Abstract

A light purplish red sapphire is heat treated in an airtight crucible. The sample changes little in color after receiving heat treatment at 1100°C, but turns to light blue and blue after being treated at 1200°C and 1300°C, 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 A₂4→T₂4 of Cr³⁺. After heating, the UV-VIS absorption spectra are dominated by the 563 nm broad absorption band contributed by the intervalence 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.

© 2016 Chinese Laser Press

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