Electromechanical properties of La and Mn co-modified 0.6BiFeO3–0.4PbTiO3 ceramics for high power applications

Piezoelectric ceramics of 0.6(Bi0.9La0.1)FeO3–0.4Pb(Ti1−xMnx)O3 (BLF–PTM) for x = 0, 0.01, 0.02 and 0.03 were fabricated by sol–gel process combined with a solid state reaction method. XRD patterns reveal that all compositions possess pure perovskite structure with a rhombohedral symmetry. Upon using Mn substituents, BLF–PTM ceramics exhibited the characteristics of hard piezoelectrics, such as (i) low polarization, (ii) low dielectric constant and loss, and (iii) high mechanical quality factor Qm. The dielectric loss, planar coupling coefficient Kp and mechanical quality factor Qm of 0.006, 0.338 and 418, respectively, have been achieved for BLF–PTM of x = 0.01. A large vibration velocity of 1.1 m/s has also been achieved for this composition, which is larger than that of commercialized Pb(Zr, Ti)O3 (0.3 m/s) and Pb(Zr, Ti)O3–Pb(Sb, Mn)O3 (0.6 m/s) piezoelectric ceramics.