废旧荧光粉中稀土元素浸出的电位-pH图

废旧稀土荧光粉经"酸浸-碱焙烧-水洗-酸浸"处理可浸出回收其中的Y, Eu, Tb, Ce等稀土。本文根据酸浸过程中的各组分的吉布斯自由能Δ_fG分别计算出各酸浸过程中各化学反应的吉布斯自由能Δ_rG,由能斯特公式计算出反应的电位与pH关系,进而绘制出两段酸浸过程中的电位-pH图,即不同活度的Al~(3+)与Y-Eu-H_2O系的电位-pH图和Tb-Ce-H_2O系电位-pH图,并分析了各组分的稳定区域。结果表明:废旧稀土荧光粉直接酸浸时,从25～100℃,在pH6的酸性条件下,红粉中的Y_2O_3, Eu_2O_3以Y~(3+), Eu~(3+)的形式稳定存在水溶液中, Al(OH)_3稳定区域在pH为4.8～8.3之间,为防止Al ~(3+)水解,酸浸出液终点pH值应控制在3.5～4.0之间;从25～100℃,在酸性条件下,经碱焙烧水洗除铝后得到的TbO_2, CeO_2很难被酸直接浸出,同时Tb~(4+), Ce~(4+)在水溶液中不能稳定存在,但通过加入适当的还原剂,可将Tb~(4+), Ce~(4+)还原成Tb~(3+), Ce~(3+),便可存在于水溶液中。     

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.     

磷酸盐基质点阵中Ce~(3 )→Tb~(3 )的转移

在具有不同结构类型的各种磷酸液盐中,特别在新化合物 Na_3Ln(PO_4)_2:Ce,Tb;NaxSr_(3-2)xlnx(PO_4)_3:Ce,Tb 和 KCaLn(PO_4)_2:Ce,Tb 中,已经表明将发生 Ce~(3 )→Tb~(3 )的转移。     

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℃.     

Luminescence of emission-tunable Na_(15.6)Ca_(3.84)Si_(12)O_(36):Ce~(3+),Tb~(3+),Na~+ phosphors for near-ultraviolet light-emitting diodes

A series of Na_(15.6)Ca_(3.84)Si_(12)O_(36):Ce~(3+),Tb~(3+),Na~+(NCS:Ce~(3+),Tb~(3+),Na~+) phosphors were prepared by conventional solid-state reaction method, and their photoluminescence properties under near-ultraviolet(NUV) excitation were studied. The excitation spectrum of Ce~(3+)-single-doped NCS showed a broad excitation band from 250 to 400 nm, which could well match with the emission wavelength of the NUV LED chip. Upon 365 nm excitation, the NCS:Ce~(3+),Na~+ phosphor demonstrated a blue emission in the range of 400–600 nm with the predominated peak at 443 nm. By co-doping Tb~(3+) into NCS:0.04Ce~(3+),0.04Na~+, tunable-emission was realized due to the energy transfer from Ce~(3+) to Tb~(3+), and nearly white light was also obtained. The investigation also revealed that warm white light could be further generated by combining the NCS:0.04Ce~(3+),y Tb~(3+),(0.04+y)Na~+ with other red-emitting phosphors. Thus, the NCS:Ce~(3+),Tb~(3+),Na~+ phosphors could be promising candidate for white LEDs.     

Luminescent properties of Ce~(3+)/Tb~(3+) co-doped glass ceramics containing YPO_4 nanocrystals for W-LEDs

Ce~(3+)/Tb~(3+) co-doped transparent glass ceramics containing YPO_4 nanocrystals were prepared using high temperature melting method,and their structural and luminous properties were investigated.XRD analysis and TEM images confirmed the existence of YPO_4 nanocrystals in glass ceramics.The transmission spectra proved that the glass ceramics specimens still maintained a high transparency.Then the excitation and emission spectra of the Ce~(3+) and Tb~(3+) single-doped and co-doped glass and glass ceramics were discussed,which proved that the glass ceramics had better luminescent properties.Under the near ultraviolet(331 nm)excitation,the broadband emission located at 385 nm was observed which was ascribed to 5d→~2F_(5/2) and ~2F_(7/2) transition of Ce~(3+) ions.Several characteristic sharp peaks centered at 489,543,578 and 620 nm originated from the ~5D_4 to ~7F_J(J=6,5,4,3)of Tb~(3+) ions.The decay time of Tb~(3+) ions at 543 nm and the relevant energy levels of Ce~(3+) ions and Tb~(3+) ions illustrated the transfer process from Ce~(3+) ions to Tb~(3+) ions.The best CIE chromaticity coordinate of the glass ceramics specimen was calculated as(x=0.3201,y=0.3749),which was close to the NTSC standard values for white(x=0.333,y=0.333).All the results suggested that the YPO~4-based Ce~(3+)/Tb~(3+) co-doped glass ceramics could act as potential luminescent materials for white light-emitting diodes.     

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。     

纳米Gd_2O_3:Tb~(3+)的多元醇法制备及发光特性

以DEG为溶剂,分别配置一定比例的GdCl_3, TbCl_3作为前驱液,利用多元醇法合成可用于生物探针的Gd_2O_3:Tb~(3+)纳米晶;将一定量的APTES和TEOS加入制备好的溶液中,使得纳米晶Gd_2O_3:Tb~(3+)的表面包裹聚硅氧烷层。本实验通过马尔文粒度仪、 X射线衍射仪(XRD)、场发射扫描电镜(SEM)、透射电镜(TEM)、荧光分光光度计等检测方法研究不同煅烧温度和不同Tb~(3+)掺杂浓度对纳米晶Gd_2O_3的粒径、物相结构、和发光性能的影响。将真空干燥过的纳米晶Gd_2O_3:Tb~(3+)置于马弗炉中分别以600, 800, 1000℃进行煅烧,得到的样品经XRD表征后发现:当煅烧温度为800℃时,得到立方相结构的纳米Gd_2O_3:Tb~(3+)。通过研究不同Tb~(3+)离子掺杂浓度下纳米晶Gd_2O_3:Tb~(3+)的荧光强度表明:当Tb~(3+)离子浓度为5.0%时,纳米晶Gd_2O_3:Tb~(3+)的发射强度最强,尤其是在主发射峰545 nm附近Tb~(3+)的~5D_4→~7F_5能级跃迁峰,其峰值强度比掺杂浓度为2.5%时提高了39%; Tb~(3+)掺杂浓度升高至7.5%时,样品发生了浓度猝灭导致光谱强度下降。     

Phase relations,microstructure, and valence transition studies on CaZr_(1-x)Ce_xTi_2O_7(0.0≤x≤1.0) system

In this study, Ce-doped zirconolite was synthesized through high-temperature solid-state reaction at 1250 ℃ in air for 96 h. The crystal phase.microstructure and valence transition were studied by X-ray diffraction(XRD), scanning electron microscopy(SEM), and X-ray photoelectron spectroscopy(XPS).Phase relations of CaZr_(1-x)Ce_xTi_2O_7 systems were determined by XRD analyses and Rietveld refinements.Four different phases are identified, namely zirconolite, perovskite, pyrochlore, and cerianite. The phase transformation(2M-zirconolite → 4M-zirconolite → Ce-pyrochlore) is caused by cations rearrangement as cerium content increases. The solubility limit of cerium ions in CaZr_(1-x)Ce_xTi_2O_7 system is estimated to be approximately 0.80. Under sintering air atmosphere, partial reduction of Ce~(4+) in Ce~(3+) is detected in Ce 3d XPS spectra, and the ratio of Ce~(3+) and Ce~(4+) significantly decreases as cerium content increases.     

Ce~(4+)掺杂对CaO-SiO_2-MgO-Al_2O_3系透辉石微晶玻璃析晶行为的影响

在采用熔融法制备含Ce~(4+)的CaO-SiO_2-MgO-Al_2O_3系透辉石微晶玻璃过程中,采用差示扫描量热法(DSC)、扫描电子显微镜(SEM)和X射线衍射(XRD)相结合的分析检测方法,研究了Ce~(4+)掺杂对基础玻璃结构的稳定性、热处理后晶体层的晶体形态及晶相组成的影响规律。研究结果表明,Ce~(4+)掺杂能显著提高基础玻璃的玻璃化转变温度,提高基础玻璃结构稳定性并抑制透辉石晶体长大,CeO_2不能作为CaO-SiO_2-MgO-Al_2O_3系微晶玻璃的有效晶核剂。Ce~(4+)掺杂对CaO-SiO_2-MgO-Al_2O_3系微晶玻璃的析晶矿物种类和数量均无明显影响。     

Synthesis,photoluminescence properties and thermal investigation by TG-MS of RE(DAS)_3·xH_2O(RE=Eu~(3+),Tb~(3+))

Rare earth(Ⅲ) diphenyl-4-amine sulfonates(RE(DAS)_3·xH_2O,RE=Eu~(3+),Tb~(3+))phosphors were synthesized by precursor method from barium diphenyl-4-amine sulfonate and rare earth sulfates.FTIR,TG/DSC coupled to mass spectrometry(TG/DSC/MS),X-ray powder diffraction(XPD),scanning electron microscopy(SEM) and photo luminesce nce(PL) spectroscopy were utilized to structurally and morphologically characterize the samples.Thermal decomposition of Eu(DAS)_3·7H_2O and Tb(DAS)_3·2H_2O at 973 K under dynamic air atmosphere results in crystalline Eu_2O_2SO_4 and Tb_2O_2SO_4 materials,respectively.Accordingly,MS spectra reveal the liberation of thermal decomposition products of precursors,largely as CO_2,NO_2 and SO_2 gases.The diphenyl-4-amine sulfonate(DAS) ligand demonstrats a good stabilizing property for Eu~(3+) and Tb~(3+) ions.The Eu(DAS)_3·7H_2O and Tb(DAS)_3·2H_2O compounds display efficient red and green emissions,under UV excitation,arising from the ~5D_0→~7F_J(J=0-4) and ~5D_4→~7F_J(J=0-6) transitions of the Eu~(3+) and Tb~(3+) ions,respectively.     

在硫酸-伯胺萃取体系中铈还原反萃取机理的探讨

本文探讨了在硫酸介质中用伯胺萃取分离Th~(4 )和Ce(4 )时铈的还原反萃取机理。通过计算和试验说明,铈的络阴离子先被置换下来后再被H_2O_2还原为Ce~(3 ),从而达到铈、钍分离的目的。对反萃取的影响因素也进行了探讨。根据其基本认识所提出的工艺条件,大大降低了H_2O_2的消耗量。     

MO_2—R_2O_3型混合稀土氧化物的研究—ⅡTb_4O_7—R_2O_3(R=La、Nd、Gd、Y和Er)体系的研究

一、引言自1939年以来MO_2—R_2O_3(M=Ce、Pr、Tb、Th和Zr)体系受到广泛的重视。[1—13]稀土倍半氧化物在高温下进入萤石型晶格中形成固溶体。此时保持萤石型结构中阳离子晶格的完善,造成晶体中阴离子晶格的空位,因而导致体系的较好的阴离子导电的特性。在MO_2—R_2O_2体系中CeO_2—R_2O_2体     

Blue-emitting Sr_(1-x)Ca_xLu_2O_4:Ce~(3+) phosphors for high CRI white LEDs

A broadband blue-emitting Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+)(x=0-0.2) phospho rs were synthesized,which can be used for near-UV pumped white light-emitting diodes(w-LEDs).The crystal structures,photoluminescence pro perties,external quantum efficiency,the rmal stability and application perfo rmance of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+),by partially substituting Sr~(2+) with Ca~(2+)(x=0-0.2),were studied by various analytical techniques.When the Ca/Sr ratio of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) gradually increases,the emission peak of Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) red-shiftes from 459 to 465 nm,corrected external quantum efficiency increases from 31.8% to 42.9%,and the thermal stability is also improved.The mechanism of the changes of the photoluminescence emission and excitation spectra,external quantum efficiency and thermal stability properties was also investigated in detail.In addition,a w-LED was fabricated by using SrLu_2 O_4:Ce~(3+)(blue),β-sialon:Eu~(2+)(green) and(Sr,Ca)AlSiN_3:Eu~(2+)(red) phosphors combined with a 405 nm near-UV LED chip,and its color rendering index(CRI) reaches 96.0.When Sr_(0.8)Ca_(0.2)Lu_2 O_4:Ce~(3+)is applied as blue phosphor to substitute SrLu_2 O_4:Ce~(3+),the obtained w-LED devices have high luminous efficiency,and CRI greater than 95.0.These re sults show that the Sr_(1-x)Ca_xLu_2 O_4:Ce~(3+) can be potential blue phosphors for n-UV pumped high CRI w-LEDs application.     

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.     

Tb_xTm_yY_(1-x-y) P_5O_(14)晶体生长和光谱特性

本文讨论了用高温溶液法从磷酸溶剂中生长Tb_xTm_yY_(1-x-y)P_6O_(14)晶体的条件并研究了晶体的光谱性质和Tm~(3+)离子浓度对Tb~(3+)离子荧光的影响。     

Dy_2O_3(Dy)-HCl-CaF_2-H_2O体系热力学研究

根据热力学计算结果,绘制25℃条件下Dy_2O_3(Dy)-HCl-CaF_2-H_2O体系在总镝浓度为0.1mol/L的溶液中各主要溶解组分的lgc-pH图,以及在不同总镝浓度溶液中Dy~(3+)与Ca~(2+)的lgc-pH图,利用热力学平衡图分析钙热还原稀土冶炼渣直接酸浸的可行性。结果表明:钙热还原稀土冶炼渣中可溶解于酸的Dy_2O_3(Dy)易与CaF_2反应重新生成难溶的DyF_3,致使浸出的镝重新沉淀。     

乙二胺四乙酸二钠模板调控碳酸铈粒子形貌的研究

以硝酸铈(Ce(NO_3)_3)为原料,碳酸氢铵(NH_4HCO_3)为沉淀剂,乙二胺四乙酸二钠(EDTA-2Na)为模板剂,通过控制EDTA-2Na与Ce~(3+)摩尔百分比,加料时间,搅拌速度和陈化时间实验条件,制备得到规则块状形貌的碳酸铈。并采用SEM、FT-IR对制得的产品进行分析表征。结果表明,制备形貌规则、分散性较好的Ce_2(CO_3)_3的最佳条件:EDTA-2Na与Ce~(3+)的摩尔百分比为0.2,加料时间为3 h,搅拌速度为300 r/min,陈化时间为8 h时。同时初步分析探讨了EDTA-2Na控制Ce_2(CO_3)_3的形貌机理。     

Energy Transfer in LaOBr:Tb,Gd

Energy transfer in LaOBr:Tb_(0.0075),Gd_x(x<0.30)was investigated via excitation spectra,emissionspectra,fluorescence decay function and X-ray diffraction.Effective energy transfer from Gd to Tb was found.With excitation of λ=275nm,no Gd~(3+)but only Tb~(3+)emission has been observed,and the integrated intensityof Tb~(3+)emission increases with increasing Gd content up to～5.5 times(in the sample of x=0.30)compared tothat of the sample without Gd.The existense of Gd in the sample slows down the Tb~(3+)flourescence decay,andmost likely the electric dipole-dipole interaction dominates the energy transfer process.