圆明园琉璃瓦片状云母氧化铁的形成机理

Forming mechanism of mica iron oxide from glazed tiles in Yuanmingyuan

使用光学显微镜、EDXRF、SEM、XPS和XRD对圆明园出土的部分黄色琉璃瓦釉黄中泛红现象进行分析,以研究琉璃瓦的变色机理。分析表明:琉璃瓦的釉层属于一种铅硅系玻璃,釉层呈现黄中泛红现象是由于红色区域和黄色区域中Fe存在形式不同所致,釉层红色区域中Fe主要是以α-Fe_2O_3晶体形式存在,黄色区域中Fe是以Fe^(3+)与Fe^(2+)的形式存在。这种现象产生的本质是由于黄色区域中的Fe^(2+)在高温条件下被O_2氧化为Fe^(3+),然而高温导致釉层流失,进而导致釉层中的Fe^(3+)析出富聚为六角片状的α-Fe_2O_3晶体颗粒所致。α-Fe_2O_3显红色又被称为云母氧化铁红,是非常重要的防锈防腐涂料以及珠光颜料。

This experiment analyzes the diffused red in yellowing phenomenon of partial yellow glazed tiles unearthed from Yuanmingyuan by means of optical microscope,EDXRF,SEM,XPS,and XRD in order to study the color change mechanism. The analyses suggest that the glaze layer of the sample tiles belongs to a kind of lead silicate glass and that the diffused red in yellowing phenomenon of glaze is due to the different forms of Fe within the glaze layer,with α-Fe2O3 crystal dominating the red area and Fe^3＋and Fe^2＋existing simultaneously in the yellow area. The study shows the phenomenon can be explained by the process of oxidation of Fe^2＋into Fe^3＋in the yellow area at high temperature during which glaze layers are lost. It further results in abundant precipitation of Fe^3＋in the form of hexagonal plate α-Fe2O3 crystal particle,which is also called micaceous iron oxide red being very important rust preventive and pearlescent pigment.