Enhanced piezoelectric activity in high-temperature Bi1-x-ySmxLayFeO3 lead-free ceramics

We have developed a high-temperature bismuth ferrite ceramics with enhanced piezoelectric activity by chemical modifications, that is, the Bi(1-x-y)SmxLayFeO(3) (0 <= x <= 0.30 and 0 <= y <= 0.15) lead-free ceramics were prepared by a conventional solid-state method. The influences of La and Sm content on their microstructure and electrical properties were systematically investigated. The ceramics with 0 < x < 0.10 (y = 0.05) or 0 <= y <= 0.15 (x = 0.025) belong to a triclinic phase, and a mixed structure with rhombohedral-like and orthorhombic phases was found in the ones with 0.10 <= x <= 0.30 (y = 0.05). The electrical properties of the ceramics can be operated by refining the x and y values. A very low dielectric loss (tan delta similar to 0.43%) was shown in the ceramics with x = 0.025 and y = 0.05 because of the involvement of low defect concentrations. In addition, the ceramics with x = 0.025 and y = 0.05 also possess a high piezoelectric activity (d(33) similar to 50 pC N-1), which is larger with the respect to the previously reported results in high-temperature piezoceramics with a Curie temperature of >600 degrees C, and a better thermal stability of piezoelectricity in 20-700 degrees C is also shown. We believe that this material system is suitable for high-temperature piezoelectric applications.