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121.
通过共沉淀法制备Tm3+和Yb3+掺杂的NaYF4上转换发光材料。其中Tm3+和Yb3+的摩尔分数分别为0.01%,0.1%。在室温下测试了NaYF4 : Tm3+,Yb3+材料在300~1 100 nm的吸收光谱。利用X射线衍射(XRD),扫描电镜(SEM)测试了合成材料的物相结构和微观形貌。结果表明:NaYF4 : Tm3+,Yb3+材料为六方相晶体,其颗粒大小约为50~60 nm,产物结晶良好,含有少量杂相。在798 nm近红外光激发下,测试了样品的上转换发光光谱。观察到了蓝、绿色上转换发光。讨论了上转换发光的可能机理,蓝光主要来源于Tm3+的激发态1G4到基态3H6的跃迁,绿光来源于Tm3+的1D2→3H5跃迁。 相似文献
122.
采用高温固相法成功制备了Ca3Y2Si3O12∶Tm3+,Yb3+上转换蓝色发光材料.在980 nm红外激光器激发下,发光粉呈现强烈的蓝光(475 nm)和近红外光(810 nm)以及较弱的红光(650 nm)发射,分别归因于Tm3+离子的1G4 →3H6、3H4→3H6和1 G4→3 F4能级跃迁.随着Yb3+离子浓度的增加,发光粉上转换发射强度和发光亮度均呈现先增强后减弱的变化趋势.在最佳掺杂浓度下(Yb3+摩尔分数为15%),蓝、红光强度分支比为12∶1,色坐标为(0.129 2,0.152 3).在3.9 W/cm2激发功率密度下,发光亮度可达6.8 cd/m2.上述结果证实,所制备发光粉呈现优异的蓝光上转换发射特性并具有潜在的应用价值.发光强度和激发光功率关系表明,所得上转换发射为三光子和双光子吸收过程.借助Tm-Yb体系能级结构详细讨论了上转换发射的跃迁机制. 相似文献
123.
124.
S. U. Campisano A. E. Barbarino 《Applied Physics A: Materials Science & Processing》1981,25(2):153-155
The growth rate during solid-phase epitaxy of Te implanted (100) silicon has been measured at 520°C as a function of the Te concentration in the range of 4×1019–1021 atoms/cm3. With increasing concentration the velocity decreases from about 50 Å/min to about 1 Å/min and it equals the value corresponding to undoped amorphous Si at 7×1019 atoms/cm3. This result and previous date on B, P, As, O, and C implantation, imply that the growth rate reaches a maximum value in a broad range of concentration close to the solid solubility limit of the considered dopant. 相似文献
125.
Zhenhui Kang Suoyuan Lian Lei Gao Wansheng You Changwen Hu Lin Xu 《Solid State Communications》2004,129(9):559-564
In this paper, we described a large-scale synthesis method of the polyoxometalates (POMs) nanoparticles and the modification of carbon nanotube (CNTs) through a chemical modified approach. Four types of POMs nanoparticles were prepared by a one-step solid-state reaction at room temperature and characterized by IR, elemental analyses, XRD and TEM. These uniform nanoparticles have an average size of 8-10 nm. Furthermore, based on chemical adsorption between POMs and carboxylic acid groups, which were introduced to the CNTs by adding dilute nitric acid, POMs nanoparticles were successfully located on the CNTs as the modifier. 相似文献
126.
The diffusion of Al in the group IVa metals Zr and Hf has been studied for the first time in the temperature ranges 600°–800°C (Zr) and 750°–900°C (Hf) using ion-beam techniques. Diffusion couples were created by ion-implantation. The time-dependent diffusion profiles were monitored by the use of the Nuclear Resonance Broadening (NRB) technique. The linear Arrhenius plots extracted from the measured diffusivities indicate that the diffusivity of implanted Al in Zr and Hf can be described by the activation energyQ=2.9±0.2eV and 3.7±0.3eV and the pre-exponential factorD
0=17±42cm2/s and 170±600cm2/s, respectively. 相似文献
127.
The two-step diffusion profile is approximated by a series of gaussian functions. Its accuracy is dependent upon the number of terms used in the series, but independent of the number and the spacing of exact data points. 相似文献
128.
J. Keinonen J. Räisänen A. Anttila 《Applied Physics A: Materials Science & Processing》1984,35(4):227-232
The diffusion of N in the group VI B metals Cr and W has been studied in the previously uninvestigated temperature ranges 300°–550 °C (Cr) and 600°–800 °C (W) using ion-beam techniques. Diffusion couples were created by ion-implantation. The timedependent diffusion profiles were monitored by the use of the Nuclear Resonance Broadening (NRB) technique. The linear Arrhenius plots extracted from the measured diffusivities indicate that the diffusivity of implanted N in Cr and W can be described by the activation energyQ=1.39±0.06 eV and 2.32±0.16 eV and the pre-exponential factorD
0=(7.0±7.2)×10–4cm2/s and 4.3±8.3cm2/s, respectively. The solubilities of N in Cr and W from the implanted distributions were found to deviate from those obtained using conventional metallographical methods. 相似文献
129.
B. A. van Hassel A. J. Burggraaf 《Applied Physics A: Materials Science & Processing》1991,53(2):155-163
Yttria-stabilized zirconia (YSZ) was implanted with 15 keV Fe or Ti ions up to a dose of 8×1016 at cm–2. The resulting dopant concentrations exceeded the concentrations corresponding to the equilibrium solid solubility of Fe2O3 or TiO2 in YSZ. During oxidation in air at 400° C, the Fe and Ti concentration in the outermost surface layer increased even further until a surface layer was formed of mainly Fe2O3 and TiO2, as shown by XPS and ISS measurements. From the time dependence of the Fe and Ti depth profiles during anneal treatments, diffusion coefficients were calculated. From those values it was estimated that the maximum temperature at which the Fe- and Ti-implanted layers can be operated without changes in the dopant concentration profiles was 700 and 800° C, respectively. The high-dose implanted layer was completely amorphous even after annealing up to 1100° C, as shown by scanning transmission electron microscopy. Preliminary measurements on 50 keV Ag implanted YSZ indicate that in this case the amorphous layer recrystallizes into fine grained cubic YSZ at a temperature of about 1000° C. The average grain diameter was estimated at 20 nm, whereas the original grain size of YSZ before implantation was 400 nm. This result implies that the grain size in the surface of a ceramic material can be decreased by ion beam amorphisation and subsequent recrystallisation at elevated temperatures. 相似文献
130.
Implantation into a confined surface area produces considerable radiation damage even outside the implanted area. The distance between the damage boundary and the implantation boundary can be determined by simultaneously recording the sample current and the characteristic x-ray signal in a scanning electron microscope. This method was applied to investigate the lateral extent of radiation damage in Si, GaAs, and GaP. Annealing studies were performed with Si. It was found that the lateral excess of damage over the implanted area can be more than 1 m even if the projected range is less than 0.1 m. In Si, this marginal damage, except for oxidation induced stacking faults, can be annealed under the same conditions as necessary for the annealing of the implanted zone itself. Experimental support is given to the prediction of Campisano and Barbarino [1] that within the implanted region the recrystallization rate of the amorphous layer reaches a maximum within a range of concentration near the maximal solid solubility. 相似文献