Luminescence characteristics of Dy~(3+) doped Gd_2O_3-CaO-SiO_2-B_2O_3 scintillating glasses

Glasses were prepared from the compositions of 25Gd_2O_3-10 CaO-10 SiO_2-(55–x)B_2O_3-xDy_2O_3(where x is 0.0 mol.%–1.0 mol.%) by the conventional melt-quenching technique at 1400 oC. The results demonstrated the increase in the glass density with respect to the increase in the doping concentrations of Dy_2O_3. Nine absorption bands were observed. The emission spectra of the developed glass showed two strong peaks at 577 nm(~4F_(9/2)→~6H_(13/2)) and 482 nm(~4F_(9/2)→~6H_(15/2)). The highest emission intensity was observed from the developed glass prepared at 0.4 mol.% of Dy_2O_3, as the efficient energy transfer took place from Gd~(3+) to Dy~(3+). From the X-ray induced optical luminescence, the emission spectra were identical to those from PL measurements, but with the highest intensity observed from the glass quenched at 0.45 mol.% of Dy_2O_3. Finally, the integral scintillation efficiency of the developed glass was determined at 27% of that of the commercially available BGO crystal.     

Gd_2O_3-Yb_2O_3-Y_2O_3-ZrO_2热障涂层材料及涂层性能研究

使用化学共沉淀法合成了纳米Gd2O3-Yb2O3-Y2O3-ZrO（2GYYZO）粉末,并最终制备了超细晶团聚的多元稀土氧化物掺杂的GYYZO热喷涂粉末,系统的研究了材料及涂层的基本性能,重点研究了材料及涂层的高温稳定性,材料和涂层的高温相稳定性相对传统纳米8YSZ材料明显提高,对高温热处理过程中涂层孔隙收缩、晶粒长大...     

Fabrication of Ce-doped(Gd_2Y)Al_5O_(12)/Y_3Al_5O_(12) composite-phase scintillation ceramic

In this paper, a novel Ce(Gd_2 Y)Al_5O_(12)/Ce:Y_3Al_5O_(12)(Ce:GYAG/Ce:YAG) composite scintillation ceramic was designed and fabricated by a solid-state reaction method. The phase, luminescence and scintillation properties were investigated. The Ce:GYAG/Ce:YAG composite ceramic consisting of two-phase has a broad emission band ranging from 500 to 750 nm. The total mass attenuation coefficient of Ce:GYAG/Ce:YAG is 0.3864 cm~(-1), in between those of Ce:YAG and Ce:GYAG ceramics. In addition, the composite ceramic had a high light yield of 20430 ph/MeV. By controlling the ratio of GYAG and YAG, the composite ceramic can realize a spectrum design and total mass attenuation coefficient control to meet the requirements for wide-X-ray-energy-range detectors.     

均匀共沉淀法合成纳米Gd_2O_3:Eu粉体及其发光特性

以六次甲基网胺(hexamethylenetetramine,(CH2)6N4,HMT)为沉淀剂,在GdCl3和EuCl3混合溶液中,利用均匀共沉淀法制得了纳米颗粒.结果表明,获得的Gd2O3:Eu纳米颗粒近似为球形,尺寸均匀,平均粒径为100 nm,且每个球形颗粒由平均粒径为20 nm的微晶聚并而成.Gd2O3:Eu荧光粉在波长612 nm的红光发射来自Eu3+的5D0-7F2电偶极跃迁,发光强度随煅烧温度提高而增强,随Eu3+掺杂摩尔分数的提高而增强.Eu3+掺杂摩尔分数超过7%时,发生浓度淬灭,发光强度减弱.     

Luminescent properties of Eu~(3+) doped Gd_2WO_6 and Gd_2(WO_4)_3 nanophosphors prepared via co-precipitation method

Eu3+ doped Gd2WO6 and Gd2(WO4)3 nanophosphors with different concentrations were prepared via a co-precipitation method. The structure and morphology of the nanocrystal samples were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. The emission spectra and excitation spectra of samples were measured. J-O parameters and quantum efficiencies of Eu3+ 5D0 energy level were calculated, and the concentration quenching of Eu3+ luminescence in dif...     

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.     

Preparation of Nd_2O_3 nanorods in SDBS micelle system

Well-crystallized Nd2O3 nanorods were prepared in the aqueous solution containing neodymium nitrate, sodium hydroxide（dissolved in ethanol） and sodium dodecyl benzene sulfonate（SDBS）. One dimensional nanorods of neodymium hydroxide were synthesized first, which was then placed at different temperatures（600 and 800 ℃） in a calcar for 10 h to form Nd2O3 nanorods. The morphology and crystal structure of the products were investigated by X-ray diffraction, transmission electron microscopy, field emission transmission electron microscopy, Fourier transform infrared spectroscopy and fluorescence spectrometry. By using SDBS micelles as a template, this method manufactured uniform morphology of hexagonal one-dimensional neodymium oxide nanorods with a diameter ranging from 20 to 70 nm. The length of the nanorods increased with prolonged reaction time.     

Enhanced photocatalytic activity of Gd~(3+) doped TiO_2 and Gd_2O_3 modified TiO_2 prepared via ball milling method

Gd~(3+)/TiO_2 and Gd_2O_3/TiO_2 nanoparticles were prepared by ball milling method.The effects of Gd~(3+)ion and Gd_2O_3 on the structure and optical property of TiO_2 were studied by XRD and UV-vis DRS.Specific surface area was determined by Brunauer-Emmett-Teller(BET)method.The morphology and elemental composition were characterized by SEM-EDS.XPS was used to determine the surface compositions and chemical character of elements.The sample sizes and microstructures were observed by TEM.The photocatalytic activities of TiO_2 nanoparticles modified with rare earth metal gadolinium(Gd~(3+)ion or Gd_2O_3)were evaluated by degradation of methylene blue(MB)under UV light.Experimental results indicate that 2,5 mol%Gd~(3+)/TiO_2 shows the best photocatalytic activity compared with Gd_2O_3/TiO_2 and pure TiO_2.The existence of gadolinium can exhibit the aggregation and induce lattice distortion of TiO_2 obtained from XRD,SEM and TEM results.The band gap energy of 2.5 mol%Gd~(3+)/TiO_2 decreases to3.07 eV and it leads to visible light absorption response which can be seen from UV-vis absorption spectra.The surface area of 2.5 mol%Gd~(3+)/TiO_2 equals to 85.8 m~2/g and average crystal size is 21.1 nm.EDS and XPS analyses reveal that gadolinium can be introduced either into TiO_2 lattice or adsorbed on the surface of TiO_2.The content of surface OH groups in 2.5 mol%Gd~(3+)/TiO_2 is 50,88%(1.55 times higher than that of pure TiO_2)and the content of lattice oxygen decreases to 11.26%.The MB(25 mg/L)degradation reaction rate constants of 2,5 mol%Gd~(3+)/TiO_2,0.5 mol%Gd_2O_3/TiO_2 and pure TiO_2 were0.0713,0.0588 and 0.0263 min~(-1),respectively.The degradation rates of rhodamine B(30 mg/L)in 60 min are 97,9%,90.1%and 84.6%for 2,5 mol%Gd~(3+)/TiO_2,0.5 mol%Gd_2O_3/TiO_2 and pure TiO_2,respectively.     

ZrO_2-Al_2O_3(Y_2O_3)材料的相结构研究

本文通过X衍射技术和多晶法计算研究了ZrO_2-Al_2O_3和ZrO_2-Al_O_3-Y_2O_3陶瓷材料的相结构变化。结果表明,在ZrO_2-Al_2O_3体系中,在低Al_2O_3含量时,主要相是单斜相。随着Al_2O_3含量增大,单斜相比率系数X_m下降,四方相含量明显增大。在ZrO_2-Al_2O_3体系中添加Y_2O_3后,Y_2O_3可以促进形成四方相和稳定相系的作用,使三元系转变为四方结构。烧结温度对ZrO_2-Al_2O_3系相结构变化影响不明显,但对ZrO_2-Al_2O_3-Y_2O_3系影响较大,低Y_2O_3含量时,温度升高可促进相系的转移;而高Y2O_3含量时,已完全转变为四方结构。所以,烧结温度对相结构变化无影响。     

Neurotoxicity and brain localization of europium doped Gd_2O_3 nanotubes in rats after intranasal instillation

Europium doped Gd_2 O_3 nanotubes(Gd_2 O_3:Eu~(3+) NTs) were synthesized and characterized. Then,the neurotoxicity and brain localization of Gd_2 O_3:Eu~(3+) NTs were evaluated. All experimental rats were administered by intranasal instillation with 30 μL Gd_2 O_3:Eu~(3+) NTs suspension 3.0 and 15.0 mg/mL respectively every other day for 35 consecutive days, and the rats of control group were administered with an equal volume of physiological saline. The Morris water maze was used to assess the rats' spatial learning and memory ability. The oxidative stress-related biomarkers and the activity of AChE in striatum and hippocampus were analyzed, and the histopathology of hippocampus and striatum was observed.The brain localization of gadolinium(Gd) was measured. The results showed that the escape latency of the rats in high-dose group prolonged significantly compared with that of control group after treatment of six weeks(p 0.05), and the swimming time in D quadrant of high-dose group shortened significantly compared with the control group(p 0.01). In addition, high-dose Gd_2 O_3:Eu~(3+) NTs could decrease the activity of GSH-Px and CAT in hippocampus and the activity of SOD in striatum(p 0.05). MDA content in hippocampus and striatum of high-dose group increased(p 0.05). High dose Gd_2 O_3:Eu~(3+) NTs could increase the activity of AChE in hippocampus(p 0.05) and in striatum(p 0.001). But there were no significant differences between the low-dose group and control group(p 0.05). The results of Gd localization in brain showed that the ranking of Gd levels was olfactory bulb striatum hippocampus cerebellum brain stem frontal cortex. The pathology results indicated that high dose Gd_2 O_3:Eu~(3+)NTs resulted in degeneration necrosis, nucleus pycnosis, and axons disappearance of the nerve cells at CA1, CA3 and DG area of hippocampus. Therefore, the results implied that Gd_2 O_3:Eu~(3+) NTs have the potential neurotoxicity and a possible danger in causing neurodegenerative disorders after intranasal instillation.     

Influence of annealing temperature on luminescent properties of Eu~(3+)/V~(5+) co-doped nanocrystalline Gd_2Ti_2O_7 powders

Nanosized Gd2(1-x)Eu2xTi2O7:yV5+ phosphors were prepared via sol-gel method and characterized with X-ray diffraction,Raman spectroscopy,diffuse reflectance spectra and photoluminescence spectra.Their PL properties were investigated as functions of the Eu3+ doping concentration and annealing temperature.The results indicated that the as-prepared samples showed a strong emission of Eu3+ under the irradiation of 303 nm.For Eu3+-doped Gd2Ti2O7,the orange emission at 586 nm was the strongest,which was correspond...     

Specific features of Eu~(3+) and Tb~(3+) magnetooptics in gadolinium-gallium garnet (Gd_3Ga_5O_(12))

We reported magnetooptical properties of Eu3+(4f(6)) and Tb3+(4f(8)) in single crystals of Gd3Ga5O12 (GGG), Y3Ga5O12 (YGG), and Eu3+(4f(6)) in Eu3Ga5O12 (EuGG) for both ions occupying sites of D2 symmetry in the garnet structure. Absorption, luminescence, and magnetic circular polarization of luminescence (MCPL) spectra of Tb3+ in GGG and YGG and absorption and magnetic circular dichroism (MCD) of Eu3+ in EuGG were studied. The data were obtained at 85 K and room temperature (RT). Magnetic susceptibility of...     

Optical Spectroscopy of Er^3 , Er^3＋/Yb^3 ＋ Co-doped Bi2O3-GeO2-B2O3-ZnO Glasses

Optical Spectroscopy of Er~(3 ), Er~(3 )/Yb~(3 ) Co-doped Bi_2O_3-GeO_2-B_2O_3-ZnO Glasses     

Colloidal(Gd_(0.98)Nd_(0.02))_2O_3 nanothermometers operating in a cell culture medium within the first and second biological windows

Non-contact,self-referenced and near-infrared luminescent nanothermometers have been recognized as emerging tools in the fields of nanomedicine and nanotechnology due to their great capability of precise temperature readout at the nanoscale and real-time deep-tissue imaging.However,the development of multifunctional and biocompatible luminescent nanothermometers operating within the optically transparent biological windows with high thermal sensitivity(>2.0%/K) remains challenging.Here,we pre...     

Tuning thermal decomposition of ammonium perchlorate by nanoporous Gd_2O_3 for improved safety and enhanced propellant efficiency

Nanoporous Gd_2O_3 powders(NGPs) with different specific surface areas were prepared by a nonaqueous sol-gel method and utilized to tune the exothermal decomposition of ammonium perchlorate(AP) for enhanced propellant efficiency and improved safety.It is found that with the increasing dosage of NGPs into AP,the two exothermal peaks of AP merge into one intense exothermal peak,indicating that an energy stacking has been achieved.Meanwhile,the unique delay of the first exothermal peak of AP is conducive to the safety of AP in application process.Furthermore,the dependence of decomposition heat of AP on dosage and calcination temperature is more evident than on the surface areas of NGPs,suggesting that the promotion effect of NGPs on the thermal decomposition of AP does not only rely on the surface interaction.Therefore,an electron transfer mechanism is proposed to illustrate the decomposition process of AP tuned by NGPs.     

Photoluminescence and radioluminescence properties of (Gd_8Ca_2)(SiO_4)_6O_2 crystals with different concentrations of Ce

(Gd_8 Ca_2)(SiO_4)_6 O_2 apatite crystals doped with different concentrations of Ce were synthesized by the Floating Zone(FZ) method, and we have evaluated the photoluminescence(PL) and radio luminescence(RL) properties. In PL, an emission band appeared around 400 nm under excitation at 300 nm due to the5 d-4 f transitions of Ce3+. The PL decay curves were approximated by a second-order exponential decay function, and the derived decay time constants ranged around 20-25 ns and 40-480 ns. Similar emission was observed in RL, but the decay time constants were much longer than those in PL. The RL afterglow was the lowest in the 1.0% Ce-doped sample. The 1.0% and 2.0% Ce-doped samples showed a full-energy peak in the pulse height spectrum measured under ~(241) Am 5.5 MeV α-ray irradiation, and the absolute scintillation light yields were estimated to be around 55 and 36 ph/5.5 MeV-a, respectively.     

Spectral properties and energy transfer of Tm~(3 )/Ho~(3 )-codoped Ga_2O_3-Bi_2O_3-GeO_2-PbO glasses

The 2.0 μm emission originating from Ho3 :5I7→5I8 transition in Ho3 /Tm3 -codoped gallate-bismuth-germanium-lead glasses were investigated upon excitation with 808 nm laser diode (LD). Energy transfer (ET) process between Tm3 : 3F4 level and Ho3 : 5I7 level was also discussed. It was noted that the measured peak wavelength and stimulated emission cross-section of Ho3 -doped bis-muth-germanium-lead glasses were ～2.02 μm and 5.1×10–21 cm2, respectively. Intense emission of Ho3 in Tm3 /Ho3 -codoped GBPG glass were observed, which resulted from the ET between Tm3 : 3F4 and Ho3 : 5I7 level upon excitation with 808 nm LD.     

Effect of Nb~(5+) and Cu~(2+) codoping on thermal properties of Gd_2Zr_2O_7 ceramic

In this work,Nb⁵⁺and Cu²⁺were selected to partially substitute Zr4+in Gd₂Zr₂O₇for studying the phase structure,microscopic morphology and thermal properties.Gd₂(Zr_(1-3 x/2)Nb_xCU_x/2)₂O₇(x=0,0.05,0.1,0.15,0.2,0.25)ceramic materials were synthesized by high-temperature solid-state reaction method.The results show that the Gd₂(Zr_(1-3 x/2)Nb_xCu_x/2)₂O₇ceramics present cubic pyrochlore structure with clear grain boundaries and dense cell structure.And the thermal expansion coefficient of Gd₂(Zr_(1-3 x/2)Nb_xCu_x/2)₂O₇ceramics gradually decreases because of the incorporation of Nb⁵⁺and Cu²⁺into Zr-site in Gd₂Zr₂O₇.Meanwhile,its thermal conductivity decreases firstly and then increases with the doping of Nb⁵⁺and Cu²⁺,which reaches the lowest value for the composition of Gd₂(Zr_0.85Nb_0.1Cu_0.05)₂O₇.     

Effect of Er_2O_3 and Pr_6O_(11) on non-isothermal kinetics of mullite formation from kaolinite

The non-isothermal kinetics of mullite formation from both non-mixed and mixed with different rare earth oxides(Pr_6O_(11) and Er_2O_3) kaolinite were studied by comprehensive thermal analysis technologies and X-ray diffraction(XRD). Meanwhile, Kissinger equation, Ozawa equation and JMA modified equation(I) and(II) were employed for analysis of the effects of Pr_6O_(11) and Er_2O_3 on the kinetics of kaolinite in phase transformation at high temperatures. The results showed that the addition of two kinds of rare earth oxides influenced the crystallization kinetic parameters of kaolinite. Crystallization activation energies and frequency factors of the kaolinite mixed with Pr_6O_(11) were obviously decreased compared with the kaolinite with none, but the kaolinite mixed with Er_2O_3 weakly decreased. Crystallization behaviors were not changed, belonging to volume crystallization. Mullite formation from kaolinite was suppressed while generation of cristobalite was promoted by Pr_6O_(11), and effect of Er_2O_3 on mullite formation from kaolinite under high temperature was not evident.     

Synthesis and characterization of Y_2O_2S:Eu~(3+),Mg~(2+),Ti~(4+) nanorods via a solvothermal routine

Y2O2S:Eu3+,Mg2+,Ti4+ nanorods were prepared by a solvothermal procedure.Rod-like Y(OH)3 was firstly synthesized by hydrothermal method to serve as the precursor.Y2O2S:Eu3+,Mg2+,Ti4+ powders were obtained by calcinating the precursor at CS2 atmosphere.The Y2O2S:Eu3+,Mg2+,Ti4+ phosphor with diameters of 30-50 nm and lengths up to 200-400 nm inherited the rod-like shape from the precursor after calcined at CS2 atmosphere.The Y2O2S:Eu3+,Mg2+,Ti4+ nanorods showed hexagonal pure phase,good dispersion and exhibite...