Phase transition behavior and high electrostrictive strains in Bi(Li0.5Nb0.5)O3-doped lead magnesium niobate-based solid solutions

Abstract

Bi(Li0.5Nb0.5)O3 (BLN) was adopted to tailor the Curie temperature (TC) and the resulting ferroelectric and electrostrictive properties of solid solutions of the morphotropic phase boundary relaxor ferroelectric 0.67 Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (0.67PMN-0.33 PT). The ceramic samples were synthesized by a solid reaction method, and the BLN content was set to 2.5 at.%, 5 at.%, 7.5 at.%, and 10 at.%. X-ray diffraction results suggested that BLN cannot enter the 0.67PMN-0.33 PT crystal lattice completely, resulting in the formation of a second phase (Pb2Ti2O6 with pyrochlore structure) in all the samples. With increasing BLN content, a decrease in TC and a ferroelectric-to-relaxor transition were revealed by the dielectric and ferroelectric properties. High electric-field-induced strains of 0.167%–0.228% with low hysteresis (<7%) were observed in the samples. Most importantly, an almost purely electrostrictive strain of 0.184% with ultralow hysteresis (<2%) was obtained in the 7.5 at.% BLN-doped sample. The thermal stability of the strains in the bipolar and unipolar modes were evaluated from 30 to 120 °C. The longitudinal electrostrictive coefficient Q33 ranged from 0.150 to 0.185 m4/C2 and was insensitive to temperature. Our results suggest that BLN-doped 0.67PMN-0.33 PT ceramics could have potential applications in actuator devices owing to their high strain response and ultralow hysteresis.