title: A metastable cubic phase of sodium niobate nanoparticles stabilized by chemically bonded solvent molecules.
abstract: Structural modification, especially the stabilization of metastable phases at room temperature, has emerged as an effective strategy to understand their stabilization mechanism and improve their functional properties. In this work, a facile solvothermal approach is developed to synthesize metastable sodium niobate (NaNbO3) crystals with the cubic symmetry. XRD, Raman and TEM results all confirmed the selective synthesis of cubic and orthorhombic NaNbO3via adjustment of the reaction medium. The fact that traditional hydrothermal synthesis often yields orthorhombic NaNbO3inspires us to elucidate the formation mechanism of cubic NaNbO3with respect to the solvent effect. With the increasing post-calcination temperature, the as-synthesized cubic NaNbO3gradually transforms into the orthorhombic structure, which is understood to be a recrystallization behavior, as evidenced by the XRD and TEM results. The organic molecules retained in the NaNbO3nanocrystals, as suggested by UV-vis, FT-IR and TGA-MS results, have contributed to the stabilization of the metastable structure, demonstrated by the different temperature-induced phase transition behaviors in air and argon atmospheres, where the phase transition from cubic to orthorhombic would take place at a relatively higher temperature in argon. This work provides an alternative approach to synthesize cubic NaNbO3nanocrystals, and the understanding of the stabilization mechanism could pave a new pathway for fabricating metastable materials.
authors.affiliation: State Key Laboratory of Mechanics and Control of Mechanical Structures, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing, 210016, China. kjzhu@nuaa.edu.cn and College of Materials Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China and Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore.
authors.forename: Qilin
authors.initials: Q
authors.lastname: Gu
authors.affiliation: State Key Laboratory of Mechanics and Control of Mechanical Structures, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing, 210016, China. kjzhu@nuaa.edu.cn.
authors.forename: Kongjun
authors.initials: K
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Mechanics and Control of Mechanical Structures, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing, 210016, China. kjzhu@nuaa.edu.cn and College of Materials Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China.
authors.forename: Qiaomei
authors.initials: Q
authors.lastname: Sun
authors.affiliation: College of Materials Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China.
authors.forename: Jinsong
authors.initials: J
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Mechanics and Control of Mechanical Structures, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing, 210016, China. kjzhu@nuaa.edu.cn.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Mechanics and Control of Mechanical Structures, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing, 210016, China. kjzhu@nuaa.edu.cn.
authors.forename: Jinhao
authors.initials: J
authors.lastname: Qiu
authors.affiliation: Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore.
authors.forename: John
authors.initials: J
authors.lastname: Wang