High-performance PMNߝPT thick films

This article describes some of our work on 0.65Pb(Mg_1/3Nb_2/3)O₃-0.35PbTiO₃ (0.65PMN-0.35PT) thick films printed on alumina substrates. These thick films, with the nominal composition 0.65Pb(Mg_1/3Nb_2/3)O₃-0.35PbTiO₃, were produced by screen-printing and firing a paste prepared from an organic vehicle and pre-reacted fine particles of a very chemically homogeneous powder. To improve the adhesion of the 0.65PMN-0.35PT to the platinized alumina substrate, a Pb(Zr_0.53Ti_0.47)O₃ layer was deposited between the electrode and the substrate. The samples were then sintered at 950°C for 2 h with various amounts of packing powder on the alumina (Al₂O₃) substrates. The sintering procedure was optimized to obtain dense 0.65PMN-0.35PT films. The films were then characterized using scanning electron microscopy as well as measurements of the dielectric and piezoelectric constants. The electrostrictive behavior of the 0.65PMN-0.35PT thick films was investigated using an atomic force microscope (AFM). Finally, substrate-free, large-displacement bending-type actuators were prepared and characterized, and the normalized displacement (i.e., the displacement per unit length) of the actuators was determined to be 55 μm/cm at 3.6 kV/cm.