微波合成PrF3空心纳米粒子和氢氧化镨纳米棒

用快速高效的微波辐射加热方法成功地合成了PrF3空心纳米粒子和氢氧化镨纳米棒,并以所制备的氢氧化镨纳米棒为前驱体通过热处理得到了氧化镨的纳米棒.对产物进行了X-射线衍射(XRD)、透射电镜(TEM)和电子能谱(EDX)的表征.结果表明,微波合成的PrF3为球形形貌的中空纳米粒子,并具有均匀的粒径大小.微波合成的氢氧化镨纳米棒具有高的结晶度和纯度.实验结果表明,较长的微波加热时间和较高的碱浓度有利于结晶度高的氢氧化镨纳米棒的形成.初步讨论了微波条件下合成氟化镨中空纳米粒子和氢氧化镨纳米棒的形成机理.     

Tunable trap depth for persistent luminescence by cationic substitution in Pr3+:K1−xNaxNbO3 perovskites

The development of efficient red-emitting persistent phosphor is still an ongoing challenge. In the search of persistent materials in red range, Pr³⁺ is a good candidate owing to its transitions between ¹D₂ and ³H₄ state at about 612 nm. In this paper, we investigated the red persistent properties of Pr³⁺-doped perovskite oxide ABO₃, (A: K, Na and B: Nb), which can be elaborated as large single crystal. KNbO₃:Pr³⁺ appears to have weak photoluminescence and no persistent luminescence. However, the cationic substituted compounds K _{1− x} Na _x NbO ₃ :Pr³⁺ (x = 0, 0.4, 0.5, 0.7 0.9, 1) exhibit intense persistent luminescence, which increases steadily with increase in Na content. We correlated persistence behavior with the position of Metal-to-Metal Charge Transfer (MMCT) band, which plays crucial role in tuning of the trap depth. The MMCT band position decreases with the addition of Na contents and the thermoluminescence peak shifts toward higher temperature indicating the formation of deeper traps. This is in good agreement with the enhancement of the persistent luminescence suggesting that a proper tailoring of MMCT is needed to design efficient Pr³⁺-persistent phosphors with better performance. A detailed analysis on the trap depth, bandgap energy, and persistent luminescence properties is reported tuning the composition in the K _{1− x} Na _x NbO ₃ :Pr powder.     

Fantastic valence impacts of Pr on microstructures and Faraday magneto-optical effects of transparent (Ho,Pr)2O3 ceramics

Polycrystalline magneto-optical (Ho_1-xPr_x)₂O₃ (x = 0.05?0.2) ceramics were fabricated by vacuum sintering using layered rare-earth hydroxides as the precursors, among which the 5 at.% Pr doped specimen exhibits the highest in-line transmittance of ～76.1 % at 700 nm (～94.5 % of the theoretical value of defect-free Ho₂O₃ single crystal) and the largest Verdet constant of ?82 ± 6 rad?T^?1 m^?1 at 1064 nm (～2.3 times that of the commercial Tb₃Ga₅O₁₂ crystal and ～1.8 times that of the pure Ho₂O₃ ceramic). More Pr addition not only leads to a higher thermal decomposition temperature for the precursor but also a decreasing particle size for the oxide. A 5 at.% Pr dopant in Ho₂O₃ matrix generally exists in the oxidation state of +3, while an increasing Pr concentration up to 10 at.% induces coexisting valences of +3 and +4. The grain growth was suppressed by the present Pr⁴⁺ based on interstitial mechanism. The substitution of Pr³⁺ for Ho³⁺ is helpful for the rising Verdet constant of the binary ceramic, but Pr⁴⁺ has little positive contribution to it.     

MCM41-CaTiO3∶Pr3+超细颗粒的制备及发光性能研究

通过溶胶-凝胶法合成了负载CaTiO3∶Pr3+的多孔SiO2复合材料,并探究了材料的最佳煅烧温度。利用SEM、XRD、FT-IR研究了材料的结构,采用荧光分光光度计检测了材料的发光性能,为选择合适的温度提供了依据。材料的激发波长为325nm和375nm;发射波长为613nm,对应于Pr3+的1 D2-3 H4跃迁。随着煅烧温度由500℃升高到1000℃,发光强度先增大后减小,在800℃发光最强,且由SEM电镜看出,合成的材料分布均匀,呈球形,颗粒尺寸在500nm左右,煅烧之后材料的形貌及颗粒尺寸并未发生明显变化。     

Pr对Sn58Bi钎料微观组织和性能的影响

通过在Sn58Bi合金钎料中添加Pr制备了新型无铅钎料,用该钎料进行焊接后,测定了Pr添加量对焊后钎料的晶格变化、润湿性和钎焊接头抗拉强度的影响.XRD衍射结果表明,Pr的添加能够导致钎料晶格畸变.SEM结果表明,微量Pr的添加可以抑制Bi相长大粗化,细化钎料晶粒.润湿性能研究表明,随着Pr量的增加,Sn58Bi钎料的...     

Pr~(3+)-doped Li_2SrSiO_4 red phosphor for white LEDs

Novel red phosphors,Li2Sr1-1.5xSiO4:xPr3+(x=0.002,0.003,0.004,0.005,0.006 and 0.008),were synthesized by conventional solid state reaction and the luminescent properties were investigated.The as-prepared phosphors showed red emission at 610 nm under excitation of blue light at 452 nm,indicating that they were promising candidates for red phosphors in the fabrication of white LEDs via blue LED chips.Their excitation bands at 452,476 and 487 nm were attributed to transitions of 3H4→3P2,3H4→3P1+1I6,3H4→3P0 of Pr3+ ion.The red emissions at 606 and 610 nm were originated from the 3P0-3H6 and 1D2-3H4 transitions of Pr3+.The optimum doping concentration of Pr3+ in Li2Sr1-1.5xSiO4:xPr3+ was determined to be x=0.004.With the concentration of Pr3+ over x=0.004,the fluorescence intensity of Li2Sr1-1.5xSiO4:xPr3+ decreased,indicating the concentration quenching occurred.     

SnCuNi-xPr焊点组织和性能分析

分析了不同稀土元素Pr的添加量对Sn0.7Cu0.05Ni无铅钎料润湿性能、焊点力学性能以及钎料显微组织的影响,并对焊点内部组织的演化规律与其性能之间的内在联系进行了初步探讨.研究发现,稀土元素Pr的适宜添加量为0.025%～0.075%,且存在一最佳添加量0.05%.微量稀土元素Pr的加入可显著降低液态钎料的表面张力...     

Structural and Electrical Properties of Bi 3.25 La 0.75 Ti 3 O 12 and Bi 3.25 Pr 0.75 Ti 3 O 12 Thin Films for Memory Applications

In this work, Bi 3.25 La 0.75 Ti 3 O 12 (BLT) and Bi 3.25 Pr 0.75 Ti 3 O 12 (BPT) thin films were prepared by chemical solution deposition and characterized by X-ray diffraction, scanning electron microscope and electrical measurements. Layered perovskite BLT and BPT films can be achieved by 180 s annealing at a temperature as low as 650 C. Both BPT and BLT films are composed of closely packed spherical grains. BPT shows larger remnant polarization ( Pr ) and smaller coercive field. The Pr values of 700 C annealed BLT and BPT films are 18.3 w C/cm 2 and 20.5 w C/cm 2 , respectively, while BLT films show better-saturated hysteresis loops. The leakage current density of BPT films is significantly (about one order) lower than that of BLT. The dielectric properties of BLT and BPT films were measured and compared. Both films exhibit large dielectric constant and small loss tangent. Under bipolar switching cycles, BLT films showed little polarization reduction but a 30% polarization loss was observed for BPT films after 2 2 10 9 cycles.     

Emission Analysis of Pr3 +& Tm3 +: B2O3-BaO-LiF/AlF3 Glasses

We report here on the preparation and emission properties of Pr³⁺(4f²) and Tm³⁺ (4f¹²) ions doped in newly developed to transparent glassy matrices of BBLi (= B₂O₃-BaO-LiF) BBAl (= B₂O₃-BaO-AlF₃). Under an UV source (355 nm), both the Tm³⁺: BBLi and Tm^{3 +}: BBAl glasses have shown bright blue emission at 452 nm. With regard to both the Pr³⁺: BBL and Pr³⁺: BBAl glasses red emission have been noticed upon excitation with blue excitation wavelength (445 nm).These results have also been obtained from the measurement of their emission spectra. For such emission bands, decay curves have been recorded to obtain their lifetimes. We have prepared optical glasses with good transparency and stability. From the measurement of XRD spectra, amorphous nature of these glasses have been confirmed. Between the two glasses studied, glass containing Li has demonstrated an extended UV transmission and also it has revealed an improved NIR transmission ability compared to the other glass with LiF.     

Influence of praseodymium oxide/cobalt oxide ratio on microstructure and electrical properties of zinc oxide varistor ceramics

The microstructure and electrical properties of varistor ceramics, which are composed of (99.5–x–y)ZnO+xPr₆O₁₁+yCoO+0.5Dy₂O₃ system, were investigated with Pr₆O₁₁/CoO mole ratio (x/y=0.5/0.5, 0.5/1.0, 1.0/0.5, 1.0/1.0) and sintering temperature. The density of varistor ceramics with Pr₆O₁₁=1.0 was almost constant with sintering temperature, whereas it was increased noticeably in Pr₆O₁₁=0.5. Increasing Pr₆O₁₁ content enhanced the densification for any CoO content and the density was greatly affected not by CoO content but by Pr₆O₁₁ content. The varistor ceramics with Pr₆O₁₁/CoO=0.5/1.0 exhibited a higher nonlinearity than any other composition ratios. In particular, the varistor ceramics sintered at 1350 °C. exhibited the best electrical properties, with nonlinear exponent of 37.8, leakage current of 7.6 μA, and dissipation factor of 0.059. It was found that Pr₆O₁₁/CoO ratio greatly affects various characteristics of varistor ceramics.