Project title: Lead-free Morphotropic Phase Boundary Ferroelectric Ceramics with high Piezoelectric Properties

Lead zirconium titanate (PZT) ceramics are high-performance piezoelectric materials, which are widely used in sensors, actuators, and other electronic devices, but PZT-based ceramics contain more than 60 weight percent lead. Lead has recently been expelled from many commercial applications due to its toxicity. Ecological restrictions in many parts of the world are demanding the elimination of Pb from all consumer items. This prohibitive trend places the ceramics industry in a precarious position, as it has been for 50 years and remains entirely dependent upon Pb-based perovskites for high piezoelectric applications. High piezoelectric properties have recently been discovered in modified (Na1/2Bi1/2)TiO3-(K1/2Bi1/2)TiO3 (NBT-KBT) and (Na1/2Bi1/2)TiO3-BaTiO3 (NBT-BT) and (Na1/2K1/2)NbO3 (KNN) ceramics of compositions close to the morphotropic phase boundaries (MPBs) possessing significant degrees of grain orientation. Investigations have shown that {100}-oriented ceramics in these MPB systems results in significantly enhanced dielectric and piezoelectric properties. This is an important and timely discovery, about which much research and development remains to be done.  The objectives of this project are (i) to investigate the mechanism by which high piezoelectricity is achieved in Pb-free materials; (ii) to identify similarities and differences between MPBs in Pb-free and Pb-based systems; and (iii) to use this understanding for optimization in grain oriented systems. Development of Pb-free ferroelectric ceramics with high piezoelectric properties is an important area of research not only scientifically, but also technically, as these Pb-free systems will ultimately be the cornerstone of a billion dollar world-wide industry.

Dr Z K Xu (apzkx@cityu.edu.hk)

Suitable for: M.Phil. or Ph.D.