SrZn2(PO4)2:Sn2+,Mn2+荧光粉的发光性质及其能量传递机理

采用高温固相法制备了SrZn₂(PO₄)₂:Sn²⁺(SZ₂P:Sn²⁺), SrZn₂(PO₄)₂:Mn²⁺(SZ₂P:Mn²⁺), SrZn₂ (PO₄)₂:Sn²⁺, Mn²⁺(SZ₂P:Sn²⁺, Mn²⁺) 荧光粉. 通过X射线衍射、激发和发射光谱详细研究了荧光粉的物相和发光性质. 在SrZn₂(PO₄)₂ 基质中, Sn²⁺离子发射光谱是峰值位于461 nm宽带谱, 归属于Sn²⁺离子的³P₁→¹S₀能级跃迁, SZ₂P:Mn²⁺激发光谱由基质吸收带(200–300 nm)和位于352, 373, 419, 431和466 nm的一系列激发峰组成, 分别对应Mn²⁺离子的⁶A₁(⁶S)→⁴E(⁴D), ⁶A₁(⁶S)→⁴T₂(⁴D), ⁶A₁(⁶S)→[⁴A₁(⁴G), ⁴E(⁴G)], ⁶A₁(⁶S)→⁴T₂(⁴G)和⁶A₁(⁶S)→⁴T₁(⁴G)能级跃迁, 因此, SZ₂P:Sn²⁺ 的发射光谱与SZ₂P:Mn²⁺的激发光谱有较大范围的重叠. 结果表明Sn²⁺对Mn²⁺发光有明显的敏化作用. 基于Dexter电多极相互作用能量传递公式和Reisfeld近似原理分析, 荧光粉SZ₂P:Sn²⁺, Mn²⁺中Sn²⁺-Mn²⁺离子之间的能量传递机理属于电四极-电四极相互作用引起的共振能量传递, 并计算出Sn²⁺-Mn²⁺离子之间能量传递临界距离R_c ≈ 1.78 nm. 通过改变Sn²⁺, Mn²⁺离子掺杂浓度, 实现了荧光粉发光颜色的调节, 在254 nm短波紫外激发下荧光粉发出较强的蓝白光. 研究结果表明SZ₂P:Sn²⁺, Mn²⁺荧光粉有望应用于紧凑型节能灯照明领域, 随着半导体紫外芯片技术的发展, 有潜力应用于未来的白光发光二极管照明领域.     

Y-型沸石上VO(H2O)42+的ESR波谱研究

本文报道了VO²⁺在Y型沸石上用不同温度灼烧处理之后测得的两种不同的ESR波谱。提出了VO(H₂O)₄²⁺离子在沸石笼中的两种可能结构,随着灼烧温度的升高,结构(Ⅰ)减少。到灼烧温度高于600。C时则结构(Ⅰ)完全消失,而对应于结构(Ⅱ)的A_⊥也渐渐变小,说明未偶电子离域性增大以致失去电子,V⁴⁺则被氧化成V⁵⁺。本文利用波谱参数计算了键参数和约化能级。     

利用Er3+光学温度传感特性研究Tm3+/Yb3+掺杂NaY(WO4)2微米球的激光辐照热效应

采用微波水热方法合成了Er³⁺/Yb³⁺及Tm³⁺/Yb³⁺两个共掺杂的绣球花状NaY（WO₄）₂微米球样品。XRD结果表明所获得的产物为纯相体心结构的NaY（WO₄）₂,利用SEM观察发现产物粒子结构为纳米片组装成的绣球花状。考虑到红外激光辐照对样品产生加热效应,采用380 nm激发下不同温度的发射光谱获得了Er³⁺/Yb³⁺共掺杂NaY（WO₄）₂微米球的温度传感特性曲线和灵敏度曲线。把Er³⁺/Yb³⁺共掺杂NaY（WO₄）₂与Tm³⁺/Yb³⁺共掺杂的NaY（WO₄）₂按质量比1：10进行混合,采用980 nm激发测量了混合物的上转换发光光谱,研究了激光持续辐照对Tm³⁺/Yb³⁺掺杂NaY（WO₄）₂样品的加热效应和Tm³⁺的¹G₄→³H₆ 跃迁发光强度随激光辐照时间的变化。实验发现980 nm激光辐照使Tm³⁺/Yb³⁺掺杂NaY（WO₄）₂样品的温度持续升高并达到某一平衡温度,Tm³⁺的蓝色上转换发光也随着激光辐照时间的延长而增强,最后达到饱和。此外,在相同条件下,Tm³⁺/Yb³⁺共掺杂样品的激光辐照热效应比Er³⁺/Yb³⁺共掺杂样品的热效应更为显著。     

不同玻璃组分对β-NaYF4:Yb3+,Er3+/Tm3+粉体的侵蚀性研究及对发光性能的影响

选用硅酸盐、硼酸盐以及磷酸盐3种常用的玻璃体系,与β-NaYF₄:Yb³⁺,Er³⁺/Tm³⁺粉体均匀混合压片后在不同的温度(400～700 ℃)下进行热处理。采用X射线衍射技术和荧光光谱技术等测试手段研究不同玻璃形成体以及碱金属离子对β-NaYF₄:Yb³⁺,Er³⁺/Tm³⁺粉体的侵蚀情况以及对发光性能的影响。研究结果表明,在硼酸盐玻璃体系与β-NaYF₄:Yb³⁺,Er³⁺/Tm³⁺粉体复合热处理过程中,Li⁺和K⁺离子会取代β-NaYF₄晶体中Na原子的位置。 在相同热处理温度下,不同玻璃体系与β-NaYF₄晶体反应剧烈程度:磷酸盐>硼酸盐>硅酸盐。     

纳米GdPO4：Eu3+的合成和光谱特性

采用EDTA二钠盐参加的共沉淀方法制备出纳米GdPO₄:Eu³⁺,利用X射线衍射,荧光光谱和电镜等测试手段对GdPO₄:Eu³⁺的相结构和发光性质进行了研究。XRD图谱结果表明700℃合成了纯的具有单斜晶系、独居石结构的纳米GdPO₄:Eu³⁺。根据Scherrer公式计算,700,800℃热处理后样品的一次颗粒度分别为18,40nm左右。激发光谱和发射光谱的研究表明,电荷迁移态和Eu³⁺的特征发射峰的强度随GdPO₄:Eu³⁺纳米粒子的增大而增强。在较小的纳米粒子中,存在结构扭曲的现象,315nm激发下的发射光谱研究表明,Gd³⁺和Eu³⁺具有较好的能量传递。     

透明β-NaYF4：Yb,Tm/PMMA 纳米复合材料的制备及其光学性能

采用高温溶剂热法制备了一系列不同Yb³⁺掺杂浓度的上转换发光纳米粒子β-NaYF₄：Yb,Tm和核壳结构的β-NaYF₄：Yb,Tm@β-NaYF₄：Yb纳米粒子。采用X射线衍射（XRD）、场发射扫描电镜（FESEM）、光致发光（PL）谱对材料的物相结构、形貌特征和发光性质进行了表征和研究,并特别研究了温度对材料发光性能的影响。结果表明：保持Tm³⁺浓度不变,随着Yb³⁺掺杂浓度的增加,β-NaYF₄：Yb,Tm的发光强度先增大后减小。当Yb³⁺掺杂摩尔分数为30%时,474 nm和645 nm处的发光强度达到最大值;当Yb³⁺掺杂摩尔分数为50%时,450 nm和692 nm处的发光强度达到最大值。在β-NaYF₄：Yb（30%）,Tm上包裹一层β-NaYF₄：Yb壳层后,其发光显著增强,随壳层Yb³⁺摩尔分数的增加,发光强度也是先增大后减小。当壳层Yb³⁺摩尔分数为10%时,核壳结构纳米粒子的发光强度达到最大值;当壳层Yb³⁺摩尔分数达到40%时,核壳结构纳米粒子的发光强度已经低于未包裹时。将样品进行热处理后,荧光增强。样品的发光强度随环境温度的升高,红光变弱,蓝光增强。采用原位聚合法将β-NaYF₄：Yb,Tm纳米粒子与PMMA制成复合材料后,仍能保持较好的透明度和发光强度。     

γ-Fe2O3中的氢含量

利用热中子透射法测定γ-Fe₂O₃的氢含量。利用差热分析、磁分析以及穆斯堡尔效应研究γ-Fe₂O₃的相变,实验结果表明在γ-Fe₂O₃结构中确实含有一定量的氢,当γ-Fe₂O₃结构中的阳离子空位被H¹⁺,Co²⁺,Si⁴⁺,P⁵⁺等离子占据时,将 关键词：     

ESR研究非晶Ag+导体的晶化

用电子自旋共振(ESR)方法对非晶Ag⁺离子导体0.85AgI~0.15Ag₄P₂O₇的热处理晶化过程进行研究,在样品中掺入微量(约1×10^-3 g/g)的Mn²⁺或V⁴⁺离子作为自旋探针离子,它们的ESR谱强度随升温线性减弱,当样品完全晶化时ESR谱消失。这样测定的样品完全晶化的温度分别为98℃(掺Mn的)和108℃(掺V的).本文还对Mn²⁺和V⁴⁺的ESR谱进行了分析。     

铒铥共掺氧化锌薄膜近红外宽带发射及变温行为的研究

采用磁控共溅射技术制备了铒铥共掺杂氧化锌发光薄膜. 通过优化退火温度, 实现了薄膜的近红外 平坦宽带发射, 总带宽可达到~ 500 nm, 覆盖了光通信S+C+L+U 区波段. 此发射带由Er³⁺ 的1535 nm (⁴I_13/2 → ⁴I_15/2) 发射峰及Tm³⁺ 的1460 nm (³H₄ → ³F₄), 1640 nm (¹G₄ → ³F₂), 1740 nm (³F₄ → ³H₆) 发射峰组成. 研究表明: 退火温度低于800 ℃ 时, 没有观察到薄膜样品明显的光致发光现象; 随着退火温度 从800 ℃ 升高到1000 ℃, I₁₆₄₀/I₁₅₃₅ 发射峰强度比从0.2 升高到0.3, I₁₇₄₀/I₁₅₃₅ 发射峰强度比从0.5 降低 到0.4, 发射峰强度比均基本保持稳定; 当退火温度高于1000 ℃ 时, I₁₆₄₀/I₁₅₃₅ 发射峰强度比从0.3 升高到 0.6, I₁₇₄₀/I₁₅₃₅ 发射峰强度比从0.4 升高到0.8, 发射峰强度比均急剧增加. 变温行为表明: 随着温度从10 K 逐渐升高到300 K, 谱线的总带宽基本不变, 在340—360 nm 之间; Tm³⁺ 在1640 和1740 nm 处的发射峰强度 分别降低了2/3 和1/2, Er³⁺ 在1535 nm 的发射峰强度增大了1.2 倍. 这是因为随着温度的升高, 声子数目增 多, Er³⁺ 与Tm³⁺ 离子之间发生能量传递的概率不断变大, 并且在Tm³⁺ 离子之间没有发生交叉弛豫现象.     

煅烧温度对Ba1.2Ca0.64SiO4：0.10Eu，0.06Mn粉体发光性能的影响

以MCM-41为硅源,在800~1 100℃下合成了Ba_1.2Ca_0.64SiO₄：0.10Eu,0.06Mn荧光粉,研究了煅烧温度对荧光粉发光性能的影响。实验结果表明,Eu²⁺的蓝绿光发射带的强度与宽度随煅烧温度的升高先增大后减小,在1 000℃时强度达到最大。最大发射峰位随温度的升高而发生红移,由800℃和900℃时的450 nm移至1 000℃和1 100℃时的480 nm。Mn²⁺的红光发射起源于Eu²⁺发射光的激发,其强度随温度的升高而增大。与Mn²⁺发生能量传递作用的Eu²⁺主要位于10配位的M（1）格位。     

Bulk magnetic properties of tetravalent ion substituted Cu-ferrite

The lattice parameter,a, increases with the increase of Ti⁴⁺ substitution while it decreases with the increase of Ge⁴⁺ substitution in Cu_1+x A _x Fe_2–2x O₄ compounds [A=Ti⁴⁺, Ge⁴⁺Sn⁴⁺]. On substitution of Sn⁴⁺,a does not vary. CuFe₂O₄ exhibits single domain (SD) behaviour that changes to multi domain (MD) type on Ti⁴⁺ substitution. On Ge⁴⁺ substitution initially all the compositions exhibit SD behaviour while forx>0.2 they show MD behaviour. All Sn⁴⁺ substituted compositions exhibit SD behaviour. The Curie temperature decreases on addition of Ti⁴⁺, Sn⁴⁺ and Ge⁴⁺. The magnetic momentn _B (77 K) initially increases and then decreases with the substitution of Ti⁴⁺, Ge⁴⁺, and Sn⁴⁺. This is explained by cation distribution and reduction of Fe³⁺ ions.The authors wish to thank Prof. R. N. Patil for encouragment and useful discussion. One of the authors (B.L.P.) is grateful to UGC (New Delhi) for granting Teacher Fellowship for Ph.D. course.     

Mössbauer spectroscopic investigation of tin-doped thiospinels

The tin-doped sulphur-containing compound of composition Fe_1.05Cr_1.90Sn_0.05S₄, in which tin is located on the octahedral sites as Sn^4?+? in the spinel-related structure, has been examined by ¹¹⁹Sn Mössbauer spectroscopy. The data complement results obtained by ⁵⁷Fe Mössbauer spectroscopy and show that tin increases the magnetic ordering temperature of pure FeCr₂S₄.     

磁控共溅射法制备的Zn2GeO4多晶薄膜结构及其光致发光研究

用射频磁控共溅射方法在不同温度的单晶硅基片上生长薄膜,然后在800℃真空环境下对薄膜进行退火处理,成功获得了结晶状态良好的Zn₂GeO₄多晶薄膜.利用X射线衍射(XRD),X射线光电子能谱(XPS)和原子力显微镜(AFM)对薄膜进行了结构、成分和形貌分析,研究了基片温度对三者的影响. 结果显示,当基片温度升高到400℃以上时,薄膜中的Zn₂GeO₄晶粒在(220)方向上显示出了明显的择优取向. 当基片温度在500—600℃范围内,有利于GeO₂结晶相的形成. XPS显示薄膜中存在着Zn₂GeO₄,GeO₂,GeO,ZnO四种化合态. 同时,随着基片温度的升高,晶粒尺寸增大且薄膜表面趋于平整. 薄膜的光致发光在绿光带存在中心波长为530和550nm两个峰,应该归因于主体材料Zn₂GeO₄中两个不同的Ge²⁺的发光中心. 关键词： 射频磁控溅射 2GeO₄')" href="#">Zn₂GeO₄ 荧光体     

Les phases Cd2Nb2-2xSn2xO7-2xF2x

The solid solution Cd₂Nb_2-2xSn_2xO_7-2xF_2x is studied by X-Ray diffraction and Mössbauer spectroscopy. Two phases I and II are observed; phase I presents a normal pyrochlore structure but phase II shows a local order around Sn⁴⁺. The difference between phases I and II is explained by the difference of electronic configuration between Sn⁴⁺ (4d¹⁰) and Nb⁵⁺ (4d⁰).     

The synthesis and afterglow luminescence properties of a novel red afterglow phosphor: ZrO2:Sm3+,Sn4+

A novel ZrO₂:Sm³⁺,Sn⁴⁺ phosphor is synthesized by solid state reaction. The ZrO₂:Sm³⁺ does not show afterglow. But, after doping Sn⁴⁺, intense red afterglow luminescence is firstly observed in ZrO₂:Sm³⁺,Sn⁴⁺ and it can last more than 1000 s at maximum. The afterglow decay curves of ZrO₂:Sm³⁺,Sn⁴⁺ are fitted by three exponential components and the decay process consists of initial fast, intermediate and slow decay. The thermoluminescence indicates that the Sn⁴⁺ ions induce suitable traps with the depth of 0.436 eV and result in efficient afterglow luminescence of ZrO₂:Sm³⁺,Sn⁴⁺. The thermoluminescence filling and fading experiments further confirm the important role of the proper shallow traps induced by doping Sn⁴⁺ on the afterglow of ZrO₂:Sm³⁺,Sn⁴⁺.     

Magneto-crystalline properties of BaFe12−2x M x Sn x O19 (M = Sn, Ni, Zn) ferrite powders

BaFe_12?2x M _x Sn _x O₁₉ compounds, where M?=?Sn²⁺, Ni²⁺ or Zn²⁺ ions, were synthesized by mechanical milling and partially by citrate precursor methods. Analysis of magneto-crystalline structure has been carried out by Mössbauer spectroscopy. The Sn⁴⁺ ions replace Fe³⁺ ions on 2b and slightly on 2a?+?4f₁ sites, Zn²⁺ ions strongly prefer 4f₁ sites, Sn²⁺ ions prefer 4f₁ sites too and Ni²⁺ ions occupy 4f₂ and 12k or 2a sites. The magnetic properties were evaluated by the vibrating sample magnetometry and the thermomagnetic analysis. A large variation of the intrinsic coercivity H _c (330 to 78 kA/m) and of temperature coefficient of coercivity of ΔH _c /Δ? (0.39 to 0.22 kA/m°C) were achieved as a function of the (Zn–Sn) and (Sn–Sn) substitutions, respectively. The Curie temperature T _c decreased with the (Ni–Sn) substitution from 447 to 399°C.     

Localisation of iron ions in NH4,Na-Y zeolite: A Mössbauer effect study

Localisation of Fe ions in deep-bed treated NH₄,Na-Y zeolite at 830K, 940K, and 1050K, as well as after reduction by hydrogen, and dealumination with subsequent calcination is studied by⁵⁷Fe Mössbauer spectroscopy. Most of the incorporated iron is present in the form of octahedrally coordinated ferric species with two distinct sets of hyperfine parameters assigned to atoms inside the zeolite structure and in extraframework positions. Fe²⁺ ions with high coordination are also detected and their amount increases with the temperature of deep-bed treatment. Low-temperature Mössbauer effect measurements at 77K and 4.2K were employed to facilitate the identification of iron sites.     

Structural and spectroscopic characterization of the quenched hexacelsian

The hexacelsian with disorder distribution of the Si⁴⁺ and Al³⁺ is synthesized by thermally induced transformation of a Ba-LTA zeolite. The initial Ba-LTA zeolite is annealed and quenched to room temperature. The crystal structure and microstructure i.e. long-range ordering is investigated from the polycrystalline material by the Rietveld refinement procedure while short-range ordering is investigated by the ²⁹Si and ²⁷Al MAS NMR, Raman and luminescence (Eu³⁺ doped hexacelsian) spectroscopy's. The crystal structure (space group P6₃/mcm) and microstructure (size-strain analysis) results indicate disorder distribution of the Si⁴⁺ and Al³⁺. Analysis of the spectra indicates disorder distribution of the Si⁴⁺ and Al³⁺ (²⁹Si and ²⁷Al MAS NMR spectroscopy), dynamical disorder in the structure and site symmetry lowering for the Ba²⁺ site at a low temperature (Raman and luminescence spectroscopy's).     

Photoluminescence and persistent luminescence properties of non-doped and Ti4+-doped Mg2SnO4 phosphors

Mg₂SnO₄ exhibits green photoluminescence and persistent luminescence, which originate from oxygen vacancies. When Ti⁴⁺ ions were doped, an interesting Mg₂SnO₄:Ti⁴⁺ phosphor with bluish white photoluminescence under ultraviolet irradiation and with green persistent luminescence was first obtained. Our investigation reveals that two emission centres exist in Mg₂SnO₄:Ti⁴⁺. The centres responsible for the green emission are considered to be the F centres (oxygen vacancies) and the blue centres are the TiO₆ complex. Trap clusters in the band gap with different depths, such as [Sn_Mg^‥—O_i^″], [Sn_Mg^‥—V_O^·], [Sn_Mg^‥—V_O^×] and Mg_Sn^″, correspond to the components at 85 ℃, 146 ℃ and 213 ℃ of the thermoluminescence curve.     

Etude par effet Mössbauer des champs magnetiques transferes sur le noyau De119Sn4+ dans FeF3

A sample of FeF₃ doped with ¹¹⁹Sn⁴⁺ was invesigated by Mössbauer spectroscopy. A transfer of spin dennsity was observed in the orbitals of tin with resulting magnetic field H(0)_77K = 129 kOe. The comparison of the Mössbauer parameters of ¹¹⁹Sn⁴⁺ in FeF₃ with those obtained by previous authors for ¹¹⁹Sn⁴⁺ in Y_0.9Ca_0.1Fe_0.9Sn_0.1O₂ suggests a growing spin polarization of the electronic charge in the 5s orbitals of Sn⁴⁺ in the FeF₃ matrix.