Crystal structure and thermal and electrical properties of the perovskite solid solution Nd1-xSrxFeO3-delta (0 <= x <= 0.4)

The crystal structure, thermal expansion and electrical conductivity of strontium-doped neodymium ferrite (Nd1-xSrxFeO3-delta where 0less than or equal toxless than or equal to0.4) were investigated. All compositions had the GdFeO3-type orthorhombic perovskite structure. The lattice parameters were determined at room temperature by X-ray powder diffraction. The orthorhombic distortion decreases with increasing Sr substitution. The pseudocubic lattice parameter shows a minimum at x=0.3. The thermal expansion curves for x=0.2-0.4 displayed rapid increase in slope at higher temperatures. The electrical conductivity increased with Sr content and temperature. The calculated activation energies for electrical conduction decreased with increasing x. The electrical conductivity can be described by the small polaron hopping mechanism. The charge compensation for divalent ion on the A-site is provided by the formation of Fe4+ ions on the B site and vacancies on the oxygen sublattice. The results indicate two defect domains: for low values of x, the predominant defect is Fe4+ ions, whereas for higher values of x, oxygen vacancies dominate. (C) 2002 Elsevier Science B.V. All rights reserved.

Synthesis of acicular hydrogoethite (alpha-FeOOH center dot xH(2)O; 0.1 < x < 0.22) particles using morphology controlling cationic additives and magnetic properties of maghemite derived from hydrogoethite

A method for the preparation of acicular hydrogoethite (alpha -FeOOH.xH(2)O, 0.1 < x < 0.22) particles of 0.3-1 mm length has been optimized by air oxidation of Fe( II) hydroxide gel precipitated from aqueous (NH4)(2)Fe(SO4)(2) solutions containing 0.005-0.02 atom% of cationic Pt, Pd or Rh additives as morphology controlling agents. Hydrogoethite particles are evolved from the amorphous ferrous hydroxide gel by heterogeneous nucleation and growth. Preferential adsorption of additives on certain crystallographic planes thereby retarding the growth in the perpendicular direction, allows the particles to acquire acicular shapes with high aspect ratios of 8-15. Synthetic hydrogoethite showed a mass loss of about 14% at similar to 280 degreesC, revealing the presence of strongly coordinated water of hydration in the interior of the goethite crystallites. As evident from IR spectra, excess H2O molecules (0.1- 0.22 per formula unit) are located in the strands of channels formed in between the double ribbons of FeO6 octahedra running parallel to the c- axis. Hydrogoethite particles constituted of multicrystallites are formed with Pt as additive, whereas single crystallite particles are obtained with Pd (or Rh). For both dehydroxylation as well as H-2 reduction, a lower reaction temperature (similar to 220 degreesC) was observed for the former (Pt treated) compared to the latter (Pd or Rh) (similar to 260 degreesC). Acicular magnetite (Fe3O4) was prepared either by reducing hydrogoethite (magnetite route) or dehydroxylating hydrogoethite to hematite and then reducing it to magnetite (hematite- magnetite route). According to TEM studies, preferential dehydroxylation of hydrogoethite along < 010 > leads to microporous hematite. Maghemite (gamma -Fe2O3 (-) (delta), 0 < < 0.25) was obtained by reoxidation of magnetite. The micropores are retained during the topotactic transformation to magnetite and finally to maghemite, whereas cylindrical mesopores are formed due to rearrangement of the oxygen sublattice from hexagonal to cubic close packing during the conversion of hydrogoethite to magnetite and then to maghemite. Accordingly, three different types of maghemite particles are realized: strongly oriented multicrystalline particles, single crystalline acicular particles with micropores or crystallites having mesopores. Higher values of saturation magnetization ((s) = 74 emu g(-1)) and coercivity (H-c = 320 Oe) are obtained for single crystalline mesoporous particles. In the other cases, the smaller size of particles and larger distribution of micropores decreases sigma (s) considerably ( < 60 emu g(-1)) due to relaxation effects of spins on the surface atoms as revealed by Mossbauer spectroscopy.

Compositionally modulated Pb(Mg1/3Nb2/3)O-3-PbTiO3 relaxor thin films deposited by pulsed excimer laser ablation technique

Thin films of (1-x)Pb(Mg1/3Nb2/3)O-3 - xPbTiO(3) (x = 0.1 to 0.3)(PMN-PT) were deposited on the platinum coated silicon substrate by pulsed excimer laser ablation technique. A template layer of LaSr0.5Co0.5O3 (LSCO) was deposited on platinum substrate prior to the deposition of PMN-PT thin films. The composition and the structure of the films were modulated via proper variation of the deposition parameter such as substrate temperature, laser fluence and thickness of the template layers. We observed the impact of the thickness of LSCO template layer on the orientation of the films. A room temperature dielectric constant varying from 2000 to 4500 was noted for different composition of the films. The dielectric properties of the films were studied over the frequency range of 100 Hz - 100 kHz over a wide range of temperatures. The films exhibited the relaxor- type behavior that was characterized by the frequency dispersion of the temperature of dielectric constant maxima (T-m) and also diffuse phase transition. C1 Indian Inst Sci, Mat Res Ctr, Bangalore, Karnataka 560012 India.

Compositionally and structurally modulated Pb(Mg1/3Nb2/3)O3-PbTiO3 relaxor thin films for microactuator application

Thin films of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3(x = 0.1 to 0.3) (PMN-PT) were successfully grown on the platinum coated silicon substrate by pulsed excimer laser ablation technique. A thin template layer of LaSr0.5Co0.5O3 (LSCO) was deposited on platinum substrate prior to the deposition of PMN-PT thin films. The composition and the structure of the films were modulated via proper variation of the deposition parameter such as substrate temperature, laser fluence and thickness of the template layers. We observed the impact of the thickness of LSCO template layer on the orientation of the films. The crystallographic structure and compositional variation were confirmed with x-ray diffraction and energy diffraction x-ray (EDX) analysis. A room temperature dielectric constant varying from 2000 to 4500 was noted for different composition of the films. The dielectric properties of the films were studied over the frequency range of 100 Hz - 100 kHz over a wide range of temperatures. The films exhibited the relaxor-type behavior that was characterized by the frequency dispersion of the temperature of dielectric constant maxima (Tm) and also diffuse phase transition. This relaxor nature in PMN-PT thin films was attributed to freezing of the dipole moment, which takes place below a certain temperature. This phenomenon was found to be very similar to spin glass system, where spins are observed to freeze after certain temperature.

2,4-dimethylene-1,3-cyclobutanediyl and 2,4-dimethylenebicyclobutane. Synthesis, spectroscopy, and reactivity of a triplet biradical and its covalent isomer

The preparation and direct observation of triplet 2,4-dimethylene-1,3- cyclobutanediyl (1), the non-Kekule isomer of benzene, is described. The biradical was generated by photolysis of 5,6-dimethylene-2,3- diazabicyclo[2.1.1]hex-2-ene (2) (which was synthesized in several steps from benzvalene) under cryogenic, matrix-isolation conditions. Biradical 1 was characterized by EPR spectroscopy (‌‌‌‌‌│D/hc│ =0.0204 cm^(-1), │E/hc│ =0.0028 cm^(-1)) and found to have a triplet ground state. The Δm_s= 2 transition displays hyperfine splitting attributed to a 7.3-G coupling to the ring methine and a 5.9-G coupling to the exocyclic methylene protons. Several experiments, including application of the magnetophotoselection (mps) technique in the generation of biradical 1, have allowed a determination of the zero-field triplet sublevels as x = -0.0040, y = +0.0136, and z = -0.0096 cm^(-1), where x and y are respectively the long and short in-plane axes and z the out-of-plane axis of 1.

Triplet 1 is yellow-orange and displays highly structured absorption (λ_(max)= 506 nm) and fluorescence (λ_(max) = 510 nm) spectra, with vibronic spacings of 1520 and 620 cm^(-1) for absorption and 1570 and 620 cm^(-1) for emission. The spectra were unequivocally assigned to triplet 1 by the use of a novel technique that takes advantage of the biradical's photolability. The absorption є = 7200 M^(-1) cm^(-1) and f = 0.022, establishing that the transition is spin-allowed. Further use of the mps technique has demonstrated that the transition is x-polarized, and the excited state 1s therefore of B_(1g) symmetry, in accord with theoretical predictions.

Thermolysis or direct photolysis of diazene 2 in fluid solution produces 2,4- dimethylenebicyclo[l.l.0]butane (3), whose ^(l)H NMR spectrum (-80°C, CD_(2)Cl_(2)) consists of singlets at δ 4.22 and 3.18 in a 2:1 ratio. Compound 3 is thermally unstable and dimerizes with second-order kinetics between -80 and -25°C (∆H^(‡) = 6.8 kcal mol^(-1), (∆s^(‡) = -28 eu) by a mechanism involving direct combination of two molecules of 3 in the rate-determining step. This singlet-manifold reaction ultimately produces a mixture of two dimers, 3,8,9- trimethylenetricyclo[5.1.1.0^(2,5)]non-4-ene (75) and trans-3,10-dimethylenetricyclo[6.2.0.0^(2,5)]deca-4,8-diene (76t), with the former predominating. In contrast, triplet-sensitized photolysis of 2, which leads to triplet 1, provides, in addition to 75 and 76t, a substantial amount of trans-5,10- dimethylenetricyclo[6.2.0.0^(3,6)]deca-3,8-diene (77t) and small amounts of two unidentified dimers.

In addition, triplet biradical 1 ring-closes to 3 in rigid media both thermally (77-140 K) and photochemically. In solution 3 forms triplet 1 upon energy transfer from sensitizers having relatively low triplet energies. The implications of the thermal chemistry for the energy surfaces of the system are discussed.

Excitation energies and decay properties of T = 3/2 states in ^(17)O, ^(17)F and ^(21)Na

The two lowest T = 3/2 levels in ²¹Na have been studied in the ¹⁹F(³He, n), ²⁰Ne (p,p) and ²⁰Ne (p,p’) reactions, and their excitation energies, spins, parities and widths have been determined. In a separate investigation, branching ratios were measured for the isospin-nonconserving particle decays of the lowest T = 3/2 levels in ¹⁷O and ¹⁷F to the ground state and first two excited states of ¹⁶O, by studying the ¹⁵N(³He,n) ¹⁷F*(p) ¹⁶O and ¹⁸O(³He, α)¹⁷O*(n) ¹⁶O reactions.

The ¹⁹F(³He,n) ²¹Na reaction was studied at incident energies between 4.2 and 5.9 MeV using a pulsed-beam neutron-time-of-flight spectrometer. Two T = 3/2 levels were identified at excitation energies of 8.99 ± 0.05 MeV (J > ½) and 9.22 ± 0.015 MeV (J ^π = ½⁺, Γ ˂ 40 keV). The spins and parities were determined by a comparison of the measured angular distributions with the results of DWBA calculations.

These two levels were also obsesrved as isospin-forbidden resonances in the ²⁰Ne(p,p) and ²⁰Ne(p,p’) reactions. Excitation energies were measured and spins, parities, and widths were determined from a single level dispersion theory analysis. The following results were obtained:

E_x = 8.973 ± 0.007 MeV, J ^π = 5/2 ⁺ or 3/2⁺, Γ ≤ 1.2 keV,

^Γp_o = 0.1 ± 0.05 keV; E_x = 9.217 ± 0.007 MeV, J^π = ½ ⁺,

Γ = 2.3 ± 0.5 keV, ^Γp_o = 1.1 ± 0.3 keV.

Isospin assignments were made on the basis of excitation energies, spins, parities, and widths.

Branching ratios for the isospin-nonconserving proton decays of the 11.20 MeV, T = 3/2 level in ¹⁷F were measured by the ¹⁵N(³He,n) ¹⁷ F*(p) ¹⁶O reaction to be 0.088 ± 0.016 to the ground state of ¹⁶O and 0.22 ± 0.04 to the unresolved 6.05 and 6.13 MeV levels of ¹⁶O. Branching ratios for the neutron decays of the analogous T = 3/2 level, at 11.08 MeV in ¹⁷O, were measured by the ¹⁶O(³He, α)¹⁷O*(n)¹⁶O reaction to be 0.91 ± 0.15 to the ground state of ¹⁶O and 0.05 ± 0.02 to the unresolved 6.05 and 6.13 MeV states. By comparing the ratios of reduced widths for the mirror decays, the form of the isospin impurity in the T = 3/2 levels is shown to depend on T_z.

Passive Q-switching of short-length Tm3+-doped silica fiber lasers by polycrystalline Cr2+:ZnSe microchips

We demonstrate passive Q-switching of short-length double-clad Tm3+-doped silica fiber lasers near 2 mu m pumped by a laser diode array (LDA) at 790 nm. Polycrystalline Cr2+:ZnSe microchips with thickness from 0.3 to 1 mm are adopted as the Q-switching elements. Pulse duration of 120 ns, pulse energy over 14 mu] and repetition rate of 53 kHz are obtained from a 5-cm long fiber laser. As high as 530 kHz repetition rate is achieved from a 50-cm long fiber laser at similar to 10-W pump power. The performance of the Q-switched fiber lasers as a function of fiber length is also analyzed. (c) 2008 Elsevier B.V. All rights reserved.

Effect of OH- content on emission properties in Er3+-doped tellurite glasses

A series of tellurite glasses of composition, 75TeO(2)-20ZnO-(5 - x)La2O3-xEr(2)O(3) (x = 0.05, 0.1, 0.3, 0.6, 1.0, 2.0, and 3.0 mol%) with different hydroxl content were prepared. The effect of Er3+ and OH- groups concentration on the emission properties of Er3+: I-4(13/2) -> I-4(15/2) transition in tellurite glasses was investigated. The constant KOH-Er for Er3+ in tellurite glasses, which represents the strength of interaction between Er3+ and OH- groups in the case of energy migration, was about 14 x 10(-19) cm(4) s(-1). The interaction parameter C-Er,C-Er for the migration rate of Er3+ : 4I(13/2) -> I-4(13/2) transition in tellurite glass was 46 x 10(-40) cm(2), which indicates that concentration quenching in Er3+-doped modified tellurite glass for a given Er3+ concentration is much stronger than in silicate and phosphate glasses. (c) 2007 Elsevier B.V. All rights reserved.

内蒙古草原温度梯度上3个典型群落的能量平衡研究

通量测量点的能量收支总是表现出不平衡，即使在地势平坦、植被分布均一、稀疏植被下垫面的情况下也有约30%的能量失衡状况。能量平衡闭合 (EBC) 问题在验证涡度相关系统质量方面，得到了广泛的关注。实验在内蒙古草原3个地点，通过涡度相关系统附近移动能量平衡系统的测定手段，采用能量平衡余项法和最小二乘 (OLS) 线性回归法，研究了土壤热通量、净辐射及可供能量空间变异对能量平衡闭合的影响。 结果显示，EBC 在三个研究点的平均余项为8~19 W m-2，OLS 斜率为0.83~0.96。EBC 在土壤湿润情况的站点要高于干旱站点。 土壤热通量的空间变异三站点平均为白天48 W m-2 (占同时间 Rn 的13%)，夜间15 W m-2 (34%)，平均29 W m-2 (24%)。通过8个工作站的测量，这个变异会造成9% (从0.93到1.01) 的 OLS 斜率差别。夜间的能量平衡不闭合可以由土壤热通量的空间变异解释。如果在本研究的的三个草原站点上忽略了土壤热通量，则会造成较大的余项 (峰值时110 W m-2) 产生，从而使 OLS 斜率增大23%。特别是通量板埋置在地面以下30 mm处时，上层的土壤热储部分占到全部土壤热通量的50%，这不仅影响到 EBC 的大小，更起到调节土壤热通量与“真实的波形” 相一致的作用。如果该部分热储被忽略掉，EBC 余项会增加60 W m-2，OLS 斜率也会变化 (减少) 9%。用大尺度多点测量与涡度塔附近的小尺度测定相比较，后者表现出稍高的闭合率，即 OLS 斜率增加4%。 相对于土壤热通量，净辐射的空间变异较小，三站点平均为白天17 W m-2 (5%)，夜间7 W m-2 (13%)，平均 12 W m-2 (5%)。可以引起3% (从0.88到0.91) 的 OLS 斜率差异。研究结果还表明，风速校正应该在 Q7.1 净辐射仪中应用，校正后的结果与 CNR1 的结果在白天有吻合较好，但在其它时段仍有较大差异，特别是在夜间，风速校正基本不起作用，使得两种仪器间差异达20 W m-2。比较表明，风速校正可以提高白天 Rn 的6%，仅降低夜间0.3%。因此，无论是用余项法还是用 OLS 线性回归法，在比较使用不同仪器的站点间的闭合状况时 (本研究的结果适用于草地 Q7.1 与 CNR1 间的比较)，可以用9：00-15：00 h 时段的数据进行比较，这样可以避免因使用不同仪器的差异所造成的影响。用该时段的数据进行比较，仪器间的差异余项法小于6 W m-2，OLS 法小于3%。 受可供能量空间变异影响，三个站点平均 EBC 的不确定性为白天66 W m-2 (19%)，夜间23 W m-2 (50%)，平均42 W m-2 (36%);或者改变 OLS 斜率11%。用最大值和最小值来衡量，EBC 最大不确定性，正午时在站点 I、II 和 III 中分别为81，114和91 W m-2。故在探讨能量平衡和能量平衡闭合问题时，必须充分考虑到这种不确定性，否则会产生偏差，或者得出错误结论。 研究还表明，即使考虑到白天所有可供能量的最大不确定性，仍然不能使能量平衡闭合。中午 (12：00 h)，站点 I，II 和 III 仍然有14±15，48±12和47±14 W m-2 的失衡不能够归因于可供能量的空间不确定性。因此，其它影响因素也需进行细致的探讨。 在两站点不同测量深度土壤热通量结果的差异性比较实验中，无论在站点 I 还是 III，均表现出一致的结论，即随通量板布置深度加深，其测量结果会越高，与浅层布置的相比，差别可高达150 W m-2。深层土壤热通量的计算仍是个难题，需进一步研究。 在不同植被结构对净辐射测定影响的实验中发现，随刈割强度增加，一天中大部分时间净辐射均减少。正午依次为413，395和388 W m-2。无论正午还是全天合计，重度刈割地点的净辐射均比不刈割对照处理少6%，而且，在整个生长季也少6%，约合40,000 W m-2。测量高度不同，不同处理间对测定结果影响不同：刈割处理中，由于下垫面较均一，结果相差不显著;而对照则表现出较高的差异，用两配对样本T检验表明差异达到极显著 (P<0.000，9:30-15:00 h data)。当使用不同新旧程度的 domes 时，对净辐射结果会产生明显的影响。新 domes 的测量结果白天明显高，晚上明显低，使用了11个月的旧 domes，峰值时，白天低估25 W m-2，晚上高估10 W m-2。说明该差异在进行能量平衡闭合计算时，不能忽略。而全用新的和全用旧的进行比较，晚上仅有2-3 W m-2差异。 考虑生态系统中非生物因子对干扰条件下生物多样性动态和功能的影响，有助于更精确地阐明生物多样性-稳定性功能的关系。为此，设计了一个单因子刈割实验——内蒙古地区一种广泛存在的土地利用方式。主要目的是研究不同强度刈割影响下，微气候变量特别是能量平衡各分量和群落结构的变化及二者的关系。连续4年刈割，占第一位的优势种明显由低矮半灌木冷蒿 (Artemisia frigida) 取代了高大丛生禾草克氏针茅 (Stipa kylovii)。重度刈割下，针茅的盖度、生物量和丛重，群落叶面积、绿色生物量、凋落物量和群落高度一致低于轻度刈割/不刈割处理。微气候由于群落特征的这些变化也呈规律性变化。与对照相比，重度刈割降低了生长季土壤含水量的47.5%，但中午和日均土壤表面温度分别增加了7.4和1.2 °C，并且增加地表下2 cm土壤温度日较差 (日最高与最低温度之差) 4.2 °C。刈割处理由于凋落物少、反射强而表现出较低的净辐射，但土壤热通量显著提高，表现为土层加热和冷却快。因此，重度刈割处理较对照降低了可供能量8%，约合52,000 W m-2 。不同刈割强度间来看，NPP 或 LAI 与土壤热通量和净辐射的比值 (G/Rn) 以及波文比 (H/LE) 间呈负相关。重度刈割处理感热通量显著提高，但潜热通量在处理间差异不显著，表明未刈割处理虽然冠层伸展大，但是并没有导致更大的水分亏缺。未刈割处理增加了抵抗物种改变的能力，而刈割处理在连续一年一割的第四年显著增加了物种数，可能与因刈割影响而导致的群落结构与微气候的改变有关。本研究表明，未刈割处理可以减轻高温干旱季节的高温和干旱胁迫，表现出对环境变化的高抵抗性。未刈割处理的凋落物层和较高的垂直结构所形成的遮荫，可以形成一个阻挡蒸发的篱笆，这是维持其水分的保证。因此，为了恢复退化草原生态系统功能，需要修复能导致微气候变化的植物群落结构，否则难以成功。 本研究立足于原创性的实验研究，在中国特有的自然草原生态系统上开展，结合不同温度梯度的三地区涡度相关系统进行了能量平衡闭合的移动比较实验，以及结合常用土地利用方式的定点能量平衡实验。在翔实的数据基础上，为涡度相关方法的陆地表面能量平衡失衡问题提供了解释。增加了对两个主要能量流——土壤热通量和净辐射空间变异规律的认识，研究对于能量平衡和湍流通量相关研究是有价值的。在三个代表性地区首次利用多个净辐射仪和土壤热通量板的结果与三个标准的涡度相关系统进行了比较，这类量化失衡原因的相关研究应受到高度重视并进一步拓展，以提高对能量失衡的认识，进而推进水热和碳循环研究向更深层次发展。

Studies on radiation pasteurisation of medium fatty fish 3. Storage properties of white pomfret (Stromateus cinereus) fillets

White pomfret fillets packed under aerobic conditions had a limited shelf life of 8 days as against 10 days for samples packed under vacuum and stored at 0-2°C. Irradiation and subsequent storage of the fillets under vacuum at 0-2°C exhibited shelf lives of 30, 50 and 60 days for radiation doses of 0.1, 0.3 and 0.5 Mrad respectively in contrast to aerobically packed fillets which showed only 20, 35 and 50 days of storage life for the same levels of radiation doses and developed yellow discolouration and rancid odours.

Third-order optical nonlinearities of lead-free (Na1-xKx)(0.5)Bi0.5TiO3 thin films

(Na1-xKx)(0.5)Bi0.5TiO3 (NKBT) (x = 0.1, 0.2, and 0.3) thin films with good surface morphology and rhombohedral perovskite structure were fabricated on quartz substrates by a sol-gel process. The fundamental optical constants (the band gaps, linear refractive indices and absorption coefficients) of the films were obtained through optical transmittance measurements. The nonlinear optical properties were investigated by Z-scan technique performed at 532 nm with a picosecond laser. A two-photon absorption effect closely related with potassium-doping content was found in thin films, and the nonlinear refractive index n(2) increases evidently with potassium-doping. The real part of the third-order nonlinear susceptibility chi((3)) is much larger than its imaginary part, indicating that the third-order optical nonlinear response of the NKBT films is dominated by the optical nonlinear refractive behavior. These results show that NKBT thin films have potential applications in nonlinear optics. (C) 2007 Elsevier B.V. All rights reserved.

Effect of the InAlAs and InGaAs combination strain-reducing layer on 1.3 mu m emission self-assembled InAs/GaAs quantum dots

Self-assembled InAs quantum dots (QDs) with differing deposition thicknesses covered by InxAl1-xAs (x = 0.2, 0.3) and In0.2Ga0.8As combination strain-reducing layers (CSRLs) were grown by molecular beam epitaxy. Their structural and optical properties were investigated by atomic force microscopy and photoluminescence spectroscopy, respectively. The emission peak position of InAs QDs capped by CSRL can reach 1.34 mum at room temperature with a relatively larger energy splitting of 93 meV between the ground and first excited states.

喷雾热解法制备Eu~(3+)掺杂的球形发光粉

喷雾热解法对合成球形形貌的发光粉极具优势，本文用喷雾热解法（先低温喷雾干燥，在慢速升温热解）合成了正硼酸盐、氧化物和硼铝酸盐发光粉，合成过程中用柠檬酸、聚乙二醇、浓氨水等修饰喷雾前驱体溶液，以优化发光粉的形貌和发光性能，同时对相应的发光机理进行了探讨。在喷雾热解法合成Y_2O_3:Eu这种单一组分的氧化物发光粉中，PEG的分子量（分子量大小决定了分子链的长短）对所制发光粉的形貌（球形、棒状和片状）起着重要的作用。形成球形是因为分子量为10000的PEG长分子链在喷雾前驱体溶液中穿插、缠结、卷曲，并通过氢键结合柠檬酸在喷雾热解溶液中形成了相对稳定的网状结构，这使得在随后的低温喷雾干燥过程中鳌合稀土离子的柠檬酸不会因溶剂的蒸发跑到喷雾小液滴的表面而造成空心结构，从而得到实心球体，这种实心球体在随后的慢速升温热解过程中逐渐收缩、结晶，最后得到了表面光滑的实心球体；至于棒状结构，则是因为短分子链的PEG（分子量600）只能在喷雾小液滴中形成区域网状结构，这种区域网在溶剂的蒸发过程中会跑到小液滴的表面形成空心结构，由于球壳上具有PEG作为“筋”而具有一定的韧性，这使得在随后的慢速升温热解过程中球壳热解形成空心的孔洞结构，并在高温下破裂、坍塌、卷曲而形成了棒状；而片状则是因为喷雾前驱体溶液中没有PEG链使得干燥过程中，鳌合稀土离子的柠檬酸随溶剂的蒸发而跑到小液滴表面，形成了空心的球壳，这种球壳由于没有PEG链做“筋”而具有脆性，在随后的慢速升温热解过程中，这种脆性的球壳破裂成片状，并随温度的升高进一步热解、收缩，形成了最终的片状Y_2O_3:Eu。在喷雾热解法合成Y_(0.9-x)Gd_xEu_(0.1)BO_3中，聚已二醇、柠檬酸、氮气压力和前驱体溶液的浓度都严重地影响着所制发光粉的形貌。对该体系来说，获得最佳形貌（球形，实心，表面光滑，尺寸在1-3μm）的条件如下：聚已二醇I狗最佳用量是。0.004M，柠檬酸的最佳用量是两倍于溶液中总金属离子的摩尔数；最佳氮气压力为6O0atm；前驱体溶液的浓度为0.07M。Y_(0.9)Eu_(0.1)BO_3在700℃时便开始结晶，比固相法低了200℃（固相法为900℃）。随着烧结温度的提高，结晶性逐渐增强，当温度超过1100℃后，结晶性开始下降，这主要是因为和该体系有关的氧化硼熔点低（600 ℃），在高温容易挥发，造成了晶粒表面出现贫硼相，使得晶粒尺寸降低所致。在Y_(0.9-x)Gd_xEu_(0.1)BO_3中，随着X值的增大，发光强度显著增强，这是因为在Y_(0.9-x)Gd_xEu_(0.1)BO_3中存在Gd~(3+)到Eu~(3+)的能量传递，X值的增加不仅增加了Gd~(3+)-Eu~(3+)的直接能量传递几率，而且增加了Gd~(3+)-（Gd~(3+)）_n-Eu~(3+)形式的能量传递的几率，从而增强了发光强度。在硼铝酸盐Y_(0.9-x)Gd_xEu_(0.1)Al_3（BO_3）_4（0.0≤X≤0.9）体系中，用浓氨水来修饰喷雾前驱体溶液，改变其pH值，发现pH值对粒子形貌有严重影响，但对光致发光强度影响不大。当pH值为3时（不加浓氨水），所制样品形貌不规则，且团聚严重；当加入适量的浓氨水，使前驱体溶液pH值增大到4.5（此时溶液呈胶体状），所制样品呈球形，表面比较粗糙；再加浓氨水，使前驱体溶液的pH值增大到12（此时溶液呈悬浊液状），所制样品仍呈球形，表面趋于光滑，粒子尺寸降低。这三种发光粉的光致发光强度相差很小，但球形的发光粉在涂屏上具有显然的优势。在Y_(0.9-x)Gd_xEu_(0.1)Al_3（BO_3）_4发光粉中，随着X值的增大，存在两个影响发光强度的因素：一是随着X值的增大，结晶性降低，这使发光强度降低；二是随着X值的增大，Gd~(3+)-Eu~(3+)或者Gd~(3+)-（Gd~(3+)）_n-Eu~(3+)形式的能量传递效率增强，这使发光强度增加。当X值比较小时（0.0≤X≤0.3），前一因素占主导地位，当X值比较大时（0.3≤X≤0.9），后一因素占主导地位。

注铒a-SiO_x:H中Er~(3+)发光与薄膜微观结构的关系

采用光致发光（PL）谱和傅里叶变换红外（FTIR）谱研究了掺铒a-SiO_x:H(a-SiO_x:H)薄膜在不同退火温度下光学性质和微观结构的变化。PL谱的测量结果表明：薄膜在1.54μm的Er~(3+)发光和750nm处的可风发光随退火温度有相同的变化趋势，这种变化和薄膜在退火过程中微观结构的变化有着密切关系。FTIR谱的分析表明：a-SiO_x:H薄膜是一种两相结构，富硅相镶嵌在富氧相中。两者的成分可近似用a-SiO_(x≈0.3):H和a-SiO_(x≈1.5):H表示，前者性质接近于氢化非晶硅（a-Si:H），后者性质接近于a-SiO_2。富硅相在退火中的变化对Er~(3+)的发光强度有重要影响。

CSR工程3维测量控制网

主要介绍了兰州重离子加速器冷却储存环CSR控制网的建立及测量分析方法,详细说明了激光跟踪仪转站原理和计算机算法。根据一般大地测量采取的建网原则,首先用全站仪建立了初级控制网,在此基础上加密形成了由168个网点构成的主环控制网;然后运用激光跟踪仪及其配套软件测量了主环控制网,其网点的点位精度可达到0.08 mm。应用2005年3月控制网的测量结果对主环磁铁进行了调节,结果显示四极铁横向就位精度达到0.15 mm,偏转角精度达到0.3 m rad。