Preparation,dielectric Property And Electrocaloric Effect Of Polymer-based Nanocomposites With Doped Fillers

The potential applications of dielectric materials in the fields of electronics,electric power,energy storage,radio communication and flexible wearable devices have attracted wide attention of researchers.At present,devices have been designed in the direction of high power density,high energy density and lightweight,which put forward higher requirements for the performance of dielectrics and functional dielectrics.Although researchers have done a lot of in-depth research on dielectric properties,energy storage behavior and electrocaloric effect of dielectric materials,there are still many areas in the field of polymer-based dielectric composites that can be improved and need to be improved,especially how to achieve a high dielectric permittivity while maintaining a low dielectric loss,so as to achieve a higher energy storage density,and how to improve the performance of electrocaloric effect.For polymer-based composite dielectric materials,there are not many choices for the matrix,such as epoxy resin,polyvinylidene fluoride and so on.However,there are more fillers to choose and have a larger space to improve.The fillers mainly include high dielectric ferroelectric ceramics,conductor,semiconductor,special structure particles,etc.The dielectric storage density and electrocaloric performance can be improved by using interfacial polarization effect and seepage effect.In order to achieve better performance,the ferroelectric polymer matrix polyvinylidene fluoride（PVDF）anditsterpolymerpolyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene[P（VDF-TrFE-CFE）]were used.Based on the above research on fillers,ferroelectric ceramics BaTiO₃ and Ba_0.67Sr_0.33TiO₃ were creatively doped with Y and Sn elements of and used as fillers,which has not been studied before.They were synthesized by hydrothermal reaction followed by heat treatment and then successfully filled into the matrix.Polymer-based dielectric nanocomposites filled with doped particles were prepared,and their dielectric,electrical conductivity,electric breakdown strength,electric polarization,energy storage properties were systematically investigated.The results showed that dielectric,electrical conductivity,electric polarization and leakage current increased with the increase of filler content,electric breakdown strength and energy storage behavior increased first and then decreased with the increase of filler content,causing a maximum value.The performance of polymer composites as ferroelectrics in the electrocaloric effect for environmentally friendly all-solid-state refrigeration were further explored.The results showed that the adiabatic temperature,isothermal entropy and electrocaloric strength of the electrocaloric effect increased with the increase of filler content,and then decreased with the increase of filler content,which has a maximum value.Finally,the doped elements entering the lattice were tested and analyzed by experiments.The electric field distribution of polymer-based nanocomposites,the electric field distribution and electric polarization in the fillers under the applied electric field were analyzed by Finite element simulation.Furthermore,the electric field intensity in the particles was obtained by integration.Based on the above results,the mechanism of enhancement in dielectric,energy storage behavior and electrocaloric effect was been well explained.