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对晶粒尺寸为19.4,8.6和5.6nm的纳米晶锐钛矿相TiO2,进行了从83到723K的变温拉曼散射测量,并对Eg(1)模式进行了详细研究.根据非简谐效应和声子局域模型,对Eg(1)拉曼峰进行了拟合与计算.结果表明,以上三种纳米晶粒的晶格振动机理,在本质上是相同的.三声子过程对频率蓝移起主要作用.为了得到很好的拟合,需要同时考虑三声子和四声子过程.随着温度的升高,四声子过程增强,并对三声子过程起抵消作用.与非简谐衰减相关的声子寿命随着晶粒尺寸的减小而增加,晶粒尺寸越小衰减越慢.在低温区,声子局域是导致5.6nm晶粒的声子寿命非常短的原因.声子局域引起Eg(1)模式在高波数段非对称展宽和频率蓝移,其对Eg(1)峰展宽的影响要大于对峰位移动的影响.
The temperature-dependent Raman scattering measurements from 83 to 723K were performed on nanocrystalline anatase TiO2 with grain sizes of 19.4, 8.6 and 5.6 nm, and the Eg (1) mode was studied in detail. According to the non-harmonic effect and Phonon local model, the Eg (1) Raman peak is fitted and calculated. The results show that the lattice vibration mechanism of the above three kinds of nano-crystalline grains is essentially the same. In order to get a good fit, we need to consider both the three-phonon and the four-phonon processes simultaneously. As the temperature rises, the four-phonon process enhances and counteracts the three-phonon process. The phonon lifetime associated with harmonic attenuation increases as the grain size decreases, and the slower the grain size, the slower the attenuation.In the low temperature region, the phonon localization is the reason that the phonon lifetime of the 5.6 nm grain is very short The phonon localization causes the Eg (1) mode to asymmetrically broaden and blue - shift at high wave number, which has greater effect on the Eg (1) peak broadening than on the peak position shift.