非洲黄色蓝宝石的致色机理及改色研究

Coloring Mechanism and Color Modification of Yellow Sapphire from Africa

利用激光剥蚀电感耦合等离子体质谱仪和紫外–可见–近红外分光光度计对产自非洲的铁含量较高而其它过渡金属元素含量较低的黄色蓝宝石的元素和光吸收谱进行测试。结果表明:非洲黄色蓝宝石的颜色是由Fe3+外层d电子跃迁和O2-与Fe3+的电荷转移两种呈色机制共同所致。利用还原退火的方法使黄色蓝宝石样品中新形成Fe2+-Fe3+同核异价离子对,同时其颜色由黄色变为深蓝色。Fe2+-Fe3+的形成及黄色蓝宝石样品颜色的改变,既证实了1993年Fritsch博士提出的"单独的Fe2+-Fe3+离子对可以使刚玉宝石呈现蓝色"的观点,也为天然黄色蓝宝石和山东昌乐深蓝色蓝宝石的改色提供了新的思路和理论依据。

The elements and optical absorption spectra of yellow sapphire with a high iron content and a low content of other transition metal elements from Africa were characterized by laser ablation inductively coupled plasma mass spectroscopy and ultraviolet visible near-infrared spectroscopy. The results show that the color of yellow sapphire is jointly contributed to outer d-electron of Fe3+ and charge transfer of O2- and Fe^3+.Fe^2+-Fe^3+ is formed in the yellow sapphire by reduction annealing, and its color changes from yellow to dark blue. The formation of Fe^2+-Fe^3+ and the change of the color of yellow sapphire support a previous conclusion that 'Fe^2+-Fe^3+ion pair can make corundum blue' proposed by Dr. Fritsch in 1993. This work could provide some ideas and theoretical basis for color modification of natural yellow sapphire and dark blue sapphire from Changle, Shandong.