Synthesis and luminescence characteristics of terbium（III） activated NaSrBO3

The thermoluminescence (TL) and photoluminescence (PL) properties of the phosphor NaSrBO 3 :Tb 3+ were reported and discussed. The combustion technique was used for the synthesis of polycrystalline samples of NaSrBO 3 :Tb 3+ . The TL glow curve of the compound had a simple structure with a single peak at 434 K. TL sensitivity of the phosphor was found to be more than that of (LiF:Mg,Cu,P). The TL glow curve was studied as a function of concentration of dopant and dose of gamma ray irradiation. The kinetic parameters of the thermoluminescence of NaSrBO 3 : Tb 3+ were calculated employing the peak shape method. The photoluminescence (PL) properties of Tb 3+ doped in NaSrBO 3 were studied over the 200-400 nm excitation range. The excitation spectra of NaSrBO 3 :Tb 3+ consisted of single narrow band peaking at about 236 nm. The emission spectra monitored at 236 nm excitation consisted of a series of sharp lines peaking at 489, 544, 586 and 622 nm corresponding to the 5 D 4 → 7 F j (j=3,4,5,6) transitions within the 4f 8 configurations of Tb 3+ .     

Thermoluminescence study of rare earth ion （Dy^3＋） doped LiF：Mg crystals grown by EFG technique

This work describes investigation of radiation dosimetry characteristics of magnesium (Mg) doped lithium fluoride (LiF) crystals co-doped with different concentrations of dysprosium (Dy). These crystals were grown by edge defined film fed crystal growth (EFG) tech-nique. Thermoluminescence (TL) measurements were made on as grown (AG) and annealed (AN) crystals after they were irradiated with a gamma dose of 15 Gy. The influence and advantage of optimized Dy3+ concentration in enhancing the thermoluminescence (TL) properties of LiF:Mg samples were discussed. The normalized peak height of the annealed crystals was nearly 3 times that of the as grown crystals for the particular concentration samples irradiated with Co60 gamma source showed linearity up to 10 Gy. Thermoluminescence signal observed over a period of one month showed negligible fading. Thermoluminescence glow curve structure of optimized phosphor remained stable for higher doses of gamma rays of 103 Gy. Glow curve was analyzed using computer glow curve deconvolution (CGCD) method and trapping parame-ters were calculated.     

Comparison of thermoluminescence spectra of MgB407 doped with dysprosium and manganese

A series of magnesium borate phosphors MgB4O7：Dy, MgB4O7：Mn and MgB4O7：Dy,Mn were prepared and their ther-moluminescence （TL） emission spectra were measured. TL emission bands in 480, 575 and 660 nm at 200 and 360 oC were observed in the MgB4O7：Dy due to the transitions of the trivalent rare earth ions Dy3＋. The glow peaks of broad wavelength band around~580 nm at 180 and~290 oC were observed in MgB4O7：Mn due to the emission of Mn2＋ions. The main glow peak of MgB4O7 co-doped with Dy and Mn appeared in 580 nm at~360 oC. When MgB4O7 was co-doped with Dy （0.5 mol.%） and different concentrations of Mn （0.01 mol.%-1.0 mol.%）, the peak in 580 nm at 360 °C was intensified and broadened as the concentration of Mn increased, while the peaks in 480, 680 and 750 nm below 300 °C remained the characteristic emission of Dy3＋and were reduced in intensity. The emission spectra of the MgB4O7：Dy,Mn phosphor showed that the competitive de-excitation processes between Dy3＋and Mn2＋existed and the energy transfer occurred from Dy3＋to Mn2＋. These results meant that rare earth and Mn ions in MgB4O7：Dy,Mn might cause the formation of defects complex that dominated the traps and recombination.     

Thermoluminescence studies on γ-irradiated CaF2：Dy：Pb：Na single crystals

Thermoluminescence (TL) glow, thermoluminescence emission (TLE) and thermal decay (TD) of optical absorption (OA) bands were studied on γ-irradiated CaF2:Dy (0.010at.%):Pb (0.188at.%):Na (0.026at.%) single crystals (hereafter called crystal-I). The TL glow ex-hibited four glow peaks in the temperature region 300-600 K. The TL response with dose was studied up to ～7.5 kGy. The total glow showed linear, supra linear and exponential growth with dose. The TLE showed bands characteristic of Dy3+ ions (around 1.65, 1.87, 2.18 and 2.63 eV) and sodium associated (SA) colour centres (CCs) such as MNa (around 1.67 eV) and XNa (a new SA CC, with an emission band around 2.63 eV). The OA bands of MNa CC around 3.23 and 2.07 eV were found to decrease with temperature almost in accordance with the TL glow. The R+A centre absorption around 2.48 eV was found to grow with temperature initially and then decayed. The formation/growth of the CCs R+A and XNa might be from the conversion of the irradiation produced CC MNa- An attempt was made to explain the TL mechanism in the present system.     

Thermoluminescence Characteristics of SrB6O10 ： Tb

SrB6010：Tb phosphor was synthesized by high-temperature solid state reaction. The influences of Ce or Li as a co-dopant, Tb concentration and irradiation dose exposure on TL of SrB6010 ： Tb were investigated. Results show that Ce or Li as a co-dopant can not improve the sensitivity of SrB6010：Tb phosphor. TL response depends on Tb concentration and 0.02 is the optimum in the concentration range from 0.01 to 0.10. Using the optimum Tb concentration, we calculated the kinetic parameters of SrB6010：Tb employing the peak shape method, and suggested the phosphor obeying the second order kinetics. TL emission intensity is linearly dependent on the irradiation dose within the dose range of 50 - 200 Gy. The characteristic Tb^3＋ ion emission was observed in TL emission spectrum.     

Luminescence and low temperature trap centers in mixed rare earth borate crystal

The single crystal of this compound has been grown from melt by using a conventional Czochralski technique. The temperature dependent luminescence spectra were measured using a 265 nm laser as an exciting source in the range of 10–300 K. The scintillation decay time profile was measured and found to have three components. The influence of the trap centers on the luminescence properties was studied by means of thermoluminescence (TL) glow peak analysis. Low temperature TL glow peaks were measured in the temperature range of 10–300 K at the heating rate of 0.1 K/s for X-ray irradiated sample. The TL glow peak consists of two dominant peaks at 88 and 109 K. Several glow peaks with a complex nature causes the decrease in the light yield at temperatures below 250 K, and along with long scintillation decay components were observed. The trap parameters such as activation energy (E), frequency factor (s) and order of kinetics (b) were calculated using various standard methods such as peak shape (PS), variable heating rate (VHR), initial rise (IR) and computerized glow curve deconvolution (CGCD).     

Combustion synthesis and luminescence characteristic of rare earth activated LiCaBO3

Lithium calcium borate (LiCaBO3) polycrystalline thermoluminescence (TL) phosphor doped with rare earth (Tb3+ and Dy3+) elements was synthesized by novel solution combustion synthesis. The reaction produced very stable crystalline LiCaBO3:D(D=Tb3+ and Dy3+) phosphors. These rare earth doped phosphors material showed maximum TL sensitivity with favorable glow curve shape. TL glow curve of X-ray irradiated that LiCaBO3:Tb3+ and LiCaBO3:Dy3+ samples showed two major well-separated glow peaks. The TL sensitivity of these phosphors to X-ray radiation was comparable with that of TLD-100(Harshaw). Photoluminescence spectra of LiCaBO3:Tb3+ and LiCaBO3:Dy3+ showed the characteristic Tb3+ and Dy3+ peaks respectively. TL response to X-ray radiation dose was linear up to 25 Gy.     

Isothermal section at 1070 K of the phase-equilibrium diagrams for {Tb,Dy, Ho}-Cr-B systems

The systems {Tb, Dy, Ho}-Cr-B have been studied by means of x-ray analysis. isothermal sections at 1070 K have ben plotted. Previously known borides of the YCrB₄ type structure (space group Pbam) have been confirmed: TbCrB₄, DyCrB₄, and HoCrB₄. A new compound Ho₃CrB₇ with a Er₃CrB₇ type structure (space group Cmcm): a=0.3422 (1), b=1.5714 (5), c=0.9304 (4) nm, R=0.12 has been obtained for the first time. The coordinates of the atoms and their temperature parameters are refined.Lvov University. Translated from Poroshkovaya Metallurgiya, No. 5, pp. 48–50, May, 1993.     

Thermoluminescence characteristics of NaSr4（BO3）3：Ce^3＋ under β-ray irradiation

The thermoluminescence (TL) properties of Ce3+ doped NaSr4(BO3)3 phosphor under the β-ray irradiation were reported. The polycrystalline sample was synthesized by high temperature solid-state reaction. The TL glow curve of NaSr4(BO3)3:Ce3+ phosphor was com-posed of only one peak. TL kinetic parameters of NaSr4(BO3)3:Ce3+ were deduced by the peak shape method, the activation energy (E) was 0.590 eV and the frequency factor was 1.008×106s-1. TL dose response was linear in the range of measurement. The 3-dimensional (3D) TL emission spectrum was also recorded, the emission spectrum consisted of two bands located at 441 and 479 nm respectively, corresponding to the characteristic 4f05d1→2F(5/2,7/2) transitions of the Ce3+ ion. The fading behavior of the NaSr4(BO3)3:Ce3+ phosphor over a period of 15 d was also studied.     

Thermoluminescence Characteristics of SrB6 O10:Tb

SrB6O10:Tb phosphor was synthesized by high-temperature solid state reaction. The influences of Ce or Li as a co-dopant, Tb concentration and irradiation dose exposure on TL of SrB6O10:Tb were investigated. Results show that Ce or Li as a co-dopant can not improve the sensitivity of SrB6O10:Tb phosphor. TL response depends on Tb concentration and 0.02 is the optimum in the concentration range from 0.01 to 0.10. Using the optimum Tb concentration, we calculated the kinetic parameters of SrB6O10:Tb employing the peak shape method, and suggestedthe phosphor obeying the second order kinetics. TL emission intensity is linearly dependent on the irradiation dose withinthe dose range of 50 ～ 200 Gy.The characteristic Tb3 ion emission was observed in TL emission spectrum.     

Photoluminescence and thermoluminescence properties of dysprosium doped zinc metaborate phosphors

Polycrystalline powder samples of dysprosium doped Zn（BO2）2 phosphors were prepared by solid state reaction in air at high temperature and characterized by X-ray powder diffraction. The IR, Photoluminescence （PL）, diffuse reflectance and three-dimensional （3D） thermoluminescence （TL） emission spectrum after 60^Co gamma ray irradiation were investigated. The characteristic 3D TL emission bands at about 425, 481 and 573 um with a main emission band of around 573 um were attributed to the host emission, 4^F9/2→6H15/2 and F9/2→6^H13/2 f-f transitions of Dy^3＋ ions. No emission from Dy^2＋ ions was observed in the measurement wavelength range. The TL-dose response of the Zn（BO2）2：Dy polycrystalline powder sample to gamma ray radiation in the range from 1 to 100 Gy at clinical dose levels was almost linear. The experimental results showed that Zn（BO2）2：Dy had potential use as the materials of gamma-ray thermoluminescence dosimeter （TLD） for clinical dosimetry.     

Luminescence properties of dysprosium doped YVO4 phosphor

Trivalent dysprosium(Dy~(3+)) activated nanocrystalline yttrium vanadate(YVO_4) phosphor was synthesized via co-precipitation method. The prepared samples were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), optical absorption and photo luminescence(PL) techniques. The XRD patterns reveal the tetragonal crystalline phase. SEM images reveal that Dy doped YVO_4 nanocrystals are agglomerated. EDAX confirms the formation of YVO_4:Dy. FTIR spectrum shows two strong absorption bands at 459 and 761 cm~(-1). Optical absorption spectrum showed the surface defects in the as-prepared samples. The PL emission spectrum shows two characteristic emission bands at 485 and 575 nm. The strong yellow emission peak at 575 nm is assigned to ~4 F_(9/2)→~6 H_(13/2) hyper sensitive transition of Dy~(3+) ions, Study of CIE chromaticity diagram indicates the suitability of the phosphor for the development of yellow-green LEDs.     

Isothermal sections of phase-equilibrium diagrams for the systems {terbium,dysprosium}-tungsten-boron at 1270 K

Interaction of components of the systems {Tb, Dy}-W-B have been studied by means of x-ray analysis. Isothermal sections of phase-equilibrium diagrams of the systems at 1270°C have been constructed. The existence of ternary borides with structures of the types YCrB₄ and Er₃CrB₇ has been confirmed. Solid solutions based on binary compounds and other components are not found.     

Effect of a catalyst on the kinetics of reduction of celestite (SrSO4) by active charcoal

Reduction of celestite (SrSO₄) powder with particles of active charcoal has been studied extensively in the absence and presence of catalysts. The optimum temperature at the charging zone has been optimized to get a maximum water-soluble strontium sulfide value. The strontium value has been analyzed using a chemical method, which was verified by the instrumental method using an inductively coupled plasma-optical emission spectrophotometer (ICP-OES). The conversion-time data have been analyzed by using a modified volume-reaction (MVR) model, and the effect of the catalyst on kinetic parameters has been elucidated. It was found that potassium carbonate, potassium dichromate, sodium carbonate, and sodium dichromate catalysts were found to enhance the reaction rate quite satisfactorily in the reduction of the celestite (SrSO₄).     

2,3,5-吡啶三酸与重稀土配合物的合成、表征及光致发光性质

采用水做溶剂,用2,3,5-吡啶三酸做配体和重稀土铽、镝、铒、镱、镥、钇六种稀土元素的氯化物在常温下反应合成了六种重稀土的配合物。通过EDTA络合滴定分析,确定了六种配合物中稀土离子含量;并对配合物进行了熔点测定、红外光谱测试,并测试了铽和镝配合物的光致发光性质,结果表明,铽和镝配合物在紫外光的激发下具有良好的发光性质。     

EXAFS investigation and luminescent properties of nanosized Tb: Lu2O3 phosphors

Nanosized terbium doped Lu2O3 phosphors were synthesized via a modified co-precipitation processing.The as-prepared Tb:Lu2O3 phosphors was consisted of well crystallized nanosized sphere particles with a diameter of about 30 nnx Local structure of Tb ions in Lu2O3 lattice was investigated by an analytical approach based on Fourier transformation of the extended X-ray absorption fine structure(EXAFS) data.X-ray near edge structure (XANES) spectra suggested that all Tb ions doped were tervalonce.EXAFS results indicated that Tb ions have entered the Lu2O3 cubic lattice by means of solid solution.The coordination number and first shell Tb-O distance dropped with the increasing of Tb concentration.Emission spectra of the phosphors was shown to be typical for Tb3+ with main components at 542,550 and 490 nm,derived from irradiative relaxation of 5D4 level.The emission intensity decreased severely with the increasing of Tb concentration from 1 mol.% to 15 tool.%,suggesting a significant concentration quenching above 1 mol.% Tb.The reduction of emission intensity was interpreted by higher distortion derived relaxation among the surface state resident Tb3+ ions.     

Experimental investigation on the enthalpies of formation of the DyFe2, DyFe3, Dy2Fe17, ErFe2, and ErFe3 intermetallic compounds

The enthalpies of formation at 298.15 K for five intermetallic phases in the Fe-Dy and Fe-Er binary systems have been determined by indirect solution calorimetry in liquid aluminum at 1100 K. The phases were Fe₂Dy, Fe₃Dy, and Fe₁₇Dy₂ in the Fe-Dy system and Fe₂Er and Fe₃Er in the Fe-Er system. The following mean values of Δ _f H _{298.15 K} are reported: −11.1 kJ/mole for Fe_2/3Dy_1/3, −7.7 kJ/mole for Fe_3/4Dy_1/4, −1.9 kJ/mole for Fe_17/19Dy_2/19, −12.5 kJ/mole for Fe_2/3Er_1/3, and −7.9 kJ/mole for Fe_3/4Er_1/4. The measured enthalpies of formation of the Fe₂Dy and Fe₂Er compounds are almost equal, as are the enthalpies of formation of the Fe₃Dy and Fe₃Er compounds. The results are compared with earlier experimental data, with values predicted by Miedema’s semiempirical method and with calculated results obtained by Colinet and Pasturel using a tight binding model.     

Low temperature thermoluminescence behaviour of Y2O3 nanoparticles

Y_2O_3 nanoparticles were investigated using low temperature thermoluminescence (TL) experiments. TL glow curve recorded at constant heating rate of 0.4 K/s exhibits seven peaks around 19, 62, 91,115,162,196 and 215 K. Activation energies and characteristics of traps responsible for observed curves were revealed under the light of results of initial rise analyses and T_(max)-T_(stop) experimental methods. Analyses of TL curves obtained at different stopping temperatures resulted in presence of one quasi-continuously distributed trap with activation energies increasing from 18 to 24 meV and six single trapping centers at49, 117, 315, 409, 651 and 740 meV. Activation energies of all revealed centers were reported in the present paper. Structural characterization of Y_2O_3 nanoparticles was accomplished using X-ray diffraction and scanning electron microscopy measurements.     

Luminescence properties of near-UV excitable yellow-orange light emitting warm CaSrAl2SiO7:Sm3+ phosphors

Single-phase CaSrAl_2 SiO_7:Sm~(3+) phosphors were synthesized by traditional high temperature solid state reaction method. Formation of samples and phase analysis were confirmed by X-ray diffraction technique. Morphology was done by field emission scanning electron microscopy and elemental compositions were confirmed by energy dispersive X-ray analysis. Present phosphors have tetragonal crystallography with space group P42_1 m. Average crystallite size was calculated by using Scherrer and Williamson-Hall method. Photoluminescence study of CaSrAl_2 SiO_7:Sm~(3+) phosphor was investigated.Under different excitation wavelengths, PL spectra consist of four emission bands at 564, 570, 601 and650 nm. The emission bands located at 564 and 570 nm are associated with the transition ~4 G_(5/2)→~6 H_(5/2)while emission bands at 601 and 650 nm are due to ~4 G_(5/2)→~6 H_(7/2) and ~4 G_(5/2)→~6 H_(9/2),respectively.Intense emission was obtained when phosphor was excited under 404 nm wavelength. Non-radiative energy transfer process involved in concentration quenching, was also discussed. CIE coordinate is found in yellow-orange region, hence CaSrAl_2SiO_7:Sm~(3+) phosphors emit yellow-orange light when efficiently excited by near UV(～400 nm) LED chip. Color purity and CCT of the phosphor were determined; CCT suggests that present phosphor is a good candidate as a warm yellow-orange color emitting phosphor. Effect of different heating rates and different UV exposure time on the TL glow curve of the phosphor was investigated. Activation energies and kinetic parameters for different traps were calculated by using peak shape method. TL emission spectrum was also recorded. Present article explains all the possible mechanisms associated with luminescence process in CaSrAl_2 SiO_7:Sm~(3+) phosphors.     

Compounds with Th6Mn23-type structures in alloys of the rare-earth metals with manganese and iron

Summary The powder metallurgy method was used for preparing alloys of the rare-earth metals (R) with manganese or iron, containing 79.2 at.% of the latter elements. The existence in these alloys of the compounds R₆Mn₂₃ (R = Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tu, Lu, Y) and R₆Fe₂₃ (R = Gd, Tb, Dy, Ho, Er, Tu, Yb, Lu, Y), having structures of the Th₆Mn₂₃ type was established or confirmed (the lattice constants are listed in Table 2).