Autonomous sampling of α-Fe2O3 hollow microspheres with carbon-stabilized defects: calcination-tuned humidity sensor performance
Document Type
Article
Publication Date
2025
Abstract
Defect control and surface chemistry remain critical bottlenecks in advancing metal-oxide humidity sensors. We report a scalable mechano-thermal strategy for fabricating carbon-doped α-Fe2O3 hollow microspheres, whose intrinsic voids act as autonomous sampling chambers. Systematic calcination (500–900 °C) enables precise tuning of crystallite size (38.2–87.6 nm), lattice strain (0.10–0.77 %), dislocation density (1.4 × 10−4–3.07 × 10−3 nm−2), and carbon content (21 → 14 wt%), thereby modulating carbon–oxygen moieties that govern water adsorption and proton-hopping conduction. Spectroscopic analyses reveal a stable Fe2+/Fe3+ surface ratio and C–Fe–O interactions, generating hydrophilic adsorption sites and activating a dual-regime mechanism: ionic conduction dominates up to 75 % RH, while Grotthuss proton transport prevails at higher humidity. Non-monotonic phase evolution with transient Fe3O4 nucleation at 800 °C highlights the role of dynamic defect activation. The Fe-500 device delivers superior performance, with a sensitivity of 0.75 kΩ/% RH, response time of 40 s, and recovery time of 85 s, surpassing benchmark hematite-based sensors
Recommended Citation
gomaa, islam; morsy, mohamed; and rizk, moustafa, "Autonomous sampling of α-Fe2O3 hollow microspheres with carbon-stabilized defects: calcination-tuned humidity sensor performance" (2025). Nanotechnology Research Centre. 199.
https://buescholar.bue.edu.eg/nanotech_research_centre/199