Electric Double‐Layer Structured Grain Boundaries in Medium‐Entropy Perovskite Enable Robust Electromagnetic Interference Shielding after 1200 °C Oxidation

ceramic also possesses the highest flexural strength (217.2 MPa) and hardness (11.6 GPa) among the perovskite oxides due to the vacancy clustering to both GBs and grains, which validates the protocol to fabricate mechanically and thermally robust EMI shielding materials for aerospace applications.