Synthesis and photoluminescence properties of novel red-emitting Ca14Mg2(SiO4)8:Eu3+/Sm3+ phosphors

Novel red-emitting Eu3+, Sm3+ singly doped and co-doped Ca14Mg2(SiO4)8 phosphors were prepared by conventional solid- state reaction. Powder X-ray diffraction patterns were employed to confirm phase pu...     

高性能各向异性Sm_2Co_(17)纳米永磁材料的制备与表征

利用表面活性剂辅助高能球磨(SA-HEBM)分别制备了高性能的各向异性Sm2Co17纳米永磁粉末材料,然后对球磨产物进行超声波分散清洗。利用高速离心技术进行纳米颗粒分级,获得颗粒尺寸分布狭窄的纳米永磁颗粒,对所得粉末进行适当的快速热处理。分别采用扫描电镜、X射线衍射和振动样品磁强计分析、测试样品的显微形貌、相结构和室温磁性能。结果表明,粉末的厚度在80 nm左右,长度为亚微米级,具有高比表面积、强形状各向异性与磁各向异性;经过磁场取向后,Sm2Co17的易磁化轴和难磁化轴方向的室温矫顽力分别达到612.9 k A/m(7.7 k Oe)和278.6 k A/m(3.5 k Oe);表面活性剂在球磨过程中起到了重要作用。     

红外上转换材料CaS：Eu，Sm的制备

采用碳还原法，制备了电子俘获型红外上转换材料（CaS：Eu，Sm）．研究了反应机理、还原原理、红外上转换机理以及灼烧温度对CaS品格形成和发光性能的影响．样品的XRD测试结果表明，CaS：Eu，Sm为面心立方结构，样品的激发谱位于200—600nm，样品的荧光发射光谱是峰值分别位于567nm，606nm和630nm的宽带谱，上转换发光峰值位于625nm，上转换发光的光谱响应范围位于800～1600nm．     

Sm2Fe17Nx型稀土永磁材料的制备与性能

研究SmFeN稀土永磁材料球磨法制备过程和材料性能.Sm-Fe母合金合适的Sm补偿量为20%,氮化前最佳的球磨时间为为1.5h,合金氮化后为各向同性的粗磁粉,经过进一步球磨细化后,可以得到各向异性的性能高的磁粉.     

高性能Sm2Fe17N x 粉体制备的研究进展

新能源汽车的高速发展,需要能稳定工作在120℃~200℃温度区间的永磁材料。居里温度为476℃、各向异性场为14.7 T的Sm₂Fe₁₇N₃,具有优良的本征磁性能,可应用在这个温度区间。为了提高Sm₂Fe₁₇N₃粉体的磁性能,必须将颗粒的粒径减小到临界单畴尺寸以实现高各向异性场;同时,还要避免颗粒尺寸减小产生的表面氧化,以保证高剩磁和最大磁能积。粉体破碎、机械合金化、甩带、薄带连铸、还原扩散以及表面镀覆等多种制备工艺,可用于制备高性能Sm₂Fe₁₇N₃。目前,实验室制备的Sm₂Fe₁₇N₃粉体的矫顽力和最大磁能积已经达到28.1 kOe和43.6 MGOe。本文评述近年来Sm₂Fe₁₇N₃粉体制备的研究成果,包括对制备机理的系统总结并提出仍待解决的关键问题：Sm₂Fe₁₇N₃粉体的矫顽力、剩磁等与其颗粒尺寸的量化规律以及与颗粒磁畴结构的关联机制;对NH₃/H₂混合气体中H₂对提高氮化效率的作用机制仍需探索;进一步开发在低氧环境下的颗粒粒径均匀化、控制形貌的二次破碎技术;对于还原扩散法,开发适合规模化应用的新前驱体及其制备方法以及快速去除钙副产物的水洗技术等。     

A位Sm掺杂对0.93Na0.5Bi0.5TiO3-0.07BaTiO3陶瓷微结构及电学性能的影响

采用固相反应烧结方法制备了Sm掺杂的[(Na_0.5Bi_0.5)_0.93Ba_0.07]_1-xSm_xTiO₃(BNBST)无铅介电储能陶瓷, 系统研究了Sm掺杂含量对BNBST陶瓷的相结构、微观结构、铁电、介电、储能和交、直流电导的影响。研究结果表明: 制备的陶瓷样品具有单一的钙钛矿结构, Sm掺杂固溶于(Na_0.5Bi_0.5)_0.93Ba_0.07TiO₃基材的晶格A位; 晶粒生长被Sm掺杂抑制, 平均晶粒尺寸在2 μm内, 且均匀致密; Sm掺杂显著降低了剩余极化和矫顽场, 表现出双电滞回线特性, 但饱和极化也略有降低; 储能密度和效率随Sm掺杂量增加先增大后减小, 在x=0.02和电场为70 kV/cm时获得最大储能密度0.70 J/cm³, 其效率为40%; BNBST陶瓷具有明显的弛豫铁电体特征, 其介电常数峰T_m随掺杂量增加而降低且平坦化; BNBST陶瓷的绝缘性有较强的温度依赖性, 300℃以下具有良好的绝缘性。     

A thermodynamic description of the Gd–Mg–Sm system

The Mg–Sm, Gd–Sm and Gd–Mg–Sm systems were thermodynamically optimized using the CALPHAD technique. The solution phases, liquid, bcc, hcp and rhombohedral, were described by the substitutional solution model. The isostructural compounds, MgGd in the Gd–Mg system and MgSm in the Mg–Sm system with a B2 structure was assumed to form a continuous range of solid solutions in the Gd–Mg–Sm system. The order–disorder transition between the bcc solution with an A2 structure and compound Mg(Gd, Sm) with a B2 structure in the system has been taken into account and thermodynamically modeled. The other isostructural compounds Mg₅Gd and Mg₅Sm, Mg₃Gd and Mg₃Sm, Mg₂Gd and Mg₂Sm in the Gd–Mg–Sm system were described according to the formulae Mg₅(Gd,Sm), Mg₃(Gd,Sm), and Mg₂(Gd,Sm), respectively. The compound Mg₄₁Sm₅ with a homogeneity range was treated as a line compound Mg₄₁(Gd,Sm)₅ in the Gd–Mg–Sm system. Based on the experimental data in the Mg-rich corner of the Gd–Mg–Sm system, a set of thermodynamic parameters describing the Gibbs energies of individual phases of the Gd–Mg–Sm system as functions of composition and temperature was obtained. In addition, the complete ternary phase diagram of the Gd–Mg–Sm system were predicted.     

Molecular Field Theory Analysis of Intermetallic Compounds Sm1-xErxFe2 (x=0.7,0.4,0.3,0.1)

The temperature dependence of magnetization of intermetallic compounds molecular field theory (MFT)were studied and the results were consistent with the experimental data, so the Curie temperatures were obtained.The exchange field HMn (T) and HGd (T) were presented.The saturation magnetization and the Curie temperature Tc decrease with the increasing Er content.But the rare earth exchange field strengthens, which leads to increasing magnetocrystalline anisotropy.The exchange coupling constants JFeFe, JFer, Jrr were caculated.JFeFe dominates the three kinds of interaction, implying that the magnetic interaction is dominated by the exchange 3d electrons.     

氮化前显微组织对SmFeN合金磁性能的影响

本文研究了Sm含量,凝固速度及Nb和Zr元素的添加对Sm-Fe合金微观组织及氮化后Sm2Fei7Nx合金磁性能的影响.研究结果表明:采用真空感应炉熔炼Sm-Fe合金,当Sm的补偿量大于10wt%时,合金铸锭组织中出现大量的富Sm相,这将导致氮化后磁体磁性能的恶化;提高铸锭的冷却速度及添加Nb和Zr等元素可以有效地细化铸锭中α-Fe相的晶粒,减少均匀化退火后α-Fe相的数量,提高磁性能.     

高温固相反应法制备CaS:Eu2+,Sm3+光存储材料及其性能研究

采用高温固相反应法在还原气氛下制备了CaS：Eu^2 ，Sm^3 光存储材料，研究了工艺因素(灼烧温度和灼烧时间)对样品性能的影响。XRD图谱表明，样品在700℃就可以形成CaS晶格。光谱分析表明，在紫外光激发后，用980nm半导体激光照射样品，具有光激励发光现象。