Research Projects

Piezoelectric materials, known for their ability to interconvert electrical and mechanical energies, are widely used as transducers in applications such as nano-positioning, SONAR, MEMS, and ultrasound imaging. Enhancing the stroke and sensitivity of these devices requires piezoceramics capable of delivering substantial longitudinal strain under an applied electric field. For decades, Pb-based perovskite piezoelectrics, particularly Pb(Zr, Ti)O3 (PZT), have been the material of choice for such applications. However, growing environmental concerns have spurred significant research into developing lead-free, non-toxic alternatives for industrial use. In this context, Pb-free systems such as BaTiO3 (BT), Na0.5Bi0.5TiO3 (NBT), K0.5Bi0.5TiO3 (KBT), K0.5Na0.5NbO3 (KNN), BiFeO3 (BF) have attracted considerable attention. While single crystals of these ceramics offer superior electrostrain performance due to the absence of grain boundaries and line defects, producing high-quality single crystals is challenging, expensive, energy-intensive, and time-consuming. In contrast, non-textured polycrystalline ceramics can be synthesized on a large scale using conventional ceramic preparation methods, although their strain performance is typically limited. Very recently, our research has yielded four significant breakthroughs in the field of piezoceramics: (i)Reducing grain boundaries and mutual clamping between grains by minimizing the thickness of disc-shaped piezoceramics. (ii) Achieving enhanced longitudinal electrostrain (more than 1%) in 0.20 mm thick PZT samples. (iii) Demonstrating ultrahigh bending strain (more than 3%) in 0.20 mm thick Pb-free ceramics under an applied electric field. (iv) Establishing that the electrostrain behavior of oxide piezoelectric ceramics is governed by the interplay between mechanical stress state (triaxial/plane) and oxygen vacancy concentration. Despite these advances, Pb-free piezoceramics often require high sintering temperatures (more than1100°C) for proper densification, which inadvertently generates unwanted oxygen vacancies. These vacancies result in bending deformation during electric field application when disc thickness is reduced below 0.40 mm, limiting their true longitudinal strain potential. Eliminating these vacancies is essential but remains unexplored in Pb-free piezoceramics. Addressing this gap is critical for unlocking their full potential in environmentally friendly piezoelectric applications.