Synthesis and Spectral Properties of Nd^3＋： Gd3Ga5O12 Nanopowder for Transparent Laser Ceramics

Nd^3＋： Gd3Ga5O12（Nd ： GGG） nanopowder for transparent laser ceramics was synthesized using sol-gel method. XRD, SEM, and fluorescence spectrum were used to study the properties of Nd^3＋ ：Gd3Ga5O12 nanopowder. XRD patterns of samples show that it has a cubic structure. Meanwhile, pure Nd：GGG crystals were obtained at 1000 ℃ for 12 h. SEM photographs show that dispersed, uniform, ball-like Nd：GGG nanopowder is obtained. Both XRD and SEM results show that the crystallization degree and the grain size increase with the increase in calcining temperature. Analysis of fluorescence spectrum shows that fluorescence emission occurs at 1062.7 nm, which is the result of Nd^3＋ （^4F3/2→^4I11/2） transition. Homogenous Nd ： GGG nanopewder with a small grain size synthesized using the sol-gel method is favorable for sintering the transparent ceramic, which proves that the nanopewder obtained is suitable as a precursor for preparing GGG transparent ceramics.     

掺钕氧化钪激光透明陶瓷纳米粉体的合成及研究

研究了化学共沉淀法合成Nd:Sc2O3纳米粉的工艺.以Sc2O3为基质材料,掺杂0.5％(原子分数)的Nd3+,添加适量聚乙二醇(PEG)和(NH4)2SO,作为分散剂,以氨水(NH3·H2O)和碳酸氢铵(NH4HCO3)混合溶液作复合沉淀剂,采用化学共沉淀法获得了碱式稀土碳酸盐前躯体,在1100℃下煅烧该前躯体4h,制备出性能良好的Nd:Sc2O3纳米粉.采用热重-差热分析仪(TG/DSC)、红外光谱分析仪(IR)、X射线衍射仪(XRD)、透射电子显微镜(TEM)等测试手段对Nd:Sc2O3前躯体和煅烧后的粉体进行表征.实验结果表明:在室温下,用氨水和碳酸氧铵混合溶液作为复合沉淀剂合成出的前躯体为碱式稀土碳酸盐.通过XRD和EDS能谱分析,Nd3+完全固溶于Sc2O3的立方晶格中,这将有利于制备激光透明陶瓷.在1100℃的温度下煅烧此前躯体得到的Nd:Sc2O3纳米粉具有颗粒粒度小(约50 nm)、分散性好、团聚程度轻、结晶良好的性能.因此,采用此工艺合成的粉体将有可能制备出的Nd:Sc2O3透明陶瓷.     

Preparation and Upconversion Luminescence of Y3Al5O12∶Yb3+, Er3+ Transparent Ceramics

YAG:1% (atom fraction) Yb3 , 0.5% (atom fraction) Er3 transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. The mixed powder compact was sintered at 1760 ℃ for 6 h in vacuum and annealed at 1500 ℃ for 10 h in an air atmosphere. The ceramics consisted of about 10 μm grains and exhibited a pore-free structure. The optical transmittance of the ceramics at 1064 nm was nearly 80%. Upconversion emissions were investigated on the ceramics pumped by a 980 nm continuous wave diode laser, and strong green emission centered at 523 and 559 nm and red emission centered at 669 nm were observed, which originated from the radiative transitions of 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 of Er3 ions, respectively.     

Structure and Waveguide Properties of Sol-Gel Derived Gd2O3 Films

Pure and rare earth doped gadolinium oxide (Gd2O3) waveguide films were prepared by a simple sol-gel process and dip-coating method. Structure of Gd2O3 films annealed at different temperature was investigated by X-ray diffraction and transmission electron microscopy. Oriented growth of (400) face of Gd2O3 has been observed when the films were deposited on amorphous substrate. The refractive index and thickness of films were determined by m-lines spectroscopy. The laser beam (λ= 632.8 nm) was coupled into the film by a prism coupler and the propagation length is about 3.5 cm. Luminescence properties of europium ions doped films were measured by waveguide fluorescence spectroscopy, which shows disordered environment for Eu^3 at 400℃.     

Synthesis and luminescent properties of Pr-doped Lu3Al5O12 translucent ceramic

Lutetium aluminum garnet (LuAG) precursors doped with different Pr3+ concentration (0.25at.%, 0.5at.%, 1.0at.%, 3.0at.%, 5.0at.%) were synthesized via a co-precipitation method using ammonium hydrogen carbonate as precipitant. The phase evolution and mor-phology of the precursor were characterized with X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The resultant LuAG:Pr3+ powder was sintered into translucent ceramic without any additives in vacuum at 1150℃ and then in nitrogen atmosphere at 1700℃. Photohiminescence spectra of LuAG:Pr3+ powder and ceramic were measured at room temperature in vacuum ultraviolet (VUV) and ultraviolet (VU) region. For the 5d-4f transition of Pr3+ ions, dominant emission of ceramic samples peaking round 311 nm had higher lumines-cence intensity. And the host absorption in ceramic samples was not as intensive as that in powder samples. The luminescent intensity of LuAG:Pr3+ varied with the Pr3+ contents and the quenching concentration was about 1.0at.% for ceramic and 3.0at.% for powder, which was much higher than 0.24at.% for LuAG:Pr3+ single crystals. This phenomenon showed that the ceramic had some superiority over single crystals.     

Synthesis and Luminescence Properties of Gd_2O_3∶Eu~(3+) Phosphors

Gd2 O3∶Eu3+ isanefficientredemittinglumines centmaterial ,whichcanbeappliedindisplays[1,2 ] .TheconventionalcommercialGd2 O3∶Eu3+ ismainlysynthesizedbyhightemperaturesolid statereactionandchemicalco precipitationmethods .Anadvancedperformanceofdisplaysrequireshighqualityphospho rssuchashighbrightnessandefficiency ,monodisper sityandfinegrainsize .Muchresearchhasanticipatedthatsubmicrometer sizedandnanometerluminescentmaterialswillhavethesepotentialadvantages[3～ 8] ,sosubmicrometer sizedan…     

Vacuum ultraviolet excited photoluminescence properties of Gd2O2CO3:Eu3+ phosphor

The Gd2O2CO3:Eu3 with type-II structure phosphor was successfully synthesized via flux method at 400℃ and their photoluminescence properties in vacuum ultraviolet (VUV) region were examined. The broad and strong excitation bands in the range of 153-205 nm owing to the CO32- host absorption and charge transfer (CT) of Gd3 -O2- were observed for Gd2O2CO3:Eu3 . Under 172 nm excitation, Gd2O2CO3:Eu3 exhibited strong red emission with good color purity, indicating Eu3 ions located at low symmetry sites and the chromaticity coordination of luminescence for Gd2O2CO3:Eu3 was (x=0.652, y=0.345). The photoluminescence quenching concentration of Eu3 excited by 172 nm for Gd2O2CO3:Eu3 was about 5%. Gd2O2CO3:Eu3 would be a potential VUV-excited red phosphor applied in mercury-free fluorescent lamps.     

Synthesis and Spectral Properties of Nd~(3+)∶Gd_3Ga_5O_(12) Nanopowder for Transparent Laser Ceramics

Recently ,ceramicsforlaser mediumhas receivedonsiderable attention . By sintering ceramics , it isossible to overcome the disadvantages of growing sin-le crystal such as high cost , long manufacturingi me , and low doping ratio . A novel technology[1 ~5]as been adoptedto produce hightransparent ceramicswithsufficiently lowscattering loss and high laser os-illation. Nd3 +∶Gd3Ga5O12[6 ~9]has high fracturetrength, good chemical stability , high thermal con-uctivity,large rare earth doping ratio…     

Synthesis of ZnO：Dy Nanopowder and Photoluminescence of Dy^3＋ in ZnO

A type of dysprosium-doped ZnO （ZnO：Dy） nanopowder was synthesized by high temperature calcinations. XRD was used to analyze the structure. Photoluminescence spectra were used to study the optical characteristic. PL of ZnO：Dy shows two different spectra which are broad band resulted from the defect of Dy in ZnO and sharp lines from the 4f→4f transition of isolated Dy^3 ＋ luminescence center. The emission and excitation spectra depend on the excitation wavelength and the concentration of Dy^3＋ . The broad bands with peaks at 600 and 760 nm are attributed to the recombination from an electron of the defect Dy in ZnO to a hole in VB.     

Growth and Spectral Properties of Crystal Er3+:Y0.5Gd0.5VO4

Er3 :Y0.5Gd0.5VO4 crystal with good optical quality was grown by Czochraski method. The structure of the crystal was determined by X-ray powder diffraction method. The segregation coefficient of Er3 ions in the crystal was measured by the ICP method. The absorption and emission spectra were also measured. On the basis of the spectra, the absorption cross-sections, emission spectrum FWHM and fluorescence lifetime of the crystal were calculated. From the properties mentioned above.     

A modified solution combustion method to superfine Gd2O3:Eu3+ phosphor:preparation, phase transformation and optical properties

Cubic and monoclinic Gd2O3:Eu3+ phosphors in the range of nano-scale and submicron-scale were prepared by a modified solution combustion method.Coexistence of cubic and monoclinic phases was found in the highest luminescent sample synthesized at 600 oC.In relation to commercial sample,the relative luminescence intensity was 49.8%.The shape of emission spectrum of the sample thus changed and the charge-transfer-state band of excitation spectrum slightly shift toward higher energies.With increasing the anneal...     

Preparation and Characterization of Gd3Sc2Ga3O12 Polycrystalline Material by Co-Precipitation Method

Gd3Sc2Ga3O12 polycrystalline material for single crystal growth was prepared with Ga, Gd2O3 and Sc2O3 as starting materials and aqueous ammonia as the precipitator by co-precipitation method. The precursors sintered at various temperatures were characterized by infrared spectra （IR）, X-ray diffractometry （XRD） and transmitted electron microscopy （TEM）. The results showed that pure GSGG phase could be obtained at 900 ℃. The sintered powders were well-dispersed and less-aggregated in the sintered temperature range of 900 - 1000 ℃. XRD and TEM show that the polycrystalline particle sizes of the polycrystalline powders were about 20 - 50 nm. Compared with the method that Ga2O3, Gd2O3 and Sc2O3 were mixed directly and sintered to get polycrystalline materials, the synthesized temperature was lower and sintered time was shorter. Thus co-precipitation was a good method to synthesize GSGG polycrystalline material.     

Synthesis of La3+ and Nd3+ co-doped yttria nanopowder for transparent ceramics by oxalate precipitation method

Polycrystalline Nd3+ and La3+ co-doped yttria nanopowder Nd3+:Y1.90La0.10O3 for transparent ceramics was synthesized by co-precipitation method using oxalate acid as the precipitant and(NH4)2SO4 as the electrical stabilizer under ultrasonic radiation.Nanopowders calcined at different temperatures were characterized with thermal gravimetric-differential thermal analysis(TG/DTA),X-ray diffraction(XRD),transmitting electron microscopy(TEM),energy dispersive spectrometry(EDS) and spectral analysis techniques.Th...     

Nanostructured Yb：GGG polycrystalline powders via gel combustion method

Gadolinium gallium garnet (GGG) nanopowders doped with ytterbium ions (Yb:GGG) were synthesized with citric acid as a fuel via gel combustion method. The optimized conditions for preparing Yb3+:Gd3Ga5O12 nanopowders were discussed. The heat behavior, struc-ture and morphology of powders were analyzed with thermal analysis (TG-DTA), X-ray diffraction (XRD), infrared spectra (IR) and trans-mission electron microscope (TEM). TG-DTA analysis revealed that the weight loss of the precursor occured below 800 ℃ and its crystalli-zation temperature was 830.6 ℃. XRD and IR analysis showed that the precursor converted directly into pure GGG at a relatively lower tem-perature (900 ℃) without any other intermediate phase. The lattice constant was 1.2377 calculated by extrapolation method. TEM results in-dicated that the spherical powders showed good dispersity and had a relatively narrow size distribution with average particle size of approxi-mately 40-50 nm, which was favorable for good sinterability of Yb:GCG laser ceramic.     

Preparation and Upconversion Luminescence of Y3Al5O12 ： Yb^3＋ , Er^3＋ Trapsparent Ceramics

YAG： 1% （atom fraction） Yb^3＋ , 0.5% （atom fraction） Er3＋ transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. The mixed powder compact was sintered at 1760 ℃ for 6 h in vacuum and annealed at 1500 ℃ for 10 h in an air atmosphere. The ceramics consisted of about 10μm grains and exhibited a pore-free structure. The optical transmittance of the ceramics at 1064 nm was nearly 80%. Upconversion emissions were investigated on the ceramics pumped by a 980 nm continuous wave diode laser, and strong green emission centered at 523 and 559 nm and red emission centered at 669 nm were observed, which originated from the radiative transitions of ^2H11/2→^4I15/2, ^4S3/2→^4I15/2, and ^4F9/2→^4I15/2 of Er^3＋ ions, respectively.     

Preparation and Magnetism of Gd2O3/X-NBR Composites

Series of Gd2O3/X-NBR composites were prepared by in-situ reaction at different temperatures (100 and 160 ℃) and different processing time. The influence of processing time and processing temperature on dispersion of Gd2O3 was investigated, and the relationship between magnetic property and temperature was also discussed. The results show that, the mass magnetizability (χg) descends as temperature rising. Processing temperature and time do not exhibit evidenced effects on the mass magnetizability (χg). All the composites show to be antiferromagnetic.     

Crystal Growth and Properties of Co2+ doped Y3Sc2Ga3O12 Single Crystal

Single crystal of cobalt (Co)-doped Y3Sc2Ga3O12 (YSGG) with the dimensions up to φ20×40mm3 and undoped YSGG crystal with the dimensions up to φ28×60mm3 have been grown using the Czochralski technique. The structure of the crystal was characterized by the X-ray powder diffraction (XRPD) method. The absorbance spectra of the crystal shows that it has strong absorption bands at 606 and 1540nm. The results indicate that the crystal Y3Sc2Ga3O12 may be a kind of good Q-switch material.     

Crystal Growth and Laser Characteristics of Nd3+ :KGd(WO4)2

The Nd3 3.2% (atom fraction):KGd(WO4)2 crystal was grown by Kyropoulos method. The absorption spectrum and fluorescence spectrum of Nd3 :KGW crystal were measured. The absorption cross sections at 808 nm(0.6799 ×10-20 cm2) were calculated, and the output wavelength of fluorescence is 1064 and 1351 nm. The diode-pumped laser was operated both in the free-running and passively Q-switched operating modes. The maximum laser output( 1064 nm) is 326mW with 62.7 % slope efficiency when input energy is 900 mW. The beam quality factor M2 ≈ 1.1. The green light of 532 nm is obtained in frequency doubling operation. The laser is passively Q-switched by using Cr4 :LuAG as saturable absorber. The pulse width is 170 ns at repetitive frequency of 15 kHZ.     

Electrical characteristics of MOS capacitor using amorphous Gd2O3-doped HfO2 insulator

This work described the electrical characteristics of a kind of amorphous Gd2O3-doped HfO2 insulator for high-k metal-oxide-semiconductor(MOS) capacitors.Compared with pure HfO2,the doped HfO2 with an optimum concentration of Gd2O3 as MOS gate dielectric exhibited a lower leakage current,thinner effective oxide thickness and less fixed oxide charges density.The result indicated that Gd2O3 doping power of 60 W exhibited the best electrical characteristics,maximum capacitance,lowest leakage current of 9.35079...