Terbium Concentration Research Articles

Hybrids based on lanthanide ions activated yttrium metal–organic frameworks: functional assembly, polymer film preparation and luminescence tuning

A series of novel lanthanide (Eu, Tb, Sm, Dy) doped yttrium 1,3,5-benzenetricarboxylate have been obtainedviasolvothermal method. With varied concentration of co-doped europium and terbium in yttrium 1,3,5-benzenetricarboxylate, the emitting colors of obtained materials changed under the same excitation wavelength.

Energy transfer mechanism between terbium and europium ions in zinc oxide and zinc silicates thin films

The aim of this study is to enhance europium ions emission by energy transfer mechanism from terbium to europium ions in codoped ZnO thin films. The samples were annealed with classical and rapid thermal anneal treatments for different temperatures (973K, 1173K and 1373K). Codoped ZnO thin films were characterized for their chemical, structural and photoluminescence properties. Two different terbium concentrations have been studied with roughly constant europium content. Terbium and europium codoping allows an energy transfer from trivalent terbium to europium ions leading to the europium emission hardly observed for ZnO thin films doped by europium only. With thermal annealing above 1173K, diffusion processes occurred with silicon substrate to form zinc silicate and rare earth oxide with a concomitant photoluminescence signal from trivalent europium ions at 615nm (5D0→7F2 transition).

Hydrogen ordering in rare-earth intermetallic (Er, Tb)Fe2 compounds with giant spontaneous magnetostriction

X-ray diffraction studies of rare-earth intermetallic Er1 − x Tb x Fe2 compounds (with 0 ≤ x ≤ 0.6) and their hydrides were performed at room temperature. As the terbium content (x) in Er1 − x Tb x Fe2 increases, the sign of the magnetostriction constant λ111 was shown to alternate from positive to negative. The lattice parameters, amount of incorporated hydrogen, and sizes of interstices were found to increase with increasing terbium content. The sizes of interstices accessible for occupation with hydrogen atoms were calculated for all alloys and their hydrides. Spontaneous anisotropic magnetostriction related to the rare-earth atoms was found to make no determining contribution to the resulting crystal lattice distortion caused by the incorporation of hydrogen atoms.

Hydrothermal formation and characteristics of rare-earth niobate phosphors and solid solutions between YNbO4 and TbNbO4

Monoclinic fergusonite-type niobate, YNbO4:Tb3+ and complete solid solutions with luminescent properties in the YNbO4–TbNbO4 system were directly formed as nanocrystals from the precursor solutions of NbCl5, TbCl3, and YCl3 under hydrothermal conditions at 240 °C. The niobate nanocrystals possessed distinguishing feature of ellipsoidal morphology. The optical band gap of the as-prepared samples, Y1−xTbxNbO4, x = 0–1.0, decreased from 3.7 to 2.9 eV as the terbium concentration increased from x = 0 to 1.0. The photoluminescence spectra of the as-prepared nanocrystals containing terbium are responsible for the characteristic blue (490 nm) and green (545 nm) luminescence, associated with 5D4 → 7F6 and 5D4 → 7F5 transitions, respectively. The strongest emission bands in the green spectral domain corresponding to 5D4 → 7F5 transition of Tb3+ are located at 545 and 550 nm under excitation at 240 nm Xe lamp. By heat treatment at 1300 °C, the luminescence intensity of the as-prepared solid solution x = 0.10 that presented the highest photoluminescence intensity increased more than 8 times as high as that before heat treatment.

Distribution of the Rare Earth Metals Concentrations in the Sediments of Algiers Bay and Surkouf Area

Sediments were collected at 33 stations from Algiers Bay to determine potential sources of pollution. The analyses were made with Phillips X-ray fluorescence (XRF) equipment. The results give information about the level of concentrations for La, Ce, Er and Tb. Except for lanthanum and erbium which present a particular distribution (unrelated to the sedimentary facies), the distribution of the different rare earth metals is irregular and depends on the bay morphology. Terbium, erbium and cerium present high concentrations in the vases. The level of pollution by rare earth metals of the botton sediments in Algiers Bay has been shown to be significant compared with that of Surkouf, considered to be a region with low anthropogenic activity

Magnetic, ferromagnetic resonance and electrical transport study of Ni1−xTbxFe2O4 spinel ferrites

The impacts of terbium (Tb) contents on magnetic, ferromagnetic resonance (FMR), electrical and dielectric properties of Ni1−xTbxFe2O4 ferrites were investigated. A vibrating sample magnetometer was employed to probe the magnetic properties of the samples at room temperature. It was found that with the increased terbium content, the coercive force and saturation magnetization were decreased which may be attributed to spin canting. Magnetic dynamics of the samples were studied by ferromagnetic resonance in X band (9.5GHz) at room temperature. The incorporation of terbium sufficiently lowers the FMR line-width. The decrease in FMR line-width is attributed to the reduction of super-exchange interactions. The DC electrical resistivity and activation energy are higher for the substituted samples. The dielectric constant, dielectric loss (tanδ) and AC-conductivity decreased on account of doping. The decrease in dielectric constant is imputed to the reduction in the internal viscosity of the doped samples. The dielectric data are explained on the basis of space charge polarization. As Ni–Tb ferrites have low value of coercivity, high dielectric constant and low tanδ, they may be attractive for application in switching and memory storage devices.

Structural and Optical Behavior of nanoCe<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>, CeF<sub>3</sub> and CePO<sub>4</sub>:Tb<sup>3+</sup> Composites Embedded in PVOH Matrix

Embedding rare earth compounds and inorganic materials in polymer matrix are of great interest due to its various applications in sensors, optical batteries etc. The hydrated form of optical compounds possesses interest due to the possibility of crystal field effect on the electronic and magnetic field structure of the 4f shell. The stiochiometric cerium compounds have attracted attention due to its high temperature phase stability, high melting point, low thermal conductivity, optical fluorescence etc. In this paper we discuss the synthesis of cerrous sulphate Ce2(SO4)3, Cerium fluoride CeF3 and Cerium Phosphate doped with terbium Ce1-xPO4:Tbx composites and dependence of their structural and optical behavior on particle size. Cerrous sulphate exists in several phases, mostly hydrated. In polymer composite the anhydrous phase of Ce2(SO4)3 is observed. Also CePO4 composites crystallize to monazite phase. The significant changes in Ce3+ emission and absorption spectra are observed due to this phase change. Cerium fluoride composites prepared with different concentration show three absorption peaks around 237, 275 and 265nm. The lower concentration of CeF3 shows different absorption. CePO4 composites doped with various concentrations of terbium shows intense green emission at 543 nm and maximum energy transfer for 10 mol % of Tb3+. The Ce3+ emission is shifted to 337nm. The S.E.M. photograph of the composite shows well separated particles with average size 300nm.

Tuning the emission colour by manipulating terbium-terbium interactions: Terbium doped aluminum nitride as an example system

Terbium-terbium interactions in terbium doped semiconductors and insulators may lead to the so-called cross-relaxation process, which increases the D54 (green) emission of the terbium ions at the cost of the D53 (blue) luminescence intensity. This effect can generally be reduced by increasing the distance between an excited ion and the nearest ion in the ground state. A straightforward measure is to use a specimen with a decreased terbium concentration. The alternative is to increase the intensity of the excitation (either by photons or electrons) and thereby to reduce the population of terbium ions in the ground state. This paper works this process out with the example of AlN:Tb on the basis of a model and respective experimental results. As will be seen, stronger excitation causes in essence more Tb ions to be excited, thus less ions in the ground state which increases the distance between an excited and the nearest ground state ions. This hinders energy transfer between the terbium ions and thus counteracts the cross-relaxation process. The advantage of changing the excitation intensity lies in the possibility to deliberately shift the apparent colour of the Tb luminescence from a single specimen between green and blue.

Ion–ion interaction in two-dimensional nanoporous alumina filled with cubic YAlO3 : Tb3+ matrix

Terbium doped YAlO3 composites, with terbium concentrations up to 2.11 at%, were fabricated by co-precipitation in porous anodic alumina films grown on silicon. The presence of the cubic YAlO3 phase was confirmed by x-ray diffraction and FT-IR analysis. The fabricated samples demonstrate photoluminescence (PL) within the range 350–640 nm, which is associated with f–f transitions from the 5D3, 5G6 and 5D4 levels of Tb3+ ion. Additionally, a broad and fast- decaying PL band in the blue range has been observed, which is associated with defect states. Based on PL excitation spectra, the main excitation channel of Tb3+ ions is due to 4f–5d transitions. Excitation bands observed at 235, 270 and 320 nm have been related to the permitted low-spin 5d2 [LS], 5d1 [LS] and forbidden high-spin 5d1 [HS] states, respectively. The PL decay spectra have been measured, with the results analysed using the maximum entropy method; a strong indication of ion–ion interaction has been observed. The distribution of Tb3+ ions in the PAA : YAlO3 structure has been proposed and its influence on optical properties of Tb3+ ions has been discussed.

The analysis of the magnetic properties and the electronic structure in the TbxGd1−xFe3 intermetallics

The polycrystalline compounds TbxGd1−xFe3 with a PuNi3 – type of crystal structure have been obtained. Based on wide-range SQUID magnetometer series of different magnetic measurements have been carried out. Moreover, magnetic properties in the paramagnetic range have been studied by means of the Faraday type magnetic balance. The partial replacement of Gd by Tb (Gd/Tb) atoms is reflected in the increase of magnetic parameters e.g. the increase of the saturation magnetic moment (MS) from 1.6 μB/f.u (x = 0.0) to 3.42 μB/f.u (x = 1.0). The study of the hysteresis loops has been performed in several chosen temperatures. A quite strong dependence of coercivity (HC) and remanent magnetization (Mr) on the temperature and the amount of Tb has been found. The exchange coupling parameters of R–R (ARR), T–T (ATT) and R-T (ART) have been evaluated from magnetization curves M(T) based on the mean field theory (MFT) calculations. The XPS spectra have been measured at the room temperature. The valence band spectra as well as the core level lines have been analyzed as the influence of Gd/Tb substitution on the electronic structure. The valence bands near the Fermi level (EF) are dominated by Fe3d states and indicate the increase of intensity of states for higher terbium content. A strong dependence of the magnetic properties on the changes within the electronic structure has been found.

An Approach for Enhancement of Saturation Magnetization in Cobalt Ferrite Nanoparticles by Incorporation of Terbium Cation

Cobalt ferrite nanoparticles were synthesized by a reverse micelle process. The optimum processing conditions required to fabricate nanocrystalline cobalt ferrite using a reverse micelle technique, especially the effect of water-to-surfactant molar ratios including w = 8, 10, 12, and 14, pH values in the range of 8 to 11, and annealing temperatures in the range of 400°C to 800°C, were evaluated. x-Ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), vibrating-sample magnetometry, and superconducting quantum interference device analysis were employed to evaluate the structural and magnetic properties of synthesized nanoparticles. XRD analysis confirms that the nanoparticles have a single-phase cubic spinel structure. The average particle size increases with increasing pH value and annealing temperature. Magnetization study reveals that the cobalt ferrite nanoparticles exhibit a superparamagnetic trend. The zero-field-cooled magnetization curves of cobalt ferrite nanoparticles indicated that, with an increase in pH value, the blocking temperature increases. Based on the obtained optimum parameters, terbium-substituted cobalt ferrite nanoparticles with composition CoFe2−xTbxO4 (x = 0.1 to 0.5) were prepared by a reverse micelle process. XRD and field-emission scanning electron microscopy evaluation demonstrated that single-phase spinel ferrites with narrow size distribution were obtained. Mossbauer spectroscopy was used to determine the site preference of terbium cation. The results confirm that terbium cations were distributed at tetrahedral and octahedral sites, but with a preference for the former. It was observed that, with an increase in terbium content, the saturation magnetization increases.

Thermoluminescent characterization of HfO2:Tb3+ synthesized by hydrothermal route

Thermo and photoluminescent properties of nanoparticles (NPs) of hafnium oxide (HfO2), both intrinsic and doped with terbium (Tb3+) are reported. The NPs of HfO2 were synthesized by hydrothermal route, using hafnium tetrachloride (HfCl4) and terbium chloride hexahydrated (TbCl3∙6H2O) as precursors and sodium hydroxide (NaOH) to adjust the pH. Deionized water was used as solvent in all cases. The synthesis was carried out at different dopant concentrations from 0 to 20at% of terbium with respect to the amount of hafnium in the precursor solution. The temperature of hydrothermal treatment was 200°C and 80min of reaction time. X-ray diffraction results show that at terbium concentrations higher than 15at% the HfO2 nanoparticles have a crystalline structure corresponding to the tetragonal phase. Thermoluminescent (TL) characterization was performed after 5min irradiation of the samples with ultraviolet light of 200nm wavelength. The highest TL emission was observed on samples with 7at% of Tb, with the TL peak centered at 128°C. Thermoluminescence analysis shows behavior associated with second-order kinetics with activation energy of 0.49eV. Photoluminescent spectrum present the characteristics 5D4→7FJ (J=3–6) terbium ion electronic transitions lines centered on 489nm, 543nm, 584nm and 622nm.

Study of the decomposition of the magnesium-based solid solutions in Mg-Sm-Tb alloys

Kinetics and structural transformations upon the decomposition of a magnesium-based supersaturated solid solution in Mg-Sm-Tb alloys have been studied at various relations between the concentrations of terbium and samarium. It has been established that with increasing terbium content in the alloys the strengthening upon the decomposition of the supersaturated magnesium-based solid solution increases. The decomposition of the supersaturated magnesium-based solid solution in the Mg-Sm-Tb alloys with a percentage ratio (wt %) Tb: Sm of about 2.5 exhibits signs characteristic of the decomposition of the supersaturated solid solution in binary Mg-Tb alloys. With allowance for the equilibrium Mg-Sm-Tb phase diagram, this gives grounds to suppose that samarium is mainly dissolved in the products of the decomposition of the magnesium solid solution that are characteristic of Mg-Tb alloys.

Chemiluminescence phenomena in inorganic Eu(III)–Tb(III)–H2O2 system in basic solution

Chemiluminescence (CL) in the system containing inorganic compounds such as Eu(III), Tb(III) ions, hydrogen peroxide in presence or absence of molybdate or tungstate or phosphate ions in basic solution (~0.1molL−1 NaOH) has been studied. The kinetic curves of CL decay and CL spectral distributions were obtained. On the basis of differences in CL intensity and its duration, as well as characteristics of CL spectra, the important role of the peroxide compound of the lanthanide molybdates or tungstates and H2O2 formed in the systems studied was proposed. A linear correlation between the CL intensity of the Eu(OH)3–Tb(OH)3–H2O2 and the concentrations of terbium(III) ions was observed.

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.

Bright Green Luminescence from Zirconium Oxide Stabilized with Tb<sup>3+</sup> Ions Synthesized by Solution Combustion Technique

In this research, the structural phase composition and room temperature luminescence properties of terbium doped zirconium oxide powders obtained by solution combustion synthesis method are presented as a function of the terbium content. The doping with terbium ions was performed during the redox combustion process and after annealing at 900°C during 20 hours. With the incorporation of the terbium ions into the zirconium oxide host, the stabilization of the high temperature tetragonal crystalline phase, as determined by x-ray diffraction technique, was obtained. Under ultraviolet radiation a bright green luminescence was observed at room temperature corresponding to the (4f) electron configuration of the Tb3+ ion, namely the electronic transitions 5D4 → 7Fn with n = 3 - 6. In addition, the undoped ZrO2 material showed green photoluminescence with high intensity.

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.

Oxygen ion conductivity of (Yb0.9 − x Tb x Ca0.1)2Ti2O7 − δ solid solutions

We have studied terbium substitution for ytterbium in (Yb0.9 − xTbxCa0.1)2Ti2O7 − δ (x = 0.1, 0.2, 0.3, 0.4) pyrochlore solid solutions synthesized through coprecipitation followed by firing at 1550°C. The results indicate that only a small amount of terbium (less than 10%) can be incorporated into the pyrochlore structure of (Yb0.9Ca0.1)2Ti2O6.9 because of the large difference in ionic radius between the terbium and ytterbium cations: Δr = r(TbCN 83+) − r(YbCN 83+) = 0.055 A. The oxygen ion conductivity of the (Yb0.9 − xTbxCa0.1)2Ti2O7 − δ solid solutions has been determined by impedance spectroscopy in air in the temperature range 300 to 900°C. At high temperatures (t > 640°C), their bulk conductivity was essentially independent of the Yb/Tb ratio. The observed decrease in density and microstructural changes were insignificant. At relatively low temperatures (t < 640°C), the bulk conductivity decreased slightly, and the decrease depended little on terbium concentration.

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.

Incompatibility of standard III–V compound semiconductor processing techniques with terbium-doped InGaAs of high terbium concentration

Terbium-doped InGaAs with a high terbium concentration shows promise as a high-efficiency thermoelectric material, with the thermal conductivity dropping to 1.27 W/m K at a TbAs concentration of 1.55% by number of atoms. However, large discrepancies are noted in Hall effect measurements on terbium-doped InGaAs grown by molecular beam epitaxy on InP substrate following standard III–V wet chemical processing techniques, when compared to samples with no processing beyond deposition of indium contacts. These discrepancies preclude systematic exposition of temperature- and composition-dependent thermoelectric figures of merit. The discrepancy is seen to be correlated with the terbium concentration and the thickness of the active material. The steps in the process sequence are examined under controlled conditions. Although the exact cause for the discrepancy has not been found, some of the obvious reasons have been ruled out. It is therefore surmised that (1) chemical reaction with photoresist, (2) ultraviolet irradiation during photolithography, or (3) reaction with photoresist developing solutions and HF are the factors responsible for the changes in Hall voltage. Evidence is presented for the creation of surface states that corrupt Hall effect measurements on the bulk semiconductor.