ANTIFERROELECTRIC THIN AND THICK-FILMS FOR HIGH-STRAIN MICROACTUATORS

Niobium-doped or lanthanum-doped lead zirconate titanate stannate anti ferroelectric thin and thick films have been prepared on platinum-buff ered silicon substrates by a modified sol-gel method and their electri c properties were characterized, with emphasis on the field-induced ph ase transition strains. Ail the films demonstrate zero remanent polari zation and a maximum polarization of more than 30 mu C/cm(2). By choos ing the appropriate compositions, the films can have either ''square'' hysteresis loops with very sharp phase transition or ''slanted'' hyst eresis loops with gradual phase transition. The strain levels of the t hin films can reach 0.32% with smaller hysteresis or 0.42% with modera te hysteresis. The thick films can either have a strain level of 0.38% with very small hysteresis or have a strain level of 0.48% with clear digital actuator response. Hence the strain levels of these antiferro electric films are comparable to that of bulk materials and double tha t of PZT ferroelectric films, and they are very promising for actuatio n applications in microelectromechanical systems.