中文摘要：

通过温度依赖的透射和反射光谱研究了在准同型相界附近的Pb（Mg_1/3Nb_2/3）O_3-0.3PbTiO_3（PMN-0.3PT）单晶光学性质.这种禁带宽度随温度范围不同变化规律不同现象,揭示了PMN-PT单晶温度依赖的复杂相结构.禁带宽度Eg在303 K是3.25 e V,临界点Ea是3.93 e V,临界点Eb是4.65 e V,它们随着温度的上升而下降,在453 K禁带宽度Eg是3.05 eV,临界点Ea是3.57 eV,临界点Eb是4.56 eV.这三个跃迁能量Eg、Ea、Eb分别对应从O 2p到Ti d、Ni d、Pb 6p轨道跃迁.它们随温度上升而下降的变化规律可以用晶格热膨胀和电子声子相互作用理论来解释.通过Tauc-Lorentz色散模型拟合得到了303 K到453 K温度范围的Pb（Mg_1/3Nb_2/3）O3-0.3PbTiO_3单晶光学常数及其随温度的变化规律,发现折射率n随着温度的升高而升高.

英文摘要：

The optical properties of Pb（Mg_1/3Nb_2/3）O_3-0.3PbTiO_3 single crystal near morphotropic phase boundary were investigated by temperature dependent transmittance and reflectance spectra. The temperature dependent absorption edges showblueshifts below300 K while they showredshifts above 300 K. At 303 K,optical band gap Egis 3. 25 eV,critical point energies Eaand Ebare 3. 93 and 4. 65 e V,respectively. With increasing temperature,Eg,Eaand Ebdecrease and they are 3. 05,3. 57,4. 56 e V at 453 K,respectively. Three critical point energies Eg,Eaand Ebare corresponding to O2p to Ti d,and Pb 6p,respectively. Such narrowing trends with increasing temperature can be explained by thermal expansion of the lattice and electron-phonon interaction. Based on Tauc-Lorentz dispersion models,the dielectric functions from 3. 1 to 6. 5 eV have been extracted from303 to 453 K. It was found that the refractive index n increases with increasing temperature.