We calculated and analyzed the effects of temperature and crystallite size on the Raman properties of nanocrystalline anatase TiO_2 by using the related models mentioned previously [Tang and Herman, Phys. Rev. B 43, 2299 (1991); Richter et al., Solid State Commun. 39, 625 (1981)]. The temperature dependence of the Raman spectra of two different crystallite sizes of anatase TiO_2 were obtained. Careful measurements of the frequency shifts of Raman modes were carried out at different temperatures. Through fitting the experimental data, pure-volume and the pure-temperature contributions to the frequency shifts of the lowest- and highest-frequency Eg modes, respectively, have been calculated. The results indicated that strongly intrinsic anharmonicity arising from optical-phonon couplings was the origin of hardening upon increasing temperature for the lowest-frequency Raman mode. The phonon-confinement effect on this mode was analyzed and anharmonic shifts of optical phonons with two different kinds of crystallite sizes were also compared.
展开▼
机译：我们使用前面提到的相关模型计算了温度和微晶尺寸对纳米晶锐钛矿型TiO_2拉曼性能的影响并进行了分析[Tang and Herman，Phys。 B 43，2299（1991）; Richter等人，Solid State Commun。 39，625（1981）]。获得了两种不同尺寸的锐钛矿型TiO_2的拉曼光谱的温度依赖性。在不同温度下仔细测量拉曼模式的频移。通过拟合实验数据，分别计算了纯量和纯温度分别对最低和最高频率Eg模式的频率偏移的影响。结果表明，对于最低频率的拉曼模，随着温度的升高，由光声子耦合引起的强固有非谐性是硬化的起源。分析了该模式的声子约束效应，并比较了两种不同晶粒尺寸的光学声子的非谐位移。
展开▼
