Department of Materials Science & Engineering, University of Tennessee, Knoxville, TN 37996, USA.
Phys Chem Chem Phys. 2012 May 14;14(18):6556-60. doi: 10.1039/c2cp40744b. Epub 2012 Mar 28.
Most 5d transition-metal (TM) pyrochlores exhibit metallic behavior, but 3d and 4d TM pyrochlores are generally electronic semiconductors or insulators. Here, we report a semiconductor-metal transition induced by introducing excess Ti metal as interstitials into Y(2)Ti(2)O(7). These Ti interstitials prefer anion vacant 8a sites or bridge sites between two neighboring cations along the <010> direction. Density functional theory calculations suggest that an increased electronic conductivity originates from the interplay between the extra Ti and its neighboring cations. These findings suggest a means for achieving metallic behavior in semiconducting pyrochlore oxides and tuning the electronic conduction in pyrochlores for their electrochemical applications in solid oxide fuel cells.
大多数 5d 过渡金属 (TM) pyrochlore 表现出金属行为，但 3d 和 4d TM pyrochlore 通常是电子半导体或绝缘体。在这里，我们报告了通过将过量的 Ti 金属作为间隙原子引入 Y(2)Ti(2)O(7)中而引起的半导体-金属转变。这些 Ti 间隙原子优先占据阴离子空位 8a 位或沿<010>方向两个相邻阳离子之间的桥位。密度泛函理论计算表明，电子电导率的增加源于额外的 Ti 和其相邻阳离子之间的相互作用。这些发现为在半导体 pyrochlore 氧化物中实现金属行为以及在 pyrochlore 中调整电子传导提供了一种方法，这对于它们在固体氧化物燃料电池中的电化学应用是有益的。
