Preparation and Characterization of Rare Earth Metal and Alloy Target Materials for Manufacturing Magneto-Optical Disks

The studies were made on the preparation processes of the rare earth metal and alloy target materials and their characterization. In this work the rare earth metals were prepared by electrolysis of the oxide in molten salt for Nd metal and metallothermic reduction of the fluorides for Gd, Tb, Dy metals. After vacuum refining and distillation purification these rare earth metals were used for manufacturing the element targets, mosaic targets and as the starting materials of preparing the rare earth-transition metal (RE-TM) alloy targets. The four kinds of Dy-FeCo, NdDy-FeCo, Tb-FeCo and GdTb-FeCo alloy targets with diameter of 100 mm and thickness of 3 mm were prepared using powder metallurgical technique. The oxygen content and microstructure of the prepared RE-TM cast alloys and sintered targets were analyzed. The features and requirements of the RE-TM alloy sputtering target materials were also discussed.

An investigation on the terbium gallium garnet magneto-optic properties of under high magnetic field

The superexchange interaction on a magnetic ion may be represented by an effective field Hm =λM in some paramagnetic materials, here λis the coefficient of effective field and M = XHe with X being the magnetic susceptibility and He being the applied field. The variation of the equivalent λX with the dynamic applied field is given and the crystal field-splitting levels of the excited configuration 4f75d1 of the Tb3＋ ion are calculated in the Tb3Ga5O12. By means of the effective field Hm and the applied field He, the Faraday rotation of Tb3CasO12 at 6 K and 41 K, under the high magnetic field and at 0.63μm wavelength, are presented. Our calculated results are in agreement with the experimental data.

Effect of Y substitution on the microstructure,magneto-optical,and thermal properties of(Tb_(1−x)Y_(x))_(3)Al_(5)O_(12)transparent ceramics

Faraday isolators can prevent the front-end system from disturbance and damage caused by a back-reflected beam,so they are important elements in laser systems.As magneto-optical materials are the most important component in Faraday isolators,the studies on magneto-optical materials have attracted much attention these years.Tb_(3)Al_(5)O_(12)(TAG)ceramics are considered to be one of the most promising magneto-optical materials for visible to near-infrared wavelength band application because of their outstanding comprehensive magneto-optical performance.However,the optical quality of TAG ceramics needs further optimization to meet the application requirements.In this work,high optical quality(Tb_(1−x)Y_(x))_(3)Al_(5)O_(12)(x=0,0.05,0.1,0.2,and 0.3)magneto-optical ceramics were fabricated successfully by solid-state reaction sintering combined with hot isostatic pressing(HIP)post-treatment.All the ceramics obtained showed a single garnet phase for different values of x in the range studied.The addition of Y_(2)O_(3) was found to suppress the secondary phase and improve optical quality significantly.The ceramic samples obtained had clear grain boundaries and possessed the in-line transmittance values of 82.9%at 1064 nm and 82.2%at 633 nm,respectively.The Verdet constants of(Tb_(1−x)Y_(x))_(3)Al_(5)O_(12)ceramics with x=0,0.05,0.1,0.2,and 0.3 were−188.1,−175.4,−168.5,−143.0,and−119.9 rad/(T·m),respectively.The thermal conductivity of TAG ceramics was found to be 5.23 W/(m·K)at 25℃,and when 20%Y was substituted in place of Tb,the thermal conductivity decreased by only 9.4%.

SGGG多晶料合成及晶体生长

掺杂钆镓石榴石(SGGG)晶体是一种性能优越的YIG液相外延片材料,解决SGGG基片内部均一性问题对生长合格的YIG外延片具有重要意义。本文采用固相法合成多晶料技术,考察了碳酸钙、碳酸镁、草酸钆等盐类化合物高温下反应生成SGGG多晶料规律,查明了掺杂元素、长晶温场对SGGG品质的影响。结果表明,使用碳酸钙、碳酸镁、草酸钆等盐类化合物有助于提高SGGG多晶料合成品质,弧顶式长晶温场生长的SGGG晶体内部质量良好,且所得切片晶胞参数满足YIG外延片使用需求。

Yttrium aluminum garnet (Y_3A_(l5)O_(12)) nanopowders synthesized by the chemical method

The homogeneously dispersed, less agglomerated YAG nanopowders are synthesized by the citrate-gel method followed by low-temperature self-propagating combustion reaction, using Y2O3, Al(NO3)3?9H2O and citric acid as starting materials. This method effectively solves the problems caused by solid-state reaction at high temperature and the hard ag-glomerates brought by the chemical precipitation method. The powders are characterized by TG-DTA, XRD, FT-IR and TEM respectively. The experiments show that the forming temperature of YAG crystal phase is 850°C and the pseudo-YAG crystalline appears during the calcination and transforms to pure YAG at 1050°C. The powders with sizes less than 50 nm are observed by TEM micrography, which is consistent with the result calculated by Scherrer's formula. The powders consist of single grains.

Preparation of Neodymium-Doped Yttrium Aluminum Garnet Transparent Ceramics by Homogeneous Precipitation Method

substitutes tion, high loosely dis Neodymium doped-yttrium aluminum garnet （Nd ： YAG） transparent polycrystalline ceramics already become of single crystals because they are provided with easy fabrication, low cost, large size, highly doped concentraheat conductivity, mass fabrication, multi-layers and multi-filnctions. The Nd：YAG precursor powders with persed , slightly agglomerated, super fine and YAG cubic crystal phase were synthesized at 1100 ℃ by the homogeneous precipitation method, using Nd2O3, Y2O3, Al（NO3）3·9H2O and urea as raw materials, （NH4）2SO4 as electrical stabilizer, TEOS as sintering additive. The Nd：YAG transparent ceramics were prepared after being vacuum sintered at 1700 ℃ for 5 h. The Nd：YAG ceramic materials were characterized by the TG-DTA, XRD, FT-IR, TEM, FEG-ESEM and FT-PL. The results show that the crystallization temperature of YAG is 850 ℃ and the intermediate crystal phase YAP forming during the heat treatment transforms to YAG cubic crystal phase at 1050 ℃. The lasing wavelength of （Nd0.01 Y0.99）3Al5O12 transparent ceramics is 1.065 μm and there exists a slight red-shift compared to the single crystal with the same chemical composition. The optical transmittance is 45 % in the visible light and 58 % in the near infrared light and the optical transmittance descends with the decreasing the wavelength.

Liquid phase epitaxy magnetic garnet films and their applications

Liquid phase epitaxy （LPE） is a mature technology. Early experiments on single magnetic crystal films fabricated by LPE were focused mainly on thick films for microwave and magneto-optical devices. The LPE is an excellent way to make a thick film, low damping magnetic garnet film and high-quality magneto-optical material. Today, the principal challenge in the applied material is to create sub-micrometer devices by using modern photolithography technique. Until now the magnetic garnet films fabricated by LPE still show the best quality even on a nanoscale （about 100 nm）, which was considered to be impossible for LPE method.

Neodymium-doped Yttrium Aluminum Garnet Transparent Laser Ceramics Prepared by Co-precipitation Method

Transparent polycrystaUine neodymiumdoped yttrium aluminum garnet ceramics （Nd：YAG） with better chemical stability, excellent optical and high temperature mechanical property is becoming a new laser host material. The Nd：YAG precursor powders with loosely dispersed, slightly agglomerated and YAG cubic crystal phase were synthesized at 1100 ℃ by the co-precipitation method combined with the reverse strike,

Characterization of Bi-substituted Dysprosium Iron Garnet Films Prepared by Sol-gel Process

Bi-substituted dysprosium iron garnet films were prepared by sol-gel process, and were annealed for crystallization. The crystallographic structures of garnet films annealed at different temperatures were analyzed by XRD, the film annealed at 650℃ was polycrystalline garnet with no preferred orientation and no impurity crystalline phase. Magnetic and magneto-optical properties were investigated, the film had magnetic anisotropy perpendicular to the film plane, and exhibited strong coercivity of 1100-1600 Oe and high squareness. These films had large figures of merit applicable to magneto-optic storage, with 2 deg. at λ=430 nm and 1.5 deg. at λ=520 nm respectively.

Faraday effect measurements of holmium oxide(Ho2O3) ceramics-based magneto-optical materials

Faraday effect measurements of holmium oxide(Ho_2O_3) ceramics-based magneto-optical materials, highly potential material candidates for high-energy laser Faraday isolators, are presented in this paper. Temperature dependence of the Verdet constant of nondoped Ho_2O_3 ceramics was measured for temperatures 15–305 K at 1.064 μm wavelength.The Verdet constant dispersion for wavelengths 0.5–1 μm and 1.064 μm was measured for both nondoped Ho_2O_3 ceramics and Ho_2O_3 ceramics doped with terbium Tb3+(0.2 at. %) and cerium Ce3+(0.1 at. %) ions. The results suggest that the relatively low level of doping of Ho_2O_3 with these ions has no significant boosting impact on the Faraday effect. Therefore, other compositions of Ho_2O_3 ceramics-based magneto-optical materials, as well as various doping concentrations, should be further examined.

Bismuth-Substituted Yttrium Iron Garnet Film/Crystal Composite for Faraday Rotators

The novel bismuth-substituted rare earth iron garnet films were grown by the modified liquid phase epitaxy (LPE) technique for use as a 45° faraday rotator in optical isolators. First,single crystals of Y_3Fe_5O_(12) (YIG),with a lattice constant of 1.2378 nm,were grown by means of the Czochralski method. Using YIG instead of the conventional non-magnetic garnet of Gd_3Ga_5O_(12) (GGG) as a substrate,a film of BiYbIG was grown by means of the LPE method from Bi_2O_3-B_2O_3 fluxes. The structural,magnetic and magneto-optical properties of BiYbIG LPE film/YIG crystal composite were investigated using X-ray diffraction (XRD),electron probe microanalysis (EPMA),vibrating sample magnetometry (VMS) and near-infrared transmission spectrometry. The saturation magnetization 4π M _s was estimated to be about 1200 G. The Faraday rotation spectrum was measured by the method of rotating analyzer ellipsometry (RAE) with the wavelength varied from 800 to 1700 nm. The resultant Bi_(0.37)Yb_(2.63)Fe_5O_(12) LPE film/YIG crystal composite shows an increased Faraday rotation coefficient due to doping Bi (3+) ions on the dodecahedral sites of the magnetic garnet without increasing absorption loss,therefore a good magneto-optic figure of merit,defined by the ratio of Faraday rotation and optical absorption loss,can achieved of 21.5 and 30.2 °/dB at 1300 and 1550 nm wavelengths respectively at room temperature. Since Yb (3+) ions and Y (3+) ions provide the opposite contributes to the wideband and temperature characteristics of Faraday rotation,the values of Faraday rotation wavelength and temperature coefficients are reduced to 0.06%/nm and 0 007 °·℃ (-1) at 1550 nm wavelength,respectively.

Rapid screening of magnetic properties in several Fe-X-Ni systems via combinatorial materials chip method

Fe-X-Ni(X=Cr,W and V)combinatorial thin-film(∼100 nm thick)materials chips covering the full composition range of ternary systems were fabricated.The crystal structure distribution was mapped by micro-beam X-ray diffractometers(XRD)and the magnetic hysteresis loops over the chip were characterized by a high-throughput magneto-optical Kerr effect(HT-MOKE)system to establish the composition-phase-magnetic properties relationships.The results showed that saturation magnetization for all systems has a strong dependency on alloying composition,and decreases with increasing dopped elements content as a general trend.Although the trend of saturation magnetization in bulk is in good agreement with that from thin films,all bulk samples show almost no coercivity,attributable to the much smaller grain size,and stronger texture in thin-film samples.Comparing the Fe-X-Ni systems under a similar condition,in the out-of-plane,Cr alloying obtained the largest coercivity(∼400 mT)followed by W alloying(∼300 mT)and then V alloying(∼200 mT).We suggest that alloying with different elements leads to the diverse orientation and crystallinity of the fcc phase resulting in different magnetic properties.Meanwhile,the effect of heat treatment on magnetic properties indicates that saturation magnetization is more closely related to the duration of heat treatment.

Preparation of (Tb_(0.8)Y_(0.2))_3Al_5O_(12)transparent ceramic as novel magneto-optical isolator material

The ion substitution characteristics of Y3＋-doped （Tb0.sY0.2）3A15012 transparent ceramics synthesized by a solid-state reaction and vacuum sintering are investigated. The sample sintered at 1 680℃ exhibits the best optical properties, yielding a transmittance 〉75% from 900 to 1 600 nm. The Verdet constant of this sample at 632.8 nm is -108.79 rad.T-l.m-1. X-ray diffraction （XRD） results show that all of the samples have a pure garnet crystal structure without secondary phases. The microstructure of the samples reveals homogeneous grain sizes that averages 〈10μm.

Growth,optical dispersion and magnetic behavior of Dy^(3+) doped yttrium iron garnet crystals

Y_(3)Fe_(5)O_(12)(YIG)crystals are highly desirable for the fabrication of mid-infrared isolators with the rapid growth of optical communications,although it is rather challenging to grow large size and high-quality single crystals.Dy^(3+)doping is expected to improve the optical and magneto-optical prope rties.However,high quality Dy:YIG crystals and the adjustment of Dy^(3+)on the structure and optical behavior of YIG crystal remain unclear,impeding its practical applications.Herein,a series of Y_(3-x)Dy_(x)Fe_(5)O_(12)(x=0,0.5,1.0,1.5,3)solid solution crystals was grown by the flux-Bridgman method and single crystals up to 25 mm were obtained.With the introduction of Dy^(3+),lattice parameters are gradually enlarged from 1.2379 nm(YIG)to 1.2420 nm(DyIG).Typical Dy^(3+)absorption peaks are observed around 1070,1265 and 1670 nm.The refractive index decreases from 2.37(500 nm)to 2.10(2500 nm)for YIG crystal,and it reduces from 2.47(500 nm)to 2.16(2500 nm)for DyIG crystal.The optical bandgaps remain almost unchanged for Dy:YIG crystals.The optical dispersion of the refractive indices was finely fitted by the Wemple and DiDomenico(WDD)and the Sellmeier models,respectively.With the increase of Dy^(3+)content,the saturation magnetization(Ms)decreases significantly from 23.62 emu/g(YIG)to 5.33 emu/g(DyIG).Small coercive field is persisted for this system,endowing small external magnetic field.These results provide valuable references for the manipulation of rare earths on the properties of magnetooptical crystals,which is beneficial to the design of high-performance garnet crystals for the application of optical switching and non-reciprocal related devices.

石榴石型微波铁氧体废料回收利用

以完成预烧的常规生产配方的钇铁石榴石铁氧体废料为主体原料,加入一定比例的新料,调整Y^(3+)、Fe^(3+)、Ca^(2+)、Sn^(4+)比例重新制备铁氧体材料,并对其结构和磁性能进行表征。结果表明,样品均为单一的立方相石榴石结构,气孔状态有了明显的改善;同时铁磁共振线宽ΔΗ从65 Oe降至12.5 Oe,介电损耗角正切tanδ保持在1×10^(-5)以下。这为工业生产中铁磁共振线宽异常的石榴石型微波铁氧体材料提供了一种通过配方设计进行回收利用的有效途径。

Synthesis of yttrium iron garnet/bismuth quantum dot heterostructures with localized plasmon enhanced magneto-optical performance

Interactions between light and magnetic matter attracted great attention lately due to their potential applications in nanophotonics,spintronics,and high-accuracy sensing.Here,we grew bismuth quantum dots(Bi–QDs)with strong spin–orbit coupling on a magnetic insulator yttrium iron garnet(YIG)via molecular beam epitaxy.The YIG/Bi–QDs material shows an enhanced magneto-optical Kerr rotation up to 130%compared with that of a bare YIG film.The Bi–QDs were also introduced onto a lutetium–bismuth co-doped YIG film to form a hybrid system with remarkably enhanced Kerr rotation(from 1626 to 2341 mdeg).Ferromagnetic resonance measurements showed an increased effective magnetization as well as interfacial spin–orbit field in the YIG/Bi–QD heterostructures.Localized plasmons were mapped using electron energy loss spectroscopy with high spatial resolution,revealing enhanced plasmon intensity at both the Bi–QD surface and YIG/Bi–QD interface.Introducing Bi-QDs onto the YIG film enhanced Kerr rotation owing to the attenuated optical reflection and increased effective magnetization.The Bi–QDenhanced magneto-optical effect enables development of efficient nanoscale light switching,spintronics,and even plasmonic nano-antennas.

钇铝石榴石透明激光陶瓷的研究进展

透明钇铝石榴石(aluminum yttriumgarnet,YAG)陶瓷具有良好的化学稳定性和光学性能,是一种很有前途的单晶激光材料的替代物。同单晶相比,多晶YAG陶瓷具有许多优点,如:大尺寸材料易于制备,成本低适合大规模生产等。此外,因掺杂浓度高可得到较大的输出功率。对透明YAG激光陶瓷的光学特性以及制备工艺做了重点介绍,并对研究进展进行综合评述。最后,展望该领域的发展前景及今后的研究趋势。

溶剂热法合成YAG:Ce荧光粉体的研究

采用溶剂热法,以乙二胺为溶剂,碳酸氢铵沉淀法制备的沉淀产物为前驱体,在低温下合成了YAG:Ce荧光粉体。研究了反应时间对合成产物的组成、分散性以及荧光性能的影响,结果表明:在200℃低温保温5h条件下,可得到颗粒尺寸为260～280nm的球形YAG:Ce颗粒,颗粒尺寸均匀,且分散性好;荧光性能表征显示,其发射光谱为一宽带,峰值在530nm附近,对应于Ce3+的最低5d能级到4f能级跃迁所发出的光,可与高效蓝光LED匹配制备双基色白光LED,用于新型节能光源。

Nd:Gd_3Ga_5O_(12)多晶原料合成及单晶生长研究

通过对晶体生长时和生长后原料挥发物的XRD分析,发现在炉膛内壁上的挥发物质是Ga2O3和Ga2O的混合物,而观察窗口及后加热器内壁上的挥发物主要是Gd2O3。为避免原料中Ga2O3的挥发,按化学计量比配料,在1300℃下,采用固相反应法合成了Nd∶Gd3Ga5O12(Nd∶GGG)多晶原料。用此多晶原料,采用提拉法进行了Nd∶GGG单晶生长研究,所获单晶的荧光发射峰位于1061 54nm。对晶体表面的开裂现象进行了分析。

均相沉淀法制备Nd∶YAG透明激光陶瓷材料研究

以A l(NO3).9H2O、Y2O3、Nd2O3、(NH4)2SO4和尿素为原料,正硅酸乙酯为添加剂,采用均相沉淀法于1000℃制备出分散均匀、团聚程度轻、纯YAG立方晶相Nd∶YAG纳米前驱体粉末,经过1700℃真空烧结5h制备出Nd∶YAG透明陶瓷材料。采用XRD、FT-IR、FT-PL和ESEM等测试手段对Nd∶YAG陶瓷材料进行表征。结果表明:Nd∶YAG陶瓷材料的激光工作波长为1.065μm,和相同组分的单晶相比存在轻微的红移现象;陶瓷微观结构中存在大量的气孔相、晶界相和杂质相,大大地降低了透明陶瓷材料的透光率。