Sun Qingbo, Zheng Changlin, Huston Larissa Q, Frankcombe Terry J, Chen Hua, Zhou Chao, Fu Zhenxiao, Withers Ray L, Norén Lasse, Bradby Jodie E, Etheridge Joanne, Liu Yun
School of Physical, Environmental and Mathematical Sciences, University of New South Wales , Australian Capital Territory, Canberra 2601, Australia.
Fenghua Advanced Technology Holding Co., Ltd. , Zhaoqing, Guangdong 526020, China.
J Phys Chem Lett. 2017 Jul 20;8(14):3249-3255. doi: 10.1021/acs.jpclett.7b01384. Epub 2017 Jul 5.
Ionic codoping offers a powerful approach for modifying material properties by extending the selection of potential dopant ions. However, it has been a major challenge to introduce certain ions that have hitherto proved difficult to use as dopants (called "difficult-dopants") into crystal structures at high concentrations, especially through wet chemical synthesis. Furthermore, the lack of a fundamental understanding of how codopants are incorporated into host materials, which types of defect structures they form in the equilibrium state, and what roles they play in material performance, has seriously hindered the rational design and development of promising codoped materials. Here we take In (difficult-dopants) and Nb (easy-dopants) codoped anatase TiO nanocrystals as an example and investigate the doping mechanism of these two different types of metal ions, the defect formation, and their associated impacts on high-pressure induced structural transition behaviors. It is experimentally demonstrated that the dual mechanisms of nucleation and diffusion doping are responsible for the synergic incorporation of these two dopants and theoretically evidenced that the defect structures created by the introduced In, Nb codopants, their resultant Ti, and oxygen vacancies are locally composed of both defect clusters and equivalent defect pairs. These formed local defect structures then act as nucleation centers of baddeleyite- and α-PbO-like metastable polymorphic phases and induce the abnormal trans-regime structural transition of codoped anatase TiO nanocrystals under high pressure. This work thus suggests an effective strategy to design and synthesize codoped nanocrystals with highly concentrated difficult-dopants. It also unveils the significance of local defect structures on material properties.
离子共掺杂通过扩展潜在掺杂离子的选择范围，为改变材料性能提供了一种强有力的方法。然而，将某些迄今被证明难以用作掺杂剂的离子（称为“难掺杂剂”）以高浓度引入晶体结构，尤其是通过湿化学合成的方法，一直是一项重大挑战。此外，由于缺乏对共掺杂剂如何掺入主体材料、它们在平衡状态下形成何种类型的缺陷结构以及它们在材料性能中起何种作用的基本认识，严重阻碍了有前景的共掺杂材料的合理设计与开发。在此，我们以铟（难掺杂剂）和铌（易掺杂剂）共掺杂的锐钛矿型二氧化钛纳米晶体为例，研究这两种不同类型金属离子的掺杂机制、缺陷形成及其对高压诱导结构转变行为的相关影响。实验证明，成核和扩散掺杂的双重机制导致了这两种掺杂剂的协同掺入，理论证明引入的铟、铌共掺杂剂所产生的缺陷结构、其生成的钛和氧空位在局部由缺陷簇和等效缺陷对组成。这些形成的局部缺陷结构随后充当板钛矿型和类α - 氧化铅亚稳多晶相的成核中心，并在高压下诱导共掺杂锐钛矿型二氧化钛纳米晶体发生异常的跨区域结构转变。因此，这项工作提出了一种设计和合成具有高浓度难掺杂剂的共掺杂纳米晶体的有效策略。它还揭示了局部缺陷结构对材料性能的重要性。
