天然针铁矿与合成针铁矿半导体性能对比

利用X射线衍射仪、透射电子显微镜、X射线荧光光谱仪、X射线吸收谱与发射谱仪、光电子发射谱仪,首次对天然针铁矿与合成针铁矿样品开展了矿物学和半导体性能的对比研究。测试结果表明,天然针铁矿样品中混有少量石英颗粒,且针铁矿晶体中存在Al替代现象,Al掺杂比例为1. 16wt%～3. 23wt%。天然针铁矿禁带宽度为2. 25 eV,小于合成针铁矿2. 55 eV的带隙宽度。绝对真空能级下,天然针铁矿的价带位置为-5. 06 eV,相对于合成针铁矿有所抬升(-5. 38 eV),推测是由于Al元素替代导致在天然针铁矿价带引入Al-2p轨道成分所致。室内甲基橙降解实验结果表明天然针铁矿光催化降解甲基橙的效率(67. 2%)要高于合成针铁矿(50. 6%),表明天然针铁矿具有更好的光催化活性。天然针铁矿相较于合成材料而言具有储量高、价格低、光响应范围宽广等特点,研究结果可为进一步拓展其在材料领域的应用提供理论基础。

Comparative Study on the Semiconducting Properties of Natural and Synthetic Goethite

Natural goethite sample was collected from Anhui Tonling deposit, and measurements including powder X-ray diffraction, transmission electron microscope, X-ray fluorescence, synchrotron-based O K-edge X-ray absorption and emission spectra and photoelectron spectrometer were employed to study its mineralogical characteristics and semiconducting properties. Photocatalytic degradation of methyl orange was also carried out using natural and synthetic goethite. Results demonstrate that Al can substitute Fe in natural goethite crystal with a doping amount of 1.16-3.23 wt%. The band gap of natural goethite and synthetic goethite is 2.25 and 2.55 eV, respectively. The valence band potential of natural goethite (-5.06 eV) is slightly lifted when compared with that of synthetic goethite (-5.38 eV), which may be caused by the incorporation of Al-2p orbits in its valence band. Furthermore, natural goethite displays better performance (67.2%) in photocatalytic degradation of methyl orange than synthetic goethite (50.6%) due to its broad responding wavelength range. Natural goethite possesses many advantages over synthetic materials such as its abundant storage, lower price and better responding capability to solar light. Our results can provide theoretical support for its application in the field of semiconducting materials.