同一上转换机理下Yb3+掺杂浓度对发光强度比值的影响

通过固相反应法制备了Ho3+/Yb3+共掺杂ZrO2-ZnO粉末和Er3+/Yb3+共掺杂不同基质材料的样品,在980nm激发下测量了各样品的绿色和红色上转换发光,分析了各波段的上转换发光机理.在同一上转换机理下,当Yb3+的掺杂浓度增加时,绿光对红光的上转换强度比值呈现出一定规律的变化趋势.这是由于Yb3+的掺杂浓度会影响样品的测试温度,从而改变样品的上转换发光特性.     

烧结温度对Er~(3+)/Yb~(3+)共掺氟氧化物粉末上转换发光的影响

采用高温固相法在600～1100 ℃范围内选择6个不同烧结温度制备了系列相同配方的Er~(3+)/Yb~(3+)共掺氟氧化物上转换发光粉末.在室温下对各样品采用波长为980 nm泵浦光激发,肉眼均可观察到峰值位于658 nm、539 nm和523 nm处的上转换红光和绿光,分别对应于Er~(3+)的~4F_(9/2)→~4I_(15/2)和~4S_(3/2)/~2H_(11/2)→~4I_(15/2)能级跃迁,且红光强度大于绿光强度.通过比较,各样品的上转换图谱形状完全相同,而红绿上转换发光强度明显不同,800 ℃烧结制得样品的红绿荧光强度最强.样品的绿色荧光强度与红色荧光强度的比值随烧结温度升高而增加.通过各样品的X射线粉末衍射图谱(XRD)分析其成分结构,发现烧结温度对样品的成分含量有较大影响.通过测量不同烧结温度下制得样品的上转换发光强度与激发功率的变化关系,发现不同烧结温度可改变样品的上转换发光机理.     

Er~(3+)-Yb~(3+)共掺杂ZrO_2-TiO_2粉末的上转换发光性质

通过共沉淀方法制备了Er3+和Yb3+共掺的ZrO2-TiO2上转换发光材料。用X射线衍射(XRD)对合成的物相结构进行了检测,并对样品在980 nm激光激发下的上转换发光性质进行了研究。观察到了位于528、550和662 nm附近的绿色和红色发光,分别对应于Er3+离子的2H11/2,4S2/3→4I15/2and4F9/2→4I15/2跃迁。样品的红光和绿光强度随着ZrO2和TiO2配比的变化而变化。随着烧结温度的升高,样品整体发光强度增加。讨论了上转换发光可能的机理:激发态吸收(ESA)和能量传递上转换(ET)过程。     

不同波长响应的Y2O2S:Er3+,Yb3+上转换发光材料的光谱特性

以Y2O2S为基质材料、Er2O3为激活剂、Yb2O3为敏化剂,采用固相反应法制备Y2O2S:Er3+,Yb3+上转换发光材料.采用X射线粉末衍射分析和荧光光谱分析表征样品的结构和发光性能,并分析上转换发光机理.结果表明:在980 nm和1 550 nm红外光激发下,样品发出源于Er3+的2H11/2→4I15/2、4...     

复合助熔剂对BaMgAl10O17∶Eu2+蓝色荧光粉晶体结构、颗粒形貌及发光性能的影响

采用先烧结后还原的高温固相法制备了BaMgAl10O17∶Eu2+ (BAM)蓝色荧光粉,研究了H3BO3+BaF2、H3 BO3+AlF3、BaF2+AlF33种不同组合的复合助熔剂对BAM蓝色荧光粉的物相纯度、颗粒形貌及发光性能的影响.结果表明:以H3BO3+BaF2为复合助熔剂的蓝粉与其它2种复合助熔剂制备的样品相比在提高BAM物相纯度、颗粒形貌貌以及发光性能方面具有更好的效果,其性能已非常接近市场上某公司生产的商业蓝粉.     

金属离子掺杂对TiO_2:Yb~(3+)/Er~(3+)上转换材料发光性能的调控研究

稀土文章采用水热法合成掺杂不同金属离子的Ti O2:Yb3+/Er3+上转换发光材料。系统的探讨了不同的金属离子对Ti O2:Yb3+/Er3+发光材料发光性能、形貌以及晶型的影响。具体到通过荧光光谱数据分析离子价态、离子半径等对红、绿光性能的影响;通过SEM数据分析掺杂不同金属离子对应样品形貌的变化;通过XRD数据分析掺杂不同金属离子对应样品的晶型的变化。结果表明离子价态以及离子半径都会改变Ti O2:Yb3+/Er3+材料的发光性能,但与Ti O2:Yb3+/Er3+材料发光性能之间不存在线性关系;掺杂不同金属离子不会改变样品的形貌;掺杂不同金属离子得到了纯相的Ti O2:Yb3+/Er3+样品,且不改变样品的晶型。     

Sc3+/Tm3+/Yb3+共掺六方NaYF4纳米粒子的上转换发光特性

稀土Tm3+和敏化剂(Yb3+)共掺NaYF4是目前发现的Tm3+上转换发光效率最高的材料,但还不能满足实际应用.实验中采用Sc3+/Tm3+/Yb3+共掺Na(Y1-x-y,Tmx,Yby)F4研究不同掺量Sc3+对Tm3+上转换发光效率的影响.用X射线多晶衍射仪和透射电子显微镜分析水热法合成样品的物相结构和晶粒尺寸...     

Er3+和Yb3+共掺锗硅酸盐玻璃的上转换发光性能

采用熔融-淬火法制备了基体为30SiO2-20GeO2-15Al2O3-5B2O3-30CaF2的Er3+和Yb3+共掺锗硅酸盐玻璃.采用X射线衍射仪、荧光光谱仪和热分析仪对样品进行了表征.结果表明:Er2O3含量从0.5％(摩尔分数,下同)增加到2.0％时,玻璃转变温度Tg和Tx-Tg(Tx为第一析晶温度)数值均有明显下降.Yb2O3含量从1.5％增加到4.5％时,玻璃上转换红光发光强度数量级由103提高到105,对其中1个样品在740℃热处理12h后发现,微晶化处理并未对Er的上转换发光产生有益影响.     

CaO对提高Er3+/Yb3+共掺ZrO2上转换发光效率的研究

采用固相反应法在1000℃烧结得到了Er3 +/Yb3共掺杂ZrO2-CaO粉末样品,样品在980 nm激发下发射较强的绿红光,发射光谱显示三个主要发射峰,中心波长依次为658nm、544 nm和530 nm,文中利用速率方程讨论了样品的上转换发光与抽运功率的关系,对绿红光的上转换发光途径进行了分析.通过XRD检测发现...     

基于Er3+/Yb3+掺杂的上转换玻璃陶瓷材料的制备和性能

采用熔融-晶化法在ZnO-Al2 O3-SiO2系玻璃陶瓷的基础上,用GeO2取代部分SiO2成功制备出Er3+/Yb3+共掺ZnO-Al2 O3-GeO2-SiO2系玻璃陶瓷,并通过对样品的硬度及上转换荧光测试分析确定了GeO2的最佳取代量为7.5wt％.研究发现在980 nm波长光的激发下,样品产生了绿色(524 nm、546 nm)和红色(659 nm)上转换发光,且当Er3+/Yb3+掺杂比为2.5:6.5时样品上转换荧光强度最强.     

Theoretical modeling of cooling of containers for the desublimation of hydrogen fluoride vapors

A physical and mathematical model of air-cooling precipitator containers has been presented for the desublimation of hydrogen fluoride from a mixture of gases. The model is based on the equations of gas dynamics for modeling the movement of cooled air in piping and thermal conductivity equations for modeling heat transfer in the walls of the pipe and the walls of the precipitator container. A numerical simulation of the cooling of two series-mounted precipitator containers is performed by the flow of cold air from a cold air source with parameters that correspond to the specifications and performance of the VKhM-0.54/0.6 air refrigerating unit. The parameters of the air heat exchanger are determined, providing efficient cooling of containers. The calculation results showed that when upon using refrigerating machine VKhM-0.54/0.6, temperature of each container is homogeneous, and the temperature difference between the first and second containers during the flow of cooling air does not exceed 1°C.     

Influence of air-cooling time on physical properties of thermoplastic polyester powder coatings

Properties such as the specular gloss, adhesive strength, viscoelasticity, and impact resistance of thermoplastic polyester powder coating film were studied as a function of air-cooling time. Thermoplastic polyester resin is known for the fact that the heating condition has an effect on the degree of crystallinity. We focused on the relationship between the air-cooling time employed in the film preparation process and the degree of crystallinity. The test pieces were dipped into a fluidized polyester powder vessel, and then cooled in air to form the film. We refer to this cooling time in air as the “air-cooling time”. It was found that the degree of crystallinity increased as the air-cooling time increased. As the degree of crystallinity increased, the specular gloss, adhesive strength, viscosity and impact resistance decreased. We therefore found that the improvement in film performance is related to the reduction in the air-cooling time. The importance of this phenomenon is considered in relation to the widespread use of thermoplastic polyester resin. Similar behavior is expected for other polyester powder coatings.     

BaF2/BaO替代对钡镓锗酸盐玻璃结构的影响

用Raman光谱技术研究了Ga2O3/GaF3GeO2二元玻璃的结构,并用XRD技术和Raman光谱技术研究了BaF2/BaOGa2O3GeO2系统玻璃的结构。讨论了BaF2替代BaO对玻璃结构的影响。结果表明:摩尔组成为20BaO15Ga2O365GeO2玻璃的主要亚稳相是BaGa2·Ge2O8,而以BaF2替代玻璃中的全部BaO后,玻璃的主要亚稳相转变为BaGe2O5。玻璃中引入氟化物后,其中频段强Raman散射峰宽化,主峰值向高频方向移动,表明在玻璃中形成一些较大的四面体环。同时玻璃高频段最强的振动峰同样移向高频,高频带低频侧的肩明显减弱。这些变化可解释为玻璃中Q2振动模的减少和Ga,Ge四面体的对称性降低,使Raman光谱中的高频成分增加。     

拉曼光谱强度可控的硼硅锌光学玻璃制备

本文采用高温固相法制备了拉曼光谱强度可控的硼硅锌(ZnO-B2O3-SiO2)玻璃。分别采用X射线衍射仪(XRD)、荧光光谱(RF)和拉曼光谱(Raman)表征了样品的结构和光学性能。结果表明,ZnO-B2O3-SiO2玻璃基质中掺杂微量BaCO3、TiO2,制备出拉曼光谱强度可控的硼硅锌玻璃。硼硅锌玻璃样品配方中SiO2和B2O3含量对玻璃拉曼光谱强度有重要影响,随着SiO2含量的增加和B2O3含量的减少,玻璃样品拉曼光谱强度逐渐降低。当SiO2含量为40%,B2O3含量为36.2%时,在514 nm波长下激发,玻璃样品与参考玻璃的荧光激发光谱最为接近。     

R2O-RO-B2O3-SiO2-Al2O3-P2O5-CaF2分相-析晶乳浊釉的形成机理

通过正交试验方法优化釉料组成和烧成工艺，制备了R2O-RO-B2O3-SiO2-Al2O3-P2O5-CaF2多元系光亮无锆的分相-析晶乳浊釉。采用X射线衍射仪、透射电子显微镜／X射线能谱、场发射扫描电子显微镜等研究了釉的显微结构及分相与析晶的形成机理。结果表明：析晶与分相结构并存，分相促进析晶；尺寸接近可见光波长的孤立液滴和所析出的钙钠长石晶体是釉面产生乳浊的根本原因。研究了不同烧成制度对分相-析晶乳浊釉显微结构的影响，发现缓冷釉样的分相液滴尺寸明显大于急冷釉样，急冷釉样中的第二相形貌表里存在明显差异，内部呈球形液滴状，表面则为蠕虫状。     

The Solubility Limit of CaO in α‐Alumina at 1600°C

The solubility limit of Ca in 99.99% pure α‐Al₂O₃ (alumina) was measured using a wavelength dispersive spectrometer mounted on a scanning electron microscope. Al₂O₃ samples were equilibrated at a concentration which ensured saturation of the Al₂O₃ grains with Ca, and were quenched in water from 1600°C. The results were compared with those from samples which were furnace cooled from 1600°C. For the quenched samples, the Ca solubility limit was found to be 51 ± 1 ppm, which is significantly larger than the solubility limit for samples which were furnace cooled (26 ± 1 ppm).     

Re-Examination of the Polymorphism of Dicalcium Silicate

Samples of Ca₂SiO₄ were prepared by three different methods. These samples were examined by differential thermal analysis, high-temperature X-ray diffraction, and air quenching of pellets. It was found that the β modification, during cooling, converted completely and rapidly to the γ modification and "dusted" only if it had been heated above 1420†± 10† C. If the sample was not heated above this critical temperature, a mixture of the β and γ forms always resulted at room temperature. The addition of 0.5 weight % of CaO, SiO₂, Al₂0₃, Fe₂0₃, or MgO had no effect on the sequence of phases for samples cooled from above the critical temperature. When, however, these same samples were cooled from below 1410†C, the final room-temperature product was not the same for all samples. On the other hand, the additional 0.5% of Na₂0, K₂O, Cr₂O₃, or B₂0₃ prevented the formation of the β modification regardless of the temperature from which the sample was cooled. The critical heating temperature correlated with the transformation temperature for the α-α inversion. A theory relating this inversion to the completeness of the β→γ transformation is presented.     

Eutectic structure from amorphous Al2O3-ZrO2-Y2O3 system by rapid quenching technique for potential hybrid solar cell application

Abstract

Ternary Al₂O₃-ZrO₂-Y₂O₃ samples with a eutectic composition were prepared using the rapid quenching method, with some samples further annealed at 1300°C for 30?min and then slow cooled. The microstructural evolution was observed with XRD, SEM, and TEM. The SEM and TEM observations of the ternary samples agreed with the XRD. The rapid quenched sample was an amorphous phase with a small amount of crystalline phase mixed in. Observations showed that the rapid quenched and annealed sample was completely crystalline with a granular structure and well defined crystals of 40-60?nm in size.     

白光LED用红色荧光粉Gd2-xMo3O9:Eux3+制备和研究

用高温固相法成功制备了Gd2-xMo3O9:Eux3+,用XRD荧光光谱仪对其物相以及粉体的激发和发射光谱进行表征和研究;结果表明:在395和464nm两主激发峰均可得到616nm处红光发射峰,属于Eu3+典型的5D0→7F2的跃迁所致。由464nm激发得到的发射峰为单峰,峰宽较窄且发射强度较强。