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含d10构型二价金属的新型红外非线性光学晶体材料的研究
李广卯
学位类型硕士
导师张方方
2017-05-31
学位授予单位中国科学院大学
学位授予地点北京
学位专业材料工程
关键词红外 倍频 光学带隙 硫属化合物 含d10构型金属
摘要

红外非线性光学晶体材料作为固体激光器重要的频率转换器件,能够广泛应用于激光制导,激光通讯,激光雷达和激光美容等军民领域。目前商业化的红外非线性光学晶体材料,例如AgGaS2,AgGaSe2和ZnGeP2等,虽然具有大的倍频效应和宽的红外透过范围,但较小的光学带隙导致了低的激光损伤阈值或严重的双光子吸收等缺点,从而限制了它们的应用。因此,探索新的红外非线性光学晶体材料要求满足大倍频和高激光损伤阈值性能之间的平衡。前期文献调研发现许多具有潜在应用前景的红外非线性光学材料中都含有d10构型的金属阳离子,此外研究结果表明该系列材料均具有较大的非线性光学系数的同时又能保持较大的带隙。因此,开展具有d10构型的金属阳离子对于材料性能调控的机理研究,对于设计和合成性能优异的新型中远红外非线性光学材料有着重要意义。基于以上考虑,以“大倍频与宽带隙”为目标,设计和合成了四种新的含d10构型阳离子的红外非线性光学材料:Na2ZnGe2S6,Na2ZnSn2S6,Na2CdGe2S6,和Na2CdGe2Se6。具体工作内容和研究成果如下:(1)采用高温固相法,合成了新的红外非线性光学晶体Na2ZnGe2S6。该材料结晶于单斜Cc空间群,晶体结构由两种三维孔道框架相互嵌套而成,其中,一个三维孔道框架是由无限长∞[GeS3]n链和孤立的[ZnS4]四面体组成;另外一个是由顶点连接的Na(1)S5和Na(2)S6组成。更重要的是,Na2ZnGe2S6具有优异的性能,包括宽的透过范围,大的光学带隙,而且很好的实现了大倍频系数和高激光损伤阈值的平衡。采用坩埚下降法初步制备了毫米级的单晶,不吸潮,具有很好的化学稳定性。借助于理论计算,分析了结构与性能之间的关系。计算结果表明材料的倍频效应来源于两种功能基元[GeS4]和[ZnS4]的共同作用。基于以上研究结果,Na2ZnGe2S6可作为红外非线性光学频率转换的备选材料;(2)通过元素替代,合成了另一种硫化物Na2ZnSn2S6。不同于Na2ZnGe2S6结晶于Cc空间群,该材料结晶于非心空间群Fdd2,在其结构中发现了比较罕见的结构特点:SnS4四面体共顶点连接形成特殊的∞[SnS3]n链。性能测试结果表明Na2ZnSn2S6具有宽的红外透过范围0.35-25微米,大的倍频效应(4倍于AgGaS2)和高的激光损伤阈值(2倍于AgGaS2);(3)为了更好地分析d10构型的金属阳离子对于材料性能调控的机理研究,通过在Na-Zn-Ge-Q (Q = S,Se)体系中用Cd取代Zn原子,获得了两种红外非线性光学材料Na2CdGe2Q6 (Q =S, Se)。与Na2ZnGe2Se6结构比较,首次发现了同主族元素(Cd取代Zn)替代之后产生的从单斜晶系到四方晶系之间的结构转变。此外,两种化合物均可在2.09 μm处实现一类相位匹配,并且具有大的倍频效应。其中Na2CdGe2S6展现了很好的综合性能,包括倍频效应是AgGaS2的0.8倍,激光损伤阈值为AgGaS2的4倍,带隙为3.21 eV,透过范围为0.3-22微米,能够很好的应用于红外非线性光学领域。上述研究结果同时表明具有d10构型的金属阳离子对材料带隙的影响并不大,但对材料的倍频效应起着重要贡献,该结果也很好的证实了d10构型的金属阳离子可以很好的调控材料性能。

其他摘要

Infrared nonlinear optical (IR NLO) materials as frequency-conversion devices in laser have drawn more and more attention because of their wide applications in civil and military regions including laser guidance, long distance laser communication, laser radar and cosmetic laser surgery etc. Commercially applied IR NLO materials, AgGaS2,AgGaSe2 and ZnGeP2 exhibit good properties like large second-harmonic generation (SHG) responses, wide IR transparent range etc., however, their small band gaps lead to their low laser damage thresholds or serious two-photon absorption, which limit their further applications. Therefore, exploring new IR NLO materials with good balance between large band gaps and large SHG response is still an imperative and meaningful work.In this work, investigations were made and the result shows that many promising IR NLO materials contain cations with d10 configuration (like Zn2+, Cd2+), with which they can display large SHG responses besides wide band gaps. Therefore, theoretical study about the mechanism how these cations adjust the properties of materials means really much for designing and synthesizing new IR NLO materials.Guided by the idea above, we successfully synthesized four compounds containing cations with d10 configuration: Na2ZnGe2S6, Na2ZnSn2S6, Na2CdGe2S6 and Na2CdGe2Se6. The main achievements in detail are as follows.1 Na2ZnGe2S6, a new IR NLO material, has been successfully synthesized with solid-state reaction technique in fused silica tubes. Its structures are composed of two 3D tunnel frameworks, one is constructed by polar wave-shaped infinite ∞[GeS3]n chains and isolated [ZnS4] tetrahedra, and the other is constructed by the Na(1)S5 and Na(2)S6 polyhedra. Remarkably, it exhibits not only wide transparent region (0.38-22 μm), large direct band gap (3.25 eV) and chemical stability, but also achieves the balance between large laser damage threshold (LDT) (228 MW/cm2, about 6 × AgGaS2) and large SHG response (30 × KDP). Moreover, single crystals of Na2ZnGe2S6 have been obtained with size up to millimeter level. Calculated SHG density and dipole moment demonstrate that the good SHG response is mainly attributed to the cooperative effects of the [GeS4] and [ZnS4] units; total and partial density of states (TDOS and PDOS) diagrams present that it has a direct band gap and the optical absorption is determined by the [GeS4] and [ZnS4] units. All the properties, especially the balance between large SHG response and high LDT, indicate that it has the potential to be a candidate crystal applied in the IR NLO region, and we will pay more attention to grow large single crystal for evaluating its application in the future.2 A mixed-metal thiostannate, Na2ZnSn2S6 has been synthesized through solid-state reaction. It crystallizes in non-centrosymmetric space group of Fdd2 and in its structure the secondary building block ∞[SnS3]n chains are rarely found among all alkali thiostannates. In addition, Na2ZnSn2S6 exhibits good optical properties, including wide IR transmission region (0.35 – 25 μm), large SHG response (4 × AgGaS2 at 55 – 88 mm crystal size range) and high LDT (2 × AgGaS2), which indicates that Na2ZnSn2S6 can be expected as a promising IR NLO material.3 We report the successful design and synthesis of two metal-mixed chalcogenides containing divalent cations with d10 electronic configuration: Na2CdGe2S6 and Na2CdGe2Se6. Both of them crystallize in the polar Cc space group and exhibits the three-dimensional tunnel structures constructed by the CdQ4 tetrahedra and ∞[GeQ3]n chains with Na+ located in the tunnels. Furthermore, an interesting space group transformation between the monoclinic (Cc) and tetragonal (I4/mcm) systems from Na2CdGe2Se6 to Na2ZnGe2Se6 was discovered, which may arise from the different connection types of their building blocks (more flexible corner-sharing type in Cc while tightly edge-sharing type in I4/mcm). Remarkably, it exhibits not only wide transparent region (0.38-22 μm), large direct band gap (3.25 eV) and chemical stability, but also achieves the balance between large LDT (228 MW/cm2, about 6 × AgGaS2) and large SHG response (30 × KDP). Moreover, single crystals of Na2ZnGe2S6 have been obtained with size up to millimeter level. Calculated SHG density and dipole moment demonstrate that the good SHG response is mainly attributed to the cooperative effects of the [GeS4] and [ZnS4] units; TDOS and PDOS diagrams present that it has a direct band gap and the optical absorption is determined by the [GeS4] and [ZnS4] units. All the properties, especially the balance between large SHG response and high LDT, indicate that it has the potential to be a candidate crystal applied in the IR NLO region, and we will pay more attention to grow large single crystal for evaluating its application in the future.Among all the compounds obtained, Na2ZnGe2S6 and Na2CdGe2S6 exhibit more comprehensive properties, including the balance between large band gap and large SHG response, which make them have the promising opportunity to be candidates as IR NLO materials.

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4959
专题材料物理与化学研究室
作者单位中国科学院新疆理化技术研究所
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李广卯. 含d10构型二价金属的新型红外非线性光学晶体材料的研究[D]. 北京. 中国科学院大学,2017.
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