Effects of W~(6+) occupying Sc~(3+) on the structure,vibration, and thermal expansion properties of scandium tungstate

We experimentally investigate effects of W~(6+)occupying the sites of Sc~(3+)in the unit cell of Sc_2 W_3 O_(12)(Sc_8 W_(12) O_(48))on the structure, vibration and thermal expansion. The composition and structure of the doped sample(Sc_6 W_2)W_(12) O_(48±δ)(with two W~(6+)occupying two sites of Sc~(3+)in the unit cell of Sc_8 W_(12) O_(48)) are analyzed and identified by combining the x-ray photoelectron spectroscopy and the synchronous x-ray diffraction with first-principles calculations based on density functional theory. Results show that the crystal with even W~(6+)occupying even Sc~(3+)in the unit cell is stable and maintains the orthorhombic structure at room temperature. The structure of the doped sample is similar to that of Sc_2 W_3 O_(12), and with even W occupying even positions of Sc in the unit cell and constituting the WO_6 octahedra. Raman analyses show that the doped sample possesses stronger W–O bonds and wider Raman linewidths than those of Sc_2 W_3 O_(12). The sample doped with W also exhibits intrinsic negative thermal expansion in the measured range of 150 K–650 K.     

红色荧光粉La2Mo2O9:Eu3+,W6+的制备及发光性能

采用高温固相法合成出La₂Mo₂O₉:Eu³⁺,W⁶⁺系列红色荧光粉,其结构为立方晶系的β- La₂Mo₂O₉。在395 nm光激发下,样品La_1.40Mo₂O₉:0.60Eu³⁺发射出很强的红光,最强发射峰位于616 nm处。适量地掺杂W⁶⁺离子可以提高样品的激发和发射强度,在395 nm光激发下,La_1.40Mo_1.84O₉:0.60Eu³⁺,0.16W⁶⁺荧光粉的Eu³⁺的⁵D₀→⁷F₂跃迁发射强度最大,是样品La_1.40Mo₂O₉:0.60Eu³⁺的1.23倍。最后,将La_1.40Eu_0.60Mo_1.84O₉:0.16W⁶⁺荧光粉与~395 nm发射的InGaN芯片一起制作成红光发光二极管(LED),该LED发射出很强的红光。     

Al~(3+)/Mo~(6+)双离子取代ZrV_2O_7中Zr~(4+)/V~(5+)实现近零膨胀

采用固相烧结法制备了Zri_(1-x)Al_(2-x)V_(2-x)Mo_xO_7(0≤x≤0.9),并通过调整Al~(3+)/Mo~(6+)对ZrV_2O_7中的Zr~(4+)/V~(5+)离子替代量来实现近零膨胀,对于较小的x值(x≤0.3),材料保持了与ZrV_2O_7相同的立方相结构.随着Al~(3+)/Mo~(6+)替代量的增加,(Al/Zr)~-和(Mo/V)~+之间的库仑相互作用逐渐加强,这种库仑相互作用导致材料中未发生畸变的立方相晶体结构逐渐减少.当x≥0.7时,材料中立方相晶体结构完全消失.在425-750 K温度区间内,Zr_(0.5)Al_(0.5)M_(0.6)O_7展示出近零膨胀性质(-0.39×l0~(-6)K~(-1)).Zr_(0.5)Al_(1.5)V_(1.5)Mo_(0.5)O_7的低热膨胀性能可能与Al~(3+)/Mo~(6+)对ZrV_2O_7中Zr~(4+)/V~(5+)部分替代引起部分晶体结构发生的畸变及其对未替代部分的晶格结构的影响有关.     

一种新型蓝光BaKBP2O8:Eu2+荧光粉的合成与性能研究

通过高温固相法成功合成了一种新型蓝光荧光粉BaKBP₂O₈:Eu²⁺,分别用XRD和荧光光谱表征了其结构与光学性能。结果表明,Eu²⁺的引入并没有显著改变其四方相的晶体结构。样品的激发光谱(监测波长为443 nm)是由主晶格吸收的307 nm吸收肩与Eu²⁺离子4f⁷-4f⁶5d 跃迁的346 nm主峰组成。在紫光激发下,样品的发射光谱为蓝色。当Eu²⁺离子摩尔分数为0.03时,样品的发射强度达到最大值。然而,随着Eu²⁺浓度的进一步增加,由于浓度猝灭机制,其发射强度开始降低。在超过370 K的温度下,荧光粉样品的相对发光强度仍然超过50%。BaKBP₂O₈:Eu²⁺的色坐标为(0.176 6,0.168 1)。     

Eu,Dy共掺杂SrAl2O4长余辉材料制备新工艺

活化Al-Sr合金粉末水解制备SrAl₂O₄长余辉材料的前驱体,并采用高温固相反应法制备出Eu,Dy共掺杂的SrAl₂O₄长余辉材料,对其微观结构和发光特性进行了研究。实验结果表明:前驱体中Al、Sr元素在微观状态下分布均匀,所制成的长余辉发光材料的发射主峰位于520nm附近,为典型的Eu²⁺离子4f5d-4f的特征发射,初始亮度达到18cd/m²,余辉时间长达46h。     

长余辉发光材料CaAl2O4∶Eu2+,Gd3+ 的制备和发光性能研究

采用高温固相法制备了CaAl₂O₄∶Eu²⁺,Gd³⁺ 长余辉发光材料。利用X射线衍射(XRD)和荧光光谱测试等手段对所制备的样品进行结构表征和发光性能的分析,探究Eu²⁺摩尔分数为3.5%,硼酸质量分数为0.5%,Gd³⁺摩尔分数分别为2%,3%,4%,5%时样品的发光性能。研究结果表明:实验成功地合成了CaAl₂O₄∶Eu²⁺,Gd³⁺粉晶,并且Eu²⁺和Gd³⁺的引入并未引起CaAl₂O₄晶体结构的改变。样品的激发光谱和发射光谱均为宽带谱,且发射光谱的最大峰值位于444 nm左右,属于Eu²⁺的4f⁶5d→4f⁷跃迁,所发光为蓝光。蓝色荧光粉CaAl₂O₄∶3.5%Eu²⁺,3%Gd³⁺的发光强度最好。     

Nd~(3+):SrY_2O_4粉体的制备、结构与光谱性能研究

为探索新型激光晶体,采用固相法合成了(3 at.%)Nd~(3+):SrY_2O_4多晶,对其结构和发光性质进行了研究.对样品的X射线衍射谱进行Rietveld精修得到了样品的晶胞参数、原子位置等.在353 nm激发下,Nd~(3+):SrY_2O_4在可见波段的最强荧光峰位于419 nm,对应Nd3+的2D15/2→4I9/2跃迁.在824 nm激发下,Nd3+的4F3/2→4I11/2跃迁的荧光谱带宽约为90 nm,最强峰为1083 nm,荧光寿命为281.7μs.宽发射光谱和长的能级寿命表明,Nd~(3+):SrY_2O_4是一种很有希望的新波长激光二极管抽运超短脉冲激光材料.     

Sr3B2O6：Eu3+,Li+荧光粉的合成与发光性能

采用高温固相法合成Sr₃B₂O₆：Eu³⁺,Li⁺红色荧光粉,考察了激活剂Eu³⁺和电荷补偿剂Li⁺浓度对Sr₃B₂O₆：Eu³⁺,Li⁺荧光粉发光性能的影响。结果表明：适量掺杂Eu³⁺、Li⁺离子并不改变Sr₃B₂O₆的结构。当Eu³⁺掺杂量为4%、Li⁺的掺杂量为8%时,在900 ℃下灼烧2 h可以得到发光性能最佳的Sr_2.9B₂O₆：0.04Eu³⁺,0.08Li⁺红色荧光粉。以394 nm的近紫外光激发时,Sr₃B₂O₆：Eu³⁺,Li⁺荧光粉发射出红光,对应于Eu³⁺的4f-4f 跃迁,其中以614 nm附近的⁵D₀→⁷F₂跃迁发光最强,是一种有潜力用于白光LED的红色荧光粉。     

Sm3+掺杂的SnNb2O6粉体的光谱特性

采用熔盐法制备了Sm³⁺掺杂的SnNb₂O₆粉体, 利用X射线粉末衍射、扫描电子显微镜对其物相和形貌进行了表征, 用激发、发射光谱和荧光寿命对样品的发光性能进行了研究.结果表明:所得样品为单斜晶系的SnNb₂O₆, 在407 nm的激发下, 有较强的橙红色发射, 最强峰位于599 nm, 属于Sm³⁺的⁴G_5/2→⁶H_7/2跃迁.     

Synthesis and characterization of NiMn2O4 nanoparticles using gelatin as organic precursor

Nanoparticles of NiMn₂O₄ were successfully obtained by mixing gelatin and inorganic salts NiCl₂·6H₂O and MnCl₂·4H₂O in aqueous solution. The mixture has been synthesized at different temperatures and resulted in NiMn₂O₄ nanoparticles with crystallites size in the range of 14–44 nm, as inferred from X-ray powder diffraction (XRPD) data. We have also observed that both the average crystallite size and the unit cell parameters increase with increasing synthesis temperature. Magnetic measurements confirmed the presence of a magnetic transition near 110 K.     

红色荧光粉Na8.33 La1.67(SiO4)6 O2:Eu3+的制备及发光特性

采用高温固相法制备了Na_(8. 33)La_(1. 67)(SiO_4)_6O_2∶Eu~(3+)红色发光材料,利用X射线衍射仪测定其晶体结构,利用Hitachi F4600表征其发光光谱。在紫外光激发下,样品Na_(8. 33)La_(1. 67)(SiO_4)_6O_2∶Eu~(3+)呈多峰发射,分别对应于Eu~(3+)的~5D_0-~7F_j(j=0,1,2,3,4)能级跃迁,主峰是位于615 nm的~5D_0-~7F_2跃迁发射。研究了Eu~(3+)掺杂浓度对材料发光性质的影响,改变Eu~(3+)掺杂浓度,样品的发射强度随之改变,Na_(8. 33)La_(1. 67)(SiO_4)_6O_2∶Eu~(3+)材料的Eu~(3+)浓度为15%时,发光强度最大。讨论了浓度猝灭的机理,理论计算表明引起Eu~(3+)离子能量弥散的主要原因是离子间交换相互作用。     

光学碱度对Tb3+掺杂Bi2O3-B2O3玻璃发光性能的影响

采用熔融法制备了Tb³⁺掺杂的Bi₂O₃-B₂O₃系统玻璃,使用激发、发射及拉曼光谱分析了光学碱度与玻璃结构及发光性能的关系,同时绘制了Tb³⁺、Bi³⁺和Bi²⁺的能级图。研究结果表明：Tb³⁺掺杂的Bi₂O₃-B₂O₃玻璃由[BO₃]、[BiO₃]、[BO₄]及[BiO₆]共同组成,且随着光学碱度由0.63增加到0.93,玻璃的结构逐渐疏松。高的光学碱度使部分Bi³⁺变为Bi²⁺,发出571 nm（²P_3/2（2）→²P_1/2）的光,Bi³⁺→Tb³⁺的能量降低。在光学碱度及Tb³⁺、Bi³⁺和Bi²⁺离子的共同作用下,随着光学碱度的提高,玻璃的发光颜色由黄绿色变为白色。     

YNbO4：Tm3+/Yb3+上转换发光特性研究

按照50Nb₂O₅-（46-x）Y₂O₃-4Yb₂O₃-xTm₂O₃（x=0.1,0.2,0.5,1,2）的配比方式,采用高温固相法制备出了掺杂Tm³⁺/Yb³⁺的YNbO₄晶体粉末。在980 nm红外光激发下,观测到波长为478,645,707 nm的上转换荧光,分别对应于Tm³⁺离子的¹G₄→³H₆、¹G₄→³F₄、³F₃→³H₆能级跃迁过程。利用上转换发射功率与980 nm激光器工作电流关系估算出跃迁过程吸收光子数目为2.72,2.69,2.01,从而确定出前两者为三光子吸收过程,最后一个对应于双光子吸收过程。运用Judd-Ofelt理论研究样品光谱特性,根据样品的吸收谱得到样品的谱线强度参数Ω_t（t=2,4,6）,进而得出理论振子强度及实验振子强度,二者均方根偏差δ_rms=1.299×10^-7。计算了Tm³⁺离子向下能级跃迁的跃迁几率、跃迁分支比等参数。最后得出结论：（1）³F₄能级寿命较长,适合作为上转换中间能级;（2）³H₅能级寿命较长,且³H₅→³H₆跃迁分支比（96.46%）接近100%,可用于产生1 216 nm激光。     

二维镨-镉异核金属配合物的水热合成、晶体结构及谱学性能研究

利用水热合成法,以柔性的乙二胺四乙酸（H₄EDTA）为配体、氧化镨以及氯化镉为金属源合成了一种镨-镉异金属-有机配合物[Pr₂Cd₃(EDTA)₃(H₂O)₁₁]·14H₂O （1）。通过X射线单晶衍射确定化合物1的结构,该化合物属单斜晶系的C2空间群,a=16.154(3) Å,b=14.863(3) Å,c=14.875(3) Å,β=115.855(3)°,V=3214.2(9) Å3, Z=2,化合物1的结构中存在纳米尺寸大小的“心形”Pr₆Cd₆O₁₂轮簇。其中Cd2+的配位数为7,采取单帽三棱柱的配位构型,而Pr3+采取十配位双帽四方反棱柱的构型。EDTA4-配体的四个羧基全部去质子化,与一个Cd2+和两个Pr3+配位,其中4个羧基氧原子和2个氮原子都与Cd2+配位,两个羧基分别桥连1个Pr3+。Pr3+和Cd2+通过μ₂-O氧原子交替连接形成Pr₆Cd₆O₁₂轮簇,每个Pr₆Cd₆O₁₂轮簇与附近的6个Pr₆Cd₆O₁₂轮簇共边连接,从而形成一个二维（6, 3）层状结构。二维层再通过…AAA…类型的堆积方式形成三维超分子结构。游离水分子填充在二维层空隙中,与羧基以及配位水分子之间形成比较强的O-H…O氢键,这些氢键有利于结构的稳定。通过热重分析、稳态荧光光谱、热微扰二维红外相关光谱（2D-IR COS）、固体紫外-可见漫反射光谱等手段进一步对化合物1的谱学性能进行表征。在红外光谱上,由于存在大量的氢键,化合物的红外光谱在3 680～2 640 cm-1波数范围内出现宽而强的吸收谱带。同时配体H₄EDTA中的羧基脱去了质子氢,并且与金属离子发生配位,因此化合物1中羧基的C=O双键的伸缩振动吸收峰与未配位配体中的C=O双键的伸缩振动吸收峰相比,向低波数移动,在1 527 cm-1波数处出现吸收峰。固体荧光测试显示在325 nm的紫外光照射下,配合物1能发出强的360 nm左右的荧光,主要是由能量在Cd2+和EDTA4-之间发生明显的LMCT跃迁转移引起的,因此化合物1可作为一类潜在的发光材料。热微扰下的二维红外光谱显示,由于水分子与羧基及水分子之间存在氢键,使得O-H的伸缩振动吸收峰对热的微扰响应比较敏感。紫外-可见光谱测试显示化合物1在位于216 nm处出现很强的紫外吸收峰,归属于化合物1中EDTA4-配体的中n→σ*跃迁及π→π*,位于444, 468和484 nm的弱吸收峰,归属为Pr3+的f-f跃迁。     

Conductivity relaxation parameters of some H and K conducting in the polycrystalline compound KDyHP3O10

Polycrystalline samples of KDyHP₃O₁₀ was obtained by heating for 12 hour at 553 K a mixture containing K₂CO₃, Dy₂O₃ and H₃PO₄. Samples were characterized through X-ray diffraction, examined by IR vibrational spectroscopy and impedance and modulus spectroscopy techniques. The conductivity relaxation parameters of some H⁺ and K⁺ conducting in this compound have been determined from an analysis of ac conductivity data measured in a wide temperature range. Transport properties in this material appears as due to H⁺ and K⁺ ions hopping mechanism. The stretched exponential function exp[−(t/τ_σ)^β] has been used to describe the conductivity relaxation. The relaxation parameters have been investigated as a function of the nature of mobile ions. The results obtained are shown to be in good agreement with the predictions of the Ngai coupling model.     

铥、铽及铕离子掺杂的BaAl2O4膜的阴极射线发光特性

利用喷雾热解法合成了Tm、Tb及Eu离子掺杂的铝酸钡(BaAl₂O₄)发光膜,研究了合成条件对其结构和发光特性的影响.在退火温度达到700℃时,生成了BaAl₂O₄膜.Tm³⁺和Tb³⁺掺杂的BaAl₂O₄膜分别发蓝光和绿光,而Eu³⁺掺杂的BaAl₂O₄膜的发光既有Eu²⁺的特征发射——宽的蓝光发射带,也有Eu³⁺的特征发射——窄的红光发射峰.BaAl₂O₄:Tm³⁺的发射主峰位于462nm,在电压为5kV和电流密度为57μA/cm²的条件下,其阴极射线发光(CL)亮度可达25cd/m²,效率可达0.11lm/W.BaAl₂O₄:Tb³⁺的发射主峰位于549nm,在相同的条件下,其阴极射线发光亮度可达120cd/m²,效率可达0.55lm/W.BaAl₂O₄:Eu³⁺的发射主峰位于616nm,其阴极射线发光亮度为50cd/m²,效率为0.23lm/W.BaAl₂O₄:Eu²⁺发蓝光,峰值位于452nm,其阴极射线发光亮度为640cd/m²,效率为2.93lm/W.     

稀土离子(Eu3+,Tb3+,Ce3+)掺杂ZnAl2O4/SiO2微晶玻璃的制备与发光性能

采用凝胶法分别制备出4.5ZnO-5.5Al₂O₃-90SiO₂(ZAS)以及ZAS[DK]:RE³⁺ (RE=Eu,Tb,Ce) 透明微晶玻璃。利用X射线衍射仪(XRD)、透射电子显微镜(TEM)和荧光光谱仪(PL)等测试手段,研究了稀土离子掺杂浓度对ZAS微晶玻璃的结构和发光性能的影响。XRD结果表明,ZAS[DK]:RE³⁺ (RE=Eu,Tb,Ce)微晶玻璃包含ZnAl₂O₄晶相和SiO₂非晶相,ZnAl₂O₄平均晶粒尺寸约为30 nm,稀土离子的掺杂没有显著改变原来的ZnAl₂O₄晶体结构。TEM结果表明,900 ℃时ZnAl₂O₄从ZAS体系中析出。PL光谱显示,Eu³⁺ 存在 ⁵D₀→⁷F₂跃迁,ZAS[DK]:Eu³⁺在611 nm 处发出强烈的红色光;由于Tb³⁺ 的⁵D₄→⁷F₅ 跃迁,ZAS[DK]:Tb³⁺在541 nm 处发出明亮的绿色光;ZAS[DK]:Ce³⁺ 在381 nm处显示了蓝光发射,对应于Ce³⁺ 的5d→4f 轨道跃迁。ZAS[DK]:RE³⁺ (RE=Eu, Tb, Ce)的PL发射光谱存在着浓度猝灭现象,Eu³⁺、Tb³⁺ 和Ce³⁺的最佳单掺杂摩尔分数分别为20%、20%和3%。CIE色度图表明,ZAS[DK]: RE³⁺ (RE=Eu,Tb,Ce)的色坐标分别位于红光、绿光和蓝光区域。实验结果表明,ZAS:RE³⁺ (RE=Eu,Tb,Ce) 微晶玻璃是一种良好的可用于全色显示的白光LED材料。     

Electrical conductivity and defect structure of Mg-doped Cr2O3

The electrical conductivity of Cr₂O₃ nominally doped with 2 mol% MgO has been studied by the four point a.c. technique as a function of the oxygen activity (O₂ + Ar, CO + CO₂ and H₂ + H₂O) in the temperature range 400–1200 °C. It is concluded that Cr₂O₃ doped with MgO is an extrinsic conductor and that the dissolved Mg-dopant is compensated by the formation of electron holes at near atmospheric oxygen pressures and by oxygen vacancies (or possibly interstitial chromium ions) at highly reduced oxygen activities (in CO + CO₂ and H₂ + H₂O gas mixtures). In H₂ + H₂O mixtures Mg-doped chromia also dissolves hydrogen as protons and significantly affects the defect structure and electrical conductivity. The defect structure of the oxide under various conditions is discussed.     

Eu3+激活硼酸盐基质新型红色荧光粉的制备及发光性能

采用传统高温固相反应法制备了一种新的白光LED用红色荧光粉LiLa2 O2 BO3:Eu3+,并对其晶体结构及发光性能进行了系统研究.XRD分析证实Lila2BO3晶体能够稳定存在,并利用Le Bail模型计算得到其晶胞参数.荧光光谱证实:Eu3+离子在LiLa2O2BO3晶体中占据非反演对称中心格位,该系列荧光粉在紫...     

Effect of co-doped metal caions on the properties of Y_2O_3:Eu~(3+) phosphors synthesized by gel-combustion method

Y_2O_3:Eu~(3+) phosphors co-doped with different metal cations(Li~+, Na~+, K~+, Mg~(2+), Ca~(2+)) are prepared by the gelcombustion method with Y_2O_3, Eu_2O_3, and R(NO3)x(R = Li, Na, K, Mg, Ca) serving as raw materials and glycine as fuel,calcined at 1000?C for 2h. The synthesized Y_2O_3:Eu~(3+) phosphors doped with different metal cations and doping ratios are characterized by x-ray diffractometry(XRD), fluorescence and phosphorescent spectrophotometer. The co-doping metal cations are advantageous to the development of Y_2O_3:Eu~(3+) lattice. All the samples can emit red light peaked at 611 nm under 254-nm excited. The luminescence intensities of co-doping samples are increased because the cations increase the electron transition probability of Eu~(3+) from ~5D_0 level to ~7F level. The fluorescence lifetime of Eu~(3+)(~5D_0→~7F_2) is increased by doping metal cations.