2  נ.ז.

דרישת קדם: מבוא למדע והנדסת חומרים

This course is an introduction to fast developing novel nanotechnological field of nanomotion. It consists of three parts: physical basis, materials and devices. It introduces a theoretical background of a basic knowledge in physics of ferroelectricity, piezoelectric and electrostrictive effects including crystallography, symmetry aspect, phase transitions and ferroelectric domains. Detail description of physics of dielectrics is combined with consideration of solid state physics of exploited materials: ferroelectrics piezoelectrics, relaxors and polymers. The unique properties of piezoelectric and electrostrictive materials allow wide using them for nanopositioners in various analytic tools for microprobe microscopy, nanofabrication, adaptive optics, optical communication systems, micromotors, acoustic imaging, biomedical diagnostics (ultrasound). The third part considers applications of piezoelectric and electrocstrictive devices mainly in micromechanic, microoptic, acoustic and medical devices.

The course is prepared in Power Point format and represents course ²on line² which contains last updated scientific and technological developments. The materials presented in the course are based on the fundamental knowledge and recently published scientific papers taking from Internet Journals on Line and computer simulations combined with graphs, drawings and computer movies extracted from various Internet Websites demonstrated by different laboratories and industrial companies leading in the field.

1. Ferroelectricity, general features of ferroelectric crystals. Spontaneous polarization. Ferroelectric and paraelectric phases. Symmetry aspect, crystallographic considerations, points groups. Classification of ferroelectrics: Single- and multi-axis ferroelectrics, Symmetry of nonpolar phase. Nature of phase transition (order-disorder and displacive). Curie-Weiss law. Antiferroelectricity. Fundamental physical properties of ferroelectrics: optical, nonlinear optical, pyroelectric, piezoelectric, etc

2. Ferroelectric Domains. Depolarization energy. Monodomain and multidoamin structures. 180 and 90-degree domains. Thermodynamic theory. Domain walls. Methods of observation. Geometry of ferroelectric domains. Optical, nonlinear optical, pyroelectric properties of domains. properties of domain-divided ferroelectrics. Ferroelectric  polarization switching.

3. Ferroelectric phase transition. Transition of the first and second order. Thermodynamic theory of Landau-Ginzburg-Devonshire. Electron-phonon interaction in ferroelectrics. Microscopic theory of ferroelectric phase transition. Physical properties of ferroelectrics in the range of phase transition. 

4. Piezoelectric effect. General definitions. Piezoelectric and electrostriction effects. Direct and converse piezoelectric effects. Piezoelectric coefficients. Crystal symmetry and piezoelectric effect. Tensor of stresses. Tensor of strains. Special forms of stress tensors. Tensor of piezoelectric coefficients. Structural mechanism of piezoelectric effect. Crystals and ceramics. Piezoelectric tensors for piezoelectric crystals and poled ferroelectric ceramics. Temperature dependence of piezoelectric coefficients near ferroelectric phase transition. Ferroelectric domain influence on piezoelectric effect. Domain engineered structures for high frequency piezoelectric devices.

5. Electrostriction effect. Electrostriction as a second order effect. Anharmonicity of potential energy. Structural mechanism of electrostriction. Tensor of electrostrictive coefficients. Properties of electrostriction effect. Electrostrictive materials.

6. Materials for piezoelectric and electrosctritive sensors and actuators. Classification of materials. Crystals, ceramics and polymer materials. Relaxor ferroelectrics. PZT based ceramics. PZT crystal structure and its symmetry. Phase diagram. Phase transitions. Morphotropic boundary. Dielectric and piezoelectric properties  at the morphotropic boundary. PZT compositions modification. Acceptor and donor doped PZT ceramics. “Soft” and “Hard” PZT ceramics and their physical properties. Photostricrive effect and ceramics. Piezoelectric composite materials, symmetry and physical properties. Piezoelectric ceramics for high temperature applications.

7. Relaxor ferroelectrics. Conventional, diffuse and relaxor phase transtions. Physical properties of PMN ferroelectric during relaxor phase transition. Macroscopic and macroscopic symmetry of  relaxor ferroelectrics. Physical models of relaxor state. Glass-like state of relaxor compositions. Relaxor Pb-based compositions. Physical propereties of relaxor compositons. Electrostrictive effect in Pb-based relaxors. PLZT  ceramics and properties.

8. Relaxor-Pb-Ti compositions. Relaxor ferroelectrics PMN and PZN. Phase diagram. Anomalous physical properties of PMN-PT relaxors. PMN-PT monocrystals. Giant electrostrictive effect. Physical models of ultrahigh strains in PMN-PT and PZN-PT relaxors. Engineered domain configuration in relaxors PMN-PT monocrystals.

9. Ferroelectric polymers.  General properties and structure. Polymer chain configurations. Molecules ttt, g⁺tg^- and tg⁺tg^- conformations. Chain conformations in PVDF polymer. Chain packing in PVDF. Structural peculiarities of a, b, d and g-phase packing. Stages of PVDF polarization. Ferroelectric polymers and copolymers. Ferroelectric, dielectric and piezoelectric properties of PVDF and copolymers. Ferroelectric phase transition in polymers. Symmetry of PVDF and tensor of piezoelectric coefficients. Polarization reversal in ferroelectric polymers. Relaxor properties of irradiated ferroelectric polymers. Giant electrostrictive effect in  b-irradiated polymers.

10. Piezoelectric actuators. Principals of engineering and applications. Classification of piezoelectrcic/electrostrictive actuaotrs. Monolayer, multilayer, monomoprh, bimorph, rainbow and flextensional actuators. Multilayer actuators, properties, parameters, electrode configuration. Pseudoshear multilayer actuators, torsional PZT actuators, Moonie and cymbal actuators. Bending elements for actuators. Ball-bearing actuators. Figures of merit of  piezo- and electrostrictive materials for various actuators.

11. Micro-electro-mechanical piezoelectric devices. Parameters, principals and areas of applications. Piezoelectric/electrostrictive actuators for probe microscopy. Piezoelectric X-Y stages for Atom Force Microscopy. Figure of merit and  materials of the actuators Piezoelectric ZnO bimorph cantilever for 3-dimensional motion in probe microscopy. Micromachined piezoelectric cantilever for scanning tip. Piezoelectric micromachined computer “Mouse”-based on piezoelectric PZT thin film arrays. Piezoelectric nanopositioners for near-field microscopy. Micromachined piezoelectric transducers for noncontact imaging. Microvalves for  micro-fluid control system. Micropumps based on piezoelectrically operated membranes. Piezoelectric microangle adjusting devices.

12. Micro-optical--electro-mechanical piezoelectric devices. Parameters, principals and areas of applications. Piezoelectrically-driven tip/tilt platform for optical precision stages. PZT piezoelectric flexure nanopositioners and scanners. Piezoelectric bending actuators for optical beams steering. PZT and ZnO-based flexural mode fiber actuators.  Piezoelectric actuators for optical switches in optical communication systems. Steering systems using microlens arrays. Microoptical shutters operated by piezoelectric substrate. Optical stabilizers. Microactuators for optical scanners. Piezoelectrically operated deformable  mirrors for adaptive optics.

13. Piezoelectric micromotors. Linear micromotors, PZT inchworms for air and vacuum applications with piezoelectric fixation, microworms for fiber optics with electrostatic fixation. Rotational micromotors with magnetic fixation. Arrangements for linear and rotational motions. Piezoelectric ultrasonic micromotors (USM). Principal, parameters and design of USM. Travelling wave USM. USM stators design. Magnification of tangential diaplacement. Dynamic picture of deformation distribution in piezoelectric stator with “teeth”. Disc microUSM. Ring microUSM. Piezoelectric PZT thin film fin micromotors.

14. Medical applications of piezoelectric materials. Buble detectors, tooth movement sensors,  medical acoustic imaging. Principals of acoustic imaging. Figure of merit of piezoelectric transducers. PZT-polymer composite materials with low acoustic impedance. Ultrasonic high frequency transducers. Pizoelectric materials for medical imaging technique. Linear and multidimensional arrays. Resolution. Computer simulations of piezoelectric tranducers.