Ti Silicate Research Articles

Experimental synthesis of ThSiO4 by fluid-induced alteration of chevkinite-(Ce): Evidence for element mobility and variable crystal structure

During a series of high P-T experiments aimed at understanding the hydrothermal alteration of the REE,Ti silicate chevkinite-(Ce), three ThSiO4 phases (thorite, huttonite, and an amorphous ThSiO4 variety) were formed, showing a wide range of textures from small discrete grains to large-scale replacement of the chevkinite-(Ce). All three phases have compositions close to ThSiO4, except that the amorphous type contains small amounts of LREE (≤ 0.025 apfu) and inferred H2O. The three different forms have been confirmed by electron backscatter diffraction, which has also provided information on the microstructure of the crystals. The earliest phase to form was huttonite, composed of many randomly oriented microcrystals. This was later replaced by thorite via fluid-aided coupled dissolution-reprecipitation. The amorphous type formed both by apparent hydrous alteration of the original crystalline thorite and huttonite. The inferred sequence of events is compatible with thermodynamic constraints on the relative stability of thorite and huttonite.

Composition and Miocene deformation of the lithospheric mantle adjacent to the Marlborough Fault System in North Canterbury

ABSTRACT Mantle xenoliths in a nephelinite in the Little Lottery River provide insight into the Miocene mantle adjacent to the Australia-Pacific plate boundary in N Canterbury. The xenoliths comprise peridotite and pyroxenite extracted from depths of ∼ 40 to 60 km. The olivine Mg# < 89, a lack of spinel and occurrence of ilmenite, elevated bulk Cr and Al, light rare Earth element (REE)-enriched clinopyroxene, and 87Sr/86Sr15 Ma clinopyroxene populations (0.7029–0.7047) in most harzburgite and dunite samples, and in all lherzolite, wehrlite, olivine websterite and orthopyroxenites, indicate that most are the product of reaction of depleted peridotite with Fe, Ti, Al and light REE-bearing silicate melts of basaltic or similar composition. Available isotopic data indicate that the xenoliths could be derived from mantle lithosphere beneath the Hikurangi Plateau, in which case the reactive melts may have been associated with the Cretaceous plateau formation. Extensive recrystallisation of olivine indicates that portions of this lithosphere mantle were affected by the deformation close to the time of entrainment. Since the eruption occurred at ∼ 15 Ma, these textures require that the mantle lithosphere in this area was deforming before formation of today's expression of the proximal Hope Fault strand of the Australia-New Zealand plate boundary.

A Novel Method of Recovery Vanadium from Vanadium Slag through CaO2‐Briquetting Roasting Process

This study proposes a clean and effective routine and aims to solve the problems of material accumulation and hypoxia during roasting vanadium slag. The vanadium slag and CaO2 powders are mixed, briquetted, and roasted at different parameters. The generated phases are Fe2O3, Fe–Mg oxides, Fe–Ti oxides, Ca3(VO4)2, silicate, and SiO2 after roasting. The solid reaction between V2O5 and CaO is described using the vacancy diffusion mechanism. Ca2+ (or V5+) jumps and diffuses through the Ca2+ (or V5+) vacancies in the Ca3(VO4)2 layer and subsequently to the Ca3(VO4)2/V2O5 (or Ca3(VO4)2/CaO) interface and reacts with V2O5 (or CaO) and O2 (decomposed from CaO2 or transported from the air) to generate Ca3(VO4)2. The vanadium leaching rate is very sensitive to the roasting parameters of CaO/V2O5 molar ratio, temperature, time, and briquetting pressure. A maximum vanadium leaching rate of 98.31% is achieved with a CaO/V2O5 molar ratio of 3/1, with temperature, time, and briquetting pressure being maintained at 900 °C, 50 min, and 10 MPa, respectively. The present routine, which greatly shortens the roasting time, can be realized through a rotary hearth furnace, and is likely to be accepted by both iron works and the environment due to its effective and clean characteristics.

Origin of Fe–Ni–Cu (Co) sulfide and Fe–Ti oxide minerals in the c. 1.77 Ga dolerite dyke, Singhbhum Craton (eastern India)

Abstract Dolerite dyke swarms are widespread within the Singhbhum Craton (eastern India) that emplaced from the Neoarchean to Paleoproterozoic era just after the stabilization of crust before c. 3 Ga. These dyke swarms are oriented in NE–SW to NNE–SSW, NW–SE to WNW–ESE, east–west and north–south directions. The WNW–ESE-trending c. 1.77 Ga Pipilia dyke swarm is sampled from the Satkosia area of Orissa state. The dyke shows a noticeable disparity in terms of the modal proportion and grain size of pyroxenes, plagioclase, Fe–Ti oxide minerals and texture across the trend. In places the primary silicates are altered to secondary hydrated mineral assemblages of amphibole, chlorite and sericite. The primary silicates are clinopyroxene (augite – Mg# = 65.7–82.6; En 37–48 Fs 11–17 Wo 36–41 ), orthopyroxene (clinoenstatite – Mg# = 68.5–78; En 63–70 Fs 20–29 Wo 4–5 ) and plagioclase (An 11–39 Ab 44–82 Or 1–7 ) and the Fe–Ti oxides are titanomagnetite (FeO, 34.38–39.50 wt%; Fe 2 O 3 , 48.26–56.21 wt%; TiO 2 , 5.05–9.60 wt%) and ilmenite (FeO, 40.75–43.79 wt%; Fe 2 O 3 , 3.54–10.03 wt%; TiO 2 , 47.82–50.87 wt%). Application of two-pyroxene thermometry yields an equilibration temperature range of 1065–978°C, and coexisting titanomagnetite–ilmenite pairs reveal 731.39–573.37°C under the oxygen fugacity ( f O 2 ) condition NNO + 0.3 to FMQ − 1.03. The dyke contains disseminated sulfides at the interstices of Fe–Ti oxides and silicates. Major sulfide minerals are pyrite, chalcopyrite and vaesite; pyrite–vaesite assemblages occur in association with secondary silicate minerals. Pyrite grains contain variable concentrations of Co (0.01–5.70 wt%) and Ni (0.02–1.95 wt%). Coexisting vaesite contains Co (2.42–10.44 wt%), Ni (26.40–47.88 wt%) and Fe (7.32–26.55 wt%). Texture, sulfide–silicate assemblage and the presence of low metal/S sulfides such as the pyrite–vaesite assemblage indicate that primary Fe–Ni sulfides (pyrrhotite–pentlandite) that segregated from immiscible sulfide liquid at high temperature are modified by late magmatic/hydrothermal fluid activities. Numerous sulfide-bearing deposits hosted in ultramafic–mafic intrusions of Paleoproterozoic age have been recorded globally and the occurrence of Fe–Ni sulfides in the c. 1.77 Ga Pipilia dyke swarm in the Singhbhum Craton enhances the exploration potential of this craton in eastern India.

Behavior of magnesium impurity during carbochlorination of magnesium-bearing titanium slag in chloride media

Abstract In this study, the phase composition, morphology, and element distribution of Mg impurities in a low-grade titanium slag and in its chlorinated residue after carbochlorination were identified using XRD, SEM-EDS, and MLA. Most Mg impurities existed as anosovite, rutile, titanaugite, and Ti silicate phases before the carbochlorination process. The thermodynamic analysis revealed that the chlorination tendencies of Mg, Ti, Ca, Fe, and Mn oxides in the original titanium slag was much higher than those of Si and Al oxides in the temperature range of 700–850 °C. In addition, the binary phase diagram analysis indicates that the magnesium chloride (MgCl2) byproduct formed Na2MgCl4 eutectic salts in the NaCl-based salt bath. The carbochlorination experiments of the Mg-bearing titanium slag show that the chlorination ratio of magnesium oxide was above 93% under the suitable industrial conditions used for the extraction of titanium from Mg-bearing titanium slag. In addition, the formation of Na2MgCl4 eutectic salts after carbochlorination was confirmed, indicating that the negative effect of MgCl2 on the chlorination process was effectively eliminated. The Mg impurities in the chlorinated residue existed as titanaugite, quartz, chlorite, and rutile phases. Furthermore, we found that the carbochlorination of Mg-bearing titanium slag in chloride media effectively improved the comprehensive utilization efficiency of the Mg-bearing titanium slag. We believe that the proposed carbochlorination mechanism of the Mg-bearing titanium slag will provide thorough understanding and useful guidance on the practical industrial application of Mg-bearing titanium slag.

The redox dependence of titanium isotope fractionation in synthetic Ti-rich lunar melts

Equilibria between Ti oxides and silicate melt lead to Ti isotope fractionation in terrestrial samples, with isotopically light Ti oxides and isotopically heavy coexisting melt. However, while Ti is mostly tetravalent in terrestrial samples, around 10% of the overall Ti is trivalent at fO2 relevant to lunar magmatism (~ IW-1). The different valences of Ti in lunar samples, could additionally influence Ti stable isotope fractionation during petrogenesis of lunar basalts to an unknown extent. We performed an experimental approach using gas mixing furnaces to investigate the effect of Ti oxide formation at different fO2 on Ti stable isotope fractionation during mare basalt petrogenesis. Two identical bulk compositions were equilibrated simultaneously during each experiment to guarantee comparability. One experiment was investigated with the EPMA to characterize the petrology of experimental run products, whereas the second experiment was crushed, and fabricated phases (i.e., oxides, silicates and glass) were handpicked, separated and digested. An aliquot of each sample was mixed with a Ti double-spike, before Ti was separated from matrix and interfering elements using a modified HFSE chemistry. Our study shows fO2-dependent fractionation within seven samples from air to IW-1, especially ∆49Tiarmalcolite-melt and ∆49Tiarmalcolite-orthopyroxene become more fractionated from oxidized to reduced conditions (− 0.092 ± 0.028- − 0.200 ± 0.033 ‰ and − 0.089 ± 0.027- − 0.250 ± 0.049 ‰, respectively), whereas ∆49Tiorthopyroxene-melt shows only a minor fractionation (− 0.002 ± 0.017-0.050 ± 0.025 ‰). The results of this study show that Ti isotope fractionation during mare basalt petrogenesis is expected to be redox dependent and mineral-melt fractionation as commonly determined for terrestrial fO2 may not be directly applied to a lunar setting. This is important for the evaluation of Ti isotope fractionation resulting from lunar magmatism, which takes place under more reducing conditions compared to the more oxidized terrestrial magmatism.

Titanium Defective Sites in TS-1: Structural Insights by Combining Spectroscopy and Simulation.

Ti silicates, and in particular, titanium silicalite-1 (TS-1), are nowadays important catalysts for several partial oxidation reactions in the presence of aqueous H2 O2 as an oxidant. Despite the numerous studies dealing with this material, some fundamental aspects are still unclear. In particular, the structure and the catalytic role of defective Ti sites, other than perfect tetrahedral sites recognized as the main active species, has not been quantitatively discussed in the literature. We assess the structural features of defective Ti sites on the basis of outcomes of electronic spectroscopies, as interpreted through quantum mechanical simulation. Strong evidence is disclosed to support the fact that the most common defective Ti sites, often reported in the TS-1 literature, are monomeric Ti centers that are embedded in the zeolite framework, and which have a distorted octahedral local symmetry.

Petrogenesis of peralkaline granite dykes of the Straumsvola complex, western Dronning Maud Land, Antarctica

Peralkaline syenite and granite dykes cut the Straumsvola nepheline syenite pluton in Western Dronning Maud Land, Antarctica. The average peralkalinity index (PI = molecular Al/[Na + K]) of the dykes is 1.20 (n = 29) and manifests itself in the presence of the Zr silicates eudialyte, dalyite and vlasovite, and the Na–Ti silicate, narsarsukite. The dykes appear to have intruded during slow cooling of the nepheline syenite pluton, and the petrogenetic relationship of the dykes and the pluton cannot be related to closed-system processes at low pressure, given the thermal divide that exists between silica-undersaturated and oversaturated magmas. Major and trace element variations in the dykes are consistent with a combination of fractional crystallization of parental peralkaline magma of quartz trachyte composition, and internal mineral segregation prior to final solidification. The distribution of accessory minerals is consistent with late-stage crystallization of isolated melt pockets. The dykes give an Rb–Sr isochron age of 171 ± 4.4 Ma, with variable initial 87Sr/86Sr ratio (0.7075 ± 0.0032), and have an average e Nd of − 12.0. Quartz phenocrysts have δ18O values of 8.4–9.2‰, which are generally in O-isotope equilibrium with bulk rock. Differences in the δ18O values of quartz and aegirine (average Δquartz−aegirine = 3.5‰) suggest aegirine formation temperatures around 500 °C, lower than expected for a felsic magma, but consistent with poikilitic aegirine that indicates subsolidus growth. The negative e Nd (< − 10) and magma δ18O values averaging 8.6‰ (assuming Δquartz−magma = 0.6‰) are inconsistent with a magma produced by closed-system fractional crystallization of a mantle-derived magma. By contrast, the nepheline syenite magma had mantle-like δ18O values and much less negative e Nd (average − 3.1, n = 3). The country rock has similar δ18O values to the granite dykes (average 8.0‰, n = 108); this means that models for the petrogenesis of the granites by assimilation are unfeasible, unless an unexposed high-δ18O contaminant is invoked. Instead, it is proposed that the peralkaline syenite and granite dykes formed by partial melting of alkali-metasomatised gneiss that surrounds the nepheline syenite, followed by fractional crystallization.

Correlation between surface properties and wettability of multi-scale structured biocompatible surfaces

The influence of surface properties of radio-frequency (RF) magnetron deposited hydroxyapatite (HA) and Si-containing HA coatings on wettability was studied. The composition and morphology of the coatings fabricated on titanium (Ti) were characterized using atomic force microscopy (AFM) and X-ray diffraction (XRD). The surface wettability was studied using contact angle analysis. Different geometric parameters of acid-etched (AE) and pulse electron beam (PEB)-treated Ti substrates and silicate content in the HA films resulted in the different morphology of the coatings at micro- and nano- length scales. Water contact angles for the HA coated Ti samples were evaluated as a combined effect of micro roughness of the substrate and nano-roughness of the HA films resulting in higher water contact angles compared with acid-etched (AE) or pulse electron beam (PEB) treated Ti substrates.

Extreme peralkalinity in delhayelite- and andremeyerite-bearing nephelinite from Nyiragongo volcano, East African Rift

Abstract Highly peralkaline leucite nephelinite from the active volcano Nyiragongo in the Virunga province of the East African Rift contains globules of iron- and volatile-rich, highly peralkaline silicate glass with (Na + K)/Al up to 18 which has formed as a late differentiate of less peralkaline precursors, probably by fractional crystallization at a shallow level in the volcanic system. A number of uncommon minerals coexist with this glass (kalsilite, kirschsteinite, chlorbartonite, gotzenite, delhayelite, umbrianite, zirconian cuspidine, andremeyerite (BaFe 2 Si 2 O 7 ), other Ba–Fe–Ti silicate minerals, and unnamed alkali-barium phosphate and Zr–Nb–Ti silicate minerals). These minerals are members of late magmatic assemblages that have survived sub-solidus recrystallization. Combeite occurs as a near-solidus mineral. Low-variance mineral assemblages in Nyiragongo nephelinite define a cooling trend from eruptive temperatures ≥ 980 °C to the solidus of extremely peralkaline residual liquids at ca. 600 °C, followed by sub-solidus recrystallization and metasomatism down to ca. 500 °C. Oxygen fugacity well below the QFM buffer (QFM-2 to -3) persisted throughout the magmatic crystallization stage, but increased to above QFM during the final stage of postmagmatic recrystallization. Highly alkaline, volatile-rich minerals such as delhayelite, gotzenite and cuspidine were stabilized by a combination of high peralkalinity and elevated activity of chlorine and fluorine; these conditions persisted to sub-solidus temperatures.

Prediction of new structural arrangements and chemical compositions in Ti silicates

Prediction of new structural arrangements and chemical compositions in Ti silicates

Petrology of nepheline syenite pegmatites in the Oslo Rift, Norway: Zr and Ti mineral assemblages in miaskitic and agpaitic pegmatites in the Larvik Plutonic Complex

Abstract Agpaitic nepheline syenites have complex, Na-Ca-Zr-Ti minerals as the main hosts for zirconium and titanium, rather than zircon and titanite, which are characteristic for miaskitic rocks. The transition from a miaskitic to an agpaitic crystallization regime in silica-undersaturated magma has traditionally been related to increasing peralkalinity of the magma, but halogen and water contents are also important parameters. The Larvik Plutonic Complex (LPC) in the Permian Oslo Rift, Norway consists of intrusions of hypersolvus monzonite (larvikite), nepheline monzonite (lardalite) and nepheline syenite. Pegmatites ranging in composition from miaskitic syenite with or without nepheline to mildly agpaitic nepheline syenite are the latest products of magmatic differentiation in the complex. The pegmatites can be grouped in (at least) four distinct suites from their magmatic Ti and Zr silicate mineral assemblages. Semiquantitative petrogenetic grids for pegmatites in log aNa2SiO5 - log aH2O - log aHF space can be constructed using information on the composition and distribution of minerals in the pegmatites, including the Zr-rich minerals zircon, parakeldyshite, eudialyte, låvenite, wöhlerite, rosenbuschite, hiortdahlite and catapleiite, and the Ti-dominated minerals aenigmatite, zirconolite (polymignite), astrophyllite, lorenzenite, titanite, mosandrite and rinkite. The chemographic analysis indicates that although increasing peralkalinity of the residual magma (given by the activity of the Na2Si2O5 or Nds component) is an important driving force for the miaskitic to agpaitic transition, water, fluoride (HF) and chloride (HCl) activity controls the actual mineral assemblages forming during crystallization of the residual magmas. The most distinctive mineral in the miaskitic pegmatites is zirconolite. At low fluoride activity, parakeldyshite, lorenzenite and wöhlerite are stable in mildly agpaitic systems. High fluorine (or HF) activity favours minerals such as låvenite, hiortdahlite,rosenbuschite and rinkite, and elevated water activity mosandrite and catapleiite. Astrophyllite and aenigmatite are stable over large ranges of Nds activity, at intermediate and low water activities, respectively.

Geochemistry, mineralogy and petrology of the Eocene potassic magmatism from the Milk River area, southern Alberta, and Sweet Grass Hills, northern Montana

New whole-rock geochemical, quantitative mineralogical and electron-microprobe data are presented from lamproite, olivine minettes and mafic trachyte of the Milk River area, southern Alberta, and latites, trachytes and high-K rhyolite of the Sweet Grass Hills, northern Montana. These rocks comprise dikes, small plugs and a pipe complex associated with mainly syenite and hornblende monzonite plutons that core several buttes in the Sweet Grass Hills and mark the northern extent of the Cenozoic Montana Alkaline Province. Minerals restricted to peralkaline lamproite at the 49th Parallel locality include Ti-rich phlogopite–annite with Fe3+ in tetrahedral coordination, Na-poor sanidine, Ba-rich and Cl-poor fluorapatite, K-rich titano-ferronyböite/ferro-obertiite, LREE-rich strontian fluorapatite (SrO=17.5–25.2wt.%, Ce2O3=2.9–3.3wt.%), ilmenite, strontian barite, barian celestine, and unidentified Zr–Ti phase (TiO2=76.7–88.0wt.%, ZrO2=2.1–7.2wt.%) perhaps replacing primary Zr–Ti silicates. The strontian fluorapatite has the highest SrO content thus far reported in the literature for apatites from lamproites. Olivine minettes and mafic trachyte of the Milk River area contain augite, Al-diopside, Ti-rich magnetite, sanidine with higher Na, hyalophane, Cl-bearing fluorapatite with negligible Ba, ferroan magnesite phenocrysts, and primary calcite, all of which are notably absent in the 49th Parallel lamproite. Mica displays distinct core-to-rim zoning trends in these rocks, characterized by increasing FeOt and TiO2 at decreasing Al2O3 in lamproite and increasing FeOt and TiO2 at increasing Al2O3 in minettes and trachytes. The 49th Parallel lamproite has higher Ti, K, P, Ba, Rb, Sr, Nb, Th, U, Zr, Hf and REE concentrations, higher K/Al, (Ce/Yb)CN, (La/Sm)CN, (Gd/Yb)CN, Rb/Cs, Ce/Pb, Th/Ta, Th/Yb, and lower Ba/La, Ba/Th and Nb/U relative to minettes of the Milk River area. Major-element, least-squares mass balance and trace-element models call for the origin of latites, trachytes and high-K rhyolite in the Sweet Grass Hills complex by two-stage fractional crystallization of primitive olivine minette magmas concurrent with negligible, if any, assimilation of crustal materials. Oscillatory and reverse zoning in phenocrysts and hybrid phenocryst assemblages record recharge of more evolved magma chambers with primitive minette magmas. The calculated evolutionary models are inconsistent with the compositional variations displayed by the olivine minettes and lamproite of the Milk River area. These rocks represent distinct low-degree partial melts of sub-lithospheric mantle enriched in K and volatiles by the recent (<100Ma) plume activity or convective upwelling of the upper mantle above subducted Farallon slab, which underwent variable assimilation of the ancient, LREE-Ba–Sr enriched and HFSE depleted Wyoming–Medicine Hat lithosphere during the post-Laramide extension. The olivine minettes derived from more oxidized, carbonated region of the mantle source, compared to the more reduced source of the 49th Parallel lamproite. The extremely negative εNd values, unradiogenic Pb and moderately radiogenic Sr isotopic compositions, correlated with LREE, Ba enrichment and relative Nb, Ta, Ti and other HFSE depletions of the Cenozoic K-rich rocks of the MAP, may reflect carbonatite metasomatism of the lithospheric mantle associated with the widespread Mesoproterozoic (1.5–1.4Ga) anorogenic magmatism and intracontinental rifting related to mantle upwelling and plume activity beneath a thick Precambrian supercontinent.

Review of melting experiments on carbonated eclogite and peridotite: insights into mantle metasomatism

Experimental studies on the partial melting of eclogite and peridotite provide important clues on mantle metasomatism. Here, we review results from some of the recent experiments and show that melting of carbonated eclogite and peridotite can produce carbonatitic to carbonated silicate melt, in which carbonates melt preferentially before Ti oxides and silicates. Low-degree melting results in carbonatitic melt coexisting with Ti oxides and silicates. This process also leads to the fractionation between some high-field strength elements (Nb, Ta, Zr, Hf, and HREE) and highly incompatible elements (U and Th) in the melt. When Ti oxides are nearly exhausted in eclogite, extremely high TiO2 contents (e.g. 19 wt.%) are present in the melt with marked concentration of Nb and Ta. These results help to explain the features of carbonatitic metasomatism and the Nb–Ta spike in oceanic island basalts as identified in experimental studies. These studies also explain the reducing conditions that stabilize diamond in the deep mantle (>150 km) as well as the occurrence of diamond at different depths reported in various studies. Melting in such a reduced mantle can happen through redox reaction between diamond, pyroxene, and olivine, in which the initial liquid is a carbonated silicate melt. However, the theoretical oxygen fugacity (fO2) in the asthenosphere is much lower than that predicted by the reaction and requires elevated fO2, which can be caused by the addition of relatively oxidized materials from the lower mantle, deep asthenospheric material, and various recycled components. A combination of these processes generates locally oxidized domains in the deep mantle.

Nitrided SrTiO3 as charge-trapping layer for nonvolatile memory applications

Charge-trapping characteristics of SrTiO3 with and without nitrogen incorporation were investigated based on Al/Al2O3/SrTiO3/SiO2/Si (MONOS) capacitors. A Ti-silicate interlayer at the SrTiO3/SiO2 interface was confirmed by x-ray photoelectron spectroscopy and transmission electron microscopy. Compared with the MONOS capacitor with SrTiO3 as charge-trapping layer (CTL), the one with nitrided SrTiO3 showed a larger memory window (8.4 V at ±10 V sweeping voltage), higher P/E speeds (1.8 V at 1 ms +8 V) and better retention properties (charge loss of 38% after 104 s), due to the nitrided SrTiO3 film exhibiting higher dielectric constant, higher deep-level traps induced by nitrogen incorporation, and suppressed formation of Ti silicate between the CTL and SiO2 by nitrogen passivation.

FERROERICSSONITE, THE Fe2+ ANALOGUE OF ERICSSONITE, FROM EASTERN FRESNO COUNTY, CALIFORNIA, U.S.A.

Ferroericssonite, ideally BaFe 2+ 2 Fe 3+ (Si 2 O 7 )O(OH), is a new mineral species found at both the Esquire #7 and #8 claims, situated along Big Creek in eastern Fresno County, and also at Trumbull Peak in Mariposa County, California, U.S.A. The mineral is the Fe 2+ analogue of ericssonite and is named accordingly. Ferroericssonite crystallized very late in a sequence of minerals resulting from fluids interacting with a quartz−sanbornite vein along its margin with the country rock. It is closely associated with anandite, bazirite, celsian, devitoite, quartz and titantaramellite. The crystals occur in dark reddish brown foliated masses of irregular, undulating striated blades up to several mm in length, flattened on {100} and elongate and striated parallel to [001]. The mineral is transparent and has a brown streak, a vitreous luster, a Mohs hardness of approximately 4½, and two cleavages: {100} perfect and {011} good. It is brittle with an irregular fracture. The calculated densities are 4.445 and 4.413 g/cm 3 on the basis of the empirical formulas for Esquire #7 and Esquire #8 material, respectively. It is optically biaxial (+), α 1.827(3), β 1.845(3), γ 1.920(6) (white light); 2 V meas = 63(2)°; 2 V calc = 63.0°; parallel dispersion, r v ; orientation: X = b , Y ≈ c , Z ≈ a ; pleochroic: brown, Z > X > Y . Electron-microprobe analyses of Esquire #7 and Esquire #8 material provided: BaO 30.11, 29.76, MgO 0.21, 0.10, MnO 1.19, 0.79, FeO 26.01, 26.24, Fe 2 O 3 15.30, 15.35, Al 2 O 3 0.02, 0.04, SiO 2 22.89, 23.34, F 0.09, 0.05, Cl 1.29, 0.88, H 2 O 1.33, 1.42, F + Cl≡ O −0.33, −0.22, total 98.11, 97.75 wt%, with FeO and Fe 2 O 3 assignments and H 2 O based on the structure. The empirical formulas for Esquire #7 and Esquire #8 material, based on Mg + Fe + Mn + Si = 5 apfu , are Ba 1.02 (Fe 2+ 1.89 Mn 2+ 0.09 Mg 0.03 ) ∑2.01 Fe 3+ 1.00 (Si 1.99 O 7 )O[(OH) 0.77 O 0.02 Cl 0.19 F 0.02 ] ∑1 and Ba 1.01 (Fe 2+ 1.90 Mn 2+ 0.06 Mg 0.01 ) ∑1.97 Fe 3+ 1.00 (Si 2.02 O 7 )O[(OH) 0.82 O 0.04 Cl 0.13 F 0.01 ] ∑1 , respectively. Ferroericssonite is monoclinic, C 2/ m , a 20.3459(10), b 7.0119(3), c 5.3879(4) A, β 94.874(7)°, V 765.89(7) A 3 and Z = 4. The strongest five lines in the X-ray powder-diffraction pattern [ d obs in A( I )( hkl )] are: 3.708(42)(311), 3.506(81)(311, 510, 020), 2.880(42)(420), 2.788(100)(221) and 2.663(83)( 202, 710). The crystal-structure determination ( R 1 = 3.56% for 885 F o > 4σ F ) shows the mineral to be a heterophyllosilicate with a Fe 2+ trioctahedral (O) sheet flanked on either side by heterophyllosilicate (H) layers, forming a HOH composite sheet. The heterophyllosilicate layers are composed of Si 2 O 7 groups linked by Fe 3+ square pyramids in a configuration referred to as a TS (Ti silicate) block, although five-coordinated Fe 3+ takes the place of Ti 4+ . The region between the composite sheets is occupied by Ba 2+ . Ferroericssonite is a member of the lamprophyllite group.

Effects of Si interlayer on resistance switching of Pt/Si/TiO[sub 2]/Pt structures

In order to improve the resistive switching reliability of devices made using TiO2 grown by atomic layer deposition at 130 °C, a thin Si layer was inserted between the Pt top electrode and the TiO2 thin films. The annealing of the Pt/Si(O)/TiO2/Pt structures at 300 °C in N2 ambient produced Pt/Pt3Si/PtSi particle-embedded SiO2/Ti-silicate/TiO2/Pt multistructures, as confirmed by x-ray diffraction, x-ray photoelectron spectroscopy, and high resolution transmission electron microscopy. The as-annealed multistructures showed enhanced adhesion properties and significantly improved resistive switching performances, especially in terms of the number of the switching cycles and device yield. Based on the analyses, the authors proposed that the interfacial formation of Pt3Si and Ti silicate is responsible for the enhanced adhesion and the improved resistive switching reliability of TiO2 devices result from the enhanced mechanical stability as well as the presence of Ti silicate, which acts as source and sink for ...

X-ray photoelectron spectroscopy study of ZrO2∕TiO2∕Si stack

A ZrO2∕TiO2∕Si gate stack has been prepared by using solid phase reaction between sputtered ZrO2∕Ti stack and underlying SiO2∕Si substrate through in situ vacuum annealing. X-ray photoelectron spectroscopy was used to analyze interfacial properties of the ZrO2∕TiO2∕Si stack after annealing at high temperatures. The interfacial silicate is composed of Ti silicate and ZrO2 layer does not take part in the interfacial reaction to form Zr silicate. Such a stack has the advantage of combining high dielectric constant of ZrO2 and excellent interfacial property of Ti silicate/Si interface, and will have potential applications in the advanced metal-oxide-semiconductor devices.

Electrical Characterization of Ti–Silicate Films Grown by Atomic Layer Chemical Vapor Deposition

Electrical characterization was performed for Ti–silicate films, which were deposited by atomic layer chemical vapor deposition (ALCVD). Before the deposition of Ti–silicate films, the silicon substrates were pretreated differently using hydrofluoric acid (HF)-etching, chemical oxidation, and thermal oxidation. Regardless of the pretreatment methods, the grown films showed a highly smooth surface with rms below 0.52 nm. The electrical properties of the grown Ti–silicate films showed a strong dependence on the substrate pretreatments. The 5-nm-thick Ti–silicate films grown on hydrogen-passivated Si and chemically oxidized Si showed rather high leakage currents, whereas the films grown on thermally oxidized Si showed low leakage currents below 1×10-7 A/cm2 at a bias of -1 V. All of the films showed a positive shift in the flatband voltage (VFB) upon annealing. Also, each film showed low a hysteresis below 180 mV and the hysteresis decreased upon annealing.

Synthesis, Characterization, and Separation Properties of Sn— and Ti—Silicate Umbite Membranes.

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