Analysis on UV-VIS Spectrumand Colouration Mechanism of Sapphire

The XRF analyses and UV-VIS absorption spectra of sapphires with different colours indicate that the content of Fe³⁺ varies from the low to the high relative to the content of Fe²⁺-Ti⁴⁺ with the colour shift from pink, purple, blue, green, yellowish green to yellow. The colour varies from light blue to dark blue with increasing of the contents of Fe and Ti. The brown sapphire is rich relatively in Fe and Cr. Irradiated yellow sapphire has absorption in 405 nm. Absorption in 450, 375, 387 nm of heat-treated blue sapphire and irradiated yellow sapphire is weaker than that of the untreated.