Preparation And Dielectric Properties Of KTa_xNb_1-xO₃-Based Polymer Composites

Polymer-based composite dielectric materials can be widely used in embedded capacitors,energy storage devices,and wearable devices due to their excellent dielectric properties,high power density,and good flexibility.Potassium tantalum niobium oxide has attracted the attention of researchers due to its excellent piezoelectric,acousto-optic,nonlinear optical and electro-optical properties,as well as the phase structure and properties that can be adjusted by Ta/Nb ratio.In this paper,KTN fillers,KTN@BT two-phase composite fillers and KTN@BT/Ag three-phase composite fillers were designed and prepared.The effects of the preparation conditions of these three fillers on the morphology and results of the respective fillers were investigated.The composites were mixed with P(VDF-TrFE-CTFE)polymer to study the effects of fillers on the microstructure,structure,crystallization behavior,dielectric and energy storage properties of the composites.(1)The morphology of the potassium tantalum niobium oxide particles and the properties of the composites were continuously optimized by changing the reaction parameters.The results reveal that the dielectric properties of the polymer-based composites of KTa0.2Nb0.8O3 powder prepared by hydrothermal method and solid-state reaction are not much different.However,they are superior to the dielectric properties of polymer-based composites prepared by hydrothermal preparation of KNbO3 particles.(2)Compared with the KTN@BT hybrid particles prepared by the solid-state reaction,the hydrothermally prepared powder not only has good dispersibility,but also has a more uniform morphology and size,so the polymer matrix composite has better dielectric properties.The composites filled with 2 vol.%KTN@BT(1:1)prepared by hydrothermal method possess a dielectric constant 39(1 kHz)which is 1.2 times than that of the pure polymer,and the dielectric loss is basically unchanged at 0.077.Breakdown strength of the composite was 374 MV m-1 higher than that of pure polymer 363 MV m-1,and the composites film show more than 61.4%increase in energy density above that of the pure polymer(7.1 J cm-3 compared to 4.4J cm-3).(3)The quantum size effect and Coulomb blockage effect of Ag nanoparticles in KTN@BT/Ag fillers make the fillers effectively increase the dielectric constant of the composites and maintain a low dielectric loss.Typically,the dielectric constant of the composite filled with 20 vol%KTN@BT/Ag reaches 125 at 100 Hz,in contrast to 37 for pristine P(VDF-TrFE-CTFE).Compared with the KTN@BT based composite,it also shows better dielectric properties.