Bastianello Michele, Gross Silvia, Elm Matthias T
Center for Materials Research (LaMa), Justus-Liebig-Universität Gießen Heinrich-Buff-Ring 16 35392 Giessen Germany.
Institute of Physical Chemistry, Justus-Liebig-Universität Gießen Heinrich-Buff-Ring 17 35392 Giessen Germany
RSC Adv. 2019 Oct 17;9(57):33282-33289. doi: 10.1039/c9ra06310b. eCollection 2019 Oct 15.
Monophasic nano-crystalline CoFeO (CFO) nanoparticles of high purity have been synthesised through a low temperature hydrothermal route, which does not involve hazardous chemicals, or conditions. The easy, green procedure involves a hydrothermal treatment at 135 °C of an aqueous suspension of the oxalate salts of the precursors. No further purification or annealing procedure was necessary to obtain the crystalline nano-structured oxide. The nanoparticles were characterized structurally and chemically by powder X-ray diffraction (PXRD), Inductively Coupled Plasma Spectrometry (ICP-MS) and Scanning Electron Microscopy (SEM), thus confirming the successful synthesis of the CoFeO particles with the expected crystal phase and stoichiometry and an almost complete inverse spinel structure. From the nanoparticles pellets were pressed to investigate the electronic conduction properties using electrochemical impedance spectroscopy (EIS). At low temperatures, the conductivity measurements reveal a semiconducting behavior originating from hopping between Co sites and a total conductivity dominated by the grain boundary contribution. At higher temperatures ( > 400 °C) a metallic-insulator transition occurs, which is attributed to additional hopping of electrons between the Fe sites.
通过低温水热法合成了高纯度的单相纳米晶钴铁氧化物（CFO）纳米颗粒，该方法不涉及危险化学品或条件。这种简便、绿色的方法包括在135℃下对前驱体草酸盐的水悬浮液进行水热处理。无需进一步的纯化或退火程序即可获得结晶纳米结构氧化物。通过粉末X射线衍射（PXRD）、电感耦合等离子体质谱（ICP-MS）和扫描电子显微镜（SEM）对纳米颗粒进行了结构和化学表征，从而证实成功合成了具有预期晶相和化学计量比以及几乎完全反尖晶石结构的CFO颗粒。将纳米颗粒压制成小球，使用电化学阻抗谱（EIS）研究其电子传导特性。在低温下，电导率测量显示出源于Co位点之间跳跃的半导体行为，且总电导率由晶界贡献主导。在较高温度（>400℃）下发生金属-绝缘体转变，这归因于Fe位点之间电子的额外跳跃。
