Thermal and optical properties of tellurite glasses doped erbium
Thermal and optical properties of tellurite glasses doped erbium
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掺铒亚碲酸盐玻璃的热学和光学性质
DOI：
10.1007/s10853-010-4820-x
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
M. Ferid
中科院分区：
文献类型：
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作者：
I. Jlassi;H. Elhouichet;M. Ferid
用熔体猝灭法制备了摩尔组成为75TeO2-20ZnO-(5-−x)Na2O-xEr2O3(x=0，0.5，1，2，3，4摩尔%)的掺Er3+碲酸盐玻璃。讨论了Er2O_3浓度对碲酸盐玻璃热稳定性和光学性质的影响。根据差示扫描量热仪(DSC)曲线，估算了玻璃化转变温度Tg和晶化起始温度Tx。热稳定性因子定义为∆T=Tx−Tg，大于10 0℃，表明碲酸盐玻璃具有良好的热稳定性，是一种潜在的拉丝候选材料。此外，稳定因子随着Er2O_3浓度的增加而增加，当浓度达到2.0mol%时，稳定因子继续减小，表明高掺杂碲酸盐玻璃开始析晶。通过分析椭圆偏振光谱仪(SE)测量的tan-Ψ和cos-∆的实验光谱，得到了它们的折射率和消光系数数据。通过回归分析估计了样品的复介电函数(ε_1=ε_1+I_ε_2)。根据Davis和Mott提出的理论，从光学吸收光谱中确定了基波吸收边，并对其进行了分析。确定了直接允许跃迁和间接允许跃迁的光学带隙。掺Er后，光学带隙明显减小。它被归类为由于形成非桥氧而引起的结构变化。吸收边下方的吸收系数随光子能量呈指数变化，表明厄巴赫尾巴的存在。Urbach能量的起源与声子辅助的间接跃迁有关。
Er3+-doped tellurite glasses with molar compositions of 75TeO2–20ZnO–(5 −x) Na2O–xEr2O3(x= 0, 0.5, 1, 2, 3, and 4 mol%) have been elaborated from the melt-quenching method. The effects of Er2O3concentration on the thermal stability and optical properties of tellurite glasses have been discussed. From the differential scanning calorimetry (DSC) profile, the glass transition temperatureTg, and crystallization onset temperatureTxare estimated. The thermal stability factor, defined as ∆T=Tx−Tg, was higher than 100 °C. It suggests that tellurite glass exhibits a good thermal stability and consequently is suitable to be a potential candidate for fiber drawing. Furthermore, the stability factor increases with Er2O3concentration up to 2 mol% then presents a continue decrease suggesting of beginning of crystallization of highly doped tellurite glasses. The refractive index and extinction coefficient data were obtained by analyzing the experimental spectra of tanΨ and cos∆ measured by spectroscopic ellipsometry (SE). The complex dielectric functions (ε = ε1+iε2) of the samples were estimated from regression analysis. The fundamental absorption edge has been identified from the optical absorption spectra and was analyzed in terms of the theory proposed by Davis and Mott. The values of optical band gap for direct and indirect allowed transitions have been determined. An important decrease of the optical band gap was found after Er doping. It was assigned to structural changes induced from the formation of non-bridging oxygen. The absorption coefficient just below the absorption edge varies exponentially with photon energy indicating the presence of Urbach’s tail. The origin of the Urbach energy is associated with the phonon-assisted indirect transitions.