Phase evolution and electric properties of 5 mol. % LiNbO3 doped xBiScO(3)-(95-x)PbTiO3 ceramics

The structure and electric properties of 5 mol. % LiNbO3 doped xBiScO(3)-(95-x)PbTiO3 (5LN-xBS-(95-x)PT, 26 <= x <= 41 mol. %) ceramics have been systematically investigated. The composition-, temperature- and electric-field-dependent phase transitions were established carefully by the temperature-dependent dielectric measurements. The results verified that the 5LN-xBS-(95-x)PT system transformed to nonergodic relaxors (NR) phase gradually from normal ferroelectrics (FE) phase with the addition of BiScO3 contents. With the increase of temperature, ergodic relaxors (ER) phase was observed before the phase transition from FE and/or NR to paraelectrics (PE) phase. By comparing the dielectric responses of the ceramics before and after polarization, it was confirmed that the electric field could induce a phase transition from NR to FE while the ceramics were polarized, which was attributed to the growth of the dipole clusters and the permutation of the macroscopical ferroelectric order under the external electric field. The phase diagram of 5LN-xBS-(95-x)PT system was then built and the morphotropic phase boundary (MPB) between tetragonal and rhombohedral phase of the system was identified at 34 <= x <= 36. The optimal properties were found at the composition of 5LN-34BS-61PT ceramic with piezoelectric coefficient d(33) value of 514 pC/N, planar electromechanical coupling factor k(p) of 0.47, relative dielectric constant epsilon(r) of 2511, and remnant polarization P-r of 37.4 mu C/cm(2). The displayed piezoelectric properties could provide alternative compositions with less lead contents comparing with the Pb(Zr, Ti) O-3 based piezoceramics.