Tb Concentration Research Articles

Optical properties of Ce3+ and Tb3+ co-doped ZnS quantum dots

Ce3+ and Tb3+ co-doped ZnS quantum dots (QDs) were synthesized using a facile and effective wet chemical method. The effect of Tb3+ concentration on the structure and optical properties of the co-doped QDs was explored thoroughly using various characterization methods. The chemical composition and oxidation state of the elements in the synthesized QDs were examined by X-ray photoelectron spectroscopy (XPS). The crystal structure and luminescence properties of the synthesized QDs were investigated using X-ray diffraction (XRD) and photoluminescence (PL). The change in the crystal structure of the Ce3+ and Tb3+ co-doped QDs with an increase in the concentration of Tb3+ dopant from 1% to 8% was observed for the first time. The excitation spectra of Ce3+ and Tb3+ co-doped QDs were investigated using the photoluminescence excitation (PLE) technique. The energy transfer (ET) from Ce3+ to Tb3+ ions in the ZnS host lattice occurred effectively because of the large spectral overlap between the emission band of Ce3+ and the excitation band of Tb3+ ions. The observed properties revealed that doping with Ce3+ enhanced the energy transfer process and the interaction mechanism in energy transfer was dominated by dipole-dipole interaction. The thermal stability of the co-doped QDs was explored by studying their PL spectra in the temperature range of 15–300 K. Ce3+ and Tb3+ co-doped ZnS QDs exhibited a very long decay time on the order of ms. The valuable optical properties of Ce3+ and Tb3+ co-doped ZnS QDs make them potentially useful for photovoltaic, photocatalyst, and biosensing applications.

Magnetic excitations and exchange interactions in the substituted multiferroics (Nd,Tb)Fe3(BO3)4 revealed by inelastic neutron scattering

Inelastic neutron scattering spectra in the antiferromagnetic ferroborates ${\mathrm{Nd}}_{1\ensuremath{-}x}{\mathrm{Tb}}_{x}{\mathrm{Fe}}_{3}{({\mathrm{BO}}_{3})}_{4}$ ($x$ = 0, 0.1, 0.2, and 1) reveal various magnetic excitations of the interacting iron and rare-earth subsystems. We observe an evolution of the magnetic system from ``easy-plane'', in the Tb-free ($x$ = 0) case, to ``easy-axis'' anisotropy for samples substituted with Tb. The spectra show hybridized Fe and Nd branches, which are determined by the Fe-Nd exchange splitting of the ground-state ${\mathrm{Nd}}^{3+}$ doublet. In the easy-plane configuration, near the Brillouin zone center, there are two different pairs of anticrossing quasiacoustic Fe and Nd modes in contrast to the easy-axis state, where the two corresponding pairs of the branches are degenerated. The high-energy (exchange) branches are similar in both spin configurations. The Ising-type anisotropy of the Tb ion prevents the magnetic moment from precession. The increasing of the Tb content changes the effective magnetic anisotropy and stabilizes the easy-axis state. The spin-wave dispersion in the substituted and pure $\mathrm{Tb}{\mathrm{Fe}}_{3}{({\mathrm{BO}}_{3})}_{4}$ compounds, which have the same, easy-axis magnetic structure, but different crystal symmetry, strongly differ. The observed spectra were analysed in the frame of linear spin-wave theory and the exchange parameters were determined.

Baseline Xpert MTB/RIF ct values predict sputum conversion during the intensive phase of anti-TB treatment in HIV infected patients in Kampala, Uganda: a retrospective study

BackgroundIn resource-limited settings, sputum smear conversion is used to document treatment response. Many People living with HIV (PLHIV) are smear-negative at baseline. The Xpert MTB/RIF test can indirectly measure bacterial load through cycle threshold (ct) values. This study aimed to determine if baseline Xpert MTB/RIF could predict time to culture negativity in PLHIV with newly diagnosed TB.MethodsA subset of 138 PLHIV from the ‘SOUTH’ study on outcomes related to TB and antiretroviral drug concentrations were included. Bacterial load was estimated by Mycobacterium Growth Indicator Tubes (MGIT) culture time-to-positivity (TTP) and Lowenstein Jensen (LJ) colony counts. Changes in TTP and colony counts were analyzed with Poisson Generalised Estimating Equations (GEE) and multilevel ordered logistic regression models, respectively, while time to culture negativity analysed with Cox proportional hazard models. ROC curves were used to explore the accuracy of the ct value in predicting culture negativity.ResultsA total of 81 patients (58.7%) were males, median age 34 (IQR 29 ̶ 40) years, median CD4 cell count of 180 (IQR 68 ̶ 345) cells/μL and 77.5% were ART naive. The median baseline ct value was 25.1 (IQR 21.0 ̶ 30.1). A unit Increase in the ct value was associated with a 5% (IRR = 1.05 95% CI 1.04 ̶ 1.06) and 3% (IRR = 1.03 95% CI 1.03 ̶ 1.04) increase in TTP at week 2 and 4 respectively. With LJ culture, a patient’s colony grade was reduced by 0.86 times (0R = 0.86 95% CI 0.74 ̶ 0.97) at week 2 and 0.84 times (OR = 0.84 95% CI 0.79 ̶ 0.95 P = 0.002) at week 4 for every unit increase in the baseline ct value. There was a 3% higher likelihood of earlier conversion to negativity for every unit increase in the ct value. A ct cut point ≥28 best predicted culture negativity at week 4 with a sensitivity of 91. 7% & specificity 53.7% while a cut point ≥23 best predicted culture negativity at week 8.ConclusionBaseline Xpert MTB/RIF ct values predict sputum conversion in PLHIV on anti-TB treatment. Surrogate biomarkers for sputum conversion in PLHIV are still a research priority.

Associations between blood heavy metal(loid)s and serum heme oxygenase-1 in pregnant women: Do their distribution patterns matter?

The relationship between heavy metal(loid)s exposure and oxidative stress damage is a matter of research interest. Our study aimed to investigate the distribution patterns of the nine heavy metal(loid)s in blood of pregnant women, including four toxic heavy metal(loid)s [arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg)] and five typical heavy metal(loid)s [manganese (Mn), cobalt (Co), copper (Cu), zinc (Zn), and selenium (Se)] in blood. Blood samples of 348 women were collected and their concentrations in the serum (sr) and blood cells (bc) were measured, as well as serum heme oxygenase-1 (HO-1) (an oxidative stress marker). Total blood (tb) concentrations of these metal(loid)s and serum-to-blood cell concentration ratios (sr/bc) were further calculated. We found Cu mainly accumulated in the serum compared to the blood cells with Cusr/bc = 2.30, whereas Co, Se, and As evenly distributed between these two fractions. Other metal(loid)s mainly concentrated in the blood cells. Cosr, Cusr, Cubc, Mnbc, Znbc, Cdbc, Cotb, Cutb, Mntb, Zntb, Cdtb, and Cusr/bc were negatively associated with serum HO-1, whereas Assr, Asbc, Astb, Znsr/bc, Cdsr/bc, and Hgsr/bc were positively, indicating of their potential toxicity. We concluded that the distribution patterns of blood heavy metal(loid)s, in particular for Cd, Hg and Zn, which either increased in serum or decreased in blood cells, might be associated with elevated serum oxidative stress, should be considered in environmental health assessments.

New magnetic polymeric hybrid composite electrode material for amperometric nitrite sensor

ABSTRACT New modified electrode materials, based on a combination of hybrid nanocomposites such as magnetic nanoparticles, inorganic polymer (SiO2) and different types of organic polymers, were studied. Three types of organic polymers were used in order to find the effect that each of polymers has on the electrochemical properties of the final material. The electrochemical properties of the synthesised materials were investigated, the best electrochemical response was for pAAc covered nanoparticles compared to the other three tested materials. This favourable electrochemical response effect is due to the fact that in case of this material we succeed in obtaining a very uniform coverage of the polymeric shell with a favourable hydrogel structure and thicknesses which is perfectly suitable for adsorption of a relatively high concentration of TB in a very easi and homogenous way. By electrochemical measurements it was proved that this electrode presents electro-catalytic effect towards nitrite oxidation and can be used for nitrite detection. By comparing with other electrodes, the electro-catalytic effect of MNPs-SiO2-pAAc is better because the nitrite oxidation peak appears in this case at a potential closer to 0 mV vs. Ag/AgCl/KClsat, which is favourable to avoid interferences in amperometric nitrite detection in real samples.

Ratiometric temperature sensing behavior of dual-emitting Ce3+/Tb3+ co-doped Na5Y9F32 single crystal with high relative sensitivity

The Na5Y9F32 single crystals doped with fixed 0.5 mol% Ce3+ and various concentrations of Tb3+ (0, 0.4, 0.6 and 0.8 mol%) were grown by Bridgeman method. The luminescent properties, energy transfer (ET) and the ratiometric temperature sensing behavior were studied thoroughly. Under 315 nm excitation, the Ce3+/Tb3+ co-doped Na5Y9F32 single crystal mainly presented two emissions at blue 385 nm (Ce3+:5d→4 f) and green 545 nm (Tb3+:5D4→7F5). The color area can undergo from the purple-blue region (0.1643, 0.0768) to the green region (0.2585, 0.3604) by altering the content of Tb3+ ion from 0 to 0.8 mol%. The energy transfer between the Ce3+ and Tb3+ ions was confirmed by decay curves with emission spectra, and the maximum energy transfer efficiency (ETE) were estimated to be 45.1%. The mechanism of dipole-dipole interaction (d-d) for energy transfer from Ce3+ to Tb3+ can be explained by the formula of Dexter’s energy transfer. The fluorescence intensity ratio (FIR) of blue and green emission showed a linear relationship with temperature varying from 298 K to 473 K in the 0.5 mol% Ce3+/0.8 mol% Tb3+ co-doped Na5Y9F32 single crystal. Meanwhile, the 0.5 mol% Ce3+/0.8 mol% Tb3+ co-doped Na5Y9F32 single crystal possessed higher absolute sensitivity (Sa) of 0.0157 K−1, relative sensitivity (Sr) of 1.18% K−1 and temperature resolution (δT) of 0.086 K. By using the integrating spheres, the quantum yield (QY) of 0.5 mol% Ce3+/0.8 mol% Tb3+ co-doped Na5Y9F32 single crystal was measured as ~16.88%. These excellent optical properties suggest that the Ce3+/Tb3+ co-doped Na5Y9F32 single crystal with stable physical-chemical properties could have a far-reaching application prospect for the ratiometric optical thermometry.

Bioaccumulation and ecotoxicological responses of clams exposed to terbium and carbon nanotubes: Comparison between native (Ruditapes decussatus) and invasive (Ruditapes philippinarum) species

In the last decades the use of rare earth elements (REEs) increased exponentially, including Terbium (Tb) which has been widely used in newly developed electronic devices. Also, the production and application of nanoparticles has been growing, being Carbon Nanotubes (CNTs) among the most commonly used. Accompanying such development patterns, emissions towards the aquatic environments are highly probable, with scarce information regarding the potential toxicity of these pollutants to inhabiting species, especially considering their mixture. In the present study the effects of Tb and CNTs exposure (acting alone or as a mixture) on native and invasive clams' species (Ruditapes decussatus and Ruditapes philippinarum, respectively) were evaluated, assessing clams' accumulation and metabolic capacities, oxidative status as well neurotoxic impacts. Results obtained after a 28-days exposure period showed that the accumulation of Tb in both species was not affected by the presence of the CNTs and similar Tb concentrations were found in both species. The effects caused by Tb and CNTs, acting alone or as a mixture induced greater alterations in R. philippinarum antioxidant capacity in comparison to native R. decussatus, but no cellular damages were observed in both species. Nevertheless, although metabolic impairment was only observed in clams exposed to Tb, loss of redox balance and neurotoxicity were evidenced by both species regardless the exposure treatment. These findings highlight the potential impacts caused by CNTs and Tb, which may affect clams' normal physiological functioning, impairing their reproduction and growth capacities. The obtained results point out the need for further investigation considering the mixture of pollutants.

Room temperature ferromagnetism in dilute magnetic semiconducting ZnO nanoparticles co-doped with Tb and Fe

Room temperature ferromagnetism with the doping of magnetic ions in the semiconducting host is the fundamental criterion for the potential use of spintronics material. In the present study, pure and (Fe, Tb) co-doped ZnO nanoparticles were well-prepared via the co-precipitation method, and corresponding microstructural, magnetic, and optical properties were investigated. The formation of Wurtzite hexagonal crystal structure of pure and doped ZnO was confirmed by X-ray diffraction (XRD) studies. No secondary phase was detected in all samples. Microstructural analysis reveals the spherical morphology of synthesized particles with the average size in the nanometer range. Fourier transforms infrared spectra show Tb–Zn–O stretching at 550 cm−1. Optical absorption spectra show that the bandgap decreases and the absorption band slightly shift toward the visible region with increasing Tb doping, which may be due to the transfer of charge between the Tb ion 4f level and ZnO valance band. The photoluminescence (PL) spectrum exhibits a strong emission in the visible range, and PL emission intensity decreases with increasing Tb concentration and is anticipated to be due to the low recombination rate of electron–hole pairs. Most importantly, the room temperature ferromagnetism (RTFM) was observed in the doped ZnO nanoparticles, ascribed to the bound magnetic polaron (BMP) mechanism. The optical and magnetic outcome demonstrates that prepared (Fe, Tb) co-doped ZnO based dilute magnetic semiconducting (DMS) material are potential candidates for spintronics applications.

Effective microstructure optimization and coercivity enhancement of sintered Nd–Fe–B magnet by grain boundary diffusion of Pr60Tb13Al27 alloy

Commercial sintered Nd-Fe-B magnet was grain boundary diffusion (GBD) processed by Pr60Tb13Al27 and Tb73Al27 alloys. Although the Tb content is only 13 at% in the Pr60Tb13Al27 alloy, the coercivity was significantly enhanced from 15.18 kOe to 26.30 kOe in the magnet diffused by Pr60Tb13Al27, higher than 24.08 kOe of the Tb73Al27 GBD magnet. This suggests that the substitution of Tb(60 at%) by Pr in the Tb73Al27 alloy can further enhance coercivity. Detailed microstructure analysis showed that, in the Pr60Tb13Al27 GBD magnet, the Tb-rich shell thickness was reduced and the two-layer Tb-rich shell was formed. Furthermore, a large number of continuous grain boundary phases was observed, which significantly enhances the exchange-decoupling effect between adjacent grains. The effect of Pr for the Tb-rich shell and grain boundary structure was discussed based on the experimental results.

Sublethal effects of terbium and praseodymium in juvenile rainbow trout

Abstract The increasing extraction of rare earth elements (REEs) and their subsequent release to freshwater ecosystems are expected to threaten aquatic organisms, yet little is known about the scope of this issue. The purpose of this study was to identify key molecular responses associated with exposure and toxicity of two data-poor REEs, terbium (Tb, heavy REE) and praesodymium (Pr, light REE) in rainbow trout juveniles. Fish were exposed for 96 h to increasing concentrations of Tb and Pr to determine impacts on survival and variation in biomarkers involved in oxidative stress, inflammation, DNA damage and metal homeostasis (metallothioneins). In surviving fish, a suite of 14 gene expression endpoints were also examined as well as genes associated with protein stability, calcium binding, immune response, protein damage, cell division, iron homeostasis and mitochondrial activity. The data showed that Tb was approximately two times more toxic than Pr, with estimated LC50 of 5.8 and 11 mg/L respectively. In addition, Tb and Pr exhibit respectively anti and pro-inflammatory responses relative to controls as demonstrated by the significant variation in the arachidonate cycloocygenase (COX) activity. However only Pr displayed a genotoxic effect due to the increase in the level of DNA strand breaks. Exposure to these two elements lead to the expression of genes involved in DNA repair activity, inflammation, protein denaturation, calcium binding, oxidative stress and divalent metal handling, ATP synthesis and hemoprotein activity. Based on the observed responses to both Tb and Pr, metal homeostasis, protein denaturation and DNA repair activity were commonly affected. The most toxic element (Tb) produced more important changes in the expression of genes involved in oxidative stress, calcium binding, hemoprotein activity and protein folding and turnover. These genes represents potential physiological targets involved in the mode of action for Tb and Pr in fish toxicity.

UV and VUV induced luminescence in Tb3+ doped Ca3La3(BO3)5 phosphors for PDP applications

Ca3La3-x(BO3)5:xTb (x = 0.005 to 0.10) phosphors were synthesized by the sol-gel process. The formation of the sol-gel products was confirmed by X-ray diffraction (XRD) analysis. The samples were also characterized by FTIR spectroscopy to study the nature of bonding between boron and oxygen ions. The luminescence properties of the synthesized products were examined under ultraviolet (UV) and vacuum UV (VUV) excitations. The phosphor exhibited green luminescence with the optimum emission peak centered at 544 nm for UV and VUV excitation. The color purity of the sample with optimum Tb concentration was 63.63 %. The prepared phosphors are a good option for the green-emitting component in plasma-display panels (PDPs).

Compositional Dependence of Curie Temperature and Magnetic Entropy Change in the Amorphous Tb-Co Ribbons.

The Curie temperature (Tc) and magnetic entropy change (−ΔSm), and their relationship to the alloy composition of Tb–Co metallic glasses, were studied systematically in this paper. It was found that, in contrast to the situation in amorphous Gd–Co ribbons, the dependence of Tc on Tb content and the maximum −ΔSm vs. Tc -2/3 plots in Tb–Co binary amorphous alloys do not follow a linear relationship, both of which are supposed to be closely related to the non-linear compositional dependence of Tb–Co interaction due to the existence of orbital momentum in Tb.

Energy transfer and the anti-thermal quenching behavior of Sr8MgCe(PO4)7:Tb3+ for temperature sensing

Novel color-adjustable phosphors Sr8MgCe(PO4)7:Tb3+ were synthesized by the solid-state reaction method. The X-ray diffraction was used to characterize the phase formation. The host shows blue emission under 310 nm excitation, ascribed to the 5d-4f transitions of Ce3+, while Sr8MgCe(PO4)7:xTb3+ phosphors exhibit the emission band of Ce3+ as well as the characteristic lines of Tb3+ under 310 nm excitation. The color variation was observed as the concentration of Tb3+ changes. Moreover, the host sensitizes the emission of Tb3+ through the energy transfer process, and the mechanism is the dipole–dipole interaction. In addition, the emission of the host declines with the increase of the temperature while that of Tb3+ increases. This anti-thermal quenching behavior was interpreted by the configurational coordinate diagram. In addition, the temperature sensing behavior based on the emission peaks of the host and Tb was studied in the range 298–523 K, and the largest sensitivity is 0.379% K−1. The results indicate that Sr8MgCe(PO4)7:Tb3+ is an attractive color-tunable phosphor for solid state lighting and temperature sensing.

Optical properties of ZnO:SiO2:Tb3+ films: the effect of DNA

Thin films of zinc oxide and those doped with terbium (at concentrations of 0.1–5.0 mol%) were synthesized on glass substrates using the sol–gel method. The UV–Vis transmission spectra showed that transparency increases from 60% to 86% with an increase of Tb content. All terbium-doped samples exhibit a rise in Eg from 3.37 eV for zinc oxide to 3.827 eV for doped films. The photoluminescence (PL) of zinc oxide doped with terbium in the UV (260 nm) region and the fluorescence of terbium in the visible region (330 nm) were studied. The intensity of green luminescence with an increase in the amount of terbium increases by an average of 6%. The yield of green fluorescence relative to PL also goes up with an increase in the concentration of terbium concentration of terbium from 5% to 7.4%. DNA deposited on the surface of the plate extinguishes PL by an average of 5.5% and has a weak effect (<3%) on terbium fluorescence in the visible region. SEM images without DNA consist of spherical structures—0.5–2.0 μm in diameter, assembled in the form of pentagons. The presence of DNA on the surface is expressed as ‘stars’ of white color of regular and irregular shapes, located on the surface inside these pentagons.

Photoluminescence characteristics and white light generation in borohydride derived co-doped (Eu3+, Tb3+) YBO3 phosphors

The prime theme of this work is to explore the excitation wavelength dependent photoluminescence characteristics and white light generation in activators [europium (Eu) and terbium (Tb)] doped yttrium borate (YBO3) phosphors. In order to study the influence of excitation wavelength on photoluminescence emission intensity, a fixed amount (5 mol%) of Tb and different concentration of Eu (1, 2, 3, 5 and 7 mol%) were co-doped into yttrium borate (YBO3) host matrix via a solution precursor route using sodium borohydride as a precipitating agent. The ratio of Tb and Eu emission peaks suggests that it is possible to produce multi-color emissions including white light. The excitation dependence of emission comes from the combined contribution of host, activator and energy transfer between host to activator as well as among individual activators, which gives rise to change in output emission color. Moreover, the optimum composition i.e. 3 mol% Eu, 5 mol% Tb co-doped YBO3 was found to be appropriate for white light emitting phosphor.

Investigation of crystal structure, dielectric response and magnetic properties of Tb3+ substituted Co2 Y-type barium hexaferrites

Y-type hexaferrites powder samples of Ba1·8Sr0·2Co2Fe12-xTbxO22 (with x = 0.0, 0.1, and 0.2) were prepared by the method of sol-gel auto combustion. XRD and Rietveld refinement analysis shows that the prepared Y-type hexaferrites samples exhibit pure crystalline phase with the absence of impurity. FTIR study gives an idea of the formation of Y-type hexaferrites by the appearance of three characteristics bands at 409, 433, and 552 cm−1. FESEM analysis shows plate-like morphology with the presence of all hosts and substituted elements observed in the EDX spectra and mapping. The grain size decreases with increase in the concentration of Tb3+, the particle size was observed to be in the range 56.48–58.54 nm. Typical dielectric response of ferrites was observed in the dielectric analysis. Cole-Cole plot shows that the contribution of grain is negligible compared to grain boundaries contribution. The multi domain magnetic nature of the prepared Y-type hexaferrite samples resulted in domain wall displacement and consequently influences the values of the coercivity.

Role of element-specific damping in ultrafast, helicity-independent, all-optical switching dynamics in amorphous (Gd,Tb)Co thin films

Ultrafast control of the magnetization in ps timescales by fs laser pulses offers an attractive avenue for applications such as fast magnetic devices for logic and memory. However, ultrafast helicity-independent all-optical switching (HI-AOS) of the magnetization has thus far only been observed in Gd-based, ferrimagnetic amorphous (\textit{a}-) rare earth-transition metal (\textit{a}-RE-TM) systems, and a comprehensive understanding of the reversal mechanism remains elusive. Here, we report HI-AOS in ferrimagnetic \textit{a}-Gd$_{22-x}$Tb$_x$Co$_{78}$ thin films, from x = 0 to x = 18, and elucidate the role of Gd in HI-AOS in \textit{a}-RE-TM alloys and multilayers. Increasing Tb content results in increasing perpendicular magnetic anisotropy and coercivity, without modifying magnetization density, and slower remagnetization rates and higher critical fluences for switching but still shows picosecond HI-AOS. Simulations of the atomistic spin dynamics based on the two-temperature model reproduce these results qualitatively and predict that the lower damping on the RE sublattice arising from the small spin-orbit coupling of Gd (with $L = 0$) is instrumental for the faster dynamics and lower critical fluences of the Gd-rich alloys. Annealing \textit{a}-Gd$_{10}$Tb$_{12}$Co$_{78}$ leads to slower dynamics which we argue is due to an increase in damping. These simulations strongly indicate that acounting for element-specific damping is crucial in understanding HI-AOS phenomena. The results suggest that engineering the element specific damping of materials can open up new classes of materials that exhibit low-energy, ultrafast HI-AOS.

Photoluminescence and Ce3+→Tb3+→Eu3+ Energy Transfer Processes of the Ce3+/Tb3+/Eu3+-doped β-NaYF4 Phosphors with Broadened Excitation Spectrum

Ce3+/Tb3+ co-doped and Ce3+/Tb3+/Eu3+ tri-doped β-NaYF4 photoluminescent microcrystals using oleic acid as surfactant were synthesized using the solvothermal method. Their microstructural characteristics and photoluminescence properties were investigated in detail. They have the shape of hexagonal prism bipyramids with uniform particle size, which decreases with the concentrations of Tb3+ and Eu3+. The energy transfer processes of both the Ce3+→Tb3+ and the Ce3+→Tb3+→Eu3+ were systematically studied. Compared with Eu3+ or Tb3+ single-doped β-NaYF4 microcrystals, the sensitization by Ce3+ for the photoluminescence of Tb3+ and Eu3+ leads to a broad excitation spectral bandwidth in the ultraviolet (UV) range. Meanwhile, the corresponding optical absorption efficiency is greatly enhanced. High energy transfer efficiencies have been observed from Ce3+ to Tb3+ and from Tb3+ to Eu3+.

High coercivity Nd-Fe-B magnet with low Tb concentration by combined diffusion

Commercial N50 Nd-Fe-B magnet was processed by a combined diffusion process with Pr65Cu15Al20, followed with Pr50Tb30Al20 (at %). The coercivity increment from the original 965.6 kA/m to 1672.5 kA/m was achieved in the combined diffusion sample by introducing 0.23 wt% Tb. However, the coercivity of the conventionally diffused sample with similar Tb content by Pr50Tb30Al20 reached only 1386.2 kA/m. Microstructural and compositional analyses revealed that relatively continuous grain boundary phases were first formed in the diffused sample by Pr65Cu15Al20, moreover, appropriate Tb-rich shells around 2:14:1 grains were further formed during the following diffusion by Pr50Tb30Al20 alloy. The combined diffusion process was helpful in promoting Tb diffusing along the grain boundary phase and further forming uniform Tb-rich shells. It provided a promising way of accelerating Tb diffusing and enhancing Tb availability.

Improved UV Photodetection of Terbium-doped NiO thin films prepared by cost-effective nebulizer spray technique

In the present study, pure and Tb-doped NiO thin films (3 and 6%) were coated on glass substrates using the cost-effective nebulizer spray technique. Their structural, morphological, photoluminescence, and UV sensing properties have been reported. The structural studies confirm the polycrystalline cubic structure with (111) preferred orientation. The structural parameters such as crystallite size, dislocation density, and strain were estimated and a considerable variation with the Tb doping was also reported. Atomic force microscope (AFM) images displaying spherical grains of the samples and the grain size is increasing with Tb concentration. The energy dispersive X-ray (EDX) studies confirmed the elements of Ni, O and Tb in the deposited thin films. The bandgap values are decreasing with doping concentration and the lowest value was observed for the 3% Tb concentration. Photoluminescence (PL) spectra reveal a sharp emission peak at 370 nm and a defect peak at 484 nm, which are attributed to the near band emission and blue emission, respectievely. The UV photodetector parameters such as Responsivity, External quantum efficiency, and Detectivity of pure and doped samples were studied and their values are in the range of 0.12–0.24 AW-1, 37–79%, and 18.74 × 109 to 1.75 × 1010 Jones, respectively. The maximum rise and decay times of 0.4 and 1.8 s, respectievely were observed for the 3% doped sample due to high grain size and reduced the trapping sites and hence improving the UV light photodetector performance.