Wavelength Dispersive X-ray Analysis Research Articles

Tetrahedral aluminum in tourmaline from a spinel-pargasite-metamorphosed mafic-ultramafic rock

Abstract Tourmaline is a widespread borosilicate mineral, which is well known for its variable chemistry. Although major amounts of octahedral Al in tourmaline is commonplace, the occurrence of significant amounts of tetrahedral Al is relatively rare. This paper focuses on tourmaline from the collection of the A.E. Fersman Mineralogical Museum (Russia) originated from Italy with up to 25% of Si replaced by Al at the tetrahedral site. The tourmaline is characterized by optical and scanning electron microscopy, Raman spectroscopy, infrared spectroscopy, Mössbauer spectroscopy, energy-dispersive and wavelength-dispersive X-ray analysis, laser ablation inductively coupled plasma optical emission spectrometry and single crystal X-ray diffraction. The studied tourmaline occurs as transparent dark blue crystals (with equant external morphology) up to 3 mm in size and forms veinlets cutting a (Mg,Al)-rich metamorphosed mafic-ultramafic rock (Mg≫Fe) composed of spinel, pargasite, clinochlore, phlogopite, and hydroxylapatite. The studied tourmaline meets the criteria defining magnesio-lucchesiite and can be compositionally formed via Tschermak-like ([6]Me2++[4]Si4+↔[6]Al3++[4]Al3+, where [6]Me2+=Mg, Fe) or plagioclase-like ([9]Ca2+ + [4]Al3+ ↔ [9]Na+ + [4]Si4+) substitutions. Zones with a relatively high Si content (Si-rich) have pronounced indications of dissolution, while silicon-depleted zones (Si-poor) overgrow Si-rich zones and eventually creates a visible replacement zone of the crystal. We suggest that Si-poor tourmaline result from the Si-rich tourmaline losing Si during a metasomatic process. The resulting empirical crystal-chemical formula for the Si-poor zone is: X(Ca0.95Na0.03□0.02)Σ1.00 Y(Mg1.08Al0.98Fe2+0.50Fe3+0.43)Σ3.00 Z(Al5.91Fe3+0.09)Σ6.00 T[(Si4.57Al1.43)Σ6.00O18] (BO3)3 V(OH)3 W[O0.95(OH)0.05]Σ1.00 (a = 15.9811(2), c = 7.12520(10) Å, R1 = 1.7 %) and for the Si-rich zone is: X(Ca0.89Na0.11)Σ1.00 Y(Mg1.55Al0.80Fe2+0.34Fe3+0.31)Σ3.00 Z(Al5.51Mg0.44Fe3+0.05)Σ6.00 T[(Si5.35Al0.65)Σ6.00O18] (BO3)3V(OH)3W[O0.93(OH)0.07]Σ1.00 (a=15.9621(3), c=7.14110(10) Å, R1=1.7 %). According to PT calculations of mineral assemblage stability and comparable data on synthetic [4]Al-rich tourmalines, the studied tourmaline was formed at 600–750 °C and 0.10-0.20 GPa. The formation of tetrahedral Al-rich tourmalines requires several unusual factors: (1) desilication of primary rocks and (2) high temperatures and relatively low pressures.

Study on Factors Hindering the Single-Phase Formation of Divalent-Ion-Stabilized W-Type Ferrites

Me-substituted W-type ferrites (AMe2Fe16O27 with A = Sr, Ba, …, and Me = Co, Ni, Zn, Mg, …) can be obtained by standard solid state reaction but always contain secondary phases. Phase stability of SrMe2Fe16O27 with Me = Co, Ni, Zn, and Mg sintered in various oxygen pressures of pO2 = 0.2, 1, 10, and 387 atm were investigated using X-ray diffraction analysis, wavelength dispersive X-ray (WDX) analysis, and transmission electron microscopy (TEM). WDX analysis revealed that the W-type ferrites are described as SrMe2−δFe16+δO27 because Fe3+ is partially reduced to Fe2+ even when synthesis is initiated from SrMe2Fe16O27. Increasing the oxygen pressure suppresses the reduction of Fe3+ and the formation of the secondary phases. In addition, TEM analysis shows that the SrCo2Fe16O27 single crystal is free of stacking faults. We conclude that the single-phase formation of the Me-substituted W-type ferrites is hampered by the discrepancy between initial and actual chemical composition caused by the appearance of Fe2+.

Synthesis of ΝbN faceted grains from oxides and boron nitride with sodium

Agglomerates of ε-NbN hexagonal prismatic faceted grains with a size between 5 and 50 μm were formed by heating Nb2O5 or NbFeO4 powder and Na lump in a BN crucible at 900–1100 °C under an Ar atmosphere. Wavelength-dispersive X-ray analysis demonstrated that the ε-NbN faceted grains have a nearly stoichiometric composition. In addition to the ε-NbN grains, powders of niobium nitrides containing δ-NbN and Nb2N, and water-soluble Na3BO3 were included in the sample prepared from Nb2O5 at 1100 °C, while powders of Fe and Na3BO3, and a trace of δ-NbN were included in the sample from NbFeO4. These reactions were attributed to metathesis reactions in which the oxygen in the oxides and the nitrogen in the solid nitrogen source, BN, were replaced by the formation of Na3BO3. An extra amount of nitrogen supplied from the starting material enhances the formation of ε-NbN and suppressed the formation of δ-NbN and Nb2N.

Study on Factors Hindering the Single-phase Formation of Divalent-ion-stabilized W-type Ferrites

Me-substituted W-type ferrites (AMe2Fe16O27 with A = Sr, Ba, …, and Me = Co, Ni, Zn, Mg, …) can be obtained by standard solid state reaction but always contain secondary phases. Phase stability of SrMe2Fe16O27 with Me = Co, Ni, Zn, and Mg sintered in various oxygen pressures of pO2 = 0.2, 1, 10 and 387 atm were investigated using X-ray diffraction analysis, wavelength-dispersive X-ray (WDX) analysis, and transmission electron microscopy (TEM). WDX analysis revealed that the W-type ferrites are described as SrMe2-δFe16+δO27 because Fe3+ is partially reduced to Fe2+ even when synthesis is initiated from SrMe2Fe16O27. Increasing the oxygen pressure suppresses the reduction of Fe3+ and the formation of the secondary phases. In addition, TEM analysis shows that the SrCo2Fe16O27 single crystal is free of stacking faults. We conclude that the single-phase formation of the Me-substituted W-type ferrites is hampered by the discrepancy between initial and actual chemical composition caused by the appearance of Fe2+.

Temperature-versus compositional-induced structural deformations of gadolinite group minerals with various Be/B ratio

Gadolinite crystals from Mogov (Tajikistan), Dorozhniy (Tajikistan), Dara-Pioz (Tajikistan) and Osterby (Sweden) with different Be/B ratio (0.56–191) were studied by single crystal X-ray diffraction, energy dispersive and wavelength-dispersive X-ray analysis and inductively coupled plasma–optical emission spectrometry to compare their crystal chemistry features. Besides, Raman spectra and thermal behavior at low (from −173 to +67 ​°C) and high (from +25 to +1100 ​°C) temperatures of gadolinite-(Y) from Osterby (Sweden) was investigated in order to study recrystallization and obtain the thermal expansion coefficients. It was shown that thermal expansion of gadolinite-(Y) (Y2Fe2+Be2Si2O10) is very close to the expansion of datolite (Ca2B2Si2O8(OH)2). Comparison of the temperature and chemical deformations confirms the main rules of comparative crystal chemistry.

Treatment of gold ore cyanidation wastewater by adsorption onto a Hydrotalcite-type anionic clay as a novel adsorbent

The treatment of cyanide contaminated wastewater from a gold processing plant was performed by the synthesized nanostructured Layered Double Hydroxide (LDH) which has known as a Hydrotalcite-type anionic clay. LDH was synthesized by the co-precipitation process, characterized by X-ray fluorescence (XRF), X-ray powder diffraction (XRD), scanning electron microscope (SEM) Brunauer-Emmett-Teller (BET), Fourier-transform infrared spectroscopy (FTIR) and Wavelength Dispersive X-ray analysis (WDX) and applied for removal of free cyanide from both synthetic solution and mining effluent. The maximum particle size of synthesized LDH was determined to be 4nm based on the Scherrer's equation. The maximum loading capacity of LDH, 60mg/g, indicates that LDH is an interesting adsorbent for cyanide removal. The data modeling showed that the kinetic and equilibrium data best fitted by FPKM and RPIM, respectively, also, rate-controlling step in the adsorption process is intra-particle diffusion based on Weber-Morris plot, and the adsorption of CN- onto LDH is a two-step process. The thermodynamic studies confirm that the adsorption of free cyanide on Mg/Al LDH is a spontaneous and endothermic process. The energy of activation for adsorption of free cyanide on Mg/Al LDH was determined to be 6.14kJ/mol, which is in the range physicochemical sorption. The mining wastewater treatment was performed by the synthesized LDH. The adsorption experiments showed that more than 90% of free cyanide was removed from the real solution during a short period of contact time, which confirms the ability of LDH for the treatment of industrial cyanide contaminated wastewater. Graphical abstract.

Surface- and volume-based investigation on influences of different Varestraint testing parameters and chemical compositions on solidification cracking in LTT filler metals

The subject of this study is how, and to what extent, Varestraint/Transvarestraint test results are influenced by both testing parameters and characteristics of evaluation methods. Several different high-alloyed martensitic LTT (low transformation temperature) filler materials, CrNi and CrMn type, were selected for examination due to their rather distinctive solidification cracking behaviour, which aroused interest after previous studies. First, the effects of different process parameter sets on the solidification cracking response were measured using standard approaches. Subsequently, microfocus X-ray computer tomography (μCT) scans were performed on the specimens. The results consistently show sub-surface cracking to significant yet varying extents. Different primary solidification types were found using wavelength dispersive X-ray (WDX) analysis conducted on filler metals with varying Cr/Ni equivalent ratios. This aspect is regarded as the main difference between the CrNi- and CrMn-type materials in matters of cracking characteristics. Results show that when it comes to testing of modern high-performance alloys, one set of standard Varestraint testing parameters might not be equally suitable for all materials. Also, to properly accommodate different solidification types, sub-surface cracking has to be taken into account.

Single crystal synthesis and magnetic properties of Co2+-substituted and non-substituted magnetoplumbite-type Na–La ferrite

Single crystals of magnetoplumbite-type Na–La ferrite with and without Co doping were grown by the flux method. Wave length dispersive X-ray analysis reveals that Na and La are present in the ratio of Na/La ​= ​0.25–0.41, and Co is successfully substituted for Fe. Magnetization measurements using single crystals indicate uniaxial magnetic anisotropy in these materials. A metamagnetic transition for the hard-axis magnetization was observed in non Co2+-substituted samples at around 7 ​kOe due to the magnetic free energy double minima originating from the Fe2+ ion. The successful introduction of Co2+ enhances the uniaxial magnetic anisotropy favorable for permanent magnets.

The effect of thermal and acid treatment of kaolin on its ability for cyanide removal from aqueous solutions

The removal of free cyanide from aqueous solutions was investigated by kaolin, calcined kaolin (metakaolin), and acid-treated metakaolin. The kaolin in raw form had no ability for cyanide adsorption, but calcination and acid treatment significantly improve its adsorptive properties. The best calcination conditions were determined to be at temperature of 600 °C and calcination time of 1 h. The scanning electron microscope (SEM), wavelength-dispersive X-ray (WDX), X-ray fluorescence (XRF), and X-ray diffraction (XRD) analysis methods were used to explain the adsorptive properties of the adsorbents. The loading capacity of metakaolin increased from 0.66 to 5.32 mg/g, and the loading capacity of acid-treated metakaolin increased from 1.33 to 10.67 mg/g by increasing the initial cyanide concentration from 25 to 531 mg/L. The kinetics of cyanide adsorption onto both adsorbents increases by increasing the initial cyanide concentration (25–531 mg/L) and solution temperature (30–50 °C). The equilibrium and kinetic data on both adsorbents are best fitted by the Freundlich isotherm and pseudo-second-order kinetic models, respectively. The thermodynamic study showed that the cyanide adsorption onto both adsorbents is endothermic and spontaneous in nature. The activation energy for the cyanide adsorption onto metakaolin and acid-treated metakaolin was determined to be 16.68 and 5.79 kJ/mol which indicates that the adsorption of cyanide ions onto metakaolin is chemisorption and onto the acid-treated metakaolin is a physicochemical process.

Single-crystal growth and magnetic properties of Co-substituted Ca–La magnetoplumbite-type ferrite

Using the flux method, we successfully synthesized Co-substituted Ca–La magnetoplumbite-type ferrite single crystals, CaxLayFezCowO19 (Ca–La–Co system), a base material for high-performance hard ferrite magnets. Wavelength-dispersive X-ray analysis revealed that the chemical compositions of the obtained crystals depended on both the starting composition and reaction atmosphere. The fraction of Fe + Co to Ca + La deviates from the canonical value of 12, and the Co content, which is essential in magnetic anisotropy, improves with the synthesis under an oxygen gas stream. In addition, the magnetic anisotropy is enhanced by the Co substitution, as expected, but also depends on the Ca/La ratio, suggesting an appreciable effect of Fe2+. The magnetocrystalline anisotropy can be larger in the Ca–La–Co system than in the Sr–La–Co system.

Effects of Ar+ etching of Cu2ZnSnSe4 thin films: An x-ray photoelectron spectroscopy and photoluminescence study

Cu2ZnSnSe4 (CZTSe) is a semiconductor used as the absorber layer in highly promising sustainable thin film solar cells. The authors study the effect of Ar+ etching of copper deficient and zinc excess CZTSe thin films deposited on Mo/glass substrates on the surface elemental composition, measured by x-ray photoelectron spectroscopy, and photoluminescence (PL) spectra. Low temperature PL spectra reveal a broad asymmetrical band at 0.95 eV. The temperature and excitation intensity dependencies of this band suggest that it is a free-to-bound (FB) recombination of electrons from the conduction band with holes localized at an acceptor affected by potential fluctuations. The surface composition of the as grown films demonstrates a strong copper deficiency: [Cu]/[Zn + Sn] = 0.33. The etching of the film surface using Ar+ beam increases [Cu]/[Zn + Sn] to 0.51, which is significantly smaller than that of 0.78 in the bulk, measured by wavelength dispersive x-ray analysis, demonstrating the presence on the surface of a copper-depleted layer. The Ar+ etching drastically reduces the FB band intensity by a factor of 4.5, broadens it and develops a low energy tail. Ar ions displace atoms in CZTSe lattice creating primary radiation defects, vacancies, and interstitials, which recombine at room temperature forming antisite defects with deep energy levels. Some of them generate the observed low energy tail and increase the mean depth of potential fluctuation γ, determined from the shape of the low energy side of FB band, from 24 meV before Ar+ etching to 35 meV after. Other deep defects work as nonradiative recombination centers reducing the intensity of the FB band.

Variable Angle Spectroscopic Ellipsometry investigation of CVD-grown monolayer graphene

Despite intensive investigations in the UV (ultraviolet) and visible range, the research on the optical properties of graphene in the extended near and mid infrared range by means of Spectroscopic Ellipsometry (SE) remains limited yet. Herein, the optical properties of a Chemical Vapor Deposition (CVD)-grown monolayer graphene, transferred from a copper substrate onto SiO2/Si, were studied in the broad energy range (0.38–6.2 eV) using Variable Angle Spectroscopic Ellipsometry (VASE). The morphological and the structural properties of the samples were investigated by Micro-Raman Spectroscopy, Wavelength Dispersive X-ray (WDX) analysis, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The Lorentz oscillator model proposed for the optical response of graphene fits very well the experimental data. An unintentional doping, revealed by Micro-Raman Spectroscopy and WDX, is reported.

Microstructural evolution of an aluminide coating on alloy 625 during wet air exposure at 900 °C and 1000 °C

The microstructural changes of the aluminized alloy 625 during cyclic oxidation in air + 6% H2O at 900 °C and 1000 °C were analyzed using optical metallography (OM), scanning electron microscopy (SEM) with energy and wave length dispersive X-ray analysis (EDX/WDX) as well as electron backscatter diffraction (EBSD). An in-house developed thermodynamic-kinetic procedure was employed to predict the microstructural evolution of aluminized alloy 625 during high temperature exposure by considering simultaneously occurring surface oxidation and interdiffusion processes. Due to the lack of mobility data for the relevant alloying elements in the σ-phase, assumptions for the mobilities were made based on the value of the mobilities in α-Cr. Despite these assumptions, the calculated results were found to be in good agreement with experimental observations. The complete depletion of β-NiAl in the coating observed during exposure at 1000 °C was correctly predicted by the model. The model was also able to predict dissolution of the precipitate phases α-Cr and σ in the interdiffusion zone during exposures at 900 °C and 1000 °C. The model was however unable to predict the formation of the μ-phase in the alloy after 1000 h of exposure at 1000 °C. The developed modelling approach offers the potential to predict microstructural changes of aluminized nickel base alloys thus reducing cost and time consuming experimental efforts.

Effect of oxygen potential on Co solubility limit in La–Co co-substituted magnetoplumbite-type strontium ferrite

La–Co co-substituted magnetoplumbite-type (M-type) strontium ferrite is typically used as a base material for high-performance hard ferrite magnets. Generally, the unquenched orbital moment of Co2+, substituted for Fe3+, is thought to enhance magnetic anisotropy and then coercivity. La3+ is substituted for Sr2+ to compensate for the charge unbalance associated with Co2+ substitution. Even if the synthesis starts with equal amounts of Co and La, the Co contents of the resulting samples are generally lower than the La contents because of the partial reduction of Fe3+ to Fe2+. We studied how the oxygen potential suppresses the formation of Fe2+ and expands the Co solubility range in this system. Polycrystalline samples, synthesized under oxygen partial pressures of 0.2, 1.0, and 387 atm, were characterized by powder X-ray diffraction, wavelength-dispersive X-ray analysis, and magnetization measurements. We reveal that the application of higher oxygen pressure dramatically expands the Co solubility range, resulting in the enhancement in magnetic anisotropy. We successfully synthesized Sr-free LaFe11CoO19 with high magnetic anisotropy using the hot isostatic pressure (HIP) technique.

Incipient low-temperature formation of MAX phase in Cr\u2013Al\u2013C films

Ceramic-metallic MAX phase of chromium aluminium carbide ternary compounds was successfully obtained through deposition by DC sputtering onto Si substrates. A study of the influence of substrate temperature and in-air post-annealing on the film crystallinity and oxidation was undertaken. Scanning electron microscopy (SEM), wavelength-dispersive X-ray analysis (WDSX), and X-ray diffraction (XRD) were used for film characterization. It is shown that, at substrate temperature of about 450 °C, as-deposited films are amorphous with small nanocrystals. Subsequent annealing in air at 700 °C leads to film crystallization and partial oxidation. WDSX spectroscopy shows that the films oxidise to a depth of around 120 nm, or 5% of total film thickness which amounts at around 2.68 μm. As a novelty, this demonstrates the possibility of in-air crystallization of Cr2AlC films without significant oxidation. Materials Analysis Using Diffraction (MAUD) software package for a full-profile analysis of the XRD patterns (Rietveld-type) was used to determine that, as a result of annealing, the average crystallite size changes from 7 to 34 nm, while microstrain decreases from 0.79% to 0.24%. A slight tendency of preferential growth along the (10ī0) direction has been observed. Such texturing of the microstructure has the potential of inducing beneficial anisotropic fracture behaviour in the coatings, potentially interesting for several industrial applications in load-bearing devices.

S and B microalloying of biodegradable Fe-30Mn-1C - Effects on microstructure, tensile properties, in vitro degradation and cytotoxicity

Austenitic Fe-Mn-C-based alloys are considered as promising candidates for biodegradable vascular implants due to their high strength, ductility and mechanical integrity during degradation.The present study demonstrates that microalloying with S and B is an effective method to further enhance the degradation rate and the mechanical properties of a Fe-30Mn-1C twinning-induced plasticity (TWIP) alloy without deteriorating the biocompatibility. For studying the microstructural changes due to S or B addition, the alloys were analysed by X-ray diffraction (XRD) as well as scanning electron microscopy (SEM) in combination with energy-dispersive X-ray spectroscopy (EDX), wavelength dispersive X-ray analysis (WDX) and electron backscatter diffraction (EBSD). Thereby precipitates of (Fe0.3Mn0.7)S and (Fe,Mn)23(C3B3) types were detected in the austenitic matrix. These precipitates have a distinct influence not only on the mechanical properties under tensile load but also on the occurring corrosion mechanism. This was displayed by potentiodynamic polarization measurements and immersion tests in simulated body fluid (SBF) and associated SEM as well as X-ray photoelectron spectroscopy (XPS) investigations. In vitro cytotoxicity analyses with L929 fibroblast cells indicated that microalloying with S and B does not affect the cytocompatibility.Thus, the novel alloy modifications show a high potential for future application as biodegradable implant material.

Experimentally Determined Phase Diagram for the Barium Sulfide-Copper(I) Sulfide System Above 873 K (600 °C)

The phase diagram of the barium sulfide-copper(I) sulfide system was investigated above 873 K (600 °C) using a custom-built differential thermal analysis (DTA) apparatus. The melting point of barium sulfide was determined utilizing a floating zone furnace. Four new compounds, Ba2Cu14S9, Ba2Cu2S3, Ba5Cu4S7, and Ba9Cu2S10, were identified through quench experiments analyzed with wavelength dispersive X-ray spectroscopy (WDS) and energy dispersive X-ray analysis (EDS). A miscibility gap was observed between 72 and 92 mol pct BaS using both DTA experiments and in situ melts observation in a floating zone furnace. A monotectic was observed at 94.5 mol pct BaS and 1288 K (1015 °C).

Synthesis, Characterization, and Low Temperature Transport Properties of Eu11-xYbxCd6Sb12 Solid-Solution Zintl Phases.

Eu11-xYbxCd6Sb12 Zintl solid solutions have been prepared by tin flux reaction by employing the elements Eu/Yb/Cd/Sb/Sn in the ratio 11 - xp:xp:6:12:30, where xp is an integer less than 11 representing the preparative amount of Eu (11 - xp) and Yb (xp). Efforts to make the Yb compositions for x exceeding ∼3 resulted in structures other than the Sr11Cd6Sb12 structure type. The crystal structures and compositions were determined by single-crystal and powder X-ray diffraction and wavelength-dispersive X-ray analysis measurements. The title solid-solution Zintl compounds crystallize in the centrosymmetric monoclinic space group C2/m (no. 12, Z = 2) as the Sr11Cd6Sb12 structure type (Pearson symbol mC58), and the lattice parameters decrease with increasing ytterbium content. Single crystal X-ray diffraction shows that Yb atoms are not randomly distributed in the Eu sites but have a site preference which can be attributed to size effects. The influence of the rare earth (RE) metal sites on thermal and electronic properties of RE11Cd6Sb12 solid solutions has been studied by measuring their thermoelectric properties from 5 to 300 K after consolidation by either spark plasma sintering (SPS) or hot pressing (HP). Electron microprobe analysis reveals that some of the rare earth metal is lost during SPS; as a result pellets formed through SPS have lower electrical resistivity by an order of magnitude due to increased hole-charge carrier concentrations. While the carrier concentration increases, the mobility decreases due to deficiencies in Eu content. Refinement of powder X-ray diffraction shows that Eu loss is mainly from the Eu1 crystallographic site, which has a unique coordination suggesting that this site plays a key role in the transport properties of RE11Cd6Sb12.

Occurrences of Slawsonite In Rocks of the Teschenite Association In the Podbeskydí Piedmont Area (Czech Republic) and Their Petrological Significance

Abstract Slawsonite is an extremely scarce natural member of the Feldspar Group, occurring in less than 10 known localities worldwide. We report three new slawsonite occurrences (in Cerťak, Krmelin, and Řepistě) in rocks of the Cretaceous teschenite association in the Czech Republic. At Cerťak, a tabular sill of “teschenite” (in fact analcime syenite, based on its mineral composition) is one of the most alkaline examples of the teschenite association rocks. It shows differentiation to a coarser-grained core enriched in amphiboles, with diffuse transition to the outer zones. Rare thin leucocratic “aplite” dikes contain slawsonite, celsian, microcline, natrolite, prehnite, analcime, and thomsonite-Ca. Slawsonite forms aggregates exhibiting symplectite-like microstructures up to 2 mm long and is associated with euhedral zoned celsian micrograins up to 100 μm in size. Wavelength dispersive X-ray analyses indicate that the chemical composition of slawsonite ranges from Sl 90.4 Cn 3.4 An 1.7 Ab 3.1 Or 1.4 to Sl 60.3 Cn 8.7 An 6.9 Ab 18.3 Or 5.8 ; the composition of celsian ranges from Cn 95.8 An 0.4 Ab 1.0 Or 2.3 Sl 0.5 to Cn 70.1 An 0.5 Ab 2.2 Or 6.3 Sl 20.9 ; and the Na-rich microcline exhibits a composition of Or 58.3 An 2.8 Ab 29.4 Cn 6.4 Sl 3.1 . Slawsonite from Krmelin and Řepistě occurs in a similar geological setting, as aggregates up to 0.3 mm in size that are confined to leucocratic dikes at the endo-contacts of teschenite sills or lava pods. We suggest that slawsonite forms pseudomorphs after nepheline or possibly after plagioclase. Whole-rock geochemistry shows that local teschenites have an affinity for alkali basaltoid rocks typical of MORBs, but are significantly enriched in incompatible elements such as Rb, Ba, Th, U, Ta, Nb, and Sr. With regard to the obvious presence of autometamorphic hydrothermal alteration, we propose that bodies of teschenite association rocks should not be described as dikes; instead, a model of lava pods should be applied.

Improvement of the DSSC Performance By Using a Phosphonium-Type Ionic Liquid Modified TiO2 Electrode

Dye-sensitized solar cells (DSSCs) have been widely investigated as next generation solar cells because of their simple structures, low-cost and facile manufacturing. However, its low energy conversion efficiency prevents the widespread use of DSSCs. The low efficiency of DSSCs is mainly caused by the dye aggregation and the electron recombination. One effective way to solve the dye aggregation and the electron recombination is the use of coadsorbents like chenodeoxycholic acid (CDCA).1) The coadsorbents form a thin layer on the TiO2 surface, which relaxes dye aggregation and/or suppresses the electron recombination. However, in this case, only slight increase of the photocurrent density often observed because the amount of dyes adsorbed on the TiO2 surface decreases. Therefore, the relaxation of the dye aggregation with keeping the amount of dyes on the TiO2 surface is required in order to improve the DSSC performance.2) To prevent the dye aggregation, we have used ionic liquid (IL)-modified TiO2 electrode. IL is a salt in the liquid state at room temperature. Recently, we reported the self-assembled monolayers (SAMs) of bulky phosphonium- and ammonium-type ILs with disulfide groups.3-5) The steric and electrostatic repulsion among the bulky IL molecules prevent them from packing closely and form the enough space to entrap external molecules on the surface. We tried to utilize the space formed by the bulky phosphonium-type IL on the TiO2 surface to trap dye molecules. The ILs on the TiO2 surface probably reduce the dyes aggregation with keeping the amount of dyes on the surface. Furthermore, it is also expected that the electron recombination between the electrolyte and the TiO2 surface is suppressed because the surface is covered with the alkyl chains of IL. In this study, a bulky phosphonium-type ionic liquid (IL) with a carboxylic acid group was newly synthesized. Subsequently, TiO2 electrodes modified with N3 6) dye and IL with various ratios were prepared. DSSCs based on the IL-modified TiO2 photoanodes have been fabricated and their photovoltaic performance have been evaluated. The surface ratio of N3 dye and IL were determined by the wavelength dispersive X-ray analysis (WDS). When the TiO2 electrode was dipped into the t BuOH/CH3CN (1/1, v/v) solution containing 0.3 mM N3 dye and 30mM IL, the electrode modified with 1/1 ratio was obtained. The DSSC using N3- and N3, IL-modified TiO2 photoanodes were fabricated and their J-V characteristics were measured. All parameters of the DSSCs (the short-circuit photocurrent (J sc), the open-circuit photovoltage (V oc), fill factor (ff), and the power conversion efficiency (η)) have been improved. These results indicate that the DSSCs based on the IL-modified TiO2 electrodes prevented the charge recombination among dyes and/or between the electrolyte and the TiO2surface.1) M. K. Nazeeruddin,et al.,Nanotechnology,2008, 19, 424005.2) K. Char, et al., ACS Appl. Mater. Interfaces, 2015, 7, 25741.3) H. Masuda, et al., Chem. Commun., 2013, 49, 10184.4) H. Masuda, et al., Chem lett, 2016, 45, 4, 436.5) H. Masuda, et al., Chem. Commun., 2016, 52, 4780.6) M. K. Nazeeruddin, et al., J. Am. Chem. Soc., 1993, 115, 6382. Figure 1