Switchable Electromagnetic Absorption and Shielding in Liquid Metal‐ZnO Ceramics via Ultralow‐Electric‐Field

ABSTRACT Conventional electromagnetic shielding and absorbing materials are constrained by intrinsic dielectric and magnetic responses, rendering them inadequate for multi‐band communication, reconfigurable electronics, and adaptive stealth technologies. Here, we report a ZnO–liquid Ga composite ceramic that enables electric‐field‐driven switching between electromagnetic absorption and shielding under ultralow external electric fields. By tailoring interfacial reactions during cold sintering, a hierarchical ZnO/ZnGa 2 O 4 /Ga 2 O 3 /Ga heterointerface network is constructed. This architecture synergistically regulates interfacial polarization and field‐dependent carrier transport, enabling simultaneously ultrahigh‐intensity and broadband electromagnetic absorption (reflection loss of −70.1 dB at 1.91 mm with an effective bandwidth exceeding 6 GHz), together with outstanding electrical nonlinearity (α ≈ 445) and an ultralow threshold field (