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Crystal of Yb3+-doped Ba3Gd(BO3)3 has been grown by the Czochralski method. The spectroscopic characterizations have been investigated at room temperature. The Yb3+:Ba3Gd(BO3)3 crystal exhibits broad absorption at 976nm with FWHM of 7nm and large overall spitting of 2F7/2 manifold (823cm-1). The absorption and emission cross sections are 5.09×10-21cm2 at 976nm and 0.97×10-21cm2 at 1040nm,respectively. The fluorescence lifetime is 2.84 ms. 相似文献
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采用光致发光光谱技术对一系列不同条件下制备的NaTaO3及不同掺杂量的NaTaO3∶Bi3 进行了研究.结果表明,NaTaO3的发光性质与其制备条件密切相关在钠离子不足的条件下合成的样品,其发光带主要位于515和745nm左右;而在钠离子充足条件下合成的样品,其发光带位于460nm左右,随着n(Na)/n(Ta)的降低,发光带向长波长方向移动;掺入Bi3 之后,其发光峰由515nm移至455nm,随着Bi3 掺入量的增加,455nm的发光带强度减弱.515nm的发光带与替位缺陷Ta.N.a..相关;745nm的发光带与VN`a缺陷相关;而460nm的发光带与本征TaO6基团相关.将Bi3 掺入到钽酸钠样品,TaN..a..由BiN..a替代,相应的发光带向高的n(Na)/n(Ta)方向移动,从而呈现出本征TaO6基团的发光带. 相似文献
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采用热重和微商热重(TG/DTA)综合热分析技术在不同升温速率下研究了掺入La(NO3)3和Pr(NO3)3的高岭石的热分解过程, 利用Coats-Redfern积分法和Achar微分法对热分析实验数据进行动力学计算, 得到了高岭石脱羟基反应过程中的控制机理函数、 活化能和指前因子等动力学参数; 分析了2种稀土掺入对高岭石脱羟基过程动力学参数的影响, 并用Ozawa法对活化能进行了验证. 结果表明, 未掺稀土和掺入Pr(NO3)3的高岭石的脱羟基反应过程均受化学反应模型F3控制, 反应的活化能分别为307.94和282.86 kJ/mol, 指前因子lnA的值分别为47.8980和44.1718; 掺入La(NO3)3的高岭石脱羟基反应过程控制机理函数发生改变, 受化学反应模型F2控制, 反应活化能为196.02 kJ/mol, 指前因子lnA的值为29.5551. 与未掺稀土的高岭石对比, 掺入Pr(NO3)3后活化能和指前因子略有降低; 而掺入La(NO3)3后则显著降低, 分别降低了36.34%和38.30%. 采用Ozawa法验证得到的活化能与Coats-Redfern积分法和Achar微分法结果一致. 相似文献
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建立了钙钛矿结构铌镁酸铅PbMg1/3Nb2/3O3(PMN)的2×2×3复晶胞模型; 采用ab initio方法讨论了PMN晶体各种可能构型的稳定性; 选取了PMN三种高、中、低稳定性的代表构型, 并对Ti替换B位离子后的结构进行了结构优化. 计算结果表明复晶胞刚性模型的最低和最高能量差约0.74 a.u. (1940 kJ); Pb2+离子结构框架的形变是PMN晶格发生形变的主要因素; 在不考虑被替换离子电荷差异的情况下, MgO6含量越少越有利于Ti离子替换Nb与晶胞的形变. PMNT材料中构型的分布和局域形变取决于生长PMNT材料的工艺过程. 相似文献
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在G3XMP2//B3LYP/6-311+G(3df,2p)水平上对CH3SO3裂解反应的机理进行了研究, 获得了6 条通道(10 条路径), 并构建了其势能剖面. 同时采用单分子反应理论计算了各个通道在温度200-3000 K区间的速率常数. 研究结果表明, 在计算温度范围内, CH3SO3裂解反应的主产物为P1(CH3+SO3), 产物P2(CH3O+SO2)和P3(HCHO+HOSO)仅在温度大于3000 K时对总产物有贡献, 而产物P4(CHSO2+H2O), P5(CH2SO3+H)和P6(CHSO3+H2)贡献相对较少. 将裂解反应总的速率常数拟合为ktotal=1.40×1012T0.15exp(7831.58/T). 此外, 根据统计热力学原理, 预测了所有物种的生成焓(DfHΘ298 K, DfH0 K), 熵(SΘ298 K)和热容(Cp, 298-2000 K), 计算的结果与实验值较接近. 相似文献
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Ca3Al2Ge3O12:Cr3+的光谱性质及晶场参数计算 总被引:1,自引:0,他引:1
为了解Cr3+离子在钙铝锗酸盐Ca3Al2Ge3O12:石榴石中的光谱性质, 合成了Ca3Al2Ge3O12:Cr3+多晶材料;测量了其X射线衍射图, 漫反射光谱, 激发、发射光谱等;分析了Cr3+离子在钙铝锗酸盐中的发光特性;计算了其晶场强度(Dq/B), Stokes位移(ΔEs)及黄昆-里斯因子(S)等. 在450 nm激发下, Ca3Al2Ge3O12:Cr3+室温发射光谱主要由三个宽带及附加其上的弱R线构成, 分别对应于Cr3+离子的4T1、 4T2、2T2到 4A2 能级跃迁. 低温时R线变得强而锐. 通过计算, Dq/B=2.43, ΔEs=1884 cm-1, S=5.21. 表明在Ca3Al2Ge3O12中Cr3+离子处于较弱的晶场强度, 电子-声子耦合较强, 为发展可调谐激光材料提供重要线索. 相似文献
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Ni-P-Zn_3(PO_4)_2(ZnSnO_3、ZnSiO_3)纳米复合化学镀层性质和组成的研究 总被引:6,自引:0,他引:6
研究了温度、时间、浓度等对 A3钢片上 Ni-P-Zn3(PO4)2、 Ni-P-ZnSnO3和 Ni-P-ZnSiO3纳米复合化学镀层外貌的影响。用扫描电子显微镜( SEM)观察外貌;称重法测定厚度;通过 10% NaCl溶液、 1% H2S气体加速腐蚀试验、 10% CuSO4溶液点滴试验等多种手段测定其耐腐蚀性能;用 X-射线光电子谱 (XPS)及俄歇电子能谱 (AES)测定其价态及组成。结果表明:在最佳施镀条件下,可得光亮、致密、耐腐蚀性强于 A3钢、磷化膜及 Ni-P镀层的纳米复合化学镀层。镀层的原子百分组成约为 (% ): Ni-P-Zn3(PO4)2: Ni 70.00,P 12.47,Zn3(PO4)2 13.93,C 3.6; Ni-P-ZnSnO3: Ni 77.56,P 10.00,ZnSnO3 9.84,C 2.6; Ni-P-ZnSiO3: Ni 83.00,P 10.96,ZnSiO3 5.15,C 0.89。 相似文献
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通过在硝酸钇水溶液浸渍并焙烧的简单工艺, 在LiCo1/3Ni1/3Mn1/3O2材料表面包覆了一层Y2O3. 采用X射线衍射(XRD), 扫描电子显微镜(SEM), 透射电子显微镜(TEM), 循环伏安(CV)和恒流充放电对包覆和未包覆的LiCo1/3Ni1/3Mn1/3O2进行了测试分析. 结果表明, Y2O3包覆并没有改变LiCo1/3Ni1/3Mn1/3O2的晶体结构, 只存在于LiCo1/3Ni1/3Mn1/3O2的表面; 与未包覆的材料相比, Y2O3包覆后的材料在高电位下具有更好的容量保持率和放电容量. CV测试表明, 包覆层的存在有效抑制了材料层状结构的转变及电极与电解液的负反应. 相似文献
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为了探究在Dy~(3+)掺杂Ba_3Y(PO_4)_3荧光粉中共掺Eu~(3+)离子对其发光性能的影响,我们采用传统高温固相法制备了一系列Dy~(3+)、Eu~(3+)单掺杂和共掺杂Ba_3Y(PO_4)_3荧光粉。通过X射线衍射(XRD)、荧光发射光谱和荧光衰减曲线对样品进行了表征。结果表明,所制备的荧光粉呈闪铋矿立方相。在近紫外光激发下,Ba_3Y(PO_4)_3∶Dy~(3+)发射光谱在487和578 nm处有两个窄带发射峰,呈冷白光发射;Ba_3Y(PO_4)_3∶Eu~(3+)发射光谱的窄带发射位于594和616 nm处,呈发橙红光。在Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)中,由于Eu~(3+)离子补偿Dy~(3+)冷白光发射所缺的红色组分,从而实现了色纯度高、色温适中的暖白光发射。进一步探索了Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)荧光粉发光机理。所制备的Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)单基质白光荧光粉在白光近紫外激发白光二极管(UVWLED)领域具有潜在应用价值。 相似文献
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The synthesis of derivatives of 3-amino-3-deoxy-L-erythrose by LAH or LAD reduction of the oxime of 1,2-O-isopropylidene α-L -glycero-tetros-3-ulofuranose is described. 相似文献
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γγγ-Trifluorocarbonyl compounds are easily obtained in a good yield by introduction of the 1,1,1-trifluoroethyl moiety (CF3-CH2-) on the -methylene group of a ketone. 相似文献
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《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1982,38(10):1083-1087
Infrared gas phase spectra of CH3GeH3 and CD3GeH3 have been investigated at a resolution of 0.06 cm−1 and Raman spectra obtained in the liquid phase at low resolution. Several reassignments of the fundamental frequencies are proposed. Q-branch maxima from the five naturally occurring Ge isotopes have been resolved in several of the fundamental vibrations and new values obtained of rotational and Coriolis coupling constants for ν7, ν8, ν10 and ν12 of CH3GeH3 and ν7, ν8, ν9, ν10 and ν12 of CD3GeH3. Germanium isotopic frequency shifts on νGeC are also reported. 相似文献
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Thin films of methylammonium lead halides, CH3NH3PbI3 and CH3NH3PbI3-xClx, were deposited onto symmetrical microstructured electrode arrays of gold or platinum on Si/SiO2 wafers. Polarization studies were carried out on perovskite films under vacuum in the dark. For poling, a constant voltage was applied to the samples while the temperature was cycled between 295 K and 4 K. The measured current densities depending on the temperature showed distinct characteristics relating strongly to the crystal phase and the dielectric properties of the perovskite films. Voltage sweeps were carried out at different scan rates at specific temperature intervals after poling. The polarization of the films due to the migration of iodide vacancies in direction of the blocking perovskite/metal interface was frozen almost up to room temperature. Charge carriers were only able to cross the blocking barrier and contribute to the current where the ions have accumulated during poling. All J-V curves showed hysteresis: inverted and regular hysteresis at room temperature and below, respectively. Inverted hysteresis originates from the slow accumulation of ions at the blocking barrier, while regular hysteresis arises from a distortion in the adjacent crystals which will be discussed. 相似文献
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The thermal behaviors of clusters [Ag3WS3Br](PPh3)3 and [Cu3WS3Br](PPh3)3 (PPh3=triphenyl phosphine) in a nitrogen atmosphere were studied under the non-isothermal conditions by simultaneous TG-DTG-DSC and EDS techniques. The results showed that the evolution of PPh3 generally proceeded before the release of the other moiety in one or two step-mode. The mechanisms, the kinetic and the thermodynamic parameters for decomposition of PPh3 of both clusters were determined and calculated by jointly using several methods, which showed that its evolution was controlled by Avrami-Erofeev equation. The results also showed that there was no new stable phase composed of W-Ag(Cu)-S-Br after release of organic moiety PPh3 and that CVD method was not applicable to their further processing. 相似文献
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Recent computational studies on the addition of ammonia (NH3) to the Al3O3- cluster anion [A. Guevara-Garcia, A. Martinez, and J. V. Ortiz, J. Chem. Phys. 122, 214309 (2005)] have motivated experimental and additional computational studies, reported here. Al3O3- is observed to react with a single NH3 molecule to form the Al3O3NH3- ion in mass spectrometric studies. This is in contrast to similarly performed studies with water, in which the Al3O5H4- product was highly favored. However, the anion PE spectrum of the ammoniated species is very similar to that of Al3O4H2-. The adiabatic electron affinity of Al3O3NH3 is determined to be 2.35(5) eV. Based on comparison between the spectra and calculated electron affinities, it appears that NH3 adds dissociatively to Al3O3-, suggesting that the time for the Al3O3-NH3 complex to either overcome or tunnel through the barrier to proton transfer (which is higher for NH3 than for water) is short relative to the time for collisional cooling in the experiment. 相似文献
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