Experimental study and theoretical prediction of dielectric permittivity in BaTiO_3/polyimide nanocomposite films

摘要

Theoretical models were used to predict dielectric permittivities of the thermosetting polyimide (PI) matrix nanocomposite films loading with BaTiO_3 (BT) nanoparticles prepared by the alkoxide route. The observed dielectric permittivities are in good agreement with calculated values using Jayasundere equation and effective medium theory when the interactions of nanoparticle-nanoparticle and nanoparticle-polymer are considered. Additionally, temperature dependence of dielectric permittivity of the BT/PI nanocomposite films at 10~3 Hz was also studied for both heating from -50 to 150℃ and cooling from 150 to -50℃. The transformation in crystal phase of BT and changes of free volume in PI were considered to be the main factors influencing the dielectric permittivities of the BT/PI nanocomposite films.