均相法和共沉淀法制备Nd：YAG透明陶瓷的对比研究

以Al(NO3)3·9H2O、Y2O3、Nd2O3、尿素和NH4HCO3为主要原料,分别采用均相法和共沉淀法制备了Nd:YAG纳米粉体和透明陶瓷。对比研究了两种方法的粉体的制备工艺,物相,形貌和陶瓷的透过率、形貌。结果发现,均相法制备的前驱体疏松,1200℃煅烧时先形成YAP相,后形成纯相粉体。共沉淀法制备的前驱体较硬,1000℃锻烧直接形成纯相粉体。最后,两种方法制备的陶瓷素坯经真空烧结、处理后,在1064 nm的透过率达80%。共沉淀法条件温和,易于得到纯相YAG,更适合于工业化开发。     

顺序共沉淀法制备Nd:YAG陶瓷

以NH4Al(SO4)2·12H2O、Y2O3、Nd2O3为原料,NH4 HCO3为沉淀剂,采用顺序共沉淀法制备Nd:YAG粉体.并研究了碳酸氢铵浓度对粉体性能的影响,研究结果表明:较佳的碳酸氢铵浓度为1.0 mol/L.制得的粉体颗粒尺寸小,粒度分布窄,分散性好,具有良好的烧结活性,在1800℃真空烧结15 h制备了Nd:YAG透明陶瓷,其近红外波段的透过率为78％.断面和表面形貌显示陶瓷晶粒尺寸均匀,晶界清晰,结晶性好,瓷体致密,平均晶粒尺寸约为15 μm.     

制备工艺对氧化铝包裹铝复合材料性能的影响

采用非匀相沉淀法和常压烧结的方法制备出了Al2O3包裹Al复合陶瓷。研究了起始Al(NO3)3浓度、氨水滴定速度、反应体系pH值以及煅烧温度等工艺条件对包裹粉体性能的影响，同时对Al2O3／Al复合陶瓷的微观结构和性能进行了研究。结果表明，Al(NO3)3溶液浓度控制在0．2mol／L，滴定速度为25ml／min，反应体系pH值为8-9时可以获得团聚少、分散性好的re(OH)3包裹Al粉体，α-Al2O3的转变温度降至1000℃左右。Al2O3／Al复合陶瓷结构致密，包裹层中的Al2O3为500nm左右．复合材料的断裂韧性有显著提高。     

Y_2O_3-Al_2O_3粉体固相反应制备Y-Al-O体系陶瓷的对比研究

研究了摩尔比n(Y2O3):n(Al2O3)分别为2:1、1:1和3:5的粉体在不同温度发生的相变及其高温烧结的陶瓷。Y2O3-Al2O3粉体经球磨后在1750℃真空烧结制备陶瓷。用差热-热重、X射线衍射及扫描电子显微镜表征制备的Y2O3-Al2O3材料。结果表明:在低于800℃时,Y2O3-Al2O3之间未发生反应;在1000℃煅烧后,出现Y4Al2O9(YAM)相;1200℃煅烧后,出现YAlO3(YAP)相和钇铝石榴石(yttrium aluminumgarnet,YAG)相。n(Y2O3):n(Al2O3)=3:5粉体在1400℃煅烧后生成YAG纯相。n(Y2O3):n(Al2O3)=2:1、3:5粉体烧结的陶瓷的物相分别为YAM相和YAG相,其相对体积密度分别为97.8%和99.95%,n(Y2O3):n(Al2O3)=1:1粉体烧结陶瓷的物相为多相共存,3种配比制备陶瓷断口的形貌差别较大。     

真空烧结技术制备Er:(Yb_(1–x)La_x)_2O_3透明陶瓷

采用冷等静压-真空烧结技术制备尺寸为?10 mm×l mm的Er:(Yb1–xLax)2O3陶瓷。通过分析粉体的X射线衍射谱和陶瓷的扫描电子显微镜照片,确定陶瓷制备条件为:在1 750℃烧结20 h和在1 450℃退火20 h。陶瓷样品在可见光波段透过率为50%左右,在近红外波段透过率最高达到82%。测试了陶瓷的吸收光谱、发射光谱和上转换发射光谱,并探讨了上转换发光机制。结果表明:陶瓷在977 nm处有强吸收,发射最强峰在1 545 nm处,上转换发出较强的绿光(542 nm)和蓝光(484 nm)。     

Sm:(YLa)_2O_3透明陶瓷的制备及发光性能

以NH4HCO_3为沉淀剂,用共沉淀法制备Sm:(YLa)_2O_3纳米粉体,采用冷等静压-真空烧结技术在1 750℃烧结20 h得到Sm:(YLa)_2O_3透明陶瓷。研究了粉体的形貌、激发和发射光谱。结果显示:制备的纳米粉体呈球形,分散性好,粒度分布均匀,平均粒径约为75 nm,该粉体Sm~(3+)最佳掺杂摩尔分数为1%;最强激发峰位于408 nm处,对应于Sm~(3+)的~6H_(5/2)→~4F_(7/2)能级跃迁;最强发射峰位于609 nm处,对应于Sm~(3+)的~4G_(5/2)→~6H_(7/2)能级跃迁。陶瓷样品的透过率和吸收光谱测试表明,陶瓷最佳烧结温度为1 750℃,在此温度下制备的陶瓷样品在可见光波段和红外波段的平均透过率分别为69.46%和74.77%。     

SPS制备MgO-Y2O3复相陶瓷及其性能研究

与单相的MgO和Y2 O3陶瓷相比,MgO-Y2 O3复相陶瓷具有更高力学性能的同时兼具良好的红外透过性,可以满足在极端条件下使用红外窗口材料的要求.本文分别采用沉淀法和软模板法制备了高比表面积的MgO和Y2 O3粉体,通过球磨将两种粉体混合均匀,利用SPS制备得到了复相陶瓷.主要探索了不同烧结温度对陶瓷微观结构、致密度、力学、热学及光学性能的影响.研究结果表明,复相陶瓷的最佳烧结温度为1200℃,密度达到完全致密,透过率最高为51％(4.17μm),硬度为10.31 GPa,断裂韧性为2.54 MPa·m1/2,杨氏模量为248 GPa,MSP强度为129 MPa以及室温热导率为15.57 W/(m·K).     

正交实验优选共沉淀法制备纯相YAG纳米粉体

为了获得制备纯相YAG纳米粉体且重现性好的工艺,本实验以Al(NO3)3·9H2O、Nd2O3、Y2O3和NH4HCO3为原料,(NH4)2SO4为静电稳定剂,采用L9(34)正交试验方案研究了金属离子溶液浓度、NH4HCO3浓度、滴速和pH值4个重要因素对YAG粉体制备的影响,结果表明pH值是影响YAG纯相的主要因素。获得最佳工艺条件并进行了重复性试验研究,均得到了纯相YAG粉体。采用TG/DTA、XRD、FT-IR、TEM等测试手段对YAG粉体及前体进行表征,结果发现在1000℃煅烧温度下前体已完全转变成YAG相,得到了类球形、分散性较好、尺寸为23nm的YAG粉体。     

非化学计量比镁铝尖晶石透明陶瓷的制备及性能

制备了一系列非化学计量比镁铝尖晶石粉体及透明陶瓷( MgO·nAl2O3,n=1,1.5,2,4),研究了n值对粉体物相的影响以及n值与陶瓷中波红外透过率、抗弯强度的关系.n值为1.5、2、4时,MgO·nAl2O3粉体仍可保持纯尖晶石相.MgO·1.5A12O3透明陶瓷在具备与计量比镁铝尖晶石透明陶瓷(MgAl2O4,即MgO·Al2O3)相当的优良中波红外透过率的同时,抗弯强度从152 MPa提高至215 MPa,提高幅度达41％.力学性能的提升有利于镁铝尖晶石透明陶瓷的应用.     

增强型镁铝尖晶石透明陶瓷的制备

以溶胶-凝胶法结合热压及热等静压工艺制备了一系列增强型镁铝尖晶石透明陶瓷(MgO·n Al2O3),研究了n值对粉体物相的影响以及与陶瓷红外透过率、抗弯强度的关系.n值为1.5、2、4时,MgO· nAl2O3粉体仍可保持纯尖晶石相,增强型镁铝尖晶石透明陶瓷MgO·1.5Al2O3在具备与镁铝尖晶石透明陶瓷(MgAl2O4,即MgO· Al2O3)相当的优良中波红外透过率的同时,抗弯强度有大幅提高.     

均相沉淀法制备掺钕钇铝石榴石纳米粉末的研究

掺钕钇铝石榴石（Nd：YAG）多晶透明陶瓷具有容易制造、成本低、光学性能好、热导率高等优点,是一种很有前途的激光工作物质。以AI（N03）·9H2O,Y2O3,Nd2O3,（NH4）2SO4和尿素为原料,正硅酸乙酯为添加剂,采用均相沉淀法制备出分散均匀、纯YAG立方晶相的Nd：YAG纳米前驱体粉末。采用XRD、FT-IR、TEM等测试手段对前驱体粉末进行表征。研究结果表明：Nd：YAG前驱体粉末在800℃时为无定型态,当温度达到890℃时析出大量的中间相YAlO3（Y=AP）和少量的Y3Al5O5（YAG）,当温度达到1000℃时就全部转化为YAG立方晶相。     

离子浓度和分散剂对合成Nd:YAG粉体晶相的影响

以碳酸氢铵为沉淀剂,共沉淀合成了Nd:YAG陶瓷粉体。分析了合成过程中盐溶液离子浓度和分散剂含量对粉体后期晶相转变的影响。研究结果表明盐溶液浓度在0.16 mol·L^-1和0.32 mol·L^-1时,煅烧过程中粉体出现Y₂O₃、YAM等过渡晶相,这些过渡相需要在更高的温度才能完全转化为纯YAG晶相。当盐溶液浓度降低到0.08 mol·L^-1, pH调节到8.0时,各组分离子和掺杂离子达到分子水平的均匀混合,合成粉体煅烧过程中直接转化为YAG晶相。添加的分散剂 对Al₂O₃和Y₂O₃扩散反应生成YAG晶相有一定的阻碍作用。采用纯相的Nd:YAG粉体制备的多晶透明陶瓷获得了1.6W的激光输出。     

Solid-State Reactive Sintering of Transparent Polycrystalline Nd:YAG Ceramics

Transparent polycrystalline Nd:YAG ceramics were fabricated by solid-state reactive sintering a mixture of commercial Al₂O₃, Y₂O₃, and Nd₂O₃ powders. The powders were mixed in methanol and doped with 0.5 wt% tetraethoxysilane (TEOS), dried, and pressed. Pressed samples were sintered from 1700° to 1850°C in vacuum without calcination. Transparent fully dense samples with average grain sizes of ∼50 μm were obtained at 1800°C for all Nd₂O₃ levels studied (0, 1, 3, and 5 at.%). The sintering temperature was little affected by Nd concentration, but SiO₂ doping lowered the sintering temperature by ∼100°C. Abnormal grain growth was frequently observed in samples sintered at 1850°C. The Nd concentration was determined by energy-dispersive spectroscopy to be uniform throughout the samples. The in-line transmittance was >80% in the 350–900 nm range regardless of the Nd concentration. The best 1 at.% Nd:YAG ceramics (2 mm thick) achieved 84% transmittance, which is equivalent to 0.9 at.% Nd:YAG single crystals grown by the Czochralski method.     

共沉淀-焙烧法制备球形铝酸锶粉体

以碳酸氢铵、硫酸铝铵和硝酸锶为原料,采用共沉淀法制备了化学组成为SrCO3•2Al(OH)3•7H2O的前体,此前体在较低温度下可合成SrAl2O4粉体。利用红外光谱（FTIR）、扫描电镜（SEM）及能量散射分光光谱（EDS）、X射线衍射（XRD）和热分析（TG-DSC）表征了前体及其热处理产物的特征。结果表明,锶铝物质的量比和pH值对粉体成分和颗粒形貌有显著影响,n(Sr)∶n(Al)=1∶1.6、pH=7.6条件下制备了球形前体,此前体在1 100 ℃于空气气氛中焙烧2 h获得了单分散、球形SrAl2O4粉体,合成温度较传统高温固相法低约400 ℃。     

Influence of Yb and Si on the fabrication of Yb:YAG transparent ceramics using spherical Y2O3 powders

Yb:YAG (yttrium aluminum garnet) transparent ceramics were fabricated by the solid-state method using monodispersed spherical Y₂O₃ powders as well as commercial Al₂O₃ and Yb₂O₃ powders. Pure YAG phase was obtained at low temperature due to homogeneous mixing of powders. Under the same sintering conditions, the Yb:YAG ceramics with different doping contents of Yb³⁺ had similar morphologies and densification rates. After being sintered at 1700 °C in vacuum, the ceramic samples had high transparencies. The Yb:YAG ceramics doped with 0.5 wt% SiO₂ formed Y–Si–O liquid phase and nonstoichiometric point defects that enhanced sintering. Compared with Nd doping, Yb doping hardly affected the YAG grain growth, sintering densification or optical transmittance, probably because Yb³⁺ easily entered the YAG lattice and had a high segregation coefficient.     

纯相尖晶石型锰酸锂纳米粉体的熔盐法制备

以碳酸锂为锂源,自制的纳米级三氧化二锰为锰源,通过熔盐法合成了纯相的纳米级的尖晶石型锰酸锂粉体。利用热重-差热分析、XRD物相分析和SEM形貌分析等,对前驱体碳酸锰、自制的三氧化二锰和合成物锰酸锂进行了系列表征。研究结果显示：在以碳酸氢铵为沉淀剂、溶液pH=9、搅拌速度为400 r/min的条件下,制得了纯相、超细（粒径在1 μm左右）、粒径均匀的球形碳酸锰粉体;在升温速率为10 ℃/min、550 ℃焙烧6 h的条件下,制得了纯相的、纳米级（75~100 nm）、无团聚、分散性好、球形及哑铃形的三氧化二锰粉体;在锂锰物质的量比为1.1∶ 2.0,以氯化钾为熔盐,700 ℃焙烧10 h的条件下,合成了纯相、纳米级（粒径为100 nm）、粒径均匀的尖晶石型锰酸锂粉体。     

Fabrication of Transparent Cerium-Doped Lutetium Aluminum Garnet Ceramics by Co-Precipitation Routes

Nanosized, highly sinterable Ce-doped lutetium aluminum garnet (LuAG:Ce) powders were synthesized by the urea homogeneous co-precipitation routes. LuAG:Ce transparent ceramics with an average grain size of about 6 μm were successfully fabricated at 1800°C for 10 h by vacuum sintering without sintering aids using the powders calcined at 1000°C for 2 h. The transmittance in the visible light region reaches 65%. The radioluminescence spectrum displays a broad band located at 480–650 nm consisting of two emissions due to the transitions from the lowest 5 d excited state to the 4 f ground state of Ce³⁺, which is consistent with that of LuAG:Ce single crystal and well coupled with the silicon photodiodes.     

Synthesis and Luminescence Properties of Y3Al5O（12）：Eu^（3＋） Phosphors under Vacuum Ultraviolet Excitation

采用凝胶–燃烧法合成了掺Eu3＋的Y3Al5O12（YAG：Eu3＋）荧光粉。分别采用X射线衍射（XRD）、扫描电子显微镜（SEM）、发光光谱等测试手段分析了不同温度下煅烧所得粉体的物相、形貌与发光性质。XRD和SEM结果表明：YAG：Eu3＋的最低合成温度为900℃,并且在该反应过程中没有中间相YAP（YAlO3）和YAM（YAl）的产生。1 100℃合成的晶粒尺寸比较均匀,平均粒径在90 nm左右。发光光谱的测试表明：在592 nm监控下的真空紫外激发光谱由峰值位于147、156、169nm和214nm的系列激发带组成,其分别归属于铝酸根的基质吸收以及Y3＋和Eu3＋的电荷迁移带吸收。在147nm激发下YAG：Eu3＋荧光粉最强发射峰位于592nm处,属于Eu3＋的5D0→7F1跃迁。Eu3＋在基质中的最佳掺杂摩尔分数为4%。     

Fabrication of transparent neodymium-doped yttrium aluminum garnet ceramics by high solid loading suspensions

Dense neodymium-doped yttrium aluminum garnet (Nd:YAG) transparent ceramic was obtained by slip casting and solid-state reaction. The colloidal behavior of the aqueous suspensions of neodymia, yttria, and alumina mixed powders using Dispex A as dispersant was investigated. The variation in zeta potential due to pH alteration was studied. The isoelectric point (IEP) was at pH 4.5 and 4 for the specimens with and without Dispex A, respectively. The optimal dispersion conditions were achieved for the suspensions at pH 9.6 with 0.4 wt% Dispex A. The green body prepared by slip casting was vacuum sintered from 1200 °C to 1750 °C. The grain size of the sintered body increased, and the pore size decreased with increasing sintering temperature. Pore-free Nd:YAG transparent ceramic with a grain size of 5–10 μm was obtained by sintering at 1750 °C for 10 h. The in-line transmittance of the annealed specimen reached 80.8% at 1064 nm.     

液相还原法制纳米镍粉

用NiSO4.6H2O为原料,N2H4.H2O为还原剂,十二烷基磺酸钠(SDS)为表面活性剂,用NaOH调节反应pH,合成了纳米Ni粉。采用XRD、SEM及FTIR等分析测试方法对所制得的粉体进行了表征。研究结果表明:在反应温度为80℃,反应时间10~25 min,Ni2+浓度为0.75 mol/L,pH=11,n(N2H4)∶n(Ni2+)=(2~3)∶1时,能得到平均粒径75~200 nm的球形纳米Ni粉。