Fatigue properties of piezoelectric-electrostrictive Pb(Mg1/3, Nb2/3)O3-PbTiO3 monolithic bilayer composites

Abstract

The fatigue response of monolithic piezoelectric 0.65Pb (Mg13 Nb23) O3 -0.35PbTi O3 -electrostrictive 0.90Pb (Mg13 Nb23) O3 -0.10PbTi O3 bilayer composites was investigated experimentally. The monomorph bilayers were cosintered at 1150 °C, and the polarization hysteresis, relative permittivity, displacement, and cyclic fatigue (107 cycles) were measured as a function of piezoelectric-electrostrictive volume fraction (PEVF) ratio. The highest tip displacement of bilayers was found in the 3:1 PEVF monolith, reaching 40 μm at 5 kVcm applied field strength. By minimizing the electrostrictive layer thickness, tip displacement substantially increased, while maintaining a lower hysteresis than the purely piezoelectric counterpart. Fatigue measurements indicated a 31% decrease in displacement after 107 cycles in 3:1 monoliths, whereas the 1:3 PEVF only showed a 12% decrease under the same conditions. There is a 30% increase in polarization after 107 cycles for 1:1 PEVF bilayers, which is attributed to self-poling due to a diffuse transition layer in the vicinity of the interface. It was found that partial 90° domain switching occurred prior to poling because of the residual stresses in the composite, imposed by the electrostrictive layer and the spontaneous strain associated with the cubic-tetragonal transition in the ferroelectric layer. The results indicate that the electrostrictive layer, which is electrically in series with the piezoelectric one, enhances the fatigue resistance of the monolithic bilayer composites in addition to the increase in tip displacement. © 2006 American Institute of Physics.