Cryogenic electromechanical behavior of multilayer piezo-actuators for fuel injector applications

This paper examines theoretically and experimentally the electromechanical behavior of multilayer piezo-actuators for fuel injectors at cryogenic temperatures. A thermodynamic model was employed to predict a monoclinic phase. A shift in the morphotropic phase boundary (MPB) between the tetragonal and rhombohedral/monoclinic phases with decreasing temperature was determined, and the temperature dependent piezoelectric coefficients were obtained. Temperature dependent coercive electric field was also predicted based on the domain wall energy. A finite element analysis was then performed to calculate the nonlinear electromechanical fields of the multilayer piezo-actuators from room to cryogenic temperatures, due to the shift in the MPB and polarization switching. In addition, experimental results on the electric field induced strain, which verify the model, were presented.