Photoluminescence properties of YAG:Ce~(3+),Pr~(3+) nano-sized phosphors synthesized by a modified co-precipitation method

Monophasic Ce~(3+) and Pr~(3+) co-doped yttrium aluminum garnet(YAG:Ce~(3+),Pr~(3+)) nanoparticles with good dispersity and uniform grain sizes in the range of 50–80 nm were prepared by a two-step route, which consisted of a modified co-precipitation preparation of mixed metal hydroxide hydrate intermediates at low temperature of about 40 oC and a subsequent calcination conversion of the synthesized intermediates to crystalline nanoparticle products at about 1000 oC. The influences of both the lanthanide ion(Ce~(3+) and Pr~(3+)) doping concentration and different doping(Ce~(3+)/Pr~(3+)) ratio on the photoluminescence intensity were systematically investigated. The synthesized (Ce_(0.6)Pr_(0.4))_(0.04)Y_(2.96)Al_5O_(12) nanoparticles were near spherical nanoclusters with good dispersity and uniform sizes in the range of 50–80 nm for about 85% of the particles. The strongest photoluminescence intensity was observed for the (Ce_(0.6)Pr_(0.4))_(0.04)Y_(2.96)Al_5O_(12) nanoparticle products.     

邻菲罗啉导向合成缆线状纳米结构CePO_4和Ce_(0.95)PO_4:Tb_(0.05)及其发光性能

采用水热法通过调节邻菲罗啉(phen)的加入量导向合成了六方相CePO_4及Ce0.95PO4∶Tb0.05纳米线。用X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、透射电镜(TEM)分析产物的相结构、晶粒尺寸及微观形貌。实验结果表明,当反应体系中不加入导向剂phen时,获得分散不均匀的CePO_4纳米棒;加入phen使Ce~(3+)∶phen摩尔比为1.0∶0.5时,得到分散均匀的直径约20 nm、长约2μm~3μm的CePO_4缆线状纳米线,phen增加到Ce~(3+)∶phen摩尔比为1.0∶3.0时,又获得直径约20 nm~30 nm、长约200 nm CePO_4纳米棒。发现反应体系中phen加入量会影响产物形貌的控制合成,所以讨论了phen对产物微观形貌的影响。不同Ce~(3+)∶phen摩尔比下所得产物CePO_4的荧光性质表明,当Ce~(3+)∶phen摩尔比为1.0∶0.5时,所合成的纳米线的发射强度比无添加phen时所获产物的荧光强度增强,随着Ce~(3+)∶phen摩尔比的减少,所合成产物的发光强度反而降低。发现随着产物长径比的增加,荧光强度增强,Ce0.95PO4∶Tb0.05中Ce~(3+)将能量传递给Tb3+,敏化Tb3+的发光。     

Tunable emission properties of tri-doped Ca_9LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+) phosphors with warm white emitting based on energy transfer

Tri-doped Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors were prepared by a high-temperature solid state method.Under UV light excitation,Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+)samples exhibit a broad band ranging from 320 to 500 nm.At 77 K,the emission spectra of Ca_9 LiY_(2/3)(PO_4)7:Ce~(3+)samples present two obvious emission peaks,indicating that Ce~(3+)ions occupy two different kinds of lattice sites(Ca(1/2) and Ca(3)),As a good sensitizer for Tb~(3+),Ce~(3+)ions in Ca_9 LiY_(2/3)(PO_4)_7 lattice can effectively transfer part of energy to Tb~(3+),and the energy trans fer mechanism is determined to be dipole-dipole interaction.Consequently,the emitting color for Ce~(3+) and Tb~(3+) co-doped Ca_9 LiY_(2/3)(PO_4)_7 samples can be tuned from bluish violet to green.In order to further enlarge the emission gamut,Mn~(2+)ions as red emission components were added,forming tri-doped single-phase Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors.The Ca_9 LiY_(2/3)(PO_4)_7:Ce~(3+),Tb~(3+),Mn~(2+)phosphors exhibit tunable emission properties through controlling the relative doping concentration of Ce~(3+),Tb~(3+)and Mn~(2+).Especially,Ca_9 LiY_(2/3)(PO_4)_7:0.09 Ce~(3+),0.12 Tb~(3+),0.30 Mn~(2+)can emit warm white light.The sample shows good thermal stability.At 150℃,the emission intensity for Ce~(3+)(360 nm),Tb~(3+)(545 nm) and Mn~(2+)(655 nm) decreases to 63%,69%,and 72% of its initial intensity,respectively.Moreover,the sample obtains good stability after 10 cycles between room temperature and150℃.     

模板剂CTAB调控制备类球形CeO_2粒子研究

采用气体扩散法,以硝酸铈和碳酸铵为铈源和沉淀剂,利用十六烷基三甲基溴化铵(CTAB)为晶体生长调节剂,得到了物性可控的氧化铈超细粉体。并探索CTAB控制球形氧化铈制备的作用机理。结果表明,CTA+通过静电匹配作用与OH~-、CO_3~(2-)结合,Ce~(3+)定向排列在球形胶束外表面与OH~-、CO_3~(2-)反应生成形貌可控前驱体晶体,焙烧后得到类球形氧化铈粉体。经BET表面积测试,添加CTAB和未加CTAB制备的氧化铈粉体的比表面积分别是100.6855 m~2·g~(-1)、83.2782 m~2·g~(-1)。     

High thermal stability and quantum yields of green-emitting Sr_3Gd_2(Si_3O_9)_2:Tb~(3+) phosphor by co-doping Ce~(3+)

A series of Tb~(3+) mono-doped and Ce~(3+)-Tb~(3+) co-doped Sr_3Gd_2(Si_3O_9)_2 phosphors with high thermal stability and quantum yields were successfully prepared via the solid state reaction. The as-prepared Sr_3Gd_2(Si_3O_9)_2:Tb~(3+) samples showed broad excitation spectrum from 250 to 400 nm and presented characteristic emission transitions ~5D_4→~7F_J(J=6, 5, 4, 3) of Tb~(3+) under 313 nm excitation, which were located at about 488, 541, 584 and 620 nm. The emission intensities of Tb~(3+) rose steadily in Sr_3Gd_2(Si_3O_9)_2 host with the increase of Tb~(3+) concentration even though Gd~(3+) ions were completely replaced by Tb~(3+) ions. The Ce~(3+) ion as a sensitizer could efficiently improve the performance of Tb~(3+) ion. First, with Ce~(3+) co-doping, the excitation spectrum of Tb~(3+) monitored at 541 nm showed a similar band that responds to the violet emission of Ce~(3+) monitored at 416 nm. Second, the quantum yields of Sr_3Gd_2(Si_3O_9)_2:Tb~(3+) phosphors could be enhanced from 26.6% to 80.2% by co-doping Ce~(3+). Finally, the co-doping of Ce~(3+) was also effective to improve the thermal stability of Sr_3Gd_2(Si_3O_9)_2:Tb~(3+). As the temperature rose to 150 oC, the emission intensity of Tb~(3+) remained at about 83.6% of that measured at room temperature, which was better than the commercial YAG:Ce phosphor in terms of their thermal quenching properties. These results indicated that the as-prepared Sr_3Gd_2(Si_3O_9)_2:Tb~(3+),Ce~(3+) samples could be used as green emission phosphors for possible applications in near ultraviolet based WLEDs.     

Color-tunable Ca10Na(PO4)7:Ce3+/Tb3+/Mn2+ phosphor via energy transfer

A series of Ca_(10)Na(PO_4)_7:Ce~(3+)/Tb~(3+)/Mn~(2+)(CNPO:Ce~(3+)/Tb~(3+)/Mn~(2+)) phosphors with high brightness were synthesized by high-temperature solid-state method. X-ray diffraction(XRD), scanning electron microscopy(SEM), diffuse reflectance spectra(DRS), photo luminescence(PL) spectra, luminescence decay curves and thermally stability were performed to characterize the as-prepared samples. For Ce~(3+)-doped samples, an intense and broad band emission is present under 265 nm excitation. When Ce~(3+) and Tb~(3+)are codoped, energy transfer(ET) process from Ce3+ to Tb3+ is demonstrated with electric dipole-dipole interaction. The internal and external quantum efficiencies(QEs) of CNPO:0.15 Ce~(3+), 0.04 Tb~(3+), 0.005 Mn~(2+)are measured to 76.79% and 54.11% under 265 nm excitation and temperature-dependent PL intensity can remain 51.78% at 150 ℃ of its initial intensity at 25 ℃. It is indicated that single-phased white lightemitting CNPO:Ce~(3+)/Tb~(3+)/Mn~(2+) phosphor can serve as a promising phosphor for illumination devices.     

铈离子含量对镁合金表面ZnAlCe-LDHs薄膜制备的影响研究

采用水热法在镁合金AZ91D表面原位制备ZnAlCe-LDHs薄膜。通过改变水热反应溶液中n(Ce~(3+))与n(Al~(3+))的比例,考察Ce~(3+)含量对ZnAlCe-LDHs薄膜制备的影响作用。结果表明:当n(Zn~(2+))/n((Al~(3+)+Ce~(3+)))摩尔比保持2.0不变的情况下,n(Ce~(3+))/n(Al~(3+))摩尔比为4∶1时,镁合金表面生成的ZnAlCe-LDHs薄膜最完整。     

Optical studies of Y_3(Al,Ga)_5O_(12):Ce~(3+),Cr~(3+),Nd~(3+) nano-phosphors obtained by the Pechini method

The Y3(AI,Ga)_5O_(12):Ce~(3+),Cr~(3+),Nd~(3+)(YAGG) nano-phosphors with homogeneous particle-size distribution,low aggregation and average crystalline size of about 65 nm were obtained using a modified Pechini method.Only slight aggregation of the crystallites occurs after post-annealing at 1100℃.The intense Ce~(3+)bands in the excitation spectra of the Ce~(3+),Cr~(3+),Nd~(3+)co-doped materials monitoring the Cr~(3+) emission at 690 nm indicate energy transfer from Ce~(3+) to Cr~(3+).Weak Nd~(3+) lines are observed,as well.In addition,the emission of Nd~(3+)at 1060 nm with excitation of Ce~(3+) and Cr~(3+) confirms the Ce~(3+)/Cr~(3+)to Nd~(3+)energy transfer.The short average luminescence decay times for the Ce~(3+) emission indicate the Ce~(3+)/Cr~(3+)to Nd~(3+)energy transfer.Eventually,the Y_3(AI,Ga)_5O_(12):Ce~(3+),Cr~(3+),Nd~(3+) nano-phosphors exhibit persistent luminescence originating from the 4f~3→4f~3 transitions of Nd~(3+) which matches well to the first biological window to be used in bioimaging applications.     

铁水预处理脱硫渣吸附稀土铈离子的研究

铁水预处理过程中所产生的脱硫渣具有较高的利用价值,目前已引起广大研究者密切关注。本文采用铁水预处理脱硫渣为吸附剂,研究脱硫渣吸附Ce~(3+)吸附性能和吸附机理,实验考察了Ce~(3+)浓度、脱硫渣加入量、吸附温度和吸附时间对Ce~(3+)吸附效果影响。结果表明,在室温,Ce~(3+)初始浓度为150 mg/L,脱硫渣加入量为0.05 g,吸附时间为2 h时,Ce~(3+)吸附率达96.84%,吸附温度对吸附效果影响不大。通过吸附动力学和吸附等温线实验得出,脱硫渣吸附Ce~(3+)的吸附曲线符合准二级动力学方程模型和Langmuir等温吸附模型,说明Ce~(3+)吸附是单分子层吸附且吸附过程是容易进行的。     

铈和铽氧化物酸分解过程热力学研究

通过热力学计算,建立了298.15K时Ce和Tb氧化物酸分解过程的φ-pH图。结果表明,CeO_2与TbO_2两种氧化物均难以被酸直接分解,但在还原性条件下采用酸分解可使其转化为Ce~(3+)和Tb~(3+);与CeO2和TbO2相比,Ce_2O_3和Tb_2O_3能在较高的pH值条件下被酸直接分解成Ce~(3+)和Tb~(3+),从而实现对Ce和Tb的提取。     

纳米氧化钕的热分解法制备及其光学特性试验研究

研究了以碳酸钕(Nd_2(CO_3)_3·H_2O)为钕源,采用热分解法制备纳米氧化钕。根据Nd_2(CO_3)_3·H_2O在空气中的热重-差热(TG-DTA)分析结果,借助X射线衍射仪(XRD)、扫描电镜(SEM)和紫外-可见分光光度计(UV-Vis)分别表征Nd_2(CO_3)_3·H_2O在空气中热分解产物的物相、形貌和光学特性。结果表明,Nd_2(CO_3)_3·H_2O的热分解过程分为3个阶段:第1阶段,室温～300℃,Nd_2(CO_3)_3·H_2O失去结晶水变为Nd_2(CO_3)_3;第2阶段,300～550℃,Nd_2(CO_3)_3受热分解产生中间产物Nd_2O_2CO_3;第3阶段,550～850℃,Nd_2O_2CO_3在850℃下保温15 min,形成纳米Nd_2O_3。第3阶段是控制Nd_2O_3粒径的主要环节。     

草酸沉淀反萃余液制备大粒度氧化钕工艺研究

以草酸为沉淀剂,P507-N235-磺化煤油-环己烷体系分离稀土过程中的氯化钕反萃余液为原料,制备了大粒度氧化钕.采用激光粒度仪结合扫描电镜对样品进行粒度、形貌分析;使用X 射线衍射对前驱体煅烧样品进行物相分析,结合差热分析研究前驱体的热分解过程.沉淀过程中草酸钕前驱体粒度的主要影响因素为反应温度、搅拌速度、沉淀剂滴加速度及陈化时间,其最佳制备条件为反应温度50℃,搅拌速度300 r/min,沉淀剂滴加速度9 mL/min,陈化时间24 h.对比实验表明,氯化钕反萃余液中残余的有机相可以有效地增大前驱体的粒度.草酸钕前驱体在煅烧温度800℃下保温2 h可完全转化为Nd2O3,氧化钕粒径达到50μm以上.     

乙二胺四乙酸二钠对钛合金表面羟基磷灰石涂层的影响

采用水热电化学方法在Ti6Al4V基体表面沉积羟基磷灰石(HA)涂层,研究乙二胺四乙酸二钠(EDTA-2Na)对HA涂层的物相组成、形貌、结合强度及生物相容性的影响.结果表明,电解液中无论添加EDTA-2Na与否,水热电化学沉积得到的仍为结晶度较高、生物相容性较好的HA涂层;不同的是,与不添加EDTA-2Na的涂层相比,添加EDTA-2Na后沉积得到的HA晶体形貌发生较大改变.随着EDTA-2Na浓度的增加,HA晶体从长薄片状到花瓣状以及纤维带状;HA涂层(002)晶面衍射峰强度随着EDTA-2Na浓度的增加逐渐减弱,涂层厚度也随之减小;HA涂层与基体的结合强度,随EDTA-2Na浓度的增加先增大后减小,在浓度为7.5×10~(-4)mol·L~(-1)时达到最大值16.8 MPa.     

pH对碳酸铈粒子团聚的影响

在不同的(NH4)2CO3和Ce(NO3)3摩尔比值R、初始料液Ce(NO3)3溶液的pH以及(NH4)2CO3加料时间条件下制备了Ce2(CO3)3粒子,并用SEM和Zeta电位仪对其进行表征。结果表明,溶液pH对Ce2(CO3)3粒子形貌无影响,只是使得溶液离子浓度及双电层厚度发生改变,进而引发Ce2(CO3)3粒子的团聚。当R=1.6、pH=4、加料时间1h时得到的Ce2(CO3)3形貌最好,颗粒分散性好。     

Eu(TTFA)_3掺杂的SiO_2微球制备及光学特性研究

采用改进的碱催化法和种子法分别制备出Eu~(3+)掺杂球形二氧化硅胶体微球,实验表明改进的碱催化法制备出的产物表面有絮状物质较多,且形貌不理想;采用种子法制备的Eu~(3+)掺杂二氧化硅合成的最终产物表面光滑、粒径均匀、单分散性和球形度均较好的Eu~(3+)掺杂的二氧化硅胶体微球。采用种子法掺杂不同浓度的Eu~(3+),其在紫外光的激发下,表现出明显的Eu~(3+)特征红光发射,并分析Eu(TTFA)_3掺杂SiO_2微球的发射光谱特性。最后得出种子法制备Eu~(3+)掺杂二氧化硅胶体微球的较佳浓度是4.5%(摩尔分数)。     

Enhanced photoluminescence property of sulfate ions modified YAG:Ce~(3+) phosphor by co-precipitation method

The sulfate ions modified YAG:Ce~(3+) phosphors were prepared by co-precipitation method and characterized by X-ray diffraction,transmission electron microscopy,and photoluminescence.Effects of sulfate ions on the photoluminescence(PL) property of the as-prepared YAG:Ce~(3+) phosphors were studied,with sodium dodecyl sulfate(SDS) being added to R~(3+)(Ce~(3+),Y~(3+),Al~(3+)) ions.Results indicated that pure YAG:Ce~(3+) phosphors with different ratios of sulfate ions could be easily obtained by calcining the as-synthesized precursor at 950 ℃ for 2 h,the YAG:Ce~(3+) phosphors with an optimal mass ratio of 3.5 wt.%SDS had the highest emission intensity and the best dispersion behavior,and the fluorescence decay of the as-obtained YAG:Ce~(3+) phosphors was related to the lattice defect,reabsorption and cross correlation.Furthermore,thermal quenching properties of the YAG:Ce~(3+) phosphors and the YAG:Ce~(3+) phosphors with 3.5 wt.%SDS were also discussed,indicating that the YAG:Ce~(3+) with SDS phosphors could have potential applications in the daylight LEDs or warm white LEDs.     

Na_2CO_3/ZnO复合添加对BaZr_(0.1)Ce_(0.7)Y_(0.2)O_(3-δ)质子导体陶瓷的影响

拟通过添加ZnO和Na_2CO_3来提高钇掺杂锆铈酸钡质子导体陶瓷的烧结性能和电导率,采用机械球磨混合结合高温常压烧结工艺制备了ZnO/Na_2CO_3复合的BaZr_(0.1)Ce_(0.7)Y_(0.2)O_(3-δ)(BZCY)质子导体陶瓷。通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱(EDS)和电化学阻抗谱(EIS)对烧结陶瓷的物相、微观形貌、化学成分和电导率进行了测试表征。XRD结果显示ZnO/Na_2CO_3复合并没有改变BZCY的晶型。当烧结温度为1550℃保温6 h时,BZCY陶瓷的致密度和线性收缩率最大,分别达到96.15%和12.44%;添加1%ZnO(摩尔分数)后,烧结温度可降低至1350℃,陶瓷的致密度和线性收缩率分别达到96.87%和16.11%,可见,ZnO的添加可以大大提高BZCY的烧结性能。当添加10%(摩尔分数)Na_2CO_3后,陶瓷的晶粒尺寸约5～10μm,且没有引起BZCY的致密度和线性收缩率的显著降低。700℃时BZCY-1%ZnO-10%Na_2CO_3陶瓷的电导率可达1.225×10~(-2)S·cm~(-1),而未添加Na_2CO_3的BZCY陶瓷的电导率仅为4.511×10~(-3) S·cm~(-1),电导率提高了约2.7倍,添加Na_2CO_3显著提高了BZCY-1%ZnO陶瓷的电导率。     

用铈盐从锌电解液中脱除氟试验研究

研究了用Ce_2(CO_3)_3作除氟剂从锌电解液中脱除氟离子。通过正交试验和单因素试验,考察了Ce_2(CO_3)_3用量、反应时间、反应温度、反应终点pH对除氟效果的影响。试验结果表明:各因素对除氟效果的影响顺序为除氟剂用量反应温度反应终点pH反应时间;在除氟剂用量1.0g(50.7g除氟剂/g F-)、反应温度50℃、反应终点pH=5.0、反应时间90min条件下,氟去除率达93.98%,除氟效果较好。     

沉淀法制备微米四氧化三钴试验研究

研究了以氯化钴为钴源,采用碳酸钠、氢氧化钠、碳酸氢铵沉淀体系制备Co_3O_4。以碳酸氢铵为沉淀剂制备前驱体,煅烧后制得四氧化三钴。结果表明,物质的量比是影响前驱体物相的主要因素:碳酸氢铵与氯化钴物质的量比≤3∶1时,前驱体为碱式碳酸钴(Co(CO_3)_(0.5)(OH)·0.11H_2O);碳酸氢铵与氯化钴物质的量比为4.5∶1时,前驱体为碳酸钴(CoCO_3)和复合碱式碳酸钴((NH_4)_2Co_8(CO_3)_6(OH)_6·4H_2O)的混合物。采用该体系,在物质的量比4.5∶1,氯化钴质量浓度13 g/L、反应温度60℃、反应时间10 h条件下,所得Co_3O_4粉体粒度分布均匀且范围窄,D_(50)为9.08μm,形貌为类球形。     

碳酸铝铵粒子的制备及控制

本研究以硫酸铝铵和碳酸氩接为原料，通过强化搅拌速度和添加聚乙二醇PEG2000，制备出纳米球形AACH。且其结晶完整、过滤性好。通过X衍射和扫描电镜，分析了AACH的物相组成和微观结构。研究表明：搅拌强度、有机表面活性剂、陈化时间对AACH晶体结构有重要影响。强化搅拌及添加有机表面活性剂对阻止纳米颗拉的团聚有较好的效果；室温下陈化时间超过30h，前驱体形貌有转变为纤维状的趋势。因此．可通过控制搅拌，表面活性剂。陈化时间来控制AACH粒子。