金刚石压腔结合拉曼光谱技术进行Pb掺杂对二氧化锡高压结构性能的影响研究

doi:10.3964/j.issn.1000-0593(2020)02-0415-05

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Abstract Based on the stable molecular structure and physicochemical property, SnO₂ has been more and more useful in the field of optical, electrical and magnetic materials in recent years. In order to broaden the application of SnO₂, the research focused on the phase transition behavior of pure SnO₂ and SnO₂ doped by lead ions under high pressure, and the changes of Raman spectrum active vibration modes were investigated at the same time. The pure SnO₂ and SnO₂ doped by lead ions with 10% content were prepared by hydrothermal method. And the Scanning Electron Microscopy (SEM) images and X-ray diffraction (XRD) patterns of samples were measured. SEM images showed that samples were arranged as divergent nanorods which from the center to form a whole flower-like shape. XRD patterns showed that the crystal structure of samples was rutile tin dioxide (space group is P₄₂) at room temperature and pressure. In this paper, the high pressure phase transition processes of materials rutile tin dioxide and SnO₂ doped by lead ions with 10% content were investigated by using Mao-Bell Diamond anvil cell and in situ Raman spectroscopy. The results showed the active Raman modes (B_1g, E_g, A_2g, B_2g) of pure SnO₂ and SnO₂ doped by lead ions all moved to high frequencies when the pressure was added to 26 GPa. The E_g peak of pure SnO₂ split and a new peak appeared in 563 cm^-1 when the pressure was added to 14GPa, which indicated that SnO₂ transformed from tetragonal rutile structure to CaCl₂ structure. The Raman peak of 577 cm^-1 happened in the sample SnO₂ doped by lead ions in room pressure, and the vibration mode of B_1g changed to Ag mode when the pressure was addeda to 13 GPa which indicated the first-order phase transition of SnO₂ doped by lead ions. Compared to pure SnO₂, SnO₂ doped by lead ions had a lower first-order phase transition pressure, which were attributed to the fact that lead ions replace tin ions in SnO₂ cells. The spacing between atoms decreased and surface defects of valence difference happened after doping, which caused the decrease of structural stability of SnO₂ and the decrease of phase transition pressure. In addition, the characteristic peaks at 577 and 639 cm^-1 of SnO₂ doped by lead ions began to coalesce into cladding peaks and its symmetry decreased when the pressure was added to 12 GPa, which indicated that the disorder degree of atoms on the surface of crystals increased and transition process from crystals to amorphous crystals occurred. The characteristic peaks of the two materials disappeared when the pressure reached to 26 GPa, and no other characteristic peaks were observed. Non-hydrostatic pressure in this research had a certain effect on the phase transformation pressure. The large stress at the grain boundary made nanocrystals form to nucleation point of high-pressure phases more easily, which might reduce the phase transformation pressure and cause some crystals tend to be amorphous more easily. In summary, the phase transition behavior of pure SnO₂ and SnO₂ doped by lead ions on different pressure conditions were studied, which enriched the diversity of physical and chemical properties of SnO₂ under extreme conditions.

Key words：SnO₂; Doping; Nanorods; High pressure Raman spectroscopy; Diamond anvil cell; Amorphous; Phase transition

Received: 2019-09-06 Accepted: 2019-12-30

ZTFLH:

O521.2

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2020)02-0415-05 OR https://www.gpxygpfx.com/EN/Y2020/V40/I02/415