Fundamentals, processes and applications of high-permittivity polymer–matrix composites

The effect of processing conditions on the morphology, thermomechanical, dielectric, and piezoelectric properties of P(VDF-TrFE)/BaTiO3 composites

“…The desired electric field was applied for 30 min at 110°C and then for further 30 min while cooling to 35°C. The piezoelectric coefficient d 33 was measured with a Berlincourt-type d 33 -meter. The first measurement was taken 1 h after poling and then further measurements were performed in the following days in order to assess aging.…”

“…In addition to this, polymer/BaTiO 3 composites are also of great interest for the fabrication of high-relative permittivity materials for, e.g., embedded capacitors [20][21][22][23][24]. For polymer/BaTiO 3 composites the reported absolute values for d 33 are usually between 1 and 30 pC/N [6,8,25,26] (the sign depending on the polarization conditions in the case of piezoelectric polymer matrices), although a d 33 higher than 50 pC/N was reported for a PVDF/BaTiO 3 composite [27].…”

“…Highly filled (0-3) composites, however, present a complex morphology due to the coexistence of several phases: not only the polymer matrix and the ceramic filler particles, but also, at high filler concentrations, filler aggregates, and porosities (at microscopic and macroscopic level), as well as residual solvent may be present depending on the processing routes and conditions. As pointed out in a recent review [33], modification of the surface of the ceramic fillers, through chemical grafting or the production of core-shell structures is key to improve filler dispersion, reduce porosity, thereby improving the mechanical, and electrical properties of the composites. Most of the existent studies focus on the dielectric [34][35][36][37][38][39][40][41][42][43] and electromechanical [4,7,13,15,17,25,44] properties of such composites and relatively few systematic studies on their thermal and mechanical behavior have been published so far.…”

Effect of silane coupling agent on the morphology, structure, and properties of poly(vinylidene fluoride–trifluoroethylene)/BaTiO3 composites

“…Extensive reviews on high-permittivity materials and their applications have been published recently [2,3]. The energy density of a dielectric material is proportional to its relative permittivity, ε, and to the square of the applied electric field.…”

“…the threshold electric field above which charges start flowing through the dielectric material. The dielectric breakdown is a complex phenomenon that has been related to several mechanisms, among which the accumulation of heat due to dissipation of energy by dielectric losses [2][3][4]. VDF based polymers have high electrical breakdown strength, however their relative permittivity, although fairly high for a polymer, is much lower than that obtainable for ceramic materials, which on the other hand suffer from lower breakdown strengths [4].…”