CaTiO_3∶Pr~(3 )的合成及发光性质

报道了稀土离子Ｐｒ３＋激活的ＣａＴｉＯ３发光材料的合成方法，ＣａＴｉＯ３∶Ｐｒ３＋位于６１３ｎｍ发射与Ｐｒ３＋离子１Ｄ２３Ｈ４光谱发射相一致。讨论了不同合成条件对ＣａＴｉＯ３∶Ｐｒ３＋发光性质的影响     

High-strength SiC joints fabricated at a low-temperature of 1400°C using a novel low activation filler of Praseodymium

High-strength SiC joints were successfully obtained by electric current field-assisted sintering technique at a low temperature of 1400°C using a Pr coating (100 nm) as the initial joining filler. A Pr₃Si₂C₂ transient phase was formed in situ by the interfacial reaction, while the eutectic reaction between Pr₃Si₂C₂ and SiC at ∼1150°C resulted in the formation of a liquid phase. The liquid phase promoted the atomic diffusion at the interface and improved consolidation of the newly precipitated nano-sized SiC with the SiC matrix. This led to the formation of partially seamless joints of SiC. When the thickness of the joining layer decreased from 1 to 100 nm, the content of the residual Pr-O phase at the interface decreased, while the bending strength of the joints increased. A sound SiC joint with a bending strength of 227 ± 12 MPa was obtained at such a low temperature as 1400°C when a 100 nm Pr coating was applied.     

Enhancement of terbium efficiency by gallium and copper co-doping in (Pr,Nd)-Fe-B sintered magnets

It is well known that Tb substitution for (Pr, Nd) in (Pr, Nd)-Fe-B based sintered magnetic materials is an effective way to increase intrinsic coercivity, but it is not quite clear whether the increment depends on the different matrix phases with various doping ingredient or not, which is essential to develop high quality magnets with high coercivity more efficiently and effectively with economic consumption of expensive Tb and other costly heavy rare earths. In this paper, we investigated the efficiency of Tb substitution for magnetic property in (Pr, Nd)-Fe-B sintered permanent magnets by co-doping Ga and Cu elements. It is shown that Ga and Cu co-doping can effectively improve the efficiency of Tb substitution to increase the thermal stability and the coercivity. The intrinsic coercivity increases up to 549 and 987 kA/m respectively by 1.5 wt% and 3.0 wt% Tb substitution in Ga and Cu co-doped magnets while the intrinsic coercivity increases up to only 334 and 613 kA/m respectively by the same amounts of Tb substitution in non-Ga and low-Cu magnets. In other words, it demonstrates that there is about 329–366 kA/m linear equivalent enhancement of intrinsic coercivity by 1.0 wt% Tb substitution for (Pr, Nd) in Ga and Cu co-doped magnets. The temperature coefficients of both intrinsic coercivity β and remanence α at 20–150 °C by 3.0 wt% Tb substitution for the magnets with Ga and Cu co-doping are −0.47%/K and −0.109%/K respectively, and in contrast those values are −0.52%/K and −0.116%/K respectively for the non-Ga and low-Cu magnets. It is the principal reason for more efficient enhancement of magnetic property by Tb substitution in the Ga and Cu co-doped magnets in which Tb atoms are expelled from triple junction phases (TJPs) to penetrate into the grain boundary phases (GB phases) and thus modify the grain boundary. It is prospected that the efficiency of Tb substitution would rely on different matrix phases with various doping constituents.     

Layered Y3Al5O12:Pr/Gd3(Ga,Al)5O12:Ce optical ceramics: Synthesis and photo-physical properties

We report a study of composite scintillating ceramics based on coupled layers of two different garnets, namely Ce-doped gadolinium gallium aluminium (GGAG:Ce) and Pr-doped yttrium aluminium (YAG:Pr), fabricated by hot isostatic pressing. Two samples were prepared, with different GGAG:Ce layer thickness, 120 µm and 690 µm respectively, but with a comparable overall thickness of 1.4 mm. The key finding is that the material architecture strongly determines the scintillation response. The radioluminescence is that expected from the irradiated material when a thick layer of ceramic is exposed to X-rays. Conversely, exposing a thin layer allows a non-null probability —about 0.3% for 120 µm of GGAG— of finding an X-ray photon in the underlying layer, and thus radioluminescence from both materials is recorded. We believe these results can extend the potential of layered optical ceramics for advanced devices, such as energy- and direction-sensitive X-ray detectors.     

Pr_(1-x)(La_(0.37)Ce_(0.63))_xCoO_3的制备及催化活性探究

采用溶胶—凝胶法制备了Pr_(1-x)(La_(0.37)Ce_(0.63))_xCoO_3,利用TG-DSC、FT-IR分析前驱体的分解特性和化学键变化规律,结合XRD、SEM-EDS检测粉体微观结构、形貌以及元素分布;通过CV、LSV和RRDE技术探讨粉体在碱性溶液中氧还原ORR电催化活性。结果表明,在700℃下焙烧,x0.4时,有La_2O_3、CeO_2杂相出现,x0.4时钙钛矿晶体结构消失,x=0.4时得到的纯相粉体呈多孔结构。与商用Pt/C相比,Pr_(1-x)(La_(0.37)Ce_(0.63))_xCoO_3粉体质量活性(质量比电流)是其1.7倍,达到172.54mA/mg,而半波电位较低仅为0.60V(vs.RHE)。以二电子发生氧化还原反应过程中,副产物H_2O_2产率为77%,作为催化材料有待进一步改性。     

Effects of Gd3+ substitution on the structure,photoluminescence, scintillation,and thermometric features of Pr3+:Lu2Zr2O7 phosphors

In this study, it is shown how the photoluminescence, scintillation, and optical thermometric properties are managed via the introduction of Gd³⁺ ions into Pr³⁺:Lu₂Zr₂O₇. Raman spectra validate that partial replacement of Lu³⁺ with Gd³⁺ can promote the phase transition of Lu₂Zr₂O₇ host from the defective fluorite structure to the ordered pyrochlore one. Upon 289 nm excitation, all the samples emit the 483 (³P₀ → ³H₄), 581 (¹D₂ → ³H₄), 611 (³P₀ → ³H₆), 636 (³P₀ → ³F₂), and 714 nm (³P₀ → ³F₄) emissions from Pr³⁺ ions, which are enhanced with the addition of Gd³⁺ ions due to the modification of crystal structure. Dissimilarly, the X-ray excited luminescence spectra consist of a strong emission located at 314 nm from Gd³⁺ ions (⁶P_7/2 → ⁸S_7/2), together with the typical emissions from Pr³⁺ ions, which exhibit different dependences on the Gd³⁺ concentration. When the luminescence intensity ratio between the ³P₀ → ³H₆ (611 nm) and ¹D₂ → ³H₄ (581 nm) transitions is selected for temperature sensing, Pr³⁺:(Lu_0.75Gd_0.25)₂Zr₂O₇ shows the optimal relative sensing sensitivity of 0.78% K⁻¹ at 303 K, which is higher than that of the Gd³⁺-free sample. Therefore, the developed Pr³⁺:(Lu, Gd)₂Zr₂O₇ phosphors have the applicative potential for optical thermometry, X-ray detection, and photodynamic therapy.