应用FTIR-SEM研究一类合成欧珀的微结构及其变彩成因机制

近些年来,相关人工合成欧泊的研究工作主要聚焦于天然与合成欧泊的鉴别与筛选,而相关合成欧泊的微结构、变彩机制及其中水的赋存状态的深入研究鲜见报道。本文通过傅里叶变换红外光谱(FTIR)、场发射扫描电镜(FE-SEM)对一类合成欧泊的微结构、结构缺陷进行较系统的研究。同时,结合对样品的热处理就该合成欧泊体色、变彩机制及其中水的赋存状态作了初步探讨。结果表明:该样品的红外光谱中,在约2900 cm~(-1)、1737 cm~(-1)处出现合成欧泊特征吸收,且在4000~6000 cm-1波段,合成欧泊相比天然欧泊的吸收峰更为复杂。合成欧泊的颜色由体色与变彩两者共同构成,该体色与存在于其微结构中准球状、粒径约205 nm的二氧化硅颗粒的间隙填充物直接关联,且在热处理条件下随着间隙物的析出而渐退。同时,该类合成欧泊的变彩归因于结构致色并由其内部SiO_2颗粒周期性排列而构成的三维的光子带隙结构所致。此外,在欧泊的微观结构发生重构前,变彩所呈现的颜色主要由准球状二氧化硅颗粒粒径与间隙填充物决定。

Investigation of the Microstructure and Play of Color Mechanism of a Synthetic Opal by FTIR-SEM

In recent years considerable research has been focused on distinguishing natural from synthetic opals. However, with regard to synthetic opals, less attention has been paid to investigate their microstructure, the formation mechanism of play of color and the form of water content. Fourier Transform Infrared Spectroscopy (FTIR) combined with Field Emission-Scanning Electron Microscopy (FE-SEM) were used to systematically investigate the microstructure of a synthetic opal. With the help of heat treatment, the formation mechanism of body color, play of color and the occurrence state of water have been preliminarily studied. Results show that the synthetic opal had typical absorption peaks at 2900 cm^-1 and 1737 cm^-1 in FTIR Spectroscopy. The absorption peaks of synthetic opal were more complex than those of natural opal-between 6000 cm^-1 and 4000 cm^-1 (in Fig.2). The color of synthetic opal consists of body color and play of color. The body color has a direct association with the substances filling in the pores among these quasi-spherical SiO₂ particles with a diameter of 205 nm, and it gradually disappeared as the substances escaped from the pores (in Fig.5). The play-of-color of synthetic opal originated from three dimensional photonic band gap structures, which consisted of periodicity-arranged SiO₂ particles. In addition, before the micro-architecture made by SiO₂ particles was broken, the main color depended on the particle size and the substances filling the pores.