Effect Of Tb3 Research Articles

Effect of Tb3+ substitution on structural, electrical and magnetic properties of sol–gel synthesized nanocrystalline nickel ferrite

Abstract A series of NiTb x Fe 2− x O 4 ( x = 0.0, 0.1, 0.2, 0.3) nanoparticles with small size have been prepared using sol–gel technique. The effect of Tb 3+ substitution on the crystalline phase, crystallite size and magnetic, electrical and dielectric properties has been investigated in detail. The lattice constant shows an increasing trend with increase in Tb 3+ ion concentration. The high frequency tetrahedral vibration band ν 1 and the low frequency octahedral vibration band ν 2 in the FTIR spectra are in the reported range. The observed shift in ν 2 towards lower wave number side with increase in terbium concentration suggests the occupation of Tb 3+ ions predominantly on octahedral sites. Saturation magnetization is found to decrease with terbium addition. Magnetic hysteresis loss is observed to decrease up to x = 0.2 and then increases. The room temperature resistivity values are found to increase with terbium content. The observed dielectric dispersion with frequency is explained on the basis of Maxwell–Wagner two-layer model and electron hopping mechanism which is responsible for conduction and polarization. Dielectric constant and dielectric loss are found to decrease by terbium addition and is explained in terms of the decrease in hopping rate due to the substitution of Fe 3+ ions by Tb 3+ ions on the octahedral sites. The increased resistivity and reduced dielectric loss attained in terbium doped ferrite is promising as it is desirable for high frequency applications.

Effect of Tb3+ concentration on luminescence properties of Ce/Tb/Eu co-doped borosilicate glasses for white LEDs

Ce, Tb and Eu single and ternary doped borosilicate glasses were prepared and effect of Tb3+ concentration on luminescence properties of ternary co-doped glasses were analyzed by utilizing emission spectra, excitation spectra, the Commission International de I’Eclairage (CIE) colorimetric system and fluorescence decay curves. The results show that Tb3+ concentration significantly affects spectral intensities of ternary co-doped glasses when excited by near ultraviolet (NUV). With the increasing of Tb3+ concentration, the blue emission of Ce3+ is weakened and the red emission of Eu3+ is slightly enhanced. Both the color coordinates and correlated color temperatures (CCTs) can be adjusted by Tb3+ concentration. Besides, the energy transfers from Ce3+ to Tb3+ and from Tb3+ to Eu3+ were observed. Measured characteristic lifetimes of Tb3+ indicate that the energy transfer from Ce3+ to Tb3+ tends to predominate in whole process. The studies show that Ce/Tb/Eu ternary doped borosilicate glasses might be promising luminescence materials for NUV pumped white LEDs.

The role of terbium cation substitution on the magnetic properties of cobalt ferrite nanoparticles

Terbium substituted cobalt ferrite nanoparticles with composition of CoFe2−xTbxO4 (x=0–0.5 in a step of 0.1) were prepared employing a reverse micelle process. The effect of Tb3+ cations substitution on structural and magnetic properties of cobalt ferrite nanoparticles was investigated. X-ray diffraction and field-emission scanning electron microscopy evaluations demonstrated that the single phase spinel ferrites with a narrow size distribution were obtained. Mössbauer spectroscopy was used to determine the site preference of constitutive elements. The results confirm the preference of terbium cations for tetrahedral sites. Vibrating sample magnetometer was employed to probe the magnetic properties of the samples at room temperature. It was found that with an increase in terbium content, the coercive field decreases while the saturation of magnetization increases. Magnetic dynamics of the samples was studied by measuring ac magnetic susceptibility versus temperature. The phenomenological Neel–Brown and Vogel–Fulcher models were employed to distinguish between the interacting or non-interacting system. Results exhibited that there is a strong interaction among fine particles.

Tunable Blue-Green Color Emission and Energy Transfer of Ca2Al3O6F:Ce3+,Tb3+Phosphors for Near-UV White LEDs

A series of new luminescent emission-tunable phosphors Ca2Al3O6F:Ce3+,Tb3+ have been synthesized by a high temperature solid-state reaction. The UV–vis reflectance, photoluminescence emission and excitation spectra, the lifetime, and the effect of Tb3+ concentration are investigated in detail. The intense green emission is realized in the Ca2Al3O6F:0.08Ce3+,0.05Tb3+ phosphors on the basis of the highly efficient energy transfer from Ce3+ to Tb3+ with an efficiency of over 90%. The energy transfer mechanism from Ce3+ to Tb3+ in the Ca2Al3O6F host was ascribed to the exchange interactions, and the formation of the Ce–Ce clusters and Ce–Tb clusters should be the reason for the high energy transfer efficiency. The critical distance of the energy transfer has also been calculated by the concentration-quenching method. These results indicate that the Ca2Al3O6F:Ce3+,Tb3+ phosphors have potential applications as a near UV-convertible phosphor for white light-emitting diodes because of its broad excitation in the near-ultraviolet range and the efficient green emission light.

Dielectric behavior and AC conductivity of Tb3+ doped Ni0.4Zn0.6Fe2O4 nanoparticles

Terbium doped Ni–Zn ferrite, Ni0.4Zn0.6TbxFe2−xO4 (x=0, 0.05, 0.1, 0.15 and 0.2) have been prepared through sol–gel technique. Formation of single phase FCC spinel structure is identified in all the compositions using X-ray diffraction technique. The effect of Tb3+ doping on the crystalline phase, crystallite size, dielectric properties and AC conductivity has been investigated in detail. Lattice constant is observed to increase with terbium content; but beyond certain concentration of terbium (x>0.15), it decreased. DC resistivity measurements were carried out in the temperature range 300–523K. All the compositions exhibited usual semiconducting nature of ferrites and the resistivity of the samples found to increase with terbium content up to x=0.15. The metallic behavior of the doped samples observed in the lower temperature region is explained in terms of elastic and inelastic scattering due to the rare earth ions. The investigations on dielectric constant, dielectric loss and AC conductivity was carried out in the frequency range 100Hz–20MHz from room temperature to 563K. Frequency dependence of dielectric constant showed normal behavior and is in good agreement with Koop’s phenomenological theory of dielectric dispersion. AC conductivity measurements suggested conduction due to small polaron hopping. AC conductivity as well as dielectric constant is found to increase with temperature and which is due to thermally enhanced drift mobility of charge carriers. The observed decrease in dielectric loss with terbium content up to x=0.15 is explained in terms of increase in resistivity.

LiZnPO4:Tb3+, Ce3+ green phosphors with high efficiency

Tb3+ and Ce3+ co-activated LiZnPO4 phosphors with high luminescence efficiency were synthesized by a high temperature solid-state reaction at 1000°C for 3 h. The XRD patterns, photoluminescence spectra and SEM were recorded and the effects of Tb3+ and Ce3+ concentration, sintering condition on the luminescent properties of as-synthesized phosphors were investigated. The emission spectra under ultraviolet (200–300 nm) radiation showed a dominant peak at 543 nm attributed to the 5D4→7F5 transition of Tb3+, which was greatly enhanced by the co-doping of Ce3+, indicating that there occurred an efficient non-radiative energy transfer from Ce3+ to Tb3+. The optimal doping concentrations of Tb3+ and Ce3+ were determined to be 9% and 10%, respectively.

Photoluminescence and decay behavior of Tb3+ ions in sodium fluoro-borate glasses for display devices

We report the optical absorption, photoluminescence and fluorescence decay properties of Tb3+-doped sodium fluoro-borate (SFB) glasses. Different concentrations of Tb3+-doped SFB glasses were prepared by conventional melt quenching technique using a chemical composition (in mol%) 25Na2O–5LaF3–10CaF2–10AlF3–(50−x) B2O3−x TbF3 (0.01≤x≥4). The Judd-Ofelt model has been adopted to determine the radiative parameters of the 5D4→7F6–3 emission transitions. The effect of Tb3+ ion concentration on the emission from the 5D3,4 excited levels is discussed in detail. The analysis of optimization of Tb3+ ion concentration for efficient green color display devises is reported. The resonance energy transfer mechanism responsible for non-radiative decay rates is clearly explored.

Green-emitting phosphor Na2Gd2B2O7:Ce3+, Tb3+ for near-UV LEDs

An intense green-emitting phosphor Na2Gd2B2O7:Ce3+, Tb3+ is developed on the basis of the highly efficient energy transfer from Ce3+ to Tb3+. The photoluminescence emission and excitation spectra, the lifetime, and the effect of Tb3+ concentration are investigated in detail. Results confirm the occurrence of non-radiative energy transfer from Ce3+ to Tb3+ with an efficiency of over 80%. The intensity ratio of blue emission from Ce3+ and green emission from Tb3+can be tuned by adjusting their concentrations. The enhanced photoluminescence of Tb3+ with sharp emission lines could be obtained by the broad band excitation peak at about 360 nm from the allowed 4f–5d absorption of Ce3+ ions. The results suggest that the phosphor Na2Gd2B2O7:0.05Ce3+, 0.12Tb3+ with the optimal composition could potentially be used for near ultraviolet light-emitting diodes (n-UV LEDs).

Preparation and Scintillating Properties of Sol-Gel Eu3+, Tb3+ Co-Doped Lu2O3 Nanopowders

Nanocrystalline Eu3+, Tb3+ co-doped Lu2O3 powders with a maximum size of 25.5 nm were prepared by the sol-gel process, using lutetium, europium and terbium nitrates as precursors, and ethanol as a solvent. Differential thermal analysis (DTA) and infrared spectroscopy (IR) were used to study the chemical changes during the xerogel annealing. After the sol evaporation at 100 °C, the formed gel was annealed from 300 to 900 °C for 30 min under a rich O2 atmosphere, and the yielded product was analyzed by X-ray diffraction (XRD) to characterize the microstructural behavior and confirm the crystalline structure. The results showed that Lu2O3 nanopowders start to crystallize at 400 °C and that the crystallite size increases along with the annealing temperature. A transmission electron microscopy (TEM) study of samples annealed at 700 and 900 °C was carried out in order to analyze the microstructure, as well as the size, of crystallites. Finally, in regard to scintillating properties, Eu3+ dopant (5 mol%), Tb3+ codoped Lu2O3 exhibited a typical red emission at 611 nm (D°→7F2), furthermore, the effect of Tb3+ molar content (0.01, 0.015 and 0.02% mol) on the Eu3+ radioluminiscence was analyzed and it was found that the higher emission intensity corresponds to the lower Tb3+ content.

Facile Mixed-Solvent-Thermal Synthesis and Characterization of Shape-Controlled Monodisperse CeF<SUB>3</SUB>:Tb<SUP>3+</SUP> Nanocrystals

Monodisperse CeF3:Tb3+ nanocrystals have been synthesized from mixed solvents-thermal synthesis under mild condition. The products have been characterized by High Resolution Transmission electron microscopy (HRTEM), X-ray diffraction (XRD), UV-visible Diffuse Reflectance spectra and luminescent spectra, respectively. Besides, different solvents ratio and different surfactants to synthesize CeF3:Tb3+ nanocrystals have been compared to investigate the influence on their microstructure and morphology. As a result, the HRTEM images reveal the products crystallize in the hexagonal structure corresponding to the XRD and illustrate the mean rod length of about 15 nm, whose preferred orientation is parallel to the growth direction, namely c axis direction. The solvent ratios have influence on the microstructure and morphology of the products to some extent. With the increase of DMF solvent, the shape of CeF3:10%Tb3+ changed from grain-like particles to rodlike ones. In addition, a disordered array of CeF3:10%Tb3+ nanocrystals can be obtained with the existence of oleic acid. The characteristic emissions of Tb3+ originated from (5)D4-->7F(J) (J = 6, 5, 4, 3) are observed, and the dominant peak was the green emission of 543 nm. Measurements of emission spectra have been performed to examine the effect of Tb3+ concentration quenching on spectroscopic properties. The optimum doping-concentration ratio of Tb3+ was found to be approximately 15 mol%.

Ultraviolet and visible upconversion emission in Tb3+/Yb3+ co-doped fluorophosphate glasses

Ultraviolet and visible upconversion emissions in Tb3+/Yb3+ co-doped YF3–BaF2–Ba(PO3)2 glasses were observed under 980-nm laser diode excitation. The dependence of the emission intensities of Tb3+ on the pump power reveals that two-photon processes account for blue cooperative emission of Yb3+ at 476 nm and green upconversion emission of Tb3+ at 543 nm, and three-photon processes for ultraviolet emission of Tb3+ in the wavelength range of 379–435 nm. The effects of Tb3+ concentration on the emission intensity and the lifetime of Tb3+ and Yb3+ are investigated in detail. It is found that the cooperative energy transfer from a pair of excited Yb3+ ions to a ground Tb3+ ion is responsible for the appearance of blue and green upconversion emissions due to the 5D4→7F J (J=6,5,4,3) transitions of Tb3+, and the resonance energy transfer from Yb3+ to Tb3+ accounts for the population on the 5D3,5G6 level and ultraviolet upconversion emission.

Preparation and characterization of monodisperse spherical particles of X-ray nano-phosphors based on Gd2O2S:Tb

Monodisperse spherical Gd2O2S:Tb nanoparticles have been prepared using an improved homogeneous precipitation method combined with solid-gas sulfuration technology. The effects of Tb3+-doped concentration on luminescent intensity and color purity of samples were investigated, and the optimal Tb3+-doped concentration was determined. Under the excitation of X-ray, the obtained sample shows excellent luminescent properties, and its luminescent intensity is increased by about 50% under lower sulfuration temperature compared with that of the Gd2O2S:Tb nanoparticles prepared by complex precipitation method.

Up-conversion Luminescence of Terbium(III) in SiO2 and ZnO–SiO2 Glasses Induced by Simultaneous Absorption of Three Photons and Saturation

ABSTRACT Green up-conversion luminescence (UCL) of Tb3+ in SiO2 and ZnO–SiO2 glasses was observed with femtosecond (fs) laser (800 nm) excitation. The UCL mechanism of Tb3+ in both glasses contributed to the simultaneous three-photon absorption. The saturation effect of Tb3+ in SiO2 glass took place. The saturation effect of excited-state levels of Tb3+ in SiO2 glass was associated with the slower decay rate of 5D4 level. This result implied that saturation power of Tb3+ in ZnO–SiO2 glass was higher than that in SiO2 glass.

Effect of Tb3+ co-doping and particle size on K2Ca2(SO4)3:EU phosphor

K2Ca2(SO4)3 doped with Eu, and co-doped with Tb were prepared by the solid state diffusion method. The nanoparticles of these phosphors were also prepared by the chemical co-precipitation method. The formation of the compounds was confirmed by XRD. The particle size was calculated by the broadening of the XRD peaks using Scherrer's formula. The particle size was found to be around 20 nm. Thermoluminescence (TL) was studied to see the effect of co-doping and particle size. Tb3+ co-doping decreases the intensity in the Eu2+ doped phosphor due to the energy transfer and multiple de-excitations through various radiative and non-radiative processes. The K2Ca2(SO4)3:Eu,Tb phosphor is found to be 0.33 times more sensitive than TLD-700H, but around 15 times more than LiF-TLD 100, and 7 times more than CaSO4:Dy. The effective atomic number Zeff is around 15, which is again comparable to CaSO4:Dy. However, very low sensitivity was observed in the case of nanoparticles. The decrease in the sensitivity is attributed to the particle size effect i.e., the volume-to-surface ratio. Study of photoluminescence (PL) of the material is also carried out.

Study of the effect of intracenter and cross-relaxation transitions on the efficiency of 1.54-μm luminescence of Er3+ ions in ZBLAN glass

Mechanisms underlying the effect of Tb3+ and Eu3+ ions on the efficiency of 1.54-μm luminescence of Er3+ ions in ZBLAN glass were studied. The cross-relaxation coefficients were measured. The ion-ion interaction channels considered were used to construct coupled balance equations describing the variation in ion level population. The optimum concentrations of the dopants were found. The experimental data obtained and theoretical estimates evidence the possibility of increasing the population of the 4 I 13/2 state of the Er3+ ion, which would enable development of more efficient erbium-based amplifiers in the case of excitation at the wavelength of 0.975 μm.

Effect of Tb3+ ions on X-ray-induced defect formation in phosphate containing glasses

The study of radiation-induced defect formation in glasses is of growing interest for applications in optics and photonics. The influence of Tb3+ ions on X-ray-induced defects has been examined in glasses with different phosphate contents. The defects have been characterized by optical absorption and ESR spectroscopy. (Tb3+)+ ions are formed by X-ray irradiation. They exhibit a broad charge transfer band at 370 nm. The formation of (Tb3+)+ hole centres suppresses the formation of intrinsic phosphate-related hole centres, absorbing in the visible region. PO3 defects absorbing in the ultraviolet region contribute mainly to the electron centres corresponding to the (Tb3+)+ hole centres. Immediately after X-ray irradiation, 5–10% of the Tb3+ ions have been oxidized. The amount of (Tb3+)+ ions increases with increasing phosphate content. The stability of the (Tb3+)+ ions at room temperature depends on glass composition and melting conditions.

Effect of Tb3+ co-doping on the electron population densities of Tm3+ in Ge–As–Ga–S glasses

The 1.48-μm emission properties and electron population densities of the excited levels were investigated for Ge–As–Ga–S glasses doped with Tm3+ or Tm3+/Tb3+. Electron population inversion between the H43 and F43 levels in Tm3+ cannot be achieved without Tb3+ addition due to the strong cross-relaxation in Tm3+. Co-doping of Tb3+ resulted in the large decrease in the population density of the Tm3+:F43 level via the energy transfer of Tm3+:3F4→Tb3+:7F0,1,2. Calculated population densities of the two levels in Tm3+ using the rate equations showed that the population inversion became possible through the addition of Tb3+.

Enhanced cell-killing action of cisplatin in the presence of terbium chloride

The literature indicates that the interaction of Tb3+ with DNA modified by the antitumour drug cis-diaminedichloroplatinum(II) (CDDP) results in substantial enhancement of the fluorescence of this cation, while no enhancement is observed in the case of DNA modified by irradiation with ionizing radiation. This study investigates the effect of Tb3+ on the survival of cultured mammalian cells treated with CDDP. HeLa cells were treated with a combination of195mPt-CDDP and TbCl3, and the relationship between lethal effect and the numbers of Tb and/or Pt atoms binding to DNA, RNA and proteins was examined. The Tb content in each fraction was determined using instrumental neutron activation analysis. It was found that the cytotoxic effect of CDDP was greatly enhanced by the presence of Tb ions (D0 of CDDP fell from 8.3 μM without Tb to 3.2 μM with 0.75 mM Tb), while no such effect was found in radiation-induced cell-killing. The number of Tb atoms bound to DNA molecules in a cell was calculated to be about 4.5·107, namely 1 per 1.400 nucleotides, under that situation.

Spectroscopic properties of Tm 3+ in fluorophosphate glasses

The optical properties of Tm3+ in a fluorophosphate glass are reported. Oscillator strengths and Ωλ parameters for Tm3+ were calculated. Energy transfer between Ce3+ → Tm3+, Tm3+ → Eu3+ and Tm3+ → Tb3+ were measured at room temperature and interpreted using the Yokota and Tanimoto scheme. Fluorescence decay results seem to support the hypothesis of a diffusion-limited relaxation. The effects of Tb3+ and especially Ce3+ on the fluorescence of Tm3+ ion point out the interest of these dopants for obtaining a better emission of Tm3+ at 450 nm.

Enhancement of Cathodoluminescence Efficiency of Rare Earth Activated Y 2 O 2 S by Tb3+ or Pr3+

Cathodoluminescence of Sm3+, Eu3+, and Yb3+ in is known to be enhanced by a trace of Tb3+ or Pr3+. Nd3+, Gd3+, Dy3+, Ho3+, Er3+, and Tm3+show similar enhancement of efficiencies by addition of Tb3+ or Pr3+. For an electron beam with a current density of about 10−4 A/cm2, in a raster of about 1 cm2 area, the efficiency of is found to be greater by a factor of 1.5–7, depending on the RE3+, than the efficiency of the corresponding Tb3+ ‐free material. The efficiency of singly activated with a rare earth depends sublinearly on the current density as a consequence of an unidentified superlinear quenching mechanism. When Tb3+ or Pr3+ is codoped, the quenching process is made ineffective, and a linear dependence on the current density is obtained. This effect of Tb3+ or Pr3+ is related to their large cross sections for holes as revealed by high efficiencies at low concentrations and also by a systematic study of thermoluminescence glow curves.