扩散处理黄玉振动谱学特征及呈色机理

VIBRATIONAL SPECTRUM FEATURES AND COLOURING MECHANISM OF THE DIFFUSED TOPAZ

一种扩散处理黄玉近期在珠宝市场上面市。它表现出的特征是内部无色 ,蓝绿色调仅限于表层 (厚度<5μm) ,表面不均匀地聚集有褐黄绿色斑点。研究表明 ,这种扩散处理黄玉由 Co2 +离子渗透致色 ,且渗色层内普遍发育由晶格缺陷致交错叠片状结构。可见光区域内 ,由 Co2 + 离子 (八面体配位 )的4 T1g( 4F)→4 T1g( 4P)、4 T1g→4 A2 g及 4 T1g→2 T1g跃迁 ,而产生 597,63 2 ,4 61 nm的吸收。研究结果证实 ,扩散温度条件、表层晶格缺陷及 Co2 + 离子浓度梯度是导致扩散处理黄玉呈色的主要缘由。提出

A variety of the diffused topaz is discovered in gem markets recently. This kind of stone is characterized by the absence of the colour in the internal and the concentration of blue green colour and brown yellow green colour speckled appearance on the surface (thickness less than 5μm). The reasearch indicates that the diffused topaz is coloured mainly by the permeance of Co 2+ , and the crisscross pile silice texture associated with crystal defects is developed commonly in the permeable colour layer. The absorption within the visible light zone of 597, 632, 461nm is resulted from the transition of . 4T 1g ( 4F) → 4T 1g ( 4P)、 4T 1g → 4A 2g 、 4T 1g → 2T 1g in Co 2+ . It has been verified that the temperature of diffusion and crystal defects on the surface and concentration gradient of Co 2+ are the main causes for the colouration of the diffused topaz. It can be concluded that the LRM is an important tool for identifying the diffused topaz.