Ag掺杂氧化锌纳米材料的制备及高压相变拉曼光谱研究

doi:10.3964/j.issn.1000-0593(2021)02-0484-05

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Abstract Zinc oxide (ZnO), a semiconductor material with a wide band gap, has the excellent properties on photoelectric performance, mechanical behavior and chemical characteristic. The structure of ZnO material has a great influence on its properties. Element doping may change the crystal structure and band gap width of ZnO, which is an effective means to improve the performances of ZnO. And Ag doped ZnO is commonly used to improve the photocatalytic efficiency. High pressure is an important method to control the structures and properties of materials besides temperature and composition. It is also an important factor to produce new materials and new regulatory principles. By comparing the high-pressure phase transition behavior of pure ZnO crystal and Ag doped ZnO crystal, the research reveals the effect of element doping on the structures and properties of ZnO nanocrystals. ZnO and Ag-doped ZnO nanomaterials (1∶150Ag/ZnO) are first prepared by hydrothermal synthesis. XRD and SEM results show that the pure ZnO and Ag-doped ZnO nanospheres are hexagonal wurtzite structure, and which morphology are formed by self-assembly of small nanoparticles. With the doping of Ag ions, the lattice constant of ZnO increases and the lattice volume expands. The high-pressure structure phase transition behaviors of pure ZnO nanomaterials Ag/ZnO nanomaterials are investigated using Diamond Anvil Cell combined with in-situ Raman spectroscopy. Compared with the pure ZnO, the Raman characteristic peak width of 1∶150Ag/ZnO (439 cm^-1in E₂ highvibration mode) becames narrower and moved to lower frequency, which is similar to the Raman spectra of amorphous ZnO. It shows that the replacement of Ag⁺ to Zn²⁺ affects the Zn—O bond and the long-range order of ZnO lattice structure. During the process of adding pressure, the Raman peak 439 cm^-1 of hexagonal wurtzite structure ZnO shows instantaneous weakening and broadening. With the pressure increased to 9.0 GPa, the Raman peak of wurtzite ZnO 439 cm^-1 disappears and a new peak of 585 cm^-1 emerges, which indicates that the structure of ZnO crystal changes from hexagonal wurtzite structure to rock salt structure. With the pressure of system adding to 11.5 GPa, which the Raman peak of 585 cm^-1 is significantly enhanced and the peak shape becomes narrow, the phase transition is completed. The transformation pressure of 1∶150Ag/ZnO from hexagonal wurtzite structure to cubic rock salt structure is 7.2 GPa, which is lower than that of pure ZnO nanomaterials by 9.0 GPa. The possible reason is that doping makes ZnO lattice expands and crystal structure relaxes, the relative volume change of two phases increases, which lead to the decrease of phase transition barrier and the phase transformation of samples happen at lower pressure. The high-pressure study of nanomaterials reveals the influence of element doping on the structural stability of materials, which is a potential method for the regulation principle of nanomaterials.

Key words：Synthesis of ZnO nanomaterials; Ag doping; High pressure; Structural phase transition; Raman spectroscopy

Received: 2020-07-17 Accepted: 2020-11-20

ZTFLH:

O521.2

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2021)02-0484-05 OR https://www.gpxygpfx.com/EN/Y2021/V41/I02/484