铁电单晶0.62Pb(Mg1/3Nb2/3)O3-0.38PbTiO3折射率的研究

用最小偏向角法在20℃下精确测量了0.62Pb(Mg_1/3Nb_2/3)O_{3< /sub>-0.38PbTiO3( 0.62PMN-0.38PT)单晶的折射率，给出了该温度下折射率色散的Sellmeier方程.研究了能带 结构与折射率的关系，计算了样品的Sellmeier光学系数：对no，E0=5.50eV,λ0=0.2 26μm，Ｓ０=1.004×10¹⁴m^-2，Ed=28.1 0eV；对ne，Ｅ0=5.57eV,λ 0=0.223μm，S0=1.017×10¹⁴m^-2，Ed=28.10eV.A BO3型钙钛矿材料中，BO6八面体基元决定了晶体的能带结构，对折 射率产生重要影响. 关键词： PMNT单晶 折射率 Sellmeier光学系数}

Study on principal refractive indices of the ferroelectric single crystal 0.62Pb (Mg1/3Nb2/3)O3-0.38PbTiO3

The refractive indices and their dispersions in 0.62Pb(Mg_1/3Nb_{2/ 3})O ₃-0.38PbTiO₃(PMNT62/38)single crystals were accurately mea sured with the min imum deviation method at 20℃.The parameters of modified Sellmeier's equation fo r both n_o and n_e are obtained.We relate the refractive ind ices to energy-ban d structure of oxygen-octahedron ferroelectrics and the Sellmeier optical coeffi cients,E₀=5.50eV,λ₀=0.226μm，Ｓ_０=1.004×10< sup>14m^-2 and E_d=28 .10eV for n₀ and Ｅ₀=5.57eV,λ₀=0.223μm，S₀=1.017×10¹⁴m^-2 and E_d=28.10eV for n_e were obtained through fitting the si ngle-term oscillat or equation.For materials with ABO₃ perovskite structure,the octahedr al BO₆ unit governs the lower lying conduction bands and the upper valence bands and ma kes a substantial contribution to the refractive indices.