【作者】 王磊；

【导师】 孙旭东；

【作者基本信息】 东北大学 ， 材料工程（专业学位）， 2017， 硕士

【摘要】 固体激光器因具有体积小巧、便于携带使用和输出功率大的特点,自问世以来,就得到了人们的广泛青睐。激光材料和谐振腔是决定固体激光器性能和效率的关键构成部分。Nd:Y₂O₃具有优异的综合性能,尤其热导率是Nd:YAG单晶的两倍左右,并且能够获得更高的激光效率,因此成为最有可能取代Nd:YAG单晶的激光材料。以氧化钇为原料制备光子晶体结构,用于激光器谐振腔,可大幅度提高激光的亮度和单色性。本文主要应用改进的焰熔法,通过智能精确的控制升降温速率和下料速度制备高熔点的Nd:Y₂O₃单晶,并通过自组装的方法制备氧化钇光子晶体的蛋白石模板。采用(Y_0.991Nd_0.009)2_O3粉体为原料,用固相法合成Nd:Y₂O₃粉料,在不同温度煅烧并采用不同的保温时间,经过对比后,确定在煅烧温度为1550℃,保温时间为24h条件下合成粉料综合性能最好,得到流动性为30.02s/50g,压缩度为13.29%,均齐度为1.9418,并且结晶性和发光性能优异的粉料。采用ANSYS有限元分析软件模拟了焰熔法生长晶体的温场,分析了氢气氧气流量、喷嘴尺寸和观察孔高度对温场的影响;以模拟得出的结论指导实践,确定喷嘴尺寸为5mm,观察孔位于距离喷嘴110mm处,氢气流量为24L/min,氧气流量为9.5L/min时,晶体出现尖锐多晶核,并逐步完成形成籽晶以及扩肩等径生长,能够得到直径为4mm长约15mm的无裂纹晶体,晶体优先沿<1 1 1>晶向方向生长,呈淡蓝色,密度为5.0154g/cm3,维氏硬度为1556.6Hv;在531nm、588nm、750nm、808nm和879nm附近有吸收峰,并以588nm、750nm和879nm三处的吸收峰最明显,这与Nd的标准吸收峰的位置是一致的,而且这三处的吸收带较强较宽,能与LD发射波长更好的匹配,对半导体激光二级泵浦是有利的。对晶体的缺陷进行了分析,发现微裂纹、包裹物以及位错是存在的主要缺陷,在大尺寸晶体的制备过程中,提高粉料的均匀程度,扩大喷嘴尺寸,对晶体品质的改善有重要意义。采用尿素均匀沉淀法合成了球形氧化钇前驱体,分析了反应物浓度对胶体颗粒尺寸和均匀性的影响,确定当硝酸钇浓度为0.015mol/L,尿素浓度为1mol/L,溶液总体积是500mL时,粒度分布范围较小,均一化标准差为0.13461;分析了分散剂和pH对氧化钇前驱体悬浮液稳定性的影响,确定以柠檬酸铵为分散剂,并当其浓度为0.5wt%时,氧化钇前驱体悬浮液稳定性最佳;探究了制备方法、蒸发速率和悬浮液浓度对光子晶体结构排列的影响,确定浓度为0.5wt%的氧化钇前驱体悬浮液,采用垂直沉降法在50℃的蒸发速度下能够制备出周期性排列的单层光子晶体结构,为制备氧化钇光子晶体的蛋白石结构奠定了基础。更多还原

【Abstract】 Since the solid-state laser is small in size,easy to use and with the characteristic of high output power,it has been widely favored since its inception.Laser materials and resonators are key components that determine the performance of solid-state lasers.Nd:Y₂O₃ has a good overall performance,especially the thermal conductivity is about twice as the Nd:YAG single crystal,and can achieve higher laser efficiency,thus becoming the most likely to replace the Nd:YAG single crystal laser material.And yttrium oxide can be used as raw material to prepare photonic crystal structure for laser resonator,it can greatly improve the brightness and monochromaticity of laser.In this paper,the high-melting-point Nd:Y₂O₃ single crystal is fabricated by the improved flame melting method by controlling the heating rate and cutting speed,and the opal template of yttrium oxide photonic crystal is prepared by self-assembly method.Powder is prepared by ball milling method with(Y_0.991Nd_0.009)₂O₃ as raw materials,then prepared by solid phase synthesis,calcined at different temperature and kept for different time,the best comprehensive performance was obtained under the condition that the calcined temperature is 1550℃ and the holding time is 24h.The flowability of the powder is 30.02s/50g,the degree of compression is 13.29%,the uniformity is 1.9418,the crystallinity and the luminescent performance are excellent.ANSYS software was used to simulate the temperature field of crystal grown by flame melting method,and the influence of hydrogen flow rate,nozzle size and observation hole height on the temperature field was analyzed.The simulation results are used to guide the experiment to determine that under the condition that the nozzle size is 5mm,the observation hole located 110mm away from the nozzle,the hydrogen flow rate is 24L/min,oxygen flow rate is 9.5L/min,the crystal appears sharp polycrystalline nucleus,and gradually complete the formation of seed and shoulder diameter growth,then a crack-free crystal with a diameter of 4 mm and a length of about 20 mm can be obtained.The crystal grows in the direction of<111>,with a light blue color,a density of 5.0154 g/cm3 and a Vickers hardness of 1556.6Hv.Absorption peaks at 531 nm,588 nm,750 nm,808 nm,and 879 nm were observed,and the absorption peaks at 588 nm,750 nm,and 879 nm were most pronounced,which coincided with the position of the standard absorption peak of Nd.The absorption bands of these three bands are relatively wide and can match the LD emission wavelength better,which is favorable to the laser diode pump.It is found that microcracks,inclusions and dislocations are the main defects in the crystal defects.And it is important to improve the uniformity of the powders and the size of the nozzles in the preparation of large-size crystals.Spherical yttrium oxide precursors were synthesized by urea homogeneous precipitation method.The effect of reactant concentration on colloidal particle size and homogeneity was discussed.When the concentration of yttrium nitrate is 0.015mol/L,urea is 1mol/L and the volume of mixed solution is 500mL,the particle size distribution range is small and the standard deviation is 0.13461.The effect of dispersant and pH on the stability of yttrium oxide precursor suspension was analyzed.It was determined that ammonium citrate was used as the dispersant,and when its concentration was 0.5wt%,the stability of yttrium oxide precursor suspension was the best.The effects of preparation method,evaporation rate and suspension concentration on the arrangement of the photonic crystal were investigated.When the particle concentration is 0.5wt%,the periodic monolayer photonic crystal structure can be prepared by the vertical sedimentation method at the evaporation temperature of 50℃,which laid the foundation for the preparation of the opal structure of the yttrium oxide photonic crystal.更多还原