共沉淀法制备YAG超细粉及透明陶瓷

研究了共沉淀法制备YAG透明陶瓷的工艺。采用Al(NO3)3和Y(NO3)3的混合溶液为母盐,以碳酸氢铵为沉淀剂,采用共沉淀法制备了化学组成为Y2(CO3)3·nH2O+NH4AlO(OH)HCO3的碳酸盐先驱沉淀物。使用透射电镜和X射线衍射对先驱沉淀物的形貌及煅烧过程的相转变进行了研究。结果表明先驱沉淀物在900℃煅烧2h后完全转变为YAG相。1100℃煅烧后得到的YAG粉体具有良好的烧结性能。使用0.5%(质量分数)的TEOS(正硅酸乙酯)作为烧结添加剂,1700℃真空烧结5h后,得到了透明YAG烧结体。     

湿化学法制备 Y2O3纳米粉及透明陶瓷

以Y(NO3)3溶液和NH3·H2O为原料,制备了Y2O3纳米粉体.先驱沉淀物的化学组成为Y2(OH)5NO3·H2O.研究了pH值及滴加过程对先驱沉淀物形貌及Y2O3产物烧结性的影响.正向滴定,pH值较低时(pH=7.9),先驱沉淀物为片状结构;pH值较高时(pH=10.0),先驱沉淀物片层状结构特性减轻,并且颗粒变的细小.反向滴加时,片层状结构特征消失,主要为块状晶粒.先驱沉淀物为片状结构时,得到的粉体活性较高.添加适量的(NH4)2SO4能够减轻Y2O3粉体的团聚,沉淀的同时控制pH值在9以下,所得到的粉体具有更好的烧结性能.采用得到的Y2O3纳米粉,不加入任何烧结助剂,经1700℃真空烧结4h得到了透明Y2O3陶瓷.     

微波均相沉淀法制备Nd:YAG纳米粉体及其表征

以Al(NO3)3,Y(NO3)3为母盐,尿素为沉淀剂,添加占母盐质量为8%的(NH4)2SO4,以不同浓度的Nd3+取代Y3+,采用微波均相沉淀法制备了具有良好分散性和可烧结性、平均粒径为71nm的Nd:YAG纳米粉体。利用IR、DTA-TG、XRD、TEM、LD等技术对YAG前驱物及其煅烧粉体进行表征。结果表明:采用微波均相法,前驱体在1100℃下煅烧,可得到分散良好的纯YAG相,无YAP、YAM中间相出现,且YAG的单相程度不随Nd3+掺杂浓度的增加而变化。     

加料方式对共沉淀法制备Nd∶YAG透明陶瓷的影响

以Nd2O3、Y2O3、NH4Al(SO4)2·12H2O为原料,NH4HCO3为沉淀剂,采用顺序、反序和并流3种不同共沉淀加料方式,在高滴加速率条件下制取了掺钕钇铝石榴石(Nd∶YAG)粉体,比较工艺操作,表征其相组成、显微形貌、粒度分布和烧结后陶瓷的透过率。结果表明,并流共沉淀工艺无需调节pH值,工艺操作最简单;经1 100℃煅烧,反序、并流法制备的粉体均为纯相YAG,顺序制备的粉体含有杂相,其中并流法制备的粉体粒径分布窄,颗粒呈类球形,粉体活性高。采用真空烧结技术于1 715℃下烧结制备了Nd∶YAG陶瓷,顺序、反序和并流样品在1 064 nm处透过率分别为68%,70%和75%。     

共沉淀法制备Nd3+:Y2O3透明陶瓷

以Y2O3为基质材料,掺杂不同含量的Nd3+添加PEG和(NH4)2SO4为分散剂,采用共沉淀法制备出性能良好的Nd3+:Y2O3纳米粉.对前驱体和不同温度下煅烧后的粉体进行差热热重、X射线衍射、比表面积和透射电镜等分析.结果表明,前驱体产物为Y2(OH)5(NO3)·nH2O时,Nd3+完全固溶于Y2O3的立方晶格中,Nd3+:Y2O3粉体大小均匀,近似球形.随着煅烧温度的升高,颗粒逐渐长大,900℃煅烧2h后颗粒尺寸约为40～60nm;粉体在1700℃和真空度为1×10-3Pa条件下烧结6h得到的Nd3+:Y2O3透明陶瓷的透光率接近78%.     

钕铁硼废渣制备锰锌铁氧体

研究了钕铁硼废渣制备锰锌铁氧体.以MnSO4·H2O、ZnSO4·7H2O、NH4HCO3、NH3·H2O和提取稀土后的钕铁硼二次废渣经H2SO4浸出除杂3次重结晶后得到的FeSO4·7H2O等为原料,采用化学共沉淀法、微波干燥、煅烧、烧结等工序制备锰锌铁氧体.通过TG-DTA、XRD、TEM、ICP-AES等系列现代分析手段对产物结构、形貌和纯度进行检测和表征.实验结果表明:前驱体在800℃下煅烧2h得到尖晶石相含量在40%以上、粒度为0.41μm、颗粒大小均匀、呈球形的锰锌铁氧体微粉,微粉经造粒、压坯,在1300℃烧结5h后得到晶粒大、气孔较少的锰锌铁氧体.     

不添加烧结助剂制备透明的Y2O3陶瓷

以Y2O3粗粉、碳酸氢铵、硝酸和氨水为原料,通过沉淀法制备了Y2O3纳米粉体.发现沉淀工艺和煅烧温度显著影响Y2O3纳米粉的颗粒大小和尺寸分布,从而影响烧结体的密度和透光性.用X射线衍射分析仪、透射电镜、图像分析仪等研究发现,pH=8时制得的沉淀先驱物经1000℃煅烧,可得到粒度为33 nm,近球形,分散性好,尺寸分布窄的Y2O3粉体.该粉体不加任何添加剂,在1700℃真空烧结4 h可得到透明Y2O3陶瓷.     

掺镱钇铝石榴石激光透明陶瓷超细粉体的研究

钇铝石榴石(YAG)透明陶瓷是制造大功率、发光效率高的小型激光器的良好材料.而制备掺镱钇铝石榴石(Yb:YAG)透明陶瓷的关键在于制备出粒度均匀、化学纯度高、分散性好的YAG超细粉体.本文以Y2O3、Yb2O3、Al2(NO3)3·9H2O为原料,以Yb:Y:Al=0.06:2.94:5的配比掺杂2%的Yb取代Y,配成硝酸盐溶液,用NH4HCO3作为沉淀剂,用碳酸盐共沉淀法制备Yb:YAG前驱超细粉体,并用TG-DTA、XRD、IR、SEM等测试方法对其粉体结构和形貌进行分析.结果表明:在1 100℃煅烧过程中,失重约为41%.所得到的Yb:YAG粉体结晶好,烧结性高、纯度较好、形状规则,粒径均匀,均在200～300 nm之间.     

LiFePO4的前驱体制备与性能

以Fe2(SO4)3、H3PO4和NH3·H2O为原料,采用控制结晶法制备了多孔的前驱体FePO4·xH2O.通过研究pH值和合成时间对前驱体的物相结构、成分、表面形貌、粒度、比表面积和振实密度的影响,发现在pH=2.1的条件下反应8h制备的前驱体性能最佳.将前驱体、Li2CO3及葡萄糖均匀混合,用碳热还原法合成了LiFePO4/C,结果表明,以pH=2.1时制备的前驱体为原料合成的LiFePO4/C在0.1C时的首次放电比容量为156mAh/g,其振实密度高达1.20g/cm3.     

液相沉淀法制备ZTA纳米复相陶瓷

以NH₄Al(SO₄ )₂·12H₂O , ZrOCl₂·8H₂O , Y(NO₃ ) 3为母盐, 用NH4 HCO₃作沉淀剂, 控制滴定速度小于5 mL/ min , 采用液相沉淀法制备了纳米3 Y-ZrO₂ / Al₂O₃前驱体。分析了添加籽晶和煅烧温度对粉体性能的影响。在1000 ℃煅烧得到了分散性良好, 平均粒径为10 nm , 两相分布均匀的纳米复合粉体, XRD 分析显示前驱体在煅烧过程中无中间相γ-Al₂O₃ 和θ-Al₂O₃生成, 粉体具有较高的烧结活性, 在1550 ℃烧结3 h 后烧结体致密度达到98. 6 % , 断裂韧性可达7. 68 MPa·m1/2 。      

Doubly Q-switched tape casting YAG/Nd:YAG/YAG ceramic laser

A doubly Q-switched 1.06 μm pulsed laser using a novel tape casting YAG/Nd:YAG/YAG composite ceramic with a sandwich structure was demonstrated for the first time. Compared to purely acousto-optical (AO) Q-switching, this laser using an AO Q-switch and Cr⁴⁺:YAG saturable absorber simultaneously can generate shorter pulses. The pulsed laser performance was investigated at two modulated repetition rates of 10 and 20 kHz.     

Efficient corner-pumped Yb:YAG/YAG composite slab laser

A high efficiency Yb:YAG/YAG composite slab laser is presented, in which the corner-pumped scheme is adopted. The slab is a composite crystal of Yb:YAG bonded thermally with undoped YAG at both edges. The pump light from diode arrays is coupled into the slab through four chamfers at the four corners independently. The pump absorption efficiency is studied, and an analysis method has been developed as a guide to optimize the geometric parameters of the composite slab, to obtain higher pump absorption efficiency and uniformity. The influence of the internal thermal lens on the laser resonator is analyzed. A 1016 W continuous-wave output has been obtained with the slope efficiency and optical-to-optical efficiency of 42.8% and 34.4%, respectively.     

Performance of diode-end-pumped Cr, Nd:YAG self-Q-switched and Nd:YAG/Cr:YAG diffusion bonded lasers

Self-passively Q-switching of a diode-pumped Cr,Nd:YAG, where the Cr⁴⁺ is used as a saturable absorber for the 1064 nm laser emission is reported. The maximum average output power was obtained using an output coupler of R=86%. The self-Q-switched diode pumped laser yielded 1.86-W average output power with low threshold pumping power (≈1.7-W), average slope efficiency of ≈34%, pulse duration of about 14–16 ns, and modulation frequency ranging from 2.4 to 73 kHz, depending on the input pumping power. These results are the highest reported for self-Q-switched lasers. Higher slope efficiency (42%) and shorter Q-switched pulses were obtained for a Q-switched Nd:YAG/Cr⁴⁺:YAG diffusion bonded laser. A comparison of the codoped Cr,Nd:YAG laser performance, with that of a diffusion bonded laser is reported and analyzed.     

光学基质粉体YAG及荧光粉体Ce:YAG的制备与表征

采用共沉淀法制备出尺寸分布均匀、分散性良好的立方相钇铝石榴石(YAG)与Ce:YAG纳米粉体.考察了煅烧温度和时间对粉体物相和颗粒大小的影响及Ce~(3+)的掺杂量对Ce:YAG粉体的荧光光谱的影响.借助IR、XRD、BET、SEM和荧光分析仪等测试手段对前驱体、YAG及Ce:YAG纳米粉体进行了表征与分析.结果表明:共沉淀前驱体经900℃煅烧2h后可得到纯立方相的YAG(Ce:YAG)纳米粉体;所得Ce:YAG粉体具有较好的荧光特性且Ce~(3+)的掺杂量增加会造成其荧光光谱红移.     

Densification behavior,doping profile and planar waveguide laser performance of the tape casting YAG/Nd:YAG/YAG ceramics

The sintering behavior and doping concentration profile of the planar waveguide YAG/Nd:YAG/YAG ceramics by the tape casting and solid-state reaction method were investigated on the basis of densification trajectory, microstructure evolution, and Nd³⁺ ions diffusion. The porosity of the green body by tape casting and cold isostatic pressing is about 38.6%. And the green bodies were consolidated from 1100 °C to 1800 °C for 0.5–20 h to study the densification and the doping diffusion behaviors. At the temperature higher than 1500 °C, pure YAG phase is formed, followed by the densification and grain growth process. With the increase of temperature, two sintering stages occur, corresponding to remarkable densification and significant grain growth, respectively. The mechanism controlling densification at 1550 °C is grain boundary diffusion. The diffusion of Nd³⁺ ions is more sensitive to temperature than the sintering time, and the minimum temperature required for the obvious diffusion of Nd³⁺ ions is higher than 1700 °C. Finally, planar waveguide YAG/1.5 at.%Nd:YAG/YAG transparent ceramics with in-line transmittance of 84.8% at 1064 nm were obtained by vacuum-sintering at 1780 °C for 30 h. The fluorescence lifetime of ⁴F_3/2 state of Nd³⁺ in the specimen is about 259 μs. The prepared ceramic waveguide was tested in a laser amplifier and the laser pulse was amplificated from 87 mJ to 238 mJ, with the pump energy of 680 mJ.     

Microwave assisted synthesis of nanocrystalline YAG

Using nitrate precursors, a novel microwave assisted citrate gel process for the preparation of nanocrystalline yttrium aluminium garnet (YAG) phase has been developed. Synthesis of single phase polycrystalline YAG was achieved at temperatures as low as 600 °C using the microwave methodology whilst conventional approaches currently available require ≥1000 °C. The microwave prepared YAG powder was characterised using X-ray diffraction, FTIR spectroscopy, TEM and EDAX. The microwave method was found to yield YAG particles of ∼40 nm diameter, whilst the conventional route yielded 150 nm particles. Also substantial morphological differences were observed between the YAG particles and their agglomerates produced by the different processing methods.     

Flux growth of large YAG crystals

Large yttrium and rare earth aluminum garnet crystals that are essentially free of flux pockets, veils or discoloration due to dispersed Pb can be grown from a PbO·PbF₂·B₂O₃ flux as a cluster alone or surrounded by plates of sapphire or ruby in a rosette fashion. Quality is improved by growth in the presence of massive Al₂O₃ at a high temperature.     

Passively Q-switched ceramic Nd3+:YAG/Cr4+:YAG lasers

Passively Q-switched ceramic Nd3+:YAG lasers with ceramic Cr4+:YAG saturable absorbers are demonstrated. When the lasers are pumped by a 1-W cw laser diode, optical-optical efficiency as great as 22% is obtained with Cr4+:YAG of initial transmission ranging from 94% to 79%. The results are similar to those in their crystalline counterparts. The operation of Brewster's angle and the polarization state of the laser output are also investigated.