Ferroelectric materials: phenomenology, properties and characterization

Abstract

The subject of this project is the synthesis, phenomenological studies, and computational simulation of physical properties and experimental characterization of ferroelectric materials, due to their high technological importance. Although there are reported innumerous theoretical and experimental works, the study of ferroelectric materials remain as an actual subject for researches. Since the discovery of ferroelectric ceramic, during the Second World War, ferroelectric materials have been subjects of investigations due to their innumerous possibilities to be used in the electro-electronic industry. Today they correspond to more than 70% of the materials used as sensor or actuator element in electronic components. Ferroelectric materials have been used as well polycrystalline as monocrystalline form in sensors and actuators. Actually, although the crescent interest for these materials over the world, in Brasil there are only a few groups working in this area. The development of this project aims to consolidate the scientific cooperation between groups, which are developing complementary investigation activities, in the DF/UFSCar and IFSC/USP. The complementarily activities and the theoretical studies, associated to experimental observations, will produce relevant information to use these materials in new technologies and understanding of their physical properties. The knowledge of the technology to produce such materials and the formation students, certainly will be a important contribution to develop this area in our country. This project aims the development and studies of physical properties of mono- and polycrystalline (ceramic or thin films) ferroelectric materials. The disposability of monocrystalline samples and the structure refinement will furnish relevant information to the modeling (phenomenological models) and simulation (by Molecular Dynamics) of some physical properties, frequently explored in sensors and actuators. It will be developed ferroelectric compositions, which are interesting for new technology as well for fundamental studies, in order to correlate structural to dynamics properties. The project will be developed by researchers and well-established groups, in their respective area. The participants have been cooperated before in the development of other project (Revista Pesq. FAPESP 10/99) or publications. The specific objectives to be reached are: 1. synthesis and characterization of ferroelectric ceramic compositions with perovskite and tungsten bronze structures: (based on Pb(Mg,Nb)O3 - PMN, PMN+PbTiO3, Pb(Zr,Ti)O3 - PZT, (Sr,Ba)Nb2O6 - SBN , (Pb,Ba) Nb2O6 PBN); 2. simulation by molecular dynamics of ceramic systems which presents perovskite structure; 3. Growth by Lasers-Heated Pedestal Growth LHPG monocrystalline fibers of SBN, ATiO3 (A=Ba, Ca e Sr) and (Ba,Me)TiO3 (Me = Ca, Sr e Ca+Sr), starting from ceramic seeds; 4. synthesis and characterization of ferroelectric thin films (PLT, PZT, PLZT, BIT, SBN, etc...); 5. study phase transition in mono- and polycrystalline samples, characterizing dielectric and structural properties and Raman spectroscopy; 6. correlate structural and electronic properties, obtained trough measurements with X rays techniques (EXAFS and XPS), with dielectric and ferroelectric properties; 7. characterize electrostrictive, piezoelectric, dielectric and pyroelectric properties to evaluate the potential of the materials to be used in technological applications (as sensors or actuators); 8. sintering of ceramic materials by uniaxial hot press (PLZT, SBN, PBN e PMN s); 9. development of phenomenological model to describe the dynamics of ferroelectric domains under an applied electric field; 10. visualization and characterization of ferroelectric domains by microscopy techniques (Optical (MO) and Atomic Force (AFM) microscopy); 11. participation of undergraduate and graduated students and Post Docs; 12. intensify the cooperation in basic and applied researches with international and national groups and institutions. Figures 1 and 2 present a schematic diagram of the activities that will be developed and the physical properties to be studied. Not necessarily all physical properties represented in figure 2 will be characterized in all prepared sample. Based on the results obtained until now and the members participating in each group we are sure about the technical/scientific potential to develop this project. Furthermore the cooperation between the groups and researchers certainly will be consolidated. Below are listed the groups participating of this project with the name of their respective coordinator and the abbreviation, which will be used to refer to each one. Grupo de Cerâmicas Ferroelétricas (GCF) DF/UFSCar- Coord. Dr. José Antonio Eiras Grupo de Dinâmica Molecular (GDM) DF/UFSCar - Coord. Dr. José Pedro Rino Grupo de Espectroscopia Raman (GER) DF/UFSCar- Coord. Dr. Paulo Sérgio PizaniGrupo de Cristalografia (GC) IFSC/USP - Coord. Profa. Dra. Yvonne Primerano Mascarenhas Grupo de Crescimento de Cristais & Materiais Cerâmicos (GCCMC) IFSC/USP - Coord. Dr. Antonio Carlos Hernandes Figure 1. schematic diagram of the activities to be developed. Figure 2. physical properties to be investigated. (AU)