Synthesis of SrAl2O4：Eu^2＋,Dy^3＋ phosphors by the coupling route of microemulsion with coprecipitation method

Nano-sized SrAl2O4：Eu^2＋,Dy^3＋ phosphors with good monodispersity and narrow size distribution were synthesized by the coupling of water-in-oil （W/O） microemulsion with coprecipitation method. The phase composition, morphology, crystallinity, excitation spectra, emission spectra, and afterglow decay of SrAl2O4：Eu^2＋,Dy^3＋ nanophosphors were measured. It was found that the amount of surfactant that was used had an important effect on the shape and average size of the phosphor particles. SrAl204 phase of the phosphors showed an increase with the increase in calcination temperature. When the calcination temperature reached 1150℃, the fine crystal of SrAl2O4 was formed and the long afterglow luminescence could be obviously observed. In comparison with the samples prepared by the high-temperature solid-state method, the calcination temperature showed an obvious decrease and a dear blue shift occurred in the excitation and emission spectra of the sample. The afterglow time could be more than 8 h.     

Roles of crystal defects in the persistent luminescence of Eu^2＋, Dy^3＋ co-doped strontium aluminate based phosphors

The roles of different point defects in persistent luminescence of SrAl2O4：Eu,Dy phosphors were investigated. The research results showed that Dyer plays an important role in the persistent luminescence of SrA1EO4：Eu, Dy phosphors. It can serve as the electron trap of suitable depth for persistent luminescence. V~ does not serve as the electron trap of suitable depth, but its existence can increase the depth of electron traps. There is interaction between the Dy^3＋（ DySr ） and the Eu^2＋（Eu^x Sr ）, and only if the distance between the Dy^3＋（DySr） and the Eu^2＋ （Eu^x Sr） is close enough, the Dyer can work as an effective electron trap. The point defect of V＂ Sr can be hole trap, but the change of its density in crystal matrix does not arouse the obvious change of persistent luminescence.     

~ ~ 3＋ Sol-gel synthesis and photoluminescence characterization of La2Ti2O7.EU3＋nanocrystals

Eu³⁺ doped La₂Ti₂O₇ nanocrystals with pure monoclinic phase and size of about 100 nm were prepared by a citric acid (CA) assisted sol-gel method. Techniques of thermo-gravimetric (TG) and differential scanning calorimetry (DSC), X-ray diffraction (XRD), as well as transmission electron microscopy (TEM) were employed to characterize the as-synthesized nanoparticles. Furthermore, photoluminescence (PL) performances of the Eu³⁺ doped La₂Ti₂O₇ nanocrystals were evaluated with focus on the effects of calcination temperature and Eu³⁺ doping concentration on the photoluminescence properties.     

Synthesis and characterization of Sm^3＋-doped CeO2 powders

Sm^3＋-doped Ce02 （denoted as Ce1-xSmxO2） powders with different morphologies were successfully synthesized via a precursor-growth-calcination approach, in which precursor was first synthesized by a hydrothermal method and Ce1-xSmxO2 powders were finally obtained through a calcination process. The products were characterized with X-ray diffractometry（XRD）, field emission scanning electron microscopy（FE-SEM） and fluorescence spectroscopy. The results reveal that the Ce1-xSmxO2 powders obtained by calcining the precursors prepared in the absence and presence of poly（vinyl pyrrolidone） （PVP） exhibit bundle-and sphere-like morphology, respectively. The possible growth process was proposed by preparing a series of intermediate morphologies during the shape evolution of CeO2 based on the SEM image observation. It is also found that the luminescence intensity of bundle-like Ce1-xSmxO2 is enhanced in comparison with that of sphere-like one due to its special morphology.     

Determination of H^＋ diffusion coefficient in the course of H^＋ response of a W/WO3 pH electrode

A WAVO3 pH electrode was prepared by a method of sol-gel. In order to study the H^＋ response dynamic mechanism, the electrochemical impedance spectroscopy （EIS） experiment was conducted. It was found that the H^＋ response course is controlled by the H^＋ diffusion from the solution to the WO3 film, based on the analysis of EIS spectra. The EIS and potential step method were used to determinate the H＋ diffusion coefficient （D） in the course of H^＋ response of this WAVO3 electrode, and the values of D calculated by these two method correspond very well, which all are about 10^-19cm^2/s The imposed different potential steps make little effect on the calculation of H^＋ diffusion coefficient, and it was found that the limiting Cottrell equation of short elapsed time fits well to the current transient caused by a potential step, based on the analysis of the time constant.     

生物复合陶瓷材料CaSiO3＋B2O3＋SrCO3＋CaF2＋ZnO／HA的制备及性能

在无压烧结条件下,制备CaSiO3 B2O3 SrCO3 CaF2 ZnO/HA生物复合材料.用XRD分析复合材料的相组成,用SEM观察其微观结构和形貌.结果表明:随着烧结温度的升高,复合材料的弯曲强度提高:硅灰石以玻璃相填充于材料的间隙,改善了复合材料的强度.     

Effect of Er^3＋ dopant on microstructure and photocatalytic property of nano-TiO2

The nano-TiO2 doped with Er^3＋ were prepared from Ti（OC4H9）4 by sol-gel method, and the effect of Er3＋ dopant on microstructure and photocatalytic activity of nano-TiO2 was studied. The phase composition and crystallite sizes of Er^3＋-doped TiO2 samples were analyzed by X-ray diffractometry （XRD） and transmission electron microscopy （TEM）. The photocatalytic activity of Er^3＋-doped TiO2 was investigated at different doping concentrations and different heat treatment temperatures in the photocatalytic degradation of phenol with 365 nm wavelength ultraviolet light irradiation. The results show that both the anatase phase and futile phase are formed in doped TiO2. Er^3＋ doping hinders the crystal transformation and makes the TiO2 crystallite size change smaller as well as increases the photocatalytic activity of TiO2 greatly. When Er3＋ doping concentration is 1.2%（mass fraction） and the heat treatment temperature is 700 ℃, the photocatalytic activity of Er^3＋-doped TiO2 is favorite in the experimental range. The photocatalytic activity is enhanced by about 18% compared with that of the pure TiO2 and almost approaches the photocatalytic activity of P25-TiO2.     

Synthesis of GdF3 from the Gd2O3-NH4HF2 system

GdF3 was synthesized with Gd2O3 and NH4HF2 under atmospheric pressure and vacuum. The effects of pressure,temperature,and reactant ratio on the reaction process were investigated. A new mechanism for the synthesis of GdF3 was proposed. Powdered Gd2O3 started to react with NH4HF2 at low temperature,and the products were GdNH4F4,NH4F,NH3,and H2O. GdNH4F4 decomposed to GdF3 and NH4F after further high-temperature treatment,accompanying the volatilization and decomposition of NH4F. The whole process could be divided into three steps： synthesis,decomposition,and deamination. The initial and final reaction temperatures decreased under vacuum condition. An optimized process for the preparation of GdF3 was obtained： synthesis under atmospheric pressure at low temperature and decomposition and deamination under vacuum at high temperature.     

Influence of La and Dy on the properties of the long afterglow phosphor CaAl2O4: Eu, Nd

The long afterglow phosphor CaAl₂O₄:Eu²⁺,Nd³⁺ was prepared by the high temperature solid-state reaction method, and the influence of La³⁺ and Dy³⁺ on the properties of the long afterglow phosphor was studied by X-ray diffraction (XRD), photoluminescence (PL), and thermoluminescence (TL). The XRD pattern shows the host phase of CaAl₂O₄ is produced and no impurity phase appears. The peak wavelength of the phosphor does not vary with La³⁺ and Dy³⁺ doping. It implies that the crystal field, which affects the 5d electron states of Eu²⁺, is not changed dramatically after doping of La³⁺ and Dy³⁺. The TL spectra indicate that the phosphor doped with La³⁺ or Dy³⁺ produces different depths of trap energy level. In the mechanism of long afterglow luminescence, it is considered that La³⁺ or Dy³⁺ works as trap energy level. The decay time lies on the number of electrons in the trap energy level and the rate of the electrons returning to the excitation level.     

Ba2+替代对Sr4Al14O25:Eu2+, Dy3+结构和发光性能的影响

采用高温固相反应按化学式Sr4-xBaxAl14O25: Eu2+, Dy3+(x＝0, 0.8, 1.6, 2.4, 3.2, 4) 配比原料,合成长余辉发光材料。X射线衍射分析表明,当x＝0.8时,产物物相为单斜结构SrAl2O4和磁铅矿结构SrAl12O19共存;当x>1.6时,产物主相转变为BaAl2O4六角结构。对所得样品采用360 nm光照,发射光谱表明,样品发光是以Eu2+为发光中心,由Eu2+电子4f65d-4f7跃迁所致,并且随着Ba掺入量的增加,样品发射光谱峰位产生移动,这是由于Sr2+取代产物中Ba2+位置后,导致晶格收缩,影响Eu2+的5d能级劈裂,从而影响电子4f65d-4f7跃迁。余辉光谱显示x>1.6时,产物的余辉发光是以BaAl2O4基质中Eu2+为发光中心。余辉衰减检测和热释光谱分析发现不同掺Ba量的样品余辉衰减快慢不同,是由于其中存在的陷阱能级深度不同,且陷阱能级越深,其余辉时间越长     

Eu^2＋在Sr4Al14O25基磷光体中能量传递行为的研究

合成了3种不同Eu掺杂量的Sr4Al14O25，Dy^3 发光粉体，发现当Eu掺杂量低于0．012mol时，发射光谱中存在2个主发射峰，分别位于407nm和494nm。随着Eu掺杂浓度增加，407nm发射峰逐渐消失，而494nm主发射峰增强。结合Sr4Al14O25，晶体结构和激发．发射光谱，建立了2种Eu发光中心之间的能量传递模型，对实验现象进行了合理的解释。余辉衰减曲线测试结果表明，3种磷光体试样均具有长余辉性能，尤其Sr4Al14O25：Eu0.0l2，Dy0.024试样，其余辉时间在人眼可视亮度水平可持续20h以上。     

掺杂的SrAl2O4:Eux2+,Dyy3+长余辉粉的合成、表征及发光性质

采用自蔓延高温合成法制备了组成为SrAl2O4:Eu2+x,Dy3+y的2组(x:y=1:1,x:y=1:2)12种铝酸锶长余辉发光粉,测试结果表明,组成为SrAl2O4:Eu2+0.0125,Dy3+0.0125的发光亮度最好。以上述配比为依据,又分别引入了可以用于制备荧光材料的阳离子Li+、Be2+,以及既可以用于制备荧光材料也可以用于制备自激活荧光材料的阳离子Zn2+、Cd2+、Pb2+,共制得5个系列22种铝酸锶(SrAl2O4)长余辉发光粉。Zn2+0.0125的掺杂使得SrAl2O4:Eu2+0.0125,Dy3+0.0125的余辉亮度得到大幅度提高,而且SrAl2O4:Eu2+0.0125,Dy3+0.0125,Zn2+0.0125的衰减速度也明显慢于SrAl2O4:Eu2+0.0125,Dy3+0.0125。X射线衍射结果表明,掺杂少量稀土离子(Eu2+和Dy3+)不会改变SrAl2O4基质的晶体结构。另外,透射电镜分析和粒度分布结果表明,产物为疏松多孔的蘑菇云状固体,粒度在10μm左右。     

掺杂离子对Gd2O2S:Eu3+磷光体结构和发光性能的影响

采用高温固相反应法制备出新型红色长余辉发光材料Gd2O2S:Eu3+,Xn+(X为Mg、Si、Ti中的一种或两种),研究掺杂离子对Gd2O2S:Eu3+磷光体的晶体结构、形貌粒度和发光性能的影响。通过X射线粉末衍射(XRD)、扫描电镜(SEM)和分光光度计等对合成产物进行分析与表征。结果表明:掺杂离子没有改变Gd2O2S:Eu3+磷光体的晶体结构,颗粒的形貌为类球形,分散性良好。同时,掺杂离子显著地延长发光材料Gd2O2S:Eu3+的余辉时间,并显示纯正的红色发光。     

SrAl2O4：Eu^2＋，Dy^3＋长余辉光致发光材料的固相反应法合成与特性

采用高温固相反应法，在还原气氛下制备了掺稀土离子Eu^2 和Dy^3 的铝酸锶长余辉光致发光材料。XRD研究表明，所制备的铝酸盐具备SrAl2O4的晶体结构。SrAl2O4：Eu^2 ，Dy^3 发光材料的发光光谱是中心位于520nm的带状谱，激发峰波长范围位于300nm～500nm，发光余辉可持续12h以上。研究了SrAl2O4：Eu^2 ，Dy^3 发光材料的耐温性和耐水性，结果表明，随热处理温度升高，发光亮度下降；水浸使发光材料与水反应生成水化物，使发光性能下降。     

Luminescent properties of Sr2MgSi2O7 and Ca2MgSi2O7 long lasting phosphors activated by Eu, Dy

Long lasting afterglow phosphors Sr₂MgSi₂O₇:Eu,Dy and Ca₂MgSi₂O₇:Eu,Dy were prepared by solid-state reaction method. It is revealed by the results that both phosphors show two emission peaks that are caused by the different emitting centers Eu²⁺ held in the host lattice. Wavelength shift was observed due to the slight differences in the structure parameters of the two hosts. Investigation on afterglow property shows that Sr₂MgSi₂O₇:Eu,Dy phosphor held a better afterglow property than Ca₂MgSi₂O₇:Eu,Dy phosphor. Thermal simulated luminescence study indicates that the long afterglow is generated by a higher trap concentration formed by the co-doped rare earth ions within the host.     

Sr/Ca比例对Sr3-xCaxAl2O6:Eu2+, Dy3+结构与发光性能的影响

采用高温固相法合成了长余辉发光材料Sr3-xCaxAl2O6:Eu2+, Dy3+（x = 0, 1, 2, 3）,研究了样品的结构、光致发光、余辉发光和热释发光性能。结果表明：所制备的样品具有相似的结构,均为立方结构的Sr3-xCaxAl2O6。Sr/Ca比例的变化并没有引起基质结构的相变,但对样品的发光性能产生了显著影响;样品的余辉衰减曲线符合双指数衰减,但不同样品的初始强度和衰减快慢不同;通过调节锶钙比的方法,可以有效调控样品光致发光的颜色和余辉衰减特性。此外,测试样品的热释光曲线发现当样品中有两种不同深度的陷阱能级时,样品的余辉强度明显减弱,这可能与电子在不同的陷阱能级的转移有关。     

Luminescent properties of CaMgSi2O6 and Ca2MgSi2O7 phosphors activated by Eu, Dyand Nd

Long lasting alkaline earth silicates, CaMgSi₂O₆:Eu,Dy,Nd, Ca₂MgSi₂O₇:Eu,Dy,Nd and Ca₂MgSi₂O₇:Eu,Dy, were prepared under a reducing atmosphere by a solid-state reaction. The obtained phosphors were characterized by means of X-ray diffraction (XRD) and their photoluminescence spectrum (PLS). The Ca₂MgSi₂O₇:Eu,Dy,Nd phosphor showed a two-peak emission at 447 and 516 nm, while the CaMgSi₂O₆:Eu,Dy,Nd phosphor generated only one peak emission at 447 nm. This phenomenon is due to the different lattice sites occupied by Eu²⁺ in the Ca₂MgSi₂O₇ and CaMgSi₂O₆ lattices. The electron affinity (ea) values for Eu²⁺ in [EuO₆] and [EuO₈] were calculated to be 4.2 and 1.9 eV, respectively. The Nd co-doped phosphor revealed a better afterglow characteristic, indicating that a deeper trap center was formed in the phosphor by the doping of trivalent Nd ions.     

BRIGHT LONG AFTERGLOW PHOSPHORESCENCE GLASS MADE OF SrAl2O4 ： Eu^2＋, Dy^3＋ AND GLASS FRITS

Bright long afterglow phosphorescence glasses were prepared by using SrAl2O4： Eu^2＋, Dy^3＋ phosphors and suitable glass frits together. The SrAl2O4： Eu^2＋, Dy^3＋ phosphors were initially prepared by the solid reaction method. Three kinds of glass frits were prepared to match the SrAl2O4： Eu^2＋, Dy^3＋ phosphors. Effects of the compositions of the glass frits, the ratios of the phosphors to the frits us well us the firing temperature and firing times on the properties of the samples were discussed. XRD analysis indicated the samples exhibited the typical diffraction peaks of SrAlwO4： Eu^2＋, Dy^3＋. The emission spectra of the samples showed broad bands peaking at 510nm.The excitation spectra of the samples showed broad bands ranging from 300 to 480hm. These are believed due to the 5d4f-4f transitions of Eu^2＋ in the SrAl2O4： Eu^2＋, Dy^3＋ phosphors. The afterglow luminescence of the samples excited by a 40W fluorescence lamp for 30min can be observed in the dark for more lOh with the naked eyes. It can find wide applications in many fields.