In a review paper, dielectric and electromechanical properties of relaxorlike polymers, which are important for their applications, are presented. The influence of dielectric constant value on these properties is explained. Concomitantly, a big potential of composites of relaxorlike polymers is presented in light of the large dielectric constant values, which can be achieved in these systems.
COBISS.SI-ID: 21090087
The first all-ceramic percolative composites (composites comprising conductive filler distributed in a dielectric matrix) have been developed. Due to almost an ideal structure – conductive ceramic grains are uniformly distributed in a dielectric ceramic matrix – the dielectric response in the Pb(Zr,Ti)O3-Pb2Ru2O6.5 composite follows the predictions of the percolation theory and the dielectric constant reaches values as high as 40,000 at room temperature. Obtained results demonstrate the potential of the composite for use as high-dielectric-constant material in various applications.
COBISS.SI-ID: 21715751
Besides the first lead-based system we have developed also the first lead-free all-ceramic percolative composite, being important as lead represents a possible ecological hazard. Similarly as in the Pb(Zr,Ti)O3-Pb2Ru2O6.5 system, in the lead-free (K,Na)NbO3–RuO2 all-ceramic percolative composite the dielectric response also follows the predictions of the percolation theory due to an almost ideal structure and, concomitantly, values of the dielectric constant are as high as in the lead-based system.
COBISS.SI-ID: 22349863
First all-ceramic percolative composites were superimposed by the development of new lead-based all-ceramic percolative composite, where 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) ceramics is used as the matrix instead of PZT. PMN-PT relaxor ceramics with this composition, being very close to the morphotrophic phase boundary, exhibits high dielectric constant by itself. Concomitantly, the PMN-PT-Pb2Ru2O6.5 composite exhibits colossal values of the dielectric constant (over 100000) at room temperature.
COBISS.SI-ID: 22425127
We have found out that in the composite polyaniline–P(VDF-TrFE-CTFE) terpolymer close to the percolation point dielectric constant reaches colossal values due to the large polarization at the polyaniline interface. The electric field, required for an electromechanical operation, is thus for several orders of magnitude lower than in the pure terpolymer. Contrary to the metal-polymer composites this system retains the flexibility of the polymer and thus does not limit its applicability. Dielectric response of the composite has been described in terms of the modified Maxwell-Wagner model.
COBISS.SI-ID: 20398887