摘要
A light purplish red sapphire is heat treated in an airtight crucible. The sample changes little in color after receiving heat treatment at 1100℃, but turns to light blue and blue after being treated at 1200℃ and 1300℃, respectively. Before heating, the UV-VIS absorption spectra of the sample are dominated by the 551 nm broad absorption band contributed by the d-electron transition 4A2 →4 4T2 of Cr3＋. After heating, the UV-VIS absorption spectra are dominated by the 563 nm broad absorption band contributed by the inter- valence charge transfer of Fe2＋ - Ti4＋. The x ray photoelectron spectroscopy test reveals that the Fe2＋ and Ti4＋ ion contents increase with increasing temperature. The sapphire changing from light purplish red to blue in the heating process is owing to the fact that the Fe2＋ and Ti4＋ contents grow and the intervalence charge transfer of Fe2＋ - Ti4＋ selectively absorbs UV-VIS light.
A light purplish red sapphire is heat treated in an airtight crucible. The sample changes little in color after receiving heat treatment at 1100℃, but turns to light blue and blue after being treated at 1200℃ and 1300℃, respectively. Before heating, the UV-VIS absorption spectra of the sample are dominated by the 551 nm broad absorption band contributed by the d-electron transition 4A2 →4 4T2 of Cr3＋. After heating, the UV-VIS absorption spectra are dominated by the 563 nm broad absorption band contributed by the inter- valence charge transfer of Fe2＋ - Ti4＋. The x ray photoelectron spectroscopy test reveals that the Fe2＋ and Ti4＋ ion contents increase with increasing temperature. The sapphire changing from light purplish red to blue in the heating process is owing to the fact that the Fe2＋ and Ti4＋ contents grow and the intervalence charge transfer of Fe2＋ - Ti4＋ selectively absorbs UV-VIS light.
