Mn-modified Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ ceramics: Improved mechanical quality factors for high-power transducer applications

Piezoelectric ceramics are potential high-power electroacoustic sources, and have been studied for many years. However, when these devices are driven under high-level vibration, the electromechanical characteristics depart significantly from the conventional linear piezoelectric relationships due to the loss and nonlinear behavior in terms of elastic and dielectric properties. In this paper, we present results concerning the development of modified Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) ceramics with improved mechanical quality factors for high-power application. We have focused efforts on base PMN-PT compositions close to the morphotropic phase boundary. Evidence will be presented which indicates that the improved mechanical quality factor results from the introduction of `hard' characteristics into PMN-PT by the substituents. Investigations of the nonlinearity of the electromechanical properties on the vibrational amplitude were performed using a constant displacement method. The degradation of the mechanical quality factor with increasing drive amplitude also presents thermal stability problems for the usage of these materials in high-power transducer applications.