【作者】 陈捷；

【导师】 阮玉忠；

【作者基本信息】 福州大学 ， 材料科学， 2010， 博士

【摘要】 掺稀土钨酸钆钾晶体（KGd(WO4)2，简称KGW）是极有发展前景的激光新材料之一，因为其一系列独特性能，正逐步受到科学界的重视。本论文主要研究了上称重法生长掺稀土钨酸钆钾及若干新晶体结构设计与制备。1.论文首先对激光晶体、晶体生长技术进行一个简单的概述和讨论，介绍了KGW晶体的基本性质，讨论对了KGW的晶体生长方法和生长条件的选择，对所涉及的顶部籽晶法、熔盐提拉法作了较为细致的分析。2.论文接着对KGW晶体相关国内外文献，从晶体生长、缺陷研究、光谱性能、激光实验等4个方面进行归纳和讨论；介绍了国内外在晶体生长装置方面研究的现状，包括温场设计、机械设计、自动化控制等，并对其未来发展作了展望。3.论文具体介绍KGW晶体生长研究工作，对实验中碰到的各种技术问题进行讨论，并提出相应的解决方案，具体内容包括：1)晶体生长实验室改造：根据熔盐法对于实验室环境中机械震动、温度波动、湿度、尘埃等特殊要求，对晶体生长室和控制室进行了改造，并介绍了实验所用2种控温仪的各自特点。2)晶体生长炉设计：讨论了熔盐炉的设计要求；根据KGW晶体生长特点，设计制备了Φ650×600mm大热容量生长炉，并对加热体密绕方式、热电偶选择和放置位置、坩埚设计进行了讨论，初步摸索出晶体生长炉设计和制备的2个关键技术点：炉体结构设计：目标是寻求最佳温度梯度分布，考虑加热功率计算、电热元件设计、温区布置及功率匹配等；重点进行炉衬材料的选择，精密计算炉壁各层的耐火及保温材料的界面温度、厚度及热流量，保证热场的维护与维修应方便实用。高精度的温度控制系统：目标是保证长时间（生长周期3个月内）温度波动小于0.1°C，由于晶体生长的系统是一个热滞很大的系统，而且其热滞后时间在整个晶体生长过程中不断变化，其变化是非线性的，关键在于控制被控系统的热滞后效应。3)温场设计论文讨论了温场设计的理论依据和需要考虑的具体问题，并通过改变加热丝的环绕方式、疏密程度、坩埚相对于加热元件的位置、坩埚上方的保温方式来实现温场调控，最终通过多层Al2O3保温筒，档板以及后热器组成一个可以灵活组合的保温系统，满足KGW晶体生长的要求。4)计算机辅助多功能熔盐法晶体生长系统的设计与制备：本人在晶体生长过程中也切身感觉到晶体生长工作强度很大，熟练技术的时间周期很长。能否设计和制备出一套计算机辅助多功能熔盐法晶体生长系统来解决这个问题。沿着这个思路，在指导教师的精心指导和同学的大力支持下，我在论文研究的后期开展了该项工作的研究，并取得了一定的进展，研究了系统硬件部分，如称重系统、信号放大器、功率控制系统等；使用软件开发工具Borland Delphi7Enterpise、数据库MicroSoft Access2000，根据应用需求，对系统管理、设备管理、通信管理、数据处理等十个功能模块进行设置和详细分析。5)原料合成首先讨论了熔盐法晶体生长助熔剂选择的基本原则和选择步骤，对比了生长KGW晶体可供选择的助熔剂性质；将与目前生长密切联系的相图K2W2O7体系的液相线重新作了测定和验证；讨论了Nd3＋掺杂浓度与荧光强度的关系，选择Nd3＋的最佳掺杂浓度；阐述了KGW原料组分的配比，具体原料制备过程，并对比了合成好的KGW原料与标准XRD谱图，发现KGW原料合作的效果很好，已经能够满足晶体的需求。6)生长工艺技术详细研究了KGW晶体生长的各个具体步骤和关键性技术，包括籽晶制备、原始料化料、晶体试种、晶体下种，不同生长阶段拉速、转动速率、降温速率的选择，晶体等径生长的控制和晶体后处理技术；以K2W2O7为助溶剂，采用熔盐提拉法，成功地生长出了一系列高质量的掺稀土KGW晶体，Nd掺杂浓度分别为1、1.6、2、3、3.5、5、8at％的不同晶体，晶体尺寸达60×60×30mm3，光学均匀性达1.25×10-5，在5mw红光照射下未见到散射通道；7)晶体缺陷探讨讨论了熔盐提拉法生长KGW晶体的包裹、开裂和生长纹等三个主要缺陷的表征、产生原因和可行的消除方式，提出在下种中，采用收脖和放斜肩技术，可以有效地提高晶体的内部质量。8)大尺寸晶片加工简述了晶体器件加工流程，包括定向、切割、粗磨、抛光、镀膜等，重点描述KGW晶体抛光中粗磨、预抛加工、加工平面度及平行度、加工光洁度等关键工艺点；经测试，加工出的KGW晶体表面的平面度为0.114λ，平行度为4.4”，表面粗糙度为0.556nm。9) Nd:KGW晶体光学和光谱性能的测试。测定了吸收和发射载面、波长、峰宽、量子效率及寿命等与激光运转有关的重要参数，测得Nd:KGW晶体在1067nm处荧光发射截面为1.483×10－20cm2，半峰宽：15nm；在810nm处吸收波长810nm，半峰宽14nm，吸收截面1.27831×10－20cm2；荧光寿命110μs。10)晶体激光实验首先在空腔的条件下对棒进行测试，得到在使用不同透过率的平面镜作为输出镜的情况下得到的输出功率与泵浦功率的关系；接着进行调Q实验，在静态条件下，使用不同透过率的平面镜作为输出镜，得到输出功率与泵浦功率的关系图，其最高的转换效率达到56%；在调Q的条件下，脉冲重复频率10Hz，泵浦脉宽385μs时，输出功率随着泵浦功率的增加而增加；在泵浦功率较小时，输出功率增长速度较快；在泵浦功率较高时，输出功率增长速度较慢；期间最大的转换效率为11.4%；实验证明Nd:KGW具有输出能量大，转换效率高的特点，可以用来研制高效率小型激光器。11）最后本章还对提高KGW晶体质量和尺寸的途径进行了展望，为下一阶段的研究工作指明方向。4.在本论文研究的后期，本人在导师的指导下，通过水热法合成了五种配位聚合物，并进行了晶体结构测定和描述，为下一阶段研究工作奠定基础。更多还原

【Abstract】 Doped lanthanon potassium gadolinium tungstate crystal (KGd(WO4)2(abbreviated asKGW), which contains a series of unique properties is gradually getting scientificcommunity’s attention as being an extremely promising new laser material. This papermainly focuses on the growth of doped lanthanon potassium gadolinium tungstate crystaland a number of new crystal structure design and preparation.1. Paper first takes a brief overview and discussion on laser crystal and crystal growthtechnology, introduces the fundamental nature of the KGW crystal, and discusses the KGWcrystal growth method and the choice of growth conditions. Top-seeded solution growth andmolten salt Czochralski method are more detailed analyzed.2. Second, from the crystal growth, defect studies, spectroscopic properties and laserexperiments, paper goes on to induce and discuss KGW crystal related domestic and foreignliteratures; introduces domestic and foreign installations in the crystal growth status quo,including design of temperature field, machine design, automation control, etc., and itsfuture development is also expected.3. Paper describes KGW crystal’s specific research work of growth, discusses thetechnical problems encountered from experiments and provides appropriate solutions, whichspecifically includes:1) Transformation of Crystal Growth Laboratory:Transform the crystal growth chamber and control room according to the mechanicalvibration, temperature fluctuations, humidity, dust and other special requirements oflaboratory environment by using molten salt method. Paper also describes the experiment byusing two kinds of temperature control instrument for their own characteristics.2) Design of Crystal Growth Furnace:Discuss the molten salt furnace design requirements; According to KGW crystal growthcharacteristics, design a large heat capacity growth furnace of Φ650×600mm and discusstight winding method for the heat body, thermocouple selection and placement, crucible design. Preparatory exploration on two key technical points of crystal growth furnace designand preparation:Furnace structural design: The goal is to find the best temperature gradientdistribution by considering the calculation of heating power, heating elementdesign, temperature zone layout and power matching, etc.; Concentrating on liningmaterial selection, precise calculation of furnace wall and the insulation layers offire-resistant materials interface temperature, thickness and heat flow, thermalfield to ensure the maintenance and repair could be convenient and practical.High-precision temperature control system：Goal is to ensure that long time(within3months of growth cycle) temperature fluctuation is less than0.1°C.Because crystal growth due to thermal hysteresis of the system is a great system,and the thermal lag time in the entire crystal growth process of changing isnonlinear, the key is to control the thermal lag effect of the controlled system.3）Temperature Field DesignPaper discusses the theoretical basis for the design of temperature field and the need toconsider specific issues, and by changing the heating wire surround mode density levelcrucible relative to the location of heating elements, thermal insulation above the cruciblemeans to achieve the temperature field control, finally passed Al2O3multilayer insulationtube, bumpers, as well as the formation of a post-heater insulation system can be flexiblycombined to meet the KGW crystal growth requirements.4) The design and preparation of computer-aided multi-flux method crystalgrowth system:I also feel great intensity of work through the crystal growth process and take a longperiod of time to be skilled. Can computer-aided design and prepare a set of multi-fluxmethod crystal growth system to solve this problem? Along with this idea and through thecareful guidance from teachers and strong supports from students, in the latter part of mythesis work, I carry out this research and make some progress by studying the systemhardware components, such as weighing systems, signal amplifier, power control systems,etc.; According to the application requirements, I set up and analyze system management,equipment management, communications management, data processing and10otherfunctional modules by using software development tools, Borland Delphi7Enterpise,database, Microsoft Access2000. 5) Material SynthesisFirst discuss the crystal growth flux method’s basic principles of choice and selectionsteps, compare the character of selective flux for growing KGW crystal; Re-determine andvalidate the close linked of current growth phase diagram K2W2O7system liquid line;Discuss Nd3+doping concentration and fluorescence intensity of the relationship betweenthe choice of the best Nd3+doping concentration; Explain KGW ratio of raw materialcomponents, specific raw material preparation process, and comparison of synthetic rawmaterials and standard XRD good KGW spectra. Find out that the effect of co-operationKGW material will have been able to meet the needs of crystals.6) The technology of growthStudy the various concrete steps and key technologies of KGW crystal’s growth indetail, including seed preparation, raw material-based material, test growth, crystal seed,different growth stages of casting speed, rotation rate, the choice of cooling rate, crystaldiameter crystal growth control and post-processing techniques; Taking K2W2O7ascosolvent, using molten salt Czochralski method, I successfully get a series of high-qualitydoped KGW crystal, Nd-doped concentrations are1,1.6,2,3,3.5,5,8at%of different crystalsand its size up to60×60×30mm3, optical homogeneity up to1.25×10-5and under the5mw red light irradiation it showing no scattering channel。7) Defects of crystalDiscuss three major defects of KGW crystal growth by using Molten salt Czochralskimethod, such as packages, cracking and growth texture’s token, appearing reason andpossible elimination methods. Propose to use control neck and release shoulder techniques toeffectively improve the internal quality of crystal during the seeding period.8) Large-size wafer processingBrief describes the process flow on crystal device, including orientation, cutting, coarsegrinding, polishing, coating and so on. Major focus on describing KGW crystal’s roughgrinding polishing, pre-polishing, machining flatness and parallelism, processing, finish andother key technique points; After processing, get surface flatness of0.114λ, parallel degree4.4", surface roughness0.556nm’s KGW crystal.9) The test of Nd: KGW crystal optical and spectral properties.Measure important parameters of laser operating such as absorption, emission section,wavelength, peak width, quantum efficiency and lifetime; Get Nd: KGW crystal’s fluorescence emission cross-section of1.483×10-20cm2at1067nm, half-peak width:15nm;absorption wavelength810nm at810nm and a half peak width14nm, absorptioncross-section1.27831×10-20cm2, fluorescence lifetime110μs.10) Laser experimentFirst, Test the crystal bar under the cavity condition, obtain the relations of outputpower and pump power by using different transmission plane mirror;Second, the Q-experiment, under static state conditions, using a differenttransmission plane mirror as the output mirror, get the output power and pumppower diagram and the highest conversion efficiency of56%;Under the Q-conditions, where pulse repetition frequency is10Hz, pump pulseduration is385μs, the output power increases with pump power; When pumppower is small, the output power rise fast; When pump power is high, the outputpower rise slow; During the experiment, the maximum conversion efficiency is11.4%;This experiment proofs that Nd: KGW has large energy output, high conversionefficiency, which can be used to develop high-efficiency small-scale lasers.11) The final chapter takes an outlook of improving the KGW crystal quality and sizeand pointing the direction of research for next stage of work.4. In the latter part of this thesis, under the guidance of instructors and through thehydrothermal synthesis of the five kinds of coordination polymers, I carry out crystalstructure determination and description in order to establish the foundations for next stage ofstudy.更多还原