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Projects / Programmes source: ARIS

Organic and inorganic percolative composites with giant dielectric constant

Research activity

Code Science Field Subfield
1.02.01  Natural sciences and mathematics  Physics  Physics of condesed matter 

Code Science Field
P250  Natural sciences and mathematics  Condensed matter: structure, thermal and mechanical properties, crystallography, phase equilibria 
P260  Natural sciences and mathematics  Condensed matter: electronic structure, electrical, magnetic and optical properties, supraconductors, magnetic resonance, relaxation, spectroscopy 
T152  Technological sciences  Composite materials 
Keywords
dielectric spectroscopy, polymer, ceramics, percolative composite
Evaluation (rules)
source: COBISS
Researchers (3)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  15644  PhD Vid Bobnar  Physics  Head  2007 - 2009  363 
2.  04347  PhD Cene Filipič  Physics  Researcher  2007 - 2009  289 
3.  00199  PhD Adrijan Levstik  Physics  Researcher  2007 - 2009  372 
Organisations (1)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0106  Jožef Stefan Institute  Ljubljana  5051606000  91,961 
Abstract
Dielectric materials, which are used to control and store charges and electric energy, play a key role in modern electronics and electric power systems. As requirements for compact and low cost systems grow substantially, development of high dielectric constant materials becomes major scientific and technology issue. Such materials are highly desirable also for use in a broad range of advanced electromechanical applications, as on increasing dielectric constant the electromechanical response can be induced under a much reduced electric field. It is predicted that in conductor-insulator composites the dielectric constant diverges at the percolation threshold (a determined volume ratio of both constituents) of the insulator-metal transition. The dielectric response of the so-called percolative mixture is thus much larger than those of the components, however, up to now only systems comprising metal particles within an insulator have been developed. We will investigate dielectric and electromechanical properties of: 1. All-organic percolative composites, where conductive polymer particles are dispersed into the insulating polymer matrix which by itself exhibits a giant electromechanical response (polyurethane, VDF-TrFE-based polymers). These composites are expected to exhibit a giant electromechanical response under low external electric fields. 2. All-ceramic percolative lead-based and lead-free composites made of ruthenium-based conductive ceramics and insulating ferroelectric or relaxor ceramics (PZT, PLZT, KNN) which by itself exhibits a high dielectric constant (relaxors in a broad temperature range). These composites are expected to exhibit giant dielectric constant values. 3. Composites comprising organic phthalocyanines within the insulating polymer. Here, due to completely delocalized electrons in phthalocyanines the interfacial polarization induces a large dielectric response. These composites will then be used as a matrix for the three-component percolative system. Not only that investigations should clear up the microscopic origin of the giant dielectric response in percolative composites, but all-ceramic composites developed at the Jožef Stefan Institute will be the first metal-particles-free inorganic percolative systems.
Significance for science
Results represent a contribution to the world's basic and applied-oriented knowledge. While up to now only organic percolative composites and inorganic systems, comprising metal particles within an insulator, have been developed, newly synthesized lead-based PZT–Pb2Ru2O6.5 and PMN-PT–Pb2Ru2O6.5 as well as lead-free KNN–RuO2 systems are the first metal-particles-free inorganic percolative composites. Their dielectric properties – due to almost an ideal structure (conductive ceramic grains are uniformly distributed in a dielectric ceramic matrix) the dielectric response follows the predictions of the percolation theory and the dielectric constant actually diverges on approaching the percolation threshold – demonstrate the potential of all-ceramic percolative composites for use as high-dielectric-constant materials in various electronic and electromechanical applications, while procedures used for their synthesis represent the basis for future development of new giant dielectric constant systems.
Significance for the country
Ceramic percolative composites, developed at the Jožef Stefan Institute (the first all-ceramic, i.e. metal-particles-free percolative systems), are due to their giant values of the dielectric constant extremely interesting for charge storage applications (capacitors, electronic circuits). On the other hand, polymer-based percolative composites are, due to the ultrahigh electromechanical response and large values of the dielectric constant (small external electrical field, required for the operation), very attractive for a broad range of applications such as sensors, actuators, artificial muscles, and integrated micro-electromechanical systems. All the above mentioned applications might potentially be interesting for the Slovenian industry. Furthermore, investigations performed within this research project enable our contact with the world-knowledge and active participation in the development of new materials. Such investigations establish an inovative research environment, which is essential for the socio-economic development of Slovenia.
Most important scientific results Annual report 2008, final report, complete report on dLib.si
Most important socioeconomically and culturally relevant results Annual report 2008, final report, complete report on dLib.si
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