Pt decorated core-shell ZnS:Cu doped epoxy composites: Achieving enhanced breakdown strength and defect visualization

Designed ZnS:Cu@SiO 2 –Pt particles for insulation enhancement and defect visualization. • Pt/SiO 2 deep traps suppress charge migration via band realignment. • 0.3 wt% loading yields 47.53 kV/mm breakdown strength (+17.56% vs EP). • Outperforms ZnS:Cu and ZnS:Cu@SiO 2 controls (+1.93% and +8.85%). • EL visualizes defects: 100 μm scratches, 300 μm high- ε $\mathrm{\epsilon }$ defects, 480 μm bubbles. Epoxy resins (EP) are widely used for power electronic encapsulation and electrical insulation, yet insulation defects (bubbles/micropores) can trigger partial discharge (PD) and accelerate degradation. Developing new methods capable of precisely detecting micro-defects has become a key focus in failure prevention. Inspired by the luminescence of Mycena chlorophos, we proposed self-reporting EP composites to visualize micro-defects, in which biomimetic designed fillers based on strawberry-like structure particles (ZSP) were incorporated. ZnS:Cu with electroluminescence characteristics was adopted as core material, whose surface is coated with SiO 2 shell and decorated with Pt nanoparticles. ZSPs synthesized via wet-chemical routes exhibit green electroluminescence under localized electric fields, enabling real-time visualization of micrometer-scale defects. Incorporating ZSPs into EP yields self-diagnosing composites (SDCs) that combine enhanced dielectric strength with defect visualization effects. DFT calculations revealed that Pt/SiO 2 interface introduces deep trap states, which suppress the charge migration. As a result, the breakdown strength of SDCs increased by 17.57% compared to pristine EP. SDCs further demonstrate broad defect-detection capability for surface and internal defects, including high-dielectric-constant defects, scratches, and bubbles. Overall, this work establishes a material-level route that integrate condition monitoring with insulation reinforcement for high-voltage equipment and electronic modules.