Solubility Of Ti Research Articles

Band engineering in silicide alloys

A relatively low conductivity of PtSi is one of the impediments to its application as a contact material in semiconductor technology. In this paper, we discuss a possible strategy to control the conductivity of PtSi by manipulating the density of states at the Fermi level through alloying. Using density functional theory, we demonstrate theoretically that alloying PtSi with Ti substantially increases the number of conducting electrons and suggest possible ways to increase the Ti solubility limit. We identify a tertiary compound with the conducting electron concentration almost three times larger than that of bulk PtSi. We analyze the effect of Ti alloying on the work function of PtSi and its Schottky barrier height to Si, and we examine the effect of alloy scattering on PtSi conductivity.

Discrimination between different water bodies from a multilayered aquifer (Kaluvelly watershed, India): Trace element signature

In the multilayered aquifer of Kaluvelly (India), comprising various sedimentary layers overlying a charnockitic basement, concentrations of trace elements were measured in aquifer formations and in groundwaters to identify geochemical tracers for water bodies. The two main sandstones (Cuddalore and Vanur) originate from the charnockites and the Cuddalore sandstone has experienced lateritization. In the studied area, two charnockite end-members were identified: a dioritic and a granitic one. Mineralogical composition and whole-rock Ti concentrations confirmed the charnockite which displayed the granitic composition as the parent rock of the two sandstones. Titanium distribution indicates that the Cuddalore sandstone originates from a more intense weathering of the parent material than the Vanur sandstone. Despite extensive differences in trace element contents recorded in aquifer formations, only a few trace elements were suitable to distinguish the water bodies. Among soluble elements, Li (in the Vanur aquifer) and Ba (in the charnockite and carbonaceous aquifers) can be used as tracers. As the input of these elements in solution is mainly regulated by the available stock, for a given mineralogical origin there is a direct link between the aquifer formation composition and water signature. With the exception of As, concentrations of redox-sensitive elements were not preserved during pumping because of oxidation, preventing their use as tracers. Low-mobility elements such as La, Ce, Th, Zr, Nb, Hf, or Ta were too insoluble to be detected in waters and/or to record the aquifer formation signature. Their input in solution was not regulated by the available stock but by the dissolution rate of rock-forming minerals. Only Ti can be used to distinguish between two out of the three aquifers (charnockite and Vanur). The specific behavior of Ti recorded in these waters may be linked to rutile inclusions within plagioclases and to the influence of climate on Ti solubility.

Authigenesis of Titania Minerals and the Mobility of Ti: New Evidence From Pro-Deltaic Sandstones, Cretaceous Scotian Basin, Canada

Titania (TiO2) minerals are minor diagenetic phases in many sandstone–shale successions, but the conditions of Ti mobility and titania authigenesis are poorly known. Here, new modes of occurrence of authigenic titania minerals, filling pores and replacing phytodetritus, are documented from Lower Cretaceous prodeltaic sandstones in the offshore Scotian Basin of southeastern Canada. Textural relationships suggest that titania minerals formed at the same time as kaolinite, most commonly below lowstand sequence boundaries, related to flux of meteoric water. Such authigenic titania is most abundant in thin-bedded sandstones interbedded with thick prodeltaic mudstone in which fine-grained detrital Ti-rich minerals are concentrated. Textures in titania that has replaced uncompacted phytodetritus suggest microbial mediation in near-surface eodiagenesis. Eogenetic titania is enriched in phosphorus (∼ 0.6% P2O5) and may co-occur with authigenic fluorapatite and crandallite crystals. Such titania resulted from prolonged flow of meteoric water that dissolved P from apatite and feldspar, thereby enhancing Ti solubility. In basins with supply of immature sediment from granitic terranes and important diagenesis by meteoric water, the assumption that Ti is an immobile element and that rutile or other titania minerals are exclusively of detrital origin may not be valid. Probable mesodiagenetic titania has low P content, suggesting that Ti mobility under these conditions was facilitated by some other agent, probably organic acids. The results of this study illustrate that even in cases where titania minerals are volumetrically insignificant, their microtextures and trace-element chemistry can provide important insights into the character of fluid flow during diagenesis of siliciclastic rocks.

Experimental Investigation on the Phase Equilibria of the Nb-Ti-Si-B System at 1500 °C

The phase equilibria at 1500 °C of the Nb-Ti-Si-B quaternary at the Nb-rich region were carefully studied. Seven alloys were arc-melted and subsequently annealed at 1500 °C for 150 h. BSE image, XRD and EPMA results show that Nbss + T2 + Nb3B2, Nbss + T2 + Nb3Si and Nbss + T2 + Nb3B2 + Nb3Si were present in these alloys. Extensive solubility of Ti and Si were found in the Nb3B2 phase. The experimental findings were compared favorably with the calculated phase equilibria. The phase equilibria in the Nb-rich region of the Nb-Ti-Si-B system have Nbss + T2, Nbss + T2 + Nb3B2, Nbss + T2 + Nb3Si and Nbss + T2 + Nb3B2 + Nb3Si. This work provides important guide lines on the effect of B addition to the microstructure of the Nb-rich Nb-Ti-Si alloys.

Rutile inclusions in quartz crystals record decreasing temperature and pressure during the exhumation of the Su-Lu UHP metamorphic belt in Donghai, East China

Donghai County in the Jiangsu Province of East China is known for its large-scale production of high-quality quartz crystals. The quartz crystals are hosted within the Su-Lu ultrahigh-pressure (UHP) metamorphic belt. They form in quartz veins hosted by eclogite and gneiss, or along contacts between eclogite and gneiss and are mined as placer deposits in the Quaternary sediments. Backscattered electron imaging of the rutile in rutile-bearing euhedral quartz crystals from this region reveal three compositionally and texturally distinct generations of rutile, encapsulated within the host quartz crystal. The earliest generation of rutile (R1) is brightest in BSE, reflecting enrichment in Fe2O3 (0.75–2.08 wt%), Nb2O5 (0.37–0.93 wt%), WO3 (0.48–2.99 wt%), and ZrO2 (0.005–0.105 wt%), relative to R2 and R3. R2 rutile overgrows R1 rutile and contains 0.66–1.11 wt% Fe2O3, 0.45–0.74 wt% Nb2O5, 0.09–0.20 wt% WO3, and <0.001–0.013 wt% ZrO2. R3 rutile, which is the only rutile generation in contact with the host quartz crystals is darkest in BSE and always overgrows R1 and rounded aggregates of R2. R3 rutile contains 0.40–0.68 wt% Fe2O3, 0.13–0.37 wt% Nb2O5, 0.03–0.12 wt% WO3, and <0.001 wt% ZrO2. Oxygen isotopes decrease progressively from 0.6 to −1.5‰ in R1 rutile to 0.1‰ in R2 rutile to −5.1 to −0.3‰ in R3 rutile, consistent with decreasing temperature of rutile crystallization. Combined application of the Zr in rutile and Ti in quartz thermobarometers indicate that these rutile generations precipitated at progressively lower pressures and temperatures, consistent with previously determined retrograde metamorphic conditions of the Su-Lu UHP belt. R1 grew after peak metamorphism during retrograde eclogite facies metamorphism at temperatures between 720 and 800 °C and pressures between 21.7 and 26.6 kbar. During subsequent retrograde metamorphism, R1 was fractured and partially brecciated and overgrown by R2 during epidote-amphibolite facies retrograde metamorphism in the range of 400 to 500 °C and 5 kbar. Zirconium concentrations of <14 ppm in R3 rutile and Ti concentrations of <1 ppm in the co-precipitated host quartz suggest that they both grew at low temperatures of <300° and pressures <2 kbars. Oscillatory growth zones in quartz revealed by cathodoluminescence suggest that no subsequent metamorphism or hydrothermal activity occurred after the formation of the host euhedral quartz crystals and is consistent with a low temperature of quartz crystallization. The random distribution of rutile crystals in the quartz and the lack of evidence for rutile transport by hydrothermal fluids indicate that the host quartz formed by a dissolution-replacement process, whereby the original host mineral, likely omphacite or garnet, was replaced by quartz, but the rutile was not significantly replaced or dissolved due to the low solubility of Ti in low-temperature hydrothermal fluids.

Effect of Ti on the interfacial reaction between Sn and Cu

The effect of Ti on the solid state reactions between Sn and Cu has been investigated in this work. Based on the experimental results the following statements about the effect of Ti can be made: Firstly, the presence of Ti does not have measurable effect on the thickness of either Cu6Sn5 or Cu3Sn during solid state annealing. However, the unevenness of both Cu6Sn5 and Cu3Sn layers is increased by the addition of Ti. Secondly, there is no marked solubility of Ti to either Cu6Sn5 or Cu3Sn. Rather Ti reacts with Sn to form large Ti2Sn3 platelets inside the solder matrix. These findings were subsequently rationalized with the help of the assessed Cu–Sn–Ti phase diagram. By utilizing this phase diagram information, the absence of any marked effects of Ti on the growth of Cu–Sn intermetallic compound (IMC) formation was rationalized. As there is a very low solubility of Ti to SnAg solder and to Cu–Sn IMC’s, Ti cannot change activities of components in the solder nor influence the stability of the IMC layers. Hence, these results throw significant doubts over the concept of trying to influence the Cu–Sn IMC layer thickness or quality by Ti alloying.

Energetics of Ti and Zr transition metals in D0 3-Fe 3Al and its Σ5 (310) [001] grain boundary

The substitution of Ti and Zr transition metals in the bulk volume as well as at the interface of a ∑5 (310)[001] grain boundary of an ordered (D0 3-Fe 3Al) intermetallic were studied by means of ab-initio calculations. The results show that both Ti and Zr prefer to segregate at the grain boundary for Fe types of site. It is demonstrated that the major difference between these two types of atoms is the solubility of Ti in the bulk while Zr substitution in the bulk is not energetically favoured. The preferred site for Ti substitution is confirmed to be Fe I. Emphasis is also given on the importance of using relaxation when determining energy formation calculation for site preference configurations.

First Phase Selection in Solid Ti/Al Diffusion Couple

Abstract Ti/Al diffusion couples fabricated by hot pressing were annealed at 525, 550, 575 and 600 °C. TiAl3 was the only observed phase at the Ti/Al interface when the unreacted Al foils remained. TiAl3 grew towards Al foil side. Few Al atoms were detected in Ti foils. The first formation of TiAl3 is explained on the basis of solubility limits of terminal solid solution, lattice mismatch among Al, Ti and TiAl3, and the increasing interfacial energy caused by newly formed interface. The first saturation of Al (Ti) solid solution due to the little solubility of Ti in Al, and the slight misfit among the close-packed planes of Al, Ti and TiAl3, advance the nucleation of TiAl3. TiAl3, rather than other compounds, has the lowest increasing interfacial energy, indicating its preferential formation. The formation of other titanium aluminides is suppressed due to their growth which is kinetically unstable.

Effect of Heat Treatment on Phase Transformation and Precipitation Behavior of Cu40Zn-1.0 Wt% Ti Brass via Powder Metallurgy

The effect of heat treatment on phase transformation, precipitation behavior and micro-hardness response of Cu40Zn-1.0Ti brass was investigated via powder metallurgy method. The volume fraction of α phase increased with elevated temperature, equaled to that of β phase at 400 °C, and reached to a maximum value of 55.9% at 500 °C. The solid solubility of Ti in Cu40Zn brass matrix decreased with elevated heat treatment temperature, showed high chemical potential for precipitates reaction in Cu40Zn brass. The micro-hardness of the BS40-1.0Ti brass was primarily dependent on the solid solubility of Ti, but also dependent on the phase ratio of α and β phase.

The structural stabilities of Al3(Sc1−xMx) by first-principles calculations

The positive effects of Al3Sc phase on Al–Sc alloys can be promoted by adding to the third elements. The structure properties of Al3Sc when it dissolves the third elements are investigated by first-principles calculations. Special quasirandom structures are developed for the quasi-binary L12 structures. The calculations indicate that the elements of Ti, Zr, Y and Ta tend to substitute for Sc in Al3Sc, while Ni and Si prefer to substitute for Al. The present lattice parameters generally follow the Vegard’s law. The high solubility of Ti and Y in Al3Sc is revealed in the calculated quasi-binary phase diagram.

The crystal and magnetic structure of Ti-substituted LaCrO3

Abstract The crystal and magnetic structures of LaCrO3 and La(Cr0.90Ti0.10)O3 have been investigated between 5 and 350 K by means of neutron powder diffraction and DC magnetic measurements. Both compounds are characterized by an antiferromagnetic Gx-type ordering at low temperature. Structural features suggest the occurrence of Ti in the tetra-valent state. Despite the mixed valence induced by Ti-substitution leading to the occurrence of the Jahn–Teller species Cr2+, no evidence for long range ferromagnetism can be detected. On account of a miscibility gap, a higher degree of Ti-substitution at the Cr site cannot be achieved; as a consequence the solid state solubility of Ti in LaCrO3 at 1573 K has been ascertained.

Ti site occupancy in zircon

Ti site occupancy in zircon (ZrSiO 4) is fundamental to thermobarometry because substitution mechanisms control Ti content–temperature relations. Here we describe the results of three independent methods used to demonstrate that Ti substitutes for Si and not Zr in zircon. Zircon grains were synthesized from oxide powders held in a Na 2WO 4 flux at 1 bar and 1300 °C. Zircon grains equilibrated with rutile + cristobalite show Ti contents (1201 ppm) nearly half that of zircon grains equilibrated with srilankite ((Ti,Zr)O 2) + tetragonal zirconia (2640 ppm). The lower Ti content of zircon grains produced at silica-saturated conditions indicates that Ti substitution predominately occurs on the Si site. Moreover, the higher Ti contents of silica-saturated experiments at 1 bar (1201 ppm), relative to those at 1 GPa (457 ppm, Ferry and Watson, 2007), indicates a substantial pressure effect on Ti solubility in zircon. Measured Ti K-α edge X-ray Absorption Near Edge Structure (XANES) spectra of synthetic zircon grains show energies and normalized intensities akin to those seen among tetrahedrally coordinated Ti-bearing standard minerals, strongly suggesting that Ti occupies the Si site. Density functional theory (DFT) calculations confirm that Ti substitution is most likely to occur on the Si site and predict a Ti–O bond length of 1.797 Å (compared to an average of 2.160 Å for substitution on the Zr site), in excellent agreement with X-ray Absorption Fine Structure (EXAFS) spectra of experimentally grown zircon grains which indicate a value of 1.76(1) Å. The software FEFF 8.4 was used to simulate XANES spectra from the defect structures determined by DFT for Ti substituting on both the Si and Zr sites. The predicted spectrum for Ti on the Si site reproduces all the key features of the experimental zircon spectra, whereas Ti on the Zr site is markedly different. All applied methods confirm that Ti substitutes for Si in zircon. Consequently, the Ti content of zircon at a given pressure is not only a function of temperature, but will increase with decreasing silica activity. Because elements that activate or quench cathodoluminescence (CL) in zircon are incorporated into the Zr site, a decoupling of CL from Ti contents – incorporated on the Si site in zircon is expected. This hypothesis has been verified by a systematic CL-trace element study of natural and experimental zircon.

ChemInform Abstract: Precipitation Phenomenon in Stoichiometric Nd2Fe14B Alloys Modified with Titanium and Titanium with Carbon.

Abstract Precipitation phenomenon has been investigated in stoichiometric Nd2Fe14B alloys modified with Ti and Ti with C. Precipitates can be used to inhibit grain growth and understanding the precipitation process is important in order to form the most effective dispersion. In the NdFeBTi system, TiB2, and in the NdFeBTiC system. TiC are found to be the precipitating phases. Depending on composition, the precipitates can form at high temperatures in the liquid, during cooling after solidification, and during heat treatment. The precipitates form on grain or phase boundaries. The TiC precipitates typically form as discrete particles while the TiB2 precipitates form generally in a globular bunched-up fashion. After a homogenization heat treatment, the equilibrium solubilities of Ti and Ti with C in the Nd2Fe14B phase are found to be 0.47 wt.% and ⩽0.06 wt.% respectively. This means that almost all of the alloyed Ti and C can be precipitated as TiC which returns the excellent intrinsic magnetic properties of the hard magnetic phase. Both the carbides and the borides are found to have excellent high-temperature stability and resist coarsening and dissolution at least to 1000°C. Since Ti and C react to form TiC the amount of hard magnetic phase is not reduced while Ti addition alone reacts with boron and reduces the amount of hard magnetic phase if extra boron is not added.

Surface Etching of MgO : LiNbO3 Crystal by Ti Metal for Integrated Optics

Surface etching of a MgO-doped crystal is demonstrated by annealing a sandwich structure formed by at in a wet atmosphere. The etching depth, raised Ti layer height and surface roughness were studied as a function of initial Ti film thickness, annealing temperature, and duration. The results show that the maximum etching depth can reach 260 nm while the surface roughness is . The features of the raised Ti layer height and surface roughness of the etched surface and raised Ti layer are discussed on the basis of the Ti diffusion mechanism. Combined studies of X-ray single-crystal diffraction, Raman scattering, energy-dispersive X-ray, waveguiding characteristics, surface refractive index, and secondary-ion mass spectrometry show that the etched surface not only retains the crystalline phase and the original crystal composition but is also Ti-free. An etching mechanism based upon an electrochemical reaction process is proposed. The MgO doping effect on the etching rate and surface roughness is discussed and explained in terms of the MgO doping effect on Ti solubility. A comparison of the and surface etching is made. Finally, the present method is compared with other etching techniques and its possible application is suggested.

ChemInform Abstract: Phase Relation in the Pr-Ti-Al Ternary System at 500 °C.

Abstract The isothermal section of the Pr–Ti–Al ternary phase diagram at 500°C was investigated by powder X-ray diffraction, electron probe microanalysis and differential thermal analysis. The 500°C isothermal section of this ternary system consists of 14 single-phase regions, 26 two-phase regions and 13 three-phase regions. Only one ternary compound Ti 2 Al 20 Pr was proved to exist in this isothermal section. A solid solution of the type Pr(Al 1− x Ti x ) 2 was found in this work. At 500°C, the maximum solid solubility of Ti in Al 2 Pr is 17 at.% Ti and of Pr in Ti 3 Al and TiAl are less than 2 at.% Pr, respectively.

Crystallization Behavior of SiO2–Al2O3–ZnO–CaO Glass System at 1123–1273 K

The crystallization characteristics of a glass, used as the matrix of high‐temperature protective coatings, based on SiO2–Al2O3–ZnO–CaO with the addition of TiO2 and ZrO2 at a temperature range of 1123–1273 K have been investigated. At 1273 and 1173 K, tetragonal zirconia doped with Ti and Ca, initially precipitated from the melt. At 1123 K, however, zirconolite instead of zirconia precipitated as the primary phase. The secondary precipitates were zircon and titanite in the glass fired at 1273 K, titanite and willemite at 1173 K, and zirconolite, titanite, and willemite at 1123 K, respectively. It is proposed that the temperature‐dependent solubility of Ca and Ti in ZrO2 significantly affects the type and volume fraction of crystals precipitated from the glass.

TitaniQ under pressure: the effect of pressure and temperature on the solubility of Ti in quartz

Quartz and rutile were synthesized from silica-saturated aqueous fluids between 5 and 20 kbar and from 700 to 940°C in a piston-cylinder apparatus to explore the potential pressure effect on Ti solubility in quartz. A systematic decrease in Ti-in-quartz solubility occurs between 5 and 20 kbar. Titanium K-edge X-ray absorption near-edge structure (XANES) measurements demonstrate that Ti4+ substitutes for Si4+ on fourfold tetrahedral sites in quartz at all conditions studied. Molecular dynamic simulations support XANES measurements and demonstrate that Ti incorporation onto fourfold sites is favored over interstitial solubility mechanisms. To account for the P–T dependence of Ti-in-quartz solubility, a least-squares method was used to fit Ti concentrations in quartz from all experiments to the simple expression $$ RT\ln X_{{{\text{TiO}}_{ 2} }}^{\text{quartz}} = - 60952 + 1.520 \cdot T(K) - 1741 \cdot P(kbar) + RT\ln a_{{{\text{TiO}}_{ 2} }} $$ where R is the gas constant 8.3145 J/K, T is temperature in Kelvin, $$ X_{{{\text{TiO}}_{ 2} }}^{\text{quartz}} $$ is the mole fraction of TiO2 in quartz and $$ a_{{{\text{TiO}}_{ 2} }} $$ is the activity of TiO2 in the system. The P–T dependencies of Ti-in-quartz solubility can be used as a thermobarometer when used in combination with another thermobarometer in a coexisting mineral, an independent P or T estimate of quartz crystallization, or well-constrained phase equilibria. If temperature can be constrained within ±25°C, pressure can be constrained to approximately ±1.2 kbar. Alternatively, if pressure can be constrained to within ±1 kbar, then temperature can be constrained to approximately ±20°C.

The Zn-rich corner of the Zn–Al–Ti system at 723 K

The Zn-rich corner of the Zn–Al–Ti ternary system at 723 K was experimentally determined using equilibrated alloys with the aid of diffusion couple approach. The specimens were investigated by means of optical microscopy, scanning electron microscopy, wave dispersive X-ray spectroscope and X-ray powder diffraction. A true ternary phase T was identified and it is in equilibrium with TiAl 3, TiAl 2, α-Al, liq.Zn, TiZn 16, TiZn 8 and TiZn in the system respectively. The solubility of Ti in liquid zinc is 0.3 at.%. The solubility of Zn in TiAl 3 and TiAl 2 is 4.4 at.% and 3.2 at.% respectively and that of Al in TiZn 16, TiZn 8, TiZn 3 and TiZn is 0.4 at.%, 0.2 at.%, 1.7 at.% and 2.5 at.% respectively.

Isothermal section of the Nd–Co–Ti ternary system at 500°C

Abstract The isothermal section of the Nd–Co–Ti system at 500 °C has been investigated by means of XRD and SEM/EDS techniques. Compound Nd2Co3 was observed to exist at 500 °C with the orthorhombic La2Ni3-type structure, space group Cmca and unit cell parameters a = 0.4986(2) nm, b = 1.0000(2) nm, c = 0.7546(2) nm. One ternary compound NdTixCo12−x with the tetragonal ThMn12-type structure (space group I4/mmm) was found with a homogeneity range of 1.43 ≤ x ≤ 1.82, i.e. 11–14 at.% Ti. The structure of NdTi1.7Co10.3 was determined by Rietveld refinement method with the unit cell parameters a = 0.84616 (1) nm, c = 0.47447 (1) nm. The maximum solid solubilities of Ti in Nd2Co17, Nd2Co7, NdCo3, NdCo2, and Nd3Co are 6, 1.5, 2, 4 and 2 at.%, respectively.

Comparisons between intrinsic bonding defects in d 0 transition metal oxide such as HfO 2, and impurity atom defects in d 0 complex oxides such as GdScO 3

This article addresses O-atom vacancy defects in the d 0 transition metal (TM) oxides HfO 2 and TiO 2, and Ti substitutions for Sc in the d 0 complex oxide GdScO 3. In each instance this results in occupied TM atoms with d 1 state representations. These are important for different aspects of the ultimate scaling limits for performance and functionality in nano-scale Si devices. The occupancy of d 1 states is cast in terms of many-electron theory in order to determine the effects of correlation on device performance and functionality. The first section of this article identifies equivalent d-state representations using on an ionic model for the effective valence states of Ti and Hf atoms bordering on O-atom vacancy defects. Removal of an O atom to create a neutral vacancy; this is equivalent to the bonding of two electrons to each vacancy site. This give rise to two coupled d 1 states for a mono-vacancy defect. Transitions from these occupied states generate spectroscopic features in the (i) pre-edge shake-up, and (ii) virtual bound state (VBS) shake-off energy regimes in O K edge XAS spectra. The number of states confirm that these are mono-vacancy defects. The second section addresses incorporation of Ti tetravalent impurities into trivalent GdScO 3, forcing Ti into a Ti 3+ state and generating a d 1 electronic structure. Vacancy defect concentrations in HfO 2 are generally <10 19 cm −3. However, the Ti solubility in GdScO 3 is higher, and relative concentrations in excess of 16–17% lead to an insulator to metal transition with a ferri-magnetic electronic structure.