Tl Incorporation Research Articles

Distribution and Enrichment of Au, Hg, and Tl in the Lanmuchang Deposit, Guizhou, China

Mineralization characterized by Au, Hg, and Tl enrichment is rare, and research on Au, Hg, and Tl mineralization is limited. The Lanmuchang Au–Hg–Tl deposit is located in the “Golden Triangle” of Yunnan, Guizhou, and Guangxi Provinces in China. In this study, we used scanning electron microscopy (SEM), electron microprobe analysis (EPMA), and a Tescan integrated mineral analyzer (TIMA) to analyze the mineral composition and distribution of the different types of ores and identify the occurrence state and enrichment mechanism of ore-forming elements in the Lanmuchang deposit. The results show that the primary ore minerals in the Lanmuchang deposit are pyrite, cinnabar, and lorandite. Cinnabar is the primary carrier of Hg (>90%), and pyrite is the primary carrier of Tl (>60%). Gold, Hg, and Tl primarily occur as solid solutions in hydrothermal pyrite, whereas they primarily occur as nano-scale particles in diagenetic pyrite. The substitution of As for S in hydrothermal pyrite promotes Au enrichment. The coupled substitution of 2Fe2+ ⇔ Tl+ + As3+ may be a significant Tl incorporation mechanism and promotes the occurrence of Hg in pyrite. The As and Se contents and Cu/Au and Co/Ni ratios of the hydrothermal pyrite demonstrate that the ore-forming fluid was mostly in a low-temperature, low-salinity, almost-neutral pH, and nearly reducing environment. The results show that the mineralization of the Lanmuchang deposit is associated with the cooling, oxidation, water–rock interaction, and boiling processes of the ore-forming fluid(s).

Single Crystal X‐Ray Structure Analyses of Binary and Ternary Compounds A49Tl108+x (A=K, Rb, Cs; x=0–1.76) Related to the K49Tl108 Type Structure

AbstractThe structural chemistry of alkali metal thallides shows a broad range of type structures. At an alkali metal : thallium proportion A : Tl 1 : 2 the perceived dependency on the alkali metal involved is conspicuous. Two main structure types are reported with A15Tl27 (A=K, Rb, Cs) and K49Tl108. The compound K49K108 with a 3‐dimensional Tl‐substructure has been known since 1993 from Cordier and Müller but so far only with potassium. We here present single crystal X‐Ray structure analyses of the compounds K49‐yRbyTl108, and K49‐yCsyTl108 ( belonging to the K49Tl108 type structure. Additionally, structures of Rb49Tl109.67, Cs3.35Rb45.65Tl109.71 and Cs7.49Rb41.51Tl109.76 are introduced, which prove the possibility of Tl incorporation in the Tl12 icosahedra in K49Tl108 type structures. The effects of the change in alkali metals on the thallium substructure are discussed as well as the preferred Wyckoff sites of the different alkali metals.

Geochemical behaviour and transport of technology critical metals (TCMs) by the Tinto River (SW Spain) to the Atlantic Ocean

This paper addresses the behaviour of several technology critical metals (TCMs), i.e., rare earth elements (REEs), Y, Sc, Ga and Tl, in the Tinto River (SW Spain), quantifying their fluxes to the Atlantic Ocean and unravelling the governing geochemical processes controlling their solubility. To accomplish this goal, a high-resolution (2–24 h) sampling was performed during the hydrological year 2017/18. Mean dissolved concentrations of 380 μg/L of REE, 99 μg/L of Y, 15 μg/L of Sc, 9.2 μg/L of Ga and 4.8 μg/L of Tl were found. Most TCMs followed a behaviour similar to that of sulphate and base metals throughout the year, exhibiting a quasi-conservative behaviour due to acidic conditions. However, dissolved Tl concentrations seem to be strongly controlled by Tl incorporation onto secondary minerals and diatoms deposited on the riverbed, especially during the dry season. The remobilization of riverbed sediments led to the transport of significant amounts of TCMs associated with particulate matter, especially Al oxy-hydroxy-sulphates or Al-silicates rather than Fe precipitates (except for Tl and Ga). Around 5.8 t of REE, 1.3 t of Y, 248 kg of Sc, 139 kg of Ga and 138 kg of Tl were delivered annually in their dissolved forms by the Tinto River to the Atlantic Ocean, which constitutes around 0.09% of the dissolved global flux into the oceans of Y, 0.02% of the REE flux, 0.01% of the Ga flux and 0.001% of the Sc flux.

Higher Tl bioaccessibility in white mustard (hyper-accumulator) grown under the soil than hydroponic conditions: A key factor for the phytoextraction use

The paper deals with the thallium (Tl) access into the white mustard (Sinapis alba L.). We were comparing two approaches: A - hydroponic, B - semi-hydroponic (artificial soil). The kinetics of Tl plant uptake at different available Tl doses (0.1, 0.05 and 0.01 mg L−1) was tested. It was revealed that the hydroponic arrangement did not accelerate the plant uptake of Tl. The concentration of plant Tl was surprisingly roughly double under the semi-hydroponic (artificial soil) conditions as compared to the hydroponic system; the highest Tl concentrations were detected in stems, proving an important role of plant grown strategy on Tl bioaccessibility. We found that almost independently of the initial dose of Tl the juvenile stadium of the mustard can preserve1-2% of the total Tl pool. Up to 95% of this Tl dose is stored in the shoots. The different strategy of the plant growing may strongly affect the path of Tl incorporation. The total Tl input into the leaf tissue in hydroponics may be from 69% (p = 0.01) explained by parallel assimilation of Ca. In contrast, the Tl entry into the leaf grown on the artificial soil could be limited by Mn path (R2 = 0.91, p = 0.01).

Band gap engineering of In2O3 by alloying with Tl2O3

Efficient modulation of the bandgap of In2O3 will open up a route to improved electronic properties. We demonstrate using ab initio calculations that Tl incorporation into In2O3 reduces the band gap and confirm that narrowing of the gap is observed by X-ray photoemission spectroscopy on ceramic surfaces. Incorporation of Tl does not break the symmetry of the allowed optical transitions, meaning that the doped thin films should retain optical transparency in the visible region, in combination with a lowering of the conduction band effective mass. We propose that Tl-doping may be an efficient way to increase the dopability and carrier mobility of In2O3.

X-ray photoelectron spectroscopy analysis of TlInGaAsN semiconductor system and their annealing-induced structural changes

TlInGaAsN thin films grown by gas-source molecular-beam epitaxy were investigated by x-ray photoelectron spectroscopy (XPS) to analyze the Tl incorporation and to study the annealing-induced transformation of the atomic configurations. XPS analysis revealed that the Tl composition in the grown TlInGaAsN is around 1.5% and that the dominant atomic configuration of the TlInGaAsN changes from the In–As and Ga–N bonds to the In–N and Ga–As bonds by 700 °C rapid thermal annealing. High-resolution x-ray diffraction and reciprocal space mapping measurements showed that no significant out-diffusion of the elements occurs in the TlInGaAsN/TlGaAsN quantum wells (QWs) even after the same annealing. It is concluded that the blueshift in the photoluminescence peak for the TlInGaAsN/TlGaAsN QWs after annealing is attributed to the transformation of the atomic configuration in TlInGaAsN.

Growth and photoluminescence properties of TlInGaAsN/TlGaAsN triple quantum wells

TlInGaAsN/TlGaAsN system was proposed to fabricate the temperature-insensitive both lasing wavelength and threshold current density laser diodes, which are important in the wavelength division multiplexing optical fiber communication system. The effects of indium and nitrogen concentrations in the quantum wells (QWs) and barriers on the properties of molecular-beam epitaxy grown TlInGaAsN/TlGaAsN triple QWs (TQWs) were investigated. The TQW samples having higher N concentration in the QWs have the highest Tl incorporation without deterioration of the crystalline quality. The temperature dependence of the photoluminescence (PL) peak energy was found to be the least for the highest Tl containing TQW sample. The incorporation of Tl causes the reduction in the coupling constant of the electron–phonon interaction, leading to the reduced temperature dependence of the PL peak shift. Thermal activation energies, which are deduced from the Arrhenius plot of PL intensity, are attributed to the delocalization of the excitons at low temperatures and to the escape of carriers from the QWs to the barriers at high temperatures.

Thallium dynamics in contrasting light sandy soils—Soil vulnerability assessment to anthropogenic contamination

The influence of different soil conditions and the presence of LMWOA (Low Molecular Weight Organic Acids) on anthropogenic Tl dynamics were discussed in this study. A shift from the “labile” to the residual fraction during the ageing was identified, indicating Tl incorporation into stable phases (e.g., illite and/or amorphous silicates). The increased water-soluble Tl concentration (1.8-fold, in maximum) after the split application of LMWOA (simulating root exudation) was observed in all soils; partial dissolution of relatively “insoluble” Tl-bearing phases (silicates and eventually oxides) in the presence of LMWOA is suggested. Thermodynamic modeling showed that Tl mobilization in the presence of citric and oxalic acids was indirect and could be attributed to complexation of major elements (Ca, Mg, Al) originating from the dissolution of various soil phases. On the contrary, H +-promoted dissolution by acetic acid was assumed as the predominant mechanism of Tl mobilization. Manganese(III,IV) oxides, illite and probably amorphous silicates were evaluated as the dominant phases responsible for Tl retention in the soils. In carbonate-rich soils, Tl coprecipitation with the newly formed carbonates seems to be an important factor influencing Tl release. Therefore, we suggest data on CEC, pH ZPC and soil mineralogy to be critical for assessment of Tl behavior in soil systems.

MBE growth and characterization of TlInGaAsN double quantum well structures

In the pursuit of reducing the temperature dependence of the emission wavelengths of devices, TlInGaAsN double quantum well (DQW) structures with different barriers grown on GaAs substrates by molecular beam epitaxy (MBE) were investigated. Higher Tl incorporation, a key parameter to reduce temperature dependence, could be obtained in the TlGaAsN barrier samples. However, the presence of many dislocations and very rough interfaces together with phase separation reduced the photoluminescence (PL) characteristics. DQW structures with combined barriers of TlGaAsN+TlGaAs+TlGaAsN and those consisting of TlGaAsN with reduced N composition showed improved crystalline characteristics. The (2 2 4) reciprocal space maps of these two samples did not show any diffraction corresponding to phase segregation. However, cross-sectional transmission electron microscopy (X-TEM) images revealed the presence of inhomogeneity (i.e., the presence of nearly perfect regions with good interfaces as well as regions with rough interfaces) in these samples.

TlGaInNAs/GaAs double quantum well structures: Effect of barrier layers and substrate orientation

The quinary TlGaInNAs-based double quantum well (DQW) structures were grown on GaAs substrates by electron cyclotron resonance (ECR)-MBE and the samples were probed by secondary ion mass spectroscopy (SIMS). Light emitting diodes (LEDs) were fabricated using these DQW wafers and their electroluminescence (EL) behaviors were studied at different temperatures. The effects of different barrier layers and substrate orientations on the amount of Tl incorporation and on the temperature dependency of the EL peak wavelengths of the LEDs were studied. Higher incorporation of Tl into the quantum well (QW) region and the ensuing change in the temperature dependency of the peak wavelengths owing to the TlGaAs barrier layer are reported. GaAs substrates having (3 1 1)B orientation were found to allow more Tl incorporation as compared to (1 0 0) and (3 1 1)A oriented substrates. The LEDs fabricated out of the TlGaInNAs/TlGaAs/(3 1 1)B GaAs DQW structures showed the least temperature dependency of the EL peak wavelengths exemplifying the usefulness of Tl in the QW as well as barrier region.

Experimental and theoretical investigation into the difficulties of thallium incorporation into III-V semiconductors

The aim of this paper is to show---from both an experimental and a theoretical point of view---why it is so difficult to incorporate thallium into III-V semiconductors. The experimental part describes how ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Tl}}_{x}\mathrm{As}$ epilayers on GaAs(001) and ${\mathrm{In}}_{1\ensuremath{-}x}{\mathrm{Tl}}_{x}\mathrm{As}$ epilayers on InAs(001) can be obtained using molecular beam epitaxy (MBE). Tl is found to be much easier to incorporate into GaAs (7% over 50 nm) than into InAs (2.5% over 50 nm) despite the higher elastic stress in the former than in the latter. Once pseudomorphic ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Tl}}_{x}\mathrm{As}$ epilayers of sufficient thickness have been successfully obtained, the lattice and elastic parameters for the Tl-As bonding in ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Tl}}_{x}\mathrm{As}$ alloys are deduced by combining results from double-crystal x-ray diffraction and Rutherford backscattering (RBS) spectrometry . The theoretical part proposes a tentative explanation---within Keating's valence force field framework---for the difficulties met when incorporating Tl into III-V compounds. When incorporated into either a GaAs or an InAs bulk matrix, the Tl atoms keep away from each other by avoiding being first neighbors in the III-element sublattice, but the magnitude of the phenomenon is clearly much smaller in the InAs case than in the GaAs case. However, this effect alone cannot explain the difference between GaAs and InAs versus Tl incorporation. Turning next to surface effects, the paper demonstrates that the dimers on the InAs surface are better stabilized by the presence of Tl than are those on the GaAs surface. Last, a stronger tendency to form diluted ordered alloy clusters for GaAs than for InAs is demonstrated, which could be a reason for the greater difficulties encountered when incorporating Tl into InAs matrix than into GaAs.

Optical absorption spectroscopy measurement of the gap shrinkage due to thallium incorporation in GaInTlAs alloys

The optical properties of Ga(1−y)0.45In(1−y)0.55TlyAs epilayers grown at low temperature (230 °C) by solid-source molecular-beam epitaxy on InP substrates were characterized using optical absorption and photoluminescence techniques. Optical absorption measurements at room temperature show a gap shrinkage toward lower energies from 0.71 to 0.61 and 0.53 eV when the Tl content increases from 0% to 4%, and 8%, in good agreement with theoretical predictions. Low-temperature photoluminescence band-gap signals from GaInAs and GaInTlAs layers are only obtained after rapid thermal annealing performed in order to improve the electronic quality of the layers. A band gap decrease as much as 41 meV for GaInTlAs with 1.9% Tl incorporation is measured by photoluminescence at 8 K.

Some experiments on the growth of InTlSb by LPE

InTlSb solid solutions have been proposed as new materials to extend the IR detecting capabilities offered by III–V compounds and there have been several reports about their predicted properties and of its growth by MBE and OMCVD. In this work two types of experiments were done. First, the results of attempts to obtain the binary compound TlSb from liquids with a stoichiometric composition are reported. Second, the determination of some liquidus points of the ternary solution and the results of attempts of growing the ternary alloy In 1− x Tl x Sb by LPE on InSb substrates are also reported. Reflectance, X-ray diffraction and EDX measurements show that the epitaxial layers are InSb. Tl incorporation into the solid could not be detected by these techniques.

Growth of GaInTlAs layers on InP by molecular beam epitaxy

Growth of GaInTlAs alloys on InP(001) has been attempted by solid source molecular beam epitaxy. Thallium incorporation into Ga1−xInxAs matrices was studied as a function of substrate temperature, arsenic overpressure, matrix composition, and growth rate. At high temperatures (>350 °C) thallium evaporates, whereas at intermediary temperatures (270–350 °C) thallium segregates into droplets on the surface. Only in the low temperature range (180–260 °C) can thallium be incorporated in some conditions, leading to mirror-like surfaces. Up to 18% Tl content was incorporated into a Ga0.70In0.30As matrix and up to 40% Tl into a GaAs matrix. For these high Tl concentrations, Tl droplets are avoided and Tl incorporation is achieved only when using high arsenic pressures. However, this limits surface adatom diffusion and leads to amorphous, polycrystalline, or twinned materials. Finally, a narrow window for single-crystal growth has been found for low Tl contents (4%) using optimized growth conditions with low V/III pressure ratios and high growth rates.

Tl incorporation in InSb and lattice contraction of In1−xTlxSb

Ternary In1−xTlxSb thin films are grown by low pressure metalorganic chemical vapor deposition in the high In composition region. Infrared photoresponse spectra of the In1−xTlxSb epilayers show a clear shift toward a longer wavelength compared to that of InSb. Tl incorporation is confirmed by Auger electron spectroscopy. In contrast to the theoretical expectation, high resolution x-ray diffraction study reveals that the lattice of the In1−xTlxSb epilayers is contracted by the incorporation of Tl. As more Tl is incorporated, the lattice contraction is observed to increase gradually in the experimental range. A possible origin of this phenomenon is discussed. Our experimental results suggest that the Tl incorporation behavior in In1−xTlxSb differs from that of other group III impurities in III antimonides.