New Perovskite Materials with Large Field-Induced Electromechanical Strains

Professor Cann will be a Visiting Scholar at the Department of Materials Science and Engineering, Sheffield for a period of 3 months from April 1st until June 30th 2011. During his study visit, he will undertake in collaboration with Professor Reaney's research in the field of PbO-free ceramics which exhibit high electromechanical strain. The main aim of the research is to combine the excellent compositional-processing-studies carried out in several promising systems at Oregon with the exceptional knowledge of crystal chemistry, structure and microstructure available within Prof. Reaney's group. In addition, Prof Cann will use his time at Sheffield to visit with other interested research groups at Leeds, Imperial, Birmingham, Liverpool and Manchester to foster further links within the UK community. He will, were appropriate, give seminars and discuss his excellent research findings at targeted UK groups who work in Electroceramics

i) Industrial and Societal Impact Piezoelectric ceramics are ubiquitous with applications increasing almost daily. Depending on the manufacturer, a typical modern car may contain 10-20 sensors and actuators currently based on PZT. The piezoelectric, pressure sensing components in personal intruder alarms are PZT based. Modern aircraft have a range of PZT based sensors and actuators which are intrinsic to their efficient and safe function. However, the regulations concerning the industrial use of PbO are becoming increasingly stringent There are currently exceptions applied to the piezoelectric industry to allow the use of PbO in the manufacture of ceramics. These exceptions will, in time, be rescinded. The negative environmental impact of PbO is well known. Bi2O3 in contrast is considered less toxic and does not fall under the same restrictions as PbO. Bi3+ has a similar electronic structure to Pb2+ with the lone electron pair providing a high ionic polarisability, particularly when in pseudo-cuboctahedral coordination. The replacement of PbO with Bi2O3 in piezoelectric ceramics will therefore have a huge societal, environmental as well as commercial impact. Small niche devices containing less performant variants of PbO-free piezoelectrics are already reaching the market. These devices use piezoelectric ceramics in a mode of operation that does not require high fields, such as at resonance or as a sensor. Therefore, the choice of ceramic is not critical. However, the work proposed here aims to develop compositions suitable for replacing PZT in the most stringent and high value added application; multilayer actuators for the fuel injector systems in diesel engines. This market is dominantly European but is worth ~100M per annum to the various PZT manufacturers such as Morgan Electroceramics and Ceramtec. ii) Academic Impact There is currently huge academic interest in the functional ceramics community in PbO-free piezoelectric ceramics. At the recent International Symposium on Applied Ferroelectrics, co-organised by the PI, >40 oral contributions were presented on this topic. The range of materials being researched is broad however, if the materials discussed in the proposal live up to their potential then focus will switch to field induced systems and the impact of any early published studies will be highly significant. Prof. Cann will ensure that the research reaches the appropriate academic scientific audience by continuing his robust publication record and by presenting at key symposia and conferences. He will also visit, whilst in the UK, many groups active in this area of research. In the UK three research groups have focused on this topic in recent years, Leeds, Warwick and Sheffield. Warwick and Leeds have published or are undertaking research on NBT-based systems whereas Sheffield have been studying BiFeO3 based ceramics. All three groups would benefit greatly from interacting with Prof. Cann whose compositions give eyecatching values of electromechanical strain.