Stable Tl205 ions have the lowest known energy threshold for capturing electron neutrinos (νe) of Eνe≥50.6 keV. The Lorandite Experiment (LOREX), proposed in the 1980s, aims at obtaining the longtime averaged solar neutrino flux by utilizing natural deposits of Tl-bearing lorandite ores. To determine the νe capture cross section, it is required to know the strength of the weak transition connecting the ground state of Tl205 and the 2.3 keV first excited state in Pb205. The only way to experimentally address this transition is to measure the bound-state beta decay (βb) of fully ionized Tl81+205 ions. After three decades of meticulous preparation, the half-life of the βb decay of Tl81+205 has been measured to be 291−27+33 days using the Experimental Storage Ring (ESR) at GSI, Darmstadt. The longer measured half-life compared to theoretical estimates reduces the expected signal-to-noise ratio in the LOREX, thus challenging its feasibility. Published by the American Physical Society 2024

Stable ^{205}Tl ions have the lowest known energy threshold for capturing electron neutrinos (ν_{e}) of E_{ν_{e}}≥50.6  keV. The Lorandite Experiment (LOREX), proposed in the 1980s, aims at obtaining the longtime averaged solar neutrino flux by utilizing natural deposits of Tl-bearing lorandite ores. To determine the ν_{e} capture cross section, it is required to know the strength of the weak transition connecting the ground state of ^{205}Tl and the 2.3 keV first excited state in ^{205}Pb. The only way to experimentally address this transition is to measure the bound-state beta decay (β_{b}) of fully ionized ^{205}Tl^{81+} ions. After three decades of meticulous preparation, the half-life of the β_{b} decay of ^{205}Tl^{81+} has been measured to be 291_{-27}^{+33}  days using the Experimental Storage Ring (ESR) at GSI, Darmstadt. The longer measured half-life compared to theoretical estimates reduces the expected signal-to-noise ratio in the LOREX, thus challenging its feasibility.

Abstract In this paper, we report on electron microscopy studies of single crystals of the natural mineral lorándite, TlAsS2. The main focus of this investigation was to address the question as to whether those lorándite crystals are chemically and structurally homogeneous, in order to be utilized as an effective neutrino detector within the lorándite experiment (LOREX) project. Apart from few secondary minerals, being present only at the surface of the lorándite samples, scanning electron microscopy (SEM) indicated homogeneous crystals. Similarly, transmission electron microscopy (TEM) imaging revealed a homogenous and undisturbed crystal structure, with the only exception of local coffee-bean contrasts; however, rarely observed. These specific contrast variations are known to be a typical strain indicator caused by a local deformation of the crystal lattice. Energy-dispersive X-ray spectroscopy (EDS) in conjunction with electron energy-loss spectroscopy (EELS) did not show any significant chemical difference when analysing regions on or off those coffee-bean features, indicating a chemically homogenous mineral. Since the presence of lattice disturbing secondary phase precipitates could be excluded by imaging and complementary chemical analysis, crystal defects such as dislocations and stacking faults or minor fluid inclusions are discussed as the probable origin of this local elastic strain. The experimental results confirm that the studied lorándite single crystals fulfil all structural and chemical requirements to be employed as the natural mineral that allows to determine solar neutrino fluxes. In addition, critical issues regarding the rather challenging sample preparation of lorándite are reported and a quantification of the maximum tolerable electron dose in the TEM is presented, since lorándite was found to be sensitive with respect to electron beam irradiation. Furthermore, the limits of EDS measurements due to peak overlapping are shown and discussed utilizing the case of Pb in lorándite. In this regard, a comparison with the Tl- and Pb-containing natural mineral hutchinsonite, TlPbAs5S9, is also included.

In the present work, the oxidation and spin state of Fe and the local structure around Fe in the supercapacitor birnessite with different contents of the Fe dopant were investigated using Mössbauer spectroscopy. It was found that Fe ions were exclusively present as high spin Fe3+ in octahedral coordination with about 70% iron occupying the Mn3+ positions and about 30% iron occupying the Mn4+ positions in the [MnO6] octahedra for all Fe-doped birnessite samples. Based on these new findings, the trend of typical cell parameters, selected bond lengths of the Fe-doped birnessites and their corresponding quadrupole splittings in the Mössbauer spectra were well explained by considering both the weakened Jahn–Teller effect during the replacement of Mn3+ by Fe3+ and the expansion of octahedra during the replacement of Mn4+ by Fe3+. The present work offers some new insights into the understanding of the mechanism of the heterogeneous atomic doping on the crystal structure of birnessite, with importance for both mineralogy and material science.

In the field of the renewables, a large effort has been devoted in the last years to obtain conventional and new materials for solar energy conversion by using methods which couple a good efficiency and scalability with energetic and environmental concerns. This research has included the so-called kesterites, materials considered interesting for the thin-film solar cell technology, consisting of relatively abundant and harmless elements: Cu3-x-yFexZnySn(S,Se)(4). In this study, we undertook the synthesis of members of the kuramite-stannite (Cu3SnS4-Cu2FeSnS4) join by means of a two-step solvothermal approach, able to provide nanocrystalline products in an easy, low-temperature, and fast way. The sample with the highest Fe concentration was characterised by means of a multi-analytical approach, aimed to assess not only its final structural, chemical and micromorphological features, but also the redox speciation of the two transition metal cations, i.e. Cu and Fe, in relation to the overall charge balance. Namely, Electron Paramagnetic Resonance (EPR), Mossbauer and X-ray Absorption Spectroscopy (XAS) and SQUID magnetometry were involved. The main results point out an excellent control of the structural features, and an intermediate Fe content in the sample, leading to the following formula unit: Cu2.2Fe0.48Sn1.2S4. The overall findings of the multi-analytical characterization imply a complex redox balance, where inferring the site occupancy is not trivial; the charge balance, in fact, can only be achieved taking into account the presence of both Fe(III) and vacancies. Moreover, Fe is distributed over two different crystallographic sites.

Mineralogy deals with the structure and related physical and chemical properties of materials in the geo- and biosphere. The knowledge about these minerals and their specific properties is increasingly used in various technical, medical and environmental fields [1]. One of the most impressive examples is garnet, a mineral which usually occurs in magmatic and metamorphic rocks. On the one hand, its chemistry is closely related to the chemistry of the host rock and, more importantly, its crystal structure reflects the pressure and temperature conditions during its formation. On the other hand, garnet is an important material for technical issues, e.g. the well-known Yttrium Aluminum Garnet (YAG)-Laser, and it finds now new applications, e.g. in the field of energy storage. Even though the chemical composition varies considerably all garnets have in common the same crystal structure. Li-oxide garnet with the composition Li7La3Zr2O12 (LLZO) is an excellent example to demonstrate the application of mineralogical knowledge in material science. Recently, these garnets have been identified as a promising material in the field of energy storage, as they can be used as solid state electrolyte in Li-based all solid state battery concepts. In Li-ion batteries, solid electrolytes are considered to replace polymer based electrolytes, which have disadvantages e.g. they are highly inflammable.The presentation of garnet stands as an example for numerous other mineral groups which build the basis for their application in material science, such as spinel, perovskite, zeolite, sphalerite, chalcopyrite, kesterite, argyrodite, etc. In our contribution some of these mineral groups and their importance as basis for functional materials will be presented.[1] S.-Heuss-Aßbichler, G. Amthauer, M. John (Eds.). Highlights in Applied Mineralogy. Dr Gruyter Berlin/Boston 2017, 344 pp.

In the present work, the oxidation and spin state of Fe and the local structure around Fe in the supercapacitor birnessite with different contents of the Fe dopant were investigated using Mössbauer spectroscopy. It was found that Fe ions were exclusively present as high spin Fe3+ in octahedral coordination with about 70% iron occupying the Mn3+ positions and about 30% iron occupying the Mn4+ positions in the [MnO6] octahedra for all Fe-doped birnessite samples. Based on these new findings, the trend of typical cell parameters, selected bond lengths of the Fe-doped birnessites and their corresponding quadrupole splittings in the Mössbauer spectra were well explained by considering both the weakened Jahn–Teller effect during the replacement of Mn3+ by Fe3+ and the expansion of octahedra during the replacement of Mn4+ by Fe3+. The present work offers some new insights into the understanding of the mechanism of the heterogeneous atomic doping on the crystal structure of birnessite, with importance for both mineralogy and material science.

In the present work, the oxidation and spin state of Fe and the local structure around Fe in the supercapacitor birnessite with different contents of the Fe dopant were investigated using Mössbauer spectroscopy. It was found that Fe ions were exclusively present as high spin Fe 3+ in octahedral coordination with about 70% iron occupying the Mn 3+ positions and about 30% iron occupying the Mn 4+ positions in the [MnO 6 ] octahedra for all Fe-doped birnessite samples. Based on these new findings, the trend of typical cell parameters, selected bond lengths of the Fe-doped birnessites and their corresponding quadrupole splittings in the Mössbauer spectra were well explained by considering both the weakened Jahn–Teller effect during the replacement of Mn 3+ by Fe 3+ and the expansion of octahedra during the replacement of Mn 4+ by Fe 3+ . The present work offers some new insights into the understanding of the mechanism of the heterogeneous atomic doping on the crystal structure of birnessite, with importance for both mineralogy and material science.

In the present work, the oxidation and spin state of Fe and the local structure around Fe in the supercapacitor birnessite with different contents of the Fe dopant were investigated using Mossbauer spectroscopy. It was found that Fe ions were exclusively present as high spin Fe3+ in octahedral coordination with about 70% iron occupying the Mn3+ positions and about 30% iron occupying the Mn4+ positions in the [MnO6] octahedra for all Fe-doped birnessite samples. Based on these new findings, the trend of typical cell parameters, selected bond lengths of the Fe-doped birnessites and their corresponding quadrupole splittings in the Mossbauer spectra were well explained by considering both the weakened Jahn-Teller effect during the replacement of Mn3+ by Fe3+ and the expansion of octahedra during the replacement of Mn4+ by Fe3+. The present work offers some new insights into the understanding of the mechanism of the heterogeneous atomic doping on the crystal structure of birnessite, with importance for both mineralogy and material science.

Investigating conductivity variations in Al stabilized LLZO by combining microelectrode impedance spectroscopy with spatially resolved chemical analysis.

Institute of Chemical Technologies and Vienna, Austria. E-mail: stefan.smetaczek@ Department of Chemistry and Physics of M Austria Institute for Chemistry and Technology of M Graz, Austria Christian Doppler Laboratory for Lithium Technology of Materials, Graz University of Austrian Institute of Technology, Vienna, A † Electronic supplementary informa 10.1039/c9ta00356h Cite this: J. Mater. Chem. A, 2019, 7, 6818

The Mössbauer spectra of a nearly stoichiometric natural bornite, Cu5FeS4, specimen were reinvestigated between 295 and 4.2 K. There is no difference between the Neél temperature T N as determined by the Mössbauer effect or by the susceptibility measurements (T N = 67.5 K). No additional paramagnetic doublet can be observed in the low-temperature MS spectra. The valence state of Fe is Fe(3−x)+ caused by a partial electron transfer from the Cu+ ions to the Fe3+ ions which increases the shielding of the s-electrons by the d-electron density and by this increases the isomer shift to a value intermediate between tetrahedral high-spin Fe2+ and tetrahedral high-spin Fe3+.

LOREX (LORandite EXperiment) is a geochemical project addressing the solar proton-proton neutrino flux for the period of 4.31(2) Ma from the reaction Tl-205 + v(e) -> (205)pb + e(-) with a very low threshold (52 keV) for solar pp-neutrino capture. A decisive step for this purpose is to obtain the precise, background-corrected ratio of Pb-205/Tl-205 in the mineral lorandite (TlAsS2) as geochemical detector occurring in the ore deposit of Allchar in Macedonia. This study presents a report on the excavation of lorandite bearing ore from adit P-21 of the ore body Crven Dol as well as on the separation of pure lorandite from the raw ore. A detailed mineralogical and chemical investigation of the separated lorandite is performed with special regard to the question of its use as detector for solar pp-neutrinos.

The interface stability versus Li represents a major challenge in the development of next-generation all-solid-state batteries (ASSB), which take advantage of the inherently safe ceramic electrolytes. Cubic Li7La3Zr2O12 garnets represent the most promising electrolytes for this technology. The high interfacial impedance versus Li is, however, still a bottleneck toward future devices. Herein, we studied the electrochemical performance of Fe3+-stabilized Li7La3Zr2O12 (LLZO:Fe) versus Li metal and found a very high total conductivity of 1.1 mS cm-1 at room temperature but a very high area specific resistance of ∼1 kΩ cm2. After removing the Li metal electrode we observe a black surface coloration at the interface, which clearly indicates interfacial degradation. Raman- and nanosecond laser-induced breakdown spectroscopy reveals, thereafter, the formation of a 130 μm thick tetragonal LLZO interlayer and a significant Li deficiency of about 1-2 formula units toward the interface. This shows that cubic LLZO:Fe is not stable versus Li metal by forming a thick tetragonal LLZO interlayer causing high interfacial impedance.

All-solid state batteries have the ability to bring us closer to a zero-emission society. Such battery systems, however, require a powerful solid Li-ion conductor with high stability and exceptionally high Li-ion conductivity. Cubic Li7La3Zr2O12 (LLZO) garnets are attractive candidates combining high ionic conductivity and thermal as well as electrochemical stability. Since the cubic LLZO polymorph is not stable at room temperature, supervalent cations, such as Al3+, are needed to stabilize the highly conductive phase. However, strong variations in conductivity values were reported even for very similar Al contents, which is critical for future battery applications. Therefore, the overall performance of 44 samples with nominally identical composition (Li6.40Al0.20La3Zr2O12), sintered at two different temperatures (1150 degrees C and 1230 degrees C, respectively) was analysed by electrochemical impedance spectroscopy. The aim of this work is to elucidate the origin of the strong variations in conductivity reported in literature. This study shows that the effective conductivities of the LLZO samples vary between 2 x 10(-5) and 8 x 10(-4) S cm(-1), which cannot be attributed to obvious differences in sample preparation. Furthermore, the stepwise reduction of the sample volume and repeated measuring of the impedance revealed conductivity variations even within a single sample. Finally, preliminary chemical analysis by laser ablation (LA) - inductively coupled plasma (ICP) - mass spectrometry (MS) identified Al in homogeneities in LLZO, which may be responsible for conductivity variations of nominally equal samples.

LOREX (LORandite EXperiment) is a geochemical experiment addressing the solar (pp) neutrino flux for the period of 4.3 Ma from the reaction 205Tl + ve → 205Pb + e- with an unprecedentedly low threshold (52 keV) for solar pp-neutrino capture. A decisive step for this purpose is getting the precise, background-corrected ratio of 205Pb/205Tl in lorandite (TlAsS2). This report presents the status of major challenges being addressed, in particular the determination of the paleo-depth of lorandite, including the eroded layer over 4.3 Ma, as well as the choice of appropriate techniques for extraction, separation and quantitative determination of the ultra-low 205Pb concentration in the extracted lorandite samples.