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 (<45 V mm −1 ). Below the threshold field, electromagnetic attenuation is dominated by interfacial polarization loss, whereas exceeding the threshold induces a sharp conductivity increase via interfacial barrier modulation, driving a transition to a shielding‐dominated state. In this regime, the composite exhibits a theoretically estimated shielding effectiveness exceeding 35 dB across 2–18 GHz based on experimentally measured conductivity, thereby realizing dynamic switching between absorption and shielding modes. This work establishes a new paradigm for heterointerface‐engineered, cold‐sintered ceramics toward intelligent electromagnetic protection materials with externally controllable functionality.
Si et al. (Mon,) studied this question.