Ultra‐Robust (>700 K) Vacuum‐Ultraviolet Radiography Enabled by Nano‐Polycrystalline hBN

To address the urgent demand for high‐temperature vacuum‐ultraviolet (VUV) imaging detection in solar storm monitoring, this study develops a nano‐polycrystalline hexagonal boron nitride (NPhBN) scintillator with exceptional thermal robustness. Enabled by high‐temperature rapid chemical vapor deposition, wafer‐scale fabrication of an 8‐inch format is achieved. Its unique 2 nm grain structure simultaneously set records with a high photoluminescence quantum yield of 69.2% and an unprecedented thermal quenching temperature of up to 720 K with outstanding stability. VUV radiography at 523 K demonstrates that NPhBN maintains superior imaging quality under extreme conditions, effectively overcoming the thermal deactivation issue plaguing conventional scintillators in high‐temperature environments. Remarkably, NPhBN also exhibits outstanding VUV scintillation properties at room temperature, including an ultrafast decay time of 4.7 ns and a high spatial resolution of approximately 45 lp/mm. This work provides a robust VUV scintillator solution for solar disaster early‐warning systems.