Modulation of the dielectric breakdown strength in polyimide nanocomposites by deep traps tailoring in interphase regions

From a novel empirical power law between the DC breakdown field and DC conductivity, an analysis of the trapping characteristics in polyimide/boron nitride (PI/BN) nanocomposites is presented based on space-charge-limited current (SCLC) measurements. The impact of the total trap density H t enhancement (increasing up to 1.1×1017 cm−3) induced by the BN nanoparticles on the space charge attenuation, the DC conductivity reduction and the DC breakdown field increase is clearly reported. This work proves that an efficient control of the trapping parameters allows huge enhancement of the insulating properties of PI nanocomposites. High temperature thermal breakdown can be delayed by free carrier reduction through deep trap formation caused by nanofiller addition.