Antiferroelectric thin and thick films for high-strain microactuators

Abstract

Niobium-doped or lanthanum-doped lead zirconate titanate stannate antiferroelectric thin and thick films have been prepared on platinum-buffered silicon substrates by a modified sol-gel method and their electric properties were characterized, with emphasis on the field-induced phase transition strains. All the films demonstrate zero remanent polarization and a maximum polarization of more than 30 μC/cm². By choosing the appropriate compositions, the films can have either “square” hysteresis loops with very sharp phase transition or “slanted” hysteresis loops with gradual phase transition. The strain levels of the thin films can reach 0.32% with smaller hysteresis or 0.42% with moderate 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 antiferroelectric films are comparable to that of bulk materials and double that of PZT ferroelectric films, and they are very promising for actuation applications in microelectromechanical systems.

Key Words:

• antiferroelectrics
• lead zirconate titanate stannate
• thin films
• thick films
• microactuators
• field-induced strain