1. Intrinsic Color: Black Bulk (micron-scale) pure Fe3O4(Magnetite) appears deep black under visible light. Reason: Fe3O4 is a narrow-bandgap semiconductor (bandgap ≈0.1≈0.1 eV), which absorbs light across the entire visible spectrum with virtually no reflection, resulting in a pure black appearance. Industrial products: Larger-particle Fe3O4powders (micron-...
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