+yFMT-0.30BT ceramics at y = 0.02.

The (1-x)Bi1+y(Fe0.96Mg0.02Ti0.02)O3-xBaTiO3 (abbreviated as B1+yFMT-xBT) system was designed to explore the morphotropic phase boundary (MPB) separating rhombohedral (R) and tetragonal (T) phases, and the mechanism of performance enhancement. The phase structure of samples was discreetly investigated by X-ray diffraction, and Rietveld refinement results of the XRD data revealed that the B1+yFMT-xBT ceramics consist of an R phase at x = 0.24, two R and T phases at 0.26 ≤ x ≤ 0.32, and a single T phase at x = 0.34. Because of the MPB and the improvement of resistivity with adding excess Bi compensation, excellent piezoelectric properties of d33 = 198 pC/N and kp = 30.9%, as well as high Curie temperature TC = 497 °C were achieved in the B1+yFMT-xBT system at x = 0.30 and y = 0.02. Here, the large d33 = 198 pC/N which is the maximum value for the BF-BT-Bi(Mg,Ti)O3 system so far, and high TC = 497 °C suggest that Bi(Fe,Mg,Ti)O3-BaTiO3 ceramics have good prospects in high-temperature piezoelectric devices.