Fantauzzi Marzia, Secci Fausto, Sanna Angotzi Marco, Passiu Cristiana, Cannas Carla, Rossi Antonella
Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, Campus di Monserrato S.S. 554 Italy
Department of Materials, ETH Zürich Vladimir-Prelog-Weg 5 Zurich Switzerland.
RSC Adv. 2019 Jun 18;9(33):19171-19179. doi: 10.1039/c9ra03488a. eCollection 2019 Jun 14.
Nanostructured spinel cobalt ferrite samples having crystallite size ranging between 5.6 and 14.1 nm were characterized by X-ray photoelectron spectroscopy and X-ray induced Auger electron spectroscopy in order to determine the chemical state of the elements, the iron/cobalt ratio and the cation distribution within tetrahedral and octahedral sites. The presence of size-dependent trends in the binding energy of the main photoelectron peaks and in the kinetic energy of the X-ray induced O KLL signal was also investigated. The results showed that iron is present as Fe and cobalt is present as Co. The iron/cobalt ratio determined by XPS ranges between 1.8 and 1.9 and it is in very good agreement, within experimental uncertainty, with the expected 2 : 1 ratio. The percentage of Fe in octahedral sites ranges between 62% and 64% for all samples. The kinetic energy of the O KLL signals increases with crystallite size. These results are explained in terms of changes in the ionicity of the metal-oxygen bonds. The results of this investigation highlight how the XPS technique represents a powerful tool to investigate the composition, the chemical state and inversion degree of cobalt spinel ferrites, contributing to the comprehension of their properties.
通过X射线光电子能谱和X射线诱导俄歇电子能谱对微晶尺寸在5.6至14.1纳米之间的纳米结构尖晶石钴铁氧体样品进行了表征，以确定元素的化学状态、铁/钴比以及四面体和八面体位置内的阳离子分布。还研究了主要光电子峰的结合能和X射线诱导的O KLL信号的动能中尺寸依赖性趋势的存在情况。结果表明，铁以Fe形式存在，钴以Co形式存在。通过XPS测定的铁/钴比在1.8至1.9之间，在实验不确定性范围内，与预期的2∶1比例非常吻合。所有样品中八面体位置的Fe百分比在62%至64%之间。O KLL信号的动能随微晶尺寸增加。这些结果根据金属-氧键离子性的变化进行了解释。本研究结果突出了XPS技术是研究钴尖晶石铁氧体的组成、化学状态和反型程度的有力工具，有助于理解其性能。
