Department of Mechanical Engineering and Temple Materials Institute, Temple University, Philadelphia, PA 19122, USA.
US Army Research Laboratory, Aberdeen Proving Ground, MD 21005, USA.
Sci Rep. 2017 Jan 6;7:39946. doi: 10.1038/srep39946.
Lanthanide (Ln) doping in alumina has shown great promise for stabilizing and promoting desirable phase formation to achieve optimized physical and chemical properties. However, doping alumina with Ln elements is generally accompanied by formation of new phases (i.e. LnAlO, LnO), and therefore inclusion of Ln-doping mechanisms for phase stabilization of the alumina lattice is indispensable. In this study, Ln-doping (400 ppm) of the alumina lattice crucially delays the onset of phase transformation and enables phase population control, which is achieved without the formation of new phases. The delay in phase transition (θ → α), and alteration of powder morphology, particle dimensions, and composition ratios between α- and θ-alumina phases are studied using a combination of solid state nuclear magnetic resonance, electron microscopy, digital scanning calorimetry, and high resolution X-ray diffraction with refinement fitting. Loading alumina with a sparse concentration of Ln-dopants suggests that the dopants reside in the vacant octahedral locations within the alumina lattice, where complete conversion into the thermodynamically stable α-domain is shown in dysprosium (Dy)- and lutetium (Lu)-doped alumina. This study opens up the potential to control the structure and phase composition of Ln-doped alumina for emerging applications.
镧系元素 (Ln) 在氧化铝中的掺杂显示出很大的前景，可以稳定和促进所需相的形成，从而获得优化的物理和化学性质。然而，Ln 元素掺杂氧化铝通常伴随着新相的形成（即 LnAlO、LnO），因此，Ln 掺杂机制对于氧化铝晶格的相稳定是不可或缺的。在这项研究中，Ln 掺杂（400ppm）氧化铝晶格会显著延迟相转变的开始，并能够控制相的数量，而不会形成新相。通过固态核磁共振、电子显微镜、差示扫描量热法和高分辨率 X 射线衍射与精修拟合的结合，研究了相变（θ→α）的延迟、粉末形貌、颗粒尺寸以及α-和θ-氧化铝相之间的组成比的变化。在氧化铝中负载稀疏浓度的 Ln 掺杂剂表明，掺杂剂位于氧化铝晶格的空位八面体位置，在镝 (Dy) 和镥 (Lu) 掺杂的氧化铝中，掺杂剂完全转化为热力学稳定的α相。这项研究为控制 Ln 掺杂氧化铝的结构和相组成开辟了新的可能性，以满足新兴应用的需求。
