Solubility Of Al2O3 Research Articles

Alumina solubility in periclase determined to lower mantle conditions and implications for ferropericlase inclusions in diamonds

A series of high-pressure multi-anvil experiments were conducted in the MgO-Al2O3 system between 15 and 50 GPa and at temperatures up to 2623 K, to determine the solubility of Al2O3 in periclase in the stability fields of coexisting spinel, corundum, the Mg2Al2O5 modified ludwigite phase, the MgAl2O4 calcium ferrite phase, and the MgAl2O4 calcium titanate phase. The Al2O3 solubility in periclase is strongly temperature-dependent over the conditions investigated. Conversely, periclase Al2O3 solubility exhibits a negative relationship with pressure. Experiments with up to 40 mol.% FeO in ferropericlase show Al2O3 solubilities that are near identical to those of periclase, within experimental uncertainties. A simple thermodynamic model incorporating significant literature on ambient pressure measurements is able to describe periclase Al2O3 solubility up to 40 GPa. This model is used to investigate the Al2O3 contents of ferropericlase inclusions observed in natural diamonds, which vary up to 0.35 mol. %. Pressure–temperature curves along which particular inclusions formed can be produced if equilibrium can be assumed with Al-bearing minerals found in the same diamond. Alternatively, the maximum possible Al2O3 content in ferropericlase can be determined for a certain pressure–temperature profile and inclusions with Al2O3 contents that exceed this curve can be excluded from those conditions. To obtain such solubility curves, calculations are performed for periclase coexisting with the Al-rich phases spinel, garnet, bridgmanite and the MgAl2O4 calcium ferrite phase. The calculations indicate that periclase, and by inference ferropericlase, Al2O3-contents cannot be greater than 0.5 mol.% under present day adiabatic mantle temperatures and go through a minimum at mantle transition zone conditions. This excludes a number of Al-rich ferropericlase inclusions found in natural diamonds from being formed in the transition zone, unless temperatures were super-adiabatic. This subset of inclusions likely formed either at the base of the upper mantle or the top of the lower mantle, but must have formed at near adiabatic temperatures. The majority of ferropericlase inclusions have Al2O3 contents that would be consistent with formation in the transition zone at near slab temperatures, but could still have been formed at higher temperatures if Al2O3 activities were low.

Slag chemistry, element distribution behaviors, and metallurgical balance of e-waste smelting process

The co-smelting of electronic waste (e-waste) in copper/lead pyrometallurgical processes is widely recognized as the preferred solution for sustainable development. However, aluminum and halogen elements in e-waste causes new challenges. To address this, the slag chemistry of high Al2O3-containing slag was studied, and the distribution behaviors of Au, Ag, Sn, and other elements in the copper alloy/slag/gas system were investigated in the presence of halogen elements (F/Cl/Br) using the equilibration method. The industrial practice of electronic waste smelting was modeled using METSIM, and the material and energy balances of one industrial process were obtained. Under the conditions of electronic waste smelting, the solubility of Al2O3 in the FexO–SiO2–Al2O3–CaO slag system decreased with increasing CaO content. When the CaO content was 20 wt%, and the Fe/SiO2 mass ratio was 0.62–0.95, the solubility of Al2O3 in the slag reached 20 wt%. When 1%–10% CaF2 was added, 93% of Au entered the metal phase. When the same amount of CaCl2 or CaBr2 was added, up to 32% Au entered the gas phase. When CaF2 was added to the system, 22%–49% of Ag entered the gas phase. However, when CaCl2 or CaBr2 was added, 3%–34% of Ag entered the gas phase. The proportion of tin in the gas and slag phases increased with increasing temperature or the addition of halides. The METSIM simulation results showed that under optimized conditions, the crude copper contained more than 90 wt% copper, the discharged slag contained approximately 0.5 wt% copper, and the recovery rates of copper, gold, and silver were ≥98%. The heat generated from raw materials and fuel accounted for the largest part of the heat income, representing 65.32% of the total.

Thermodynamic assessment of the Al2O3–ZrO2, CaO–Al2O3–ZrO2, and Al2O3–SiO2–ZrO2 systems

All available thermodynamic data and phase diagram data in the Al2O3–ZrO2, CaO–Al2O3–ZrO2, and Al2O3–SiO2–ZrO2 systems at 1 bar total pressure were critically evaluated and assessed simultaneously to obtain a set of the optimized Gibbs energies of all phases in the systems. Due to the lack of reliable data on the mutual solubility of Al2O3 and ZrO2, key phase diagram experiments in the Al2O3–ZrO2 binary system were carried out by using a classical phase equilibrium and quenching technique followed by the EPMA phase analysis. Based on the optimized Gibbs energies, the reliable experimental phase diagram and thermodynamic property data of the Al2O3–ZrO2, CaO–Al2O3–ZrO2, and Al2O3–SiO2–ZrO2 systems are well reproduced, and unknown phase diagram and thermodynamic properties are predicted.

Water diffusion and solubility in sodium aluminosilicate melts

The diffusivity and solubility of water at 1200°C has been measured in a series of sodium aluminosilicate melts. Both the diffusivity and solubility of water in these melts decrease as Na2O is replaced by Al2O3. The partial molar solubilities of SiO2, Na2O and Al2O3 have been determined. The diffusivity of water in these melts exhibits an inverse relationship with the viscosity of the melt, which can be extended to include sodium silicate melts at the same temperature. The glass transformation temperature of these glasses decreases with increasing water concentration. The magnitude of this effect is shown to be similar to that for many other compositional systems.

Optimization of thermoelectric properties of Al-doped Zn1−xAlxO under high pressure and high temperature

ZnO has excellent electrical properties such as high conductivity (σ) and Seebeck coefficient (S) that are important for its thermoelectric properties and have provided the basis for obtaining improved ZnO-based thermoelectric materials by doping. In particular, the most representative Al-doped ZnO (AZO) has excellent thermoelectric performance. Although the Al doping is beneficial for reducing the lattice thermal conductivity of ZnO, the solubility of Al2O3 in ZnO is limited and excessive doping of Al gives rise to the generation of a large amount of the ZnAl2O4 secondary phase that limits the further improvement of the electrical properties. Thus, it is crucial to develop approaches to reduce thermal conductivity while still maintaining high electrical properties. In this work, high pressure and high temperature (HPHT) synthesis was used to adjust the ZnO optical band gap by modifying the lattice parameters of ZnO, and thereby improving the electrical properties of the sample. It was found that the optimal doping content for the samples synthesized at high pressure is different from that of the samples synthesized at normal pressure, providing a new approach for the further improvement of the thermoelectric properties of ZnO. Additionally, high pressure can promote grain refinement that is conducive to the generation of the multi-scale hierarchical structure of the sample that introduces a variety of phonon scattering mechanisms to reduce the thermal conductivity while maintaining a high power factor. The Zn0.96Al0.04O material obtained by sintering at a pressure of 3 GPa and a temperature of 1053 K for 30 min reached the highest power factor (7.8 µW cm−1 K−2) and the highest zT (0.16) at 973 K.

Aluminum solubility in bridgmanite up to 3000 ​K ​at the top lower mantle

The temperature dependence of the Al2O3 solubility in bridgmanite has been determined in the system MgSiO3–Al2O3 at temperatures of 2750–3000 ​K under a constant pressure of 27 ​GPa using a multi-anvil apparatus. Bridgmanite becomes more aluminous with increasing temperatures. A LiNbO3-type phase with a pyrope composition (Mg3Al2Si3O12) forms at 2850 ​K, which is regarded as to be transformed from bridgmanite upon decompression. This phase contains 30 ​mol% Al2O3 at 3000 ​K. The MgSiO3 solubility in corundum also increases with temperatures, reaching 52 ​mol% at 3000 ​K. Molar volumes of the hypothetical Al2O3 bridgmanite and MgSiO3 corundum are constrained to be 25.95 ​± ​0.05 and 26.24 ​± ​0.06 ​cm3/mol, respectively, and interaction parameters of non-ideality for these two phases are 5.6 ​± ​0.5 and 2.2 ​± ​0.5 ​KJ/mol, respectively. The increases in Al2O3 and MgSiO3 contents, respectively, in bridgmanite and corundum are caused by a larger entropy of Al2O3 bridgmanite plus MgSiO3 corundum than that of MgSiO3 bridgmanite plus Al2O3 corundum with temperature, in addition to the configuration entropy. Our study may help explain dynamics of the top lower mantle and constrain pressure and temperature conditions of shocked meteorites.

Precipitation mechanism and microstructural evolution of Al2O3/ZrO2(CeO2) solid solution powders consolidated by spark plasma sintering

It is difficult to synthesize Al2O3/ZrO2 solid solution because of its low solubility under equilibrium solidification conditions. In this work, a new combustion synthesis combined with water atomization (CS-WA) method was developed to prepare supersaturated Al2O3/ZrO2(CeO2) solid solution powders. The ultra-high cooling rate supplied by CS-WA greatly extends solid solubility of Al2O3 in ZrO2. The precipitation mechanism of solid solution was investigated by systematic heat treatments. The initial temperature of the metastable phase decomposed into Al2O3 and ZrO2 is 1050 °C, and it could be completely precipitated at 1400 °C in 0.5 h. The precipitated ZrO2 particles were uniformly dispersed in Al2O3 matrix and grew into submicron scale at annealing temperature of 1450 °C. Subsequently, together with detailed microstructure, phase composition, as well as mechanical properties were collaboratively outlined to discuss spark plasma sintering (SPS) behavior. The solid solution precipitated Al2O3 matrix and ZrO2 particles during the SPS process. Partial ZrO2 particles were uniformly distributed within Al2O3 matrix, while the residuary ZrO2 located at the grain boundaries and formed special transgranular/intergranular structure. The average size of nanoscale transgranular ZrO2 particles was only ∼11.5 nm. The compact ZrO2 toughened Al2O3 nano ceramic (N-ZTA) exhibits excellent mechanical properties. This work provides a guidance to produce nanostructured ZTA with high performance.

Microstructural evolution of supra‐nanostructure Al2O3/ZrO2 eutectic powders by combustion synthesis‐spray cooling

AbstractEutectic powders with fine microstructure are difficult to synthesize by crushing eutectic bulk because of the damage of crystal structure and the introduction of milling media during preparation process. In this work, a novel combustion synthesis‐spray cooling (CSSC) method is developed to fabricate supra‐nanostructure Al2O3/ZrO2 eutectic powders. CSSC is a kind of self‐heating technique, which simplifies operations, reduces costs and supplies ultra‐high cooling rate. The phase composition and the microstructural evolution are investigated using experiment studies and ANSYS simulation. During the process, the t‐ZrO2 are stabilized at room temperature because of the solubility of Al2O3 in ZrO2. The ultra‐high cooling rate greatly refined eutectic structure. Although the eutectic structure coarsens with increases in particle size, the interphase spacing of all particles reaches supra nanoscale. The work provides a route for preparing supra‐nanostructure Al2O3/ZrO2 eutectic powders and for better understanding the microstructural evolution.

The <i>In Situ</i> Preparation of MgAl<sub>2</sub>O<sub>4</sub>/YAG Eutectic Composites by Reaction Sintering Using Induction Heating

High density MgAl2O4/YAG (yttrium aluminum garnet) eutectic composites were successfully prepared by in-situ reaction sintering using induction heating (IH). The effects of IH time and the starting materials composition on the phase composition and microstructure were investigated. The results showed that the eutectic composites consisted of only MgAl2O4 and YAG phase could be prepared by IH in a short time in a range of Al2O3/MgO ratio between 1~1.54. Compared to conventional sintering (CS), the solubility of Al2O3 in spinel is remarkably enhanced under the synergistic effects of high temperature and induced electromagnetic field. The higher YAG content facilitates the formation of more eutectic liquid phase, which favors to obtain a more homogeneous and denser interpenetrating network structure.

Phase Relations in the System MgSiO3‐Al2O3 up to 2300 K at Lower Mantle Pressures

AbstractPhase relations in the system MgSiO3‐Al2O3 were investigated at pressures of 27–45 GPa and temperatures of 1700, 2000, and 2300 K using sintered diamond and tungsten carbide anvils in a multianvil apparatus. The bulk compositions in the MgSiO3‐Al2O3 binary system crystallize a phase assemblage of pyrope and corundum at pressures below 27 GPa and an assemblage of bridgmanite and corundum at pressures above 27 GPa regardless of temperatures. The solubility of Al2O3 in bridgmanite and that of MgSiO3 in corundum increases significantly with increasing temperature. The solubility of Al2O3 in bridgmanite increases from 6.7 mol % at 1700 K to 21.8 mol % at 2500 K under a constant pressure of 27 GPa. Bridgmanite becomes more aluminous with increasing pressure from 27 to 45 GPa at a given temperature. The MgSiO3 content in corundum increases with increasing pressure at pressure lower than 27 GPa, while it decreases at pressure higher than 27 GPa. Our results suggest that bridgmanite can incorporate a considerably higher Al2O3 content than that of the pyrope composition (25 mol % Al2O3). The present study further suggests that the entire Al2O3 component is accommodated into bridgmanite in the pyrolite lower mantle. However, Al2O3 cannot be fully accommodated into bridgmanite in the coldest parts of subducted slabs in the shallow part of the lower mantle, and therefore, additional phases such as MgAl2O4 with calcium ferrite‐type structure are necessary to host the excess Al2O3.

High-pressure high-temperature phase relations in FeTiO3 up to 35 GPa and 1600 °C

Phase relations in FeTiO3 were precisely determined at 25–35 GPa and 600–1600 °C using multianvil high-pressure experiments with tungsten carbide anvils. Pressure generation up to about 36 GPa at 1600 °C was evaluated using Al2O3 solubility in MgSiO3 perovskite (Pv) in the system MgSiO3–Al2O3. At about 28 GPa, FeTiO3 Pv dissociates into an assemblage of calcium titanate (CT)-type Fe2TiO4 + orthorhombic-I (OI)-type TiO2 below 1200 °C. However, above 1200 °C at 28 GPa, FeTiO3 Pv decomposes into a new, denser phase assemblage of CT-type Fe2TiO4 + a new compound of FeTi2O5. The new phase FeTi2O5 was recovered as an amorphous phase at 1 atm. In situ X-ray diffraction experiments at 35.1 GPa indicated that the new phase (N-p) FeTi2O5 has orthorhombic symmetry with cell parameters a = 8.567(2) A, b = 5.753(1) A and c = 5.257(1) A. In addition, the assemblage of CT-type Fe2TiO4 + OI-type TiO2 changes to FeO wustite (Wu) + OI-type TiO2 at about 33 GPa below 1000 °C. The phase assemblages in FeTiO3 are denser in the order: FeTiO3 (Pv) → 1/2Fe2TiO4 (CT) + 1/2TiO2 (OI) → 1/3Fe2TiO4 (CT) + 1/3FeTi2O5 (N-p) → FeO (Wu) + TiO2 (OI). Our results indicate that the upper stability limit of FeTiO3 Pv is about 28 GPa at 600–1600 °C. This puts a constraint on peak shock pressure for formation of naturally discovered lithium niobate-type FeTiO3 which was interpreted to be retrograde transition product of FeTiO3 Pv on release of shock pressure.

Phase relations in the system MgSiO3–Al2O3 up to 52 GPa and 2000 K

Phase relations in the system MgSiO3–Al2O3 have been determined for pressures from 15 to 52GPa and at a temperature of 2000K from in situ synchrotron X-ray diffraction measurements obtained using sintered diamond anvils in a multi-anvil apparatus. A wide two-phase region of garnet and corundum is found to exist up to 27GPa; at higher pressures, a phase assemblage of aluminous bridgmanite and corundum is stabilized. The solubility of Al2O3 in bridgmanite and that of MgSiO3 in corundum are highly dependent on pressure; the Al2O3 content in bridgmanite increases from 12mol% at 27GPa to 29mol% at 52GPa, forming bridgmanite with the pyrope composition (25mol% Al2O3) at about 45GPa. In contrast, the MgSiO3 content in corundum decreases from 24mol% at 27GPa to 9mol% at 52GPa. The minimum pressure where the pyropic bridgmanite is formed is significantly higher than the result of the earlier study (∼37GPa) on the pyrope composition. These results suggest the Al2O3 content in bridgmanite and the MgSiO3 content in corundum are good pressure indicators in the mixed-phase region at pressures above 30GPa, where virtually no pressure references are available for quench experiments. The new phase diagram in the system MgSiO3–Al2O3 confirms that bridgmanite is the dominant host mineral for Al2O3 in the pyrolitic or peridotitic compositions under the pressure and temperature conditions of the Earth’s lower mantle.

The Effects of Na2O and SiO2 on Liquid Phase Sintering of Bayer Al2O3

To determine how grain‐boundary composition affects the liquid phase sintering of MgO‐free Bayer process aluminas, samples were singly or co‐doped with up to 1029 ppm Na2O and 603 ppm SiO2 and heated at 1525°C up to 8 h. Na2O retards densification of samples from the onset of sintering and up to hold times of 30 min at 1525°C compared to the undoped samples, but similar to the as‐received, MgO‐free Al2O3, Na2O‐doped samples sinter to 98% density with average grain sizes of ~3 μm after 8 h. Increasing SiO2 concentration significantly retards densification at all hold times up to 8 h. The estimated viscosities (20−400 Pa·s) of the 0.3 to 1.8 nm thick siliceous grain‐boundary films in this study indicate that diffusion greatly depends on the composition of the liquid grain‐boundary phase. For low Na2O/SiO2 ratios, densification of Bayer Al2O3 at 1525°C is controlled by diffusion of Al3+ through the grain‐boundary liquid, whereas for high Na2O/SiO2 ratios, densification can be governed by either the interface reaction (i.e., dissolution) of Al2O3 or diffusion of Al3+. Increasing Na2O in SiO2‐doped samples increases diffusion of Al3+ and Al2O3 solubility in the liquid, and thus densification increases by 1%. Based on these findings, we conclude that Bayer Al2O3 densification can be manipulated by adjusting the Na2O to SiO2 ratio.

High-temperature phase equilibria of Cu–O–Al2O3 system in air

Phase equilibria of Cu–O–Al2O3 system were experimentally investigated in a temperature range of 1100–1400°C under 0.21 atm oxygen pressure. The experiments were conducted employing a high-temperature equilibration and quenching method. Microstructures of the quenched samples were observed with scanning electron microscope. The phase compositions in the samples were analysed with electron probe microanalysis technique. Measured solubility of Al2O3 into the molten oxide ranged from 0.0 to 1.8 wt-%. A small solubility of Cu2O into Al2O3 was also observed ranging from 1.20 to 1.58 wt-%.

Potentiodynamic anodizing of aluminum alloys in Cr(VI)‐free electrolytes

The aerospace industry progressively develops alternatives for chromic acid anodizing, because Cr(VI) is known to be toxic and carcinogenic. In this work, potentiodynamic anodizing of AA1050 and AA2024‐T3 clad was performed in phosphoric‐sulfuric acid (PSA) and sulfuric acid (SAA). All anodizing cycles started with a linear voltage sweep, followed by a constant voltage, or a dynamic voltage. Current density responses were recorded during each anodizing cycle and comprised different stages, which could be related to growth phases of the anodic oxide film. Interesting differences were found between cycles with an intermediate increase in anodizing voltage versus cycles with an intermediate decrease in voltage. Cycles including an increase in voltage resulted in higher anodic oxide formation efficiencies because of a temporary exceedance of the steady state current (recovery period) directly after the voltage step. Also, a sudden decrease in voltage led to distinct border between a fine and coarse region in the film morphology, while a sudden increase in voltage did not. For prolonged anodizing in PSA, coarsening of the upper film part was observed because of the high solubility of Al2O3 in phosphoric acid. Pore walls close to the outer surface did not only get thinner, but completely dissolved in the electrolyte. Consequently, anodic oxide formation efficiencies were higher for SAA than for PSA. Copyright © 2016 John Wiley & Sons, Ltd.

Critical Assessment and Thermodynamic Modeling of the Al-Fe-O System

A complete literature review, critical evaluation, and thermodynamic modeling of the phase diagrams and thermodynamic properties of phases in the Al-Fe-O system at 1 atm total pressure are presented. Optimized model equations for the thermodynamic properties of all phases are obtained, which reproduce all available thermodynamic and phase-equilibrium data within experimental error limits from 298.15 K (25 °C) to above the liquidus temperatures at all compositions and oxygen partial pressures from metal saturation to 1 atm. The complex phase relationships in the system have been elucidated, and discrepancies among the data have been resolved. The database of the model parameters can be used along with software for Gibbs-energy minimization in order to calculate all thermodynamic properties and any type of phase diagram section. The modified quasichemical model was used for the liquid oxide phase. A sublattice model, based upon the Compound Energy Formalism, was developed for spinel, which expands from magnetite, Fe3O4, to hercynite, FeAl2O4. The distribution of cations between octahedral and tetrahedral sites and oxygen nonstoichiometry in spinel are taken into account. The model for metallic liquid assumes random mixing of associates: Fe, Al, O, AlO, and Al2O. It describes well the minimum that is observed on the solubility of oxygen in liquid iron as a function of the Al content. The solid solution between hematite and corundum exhibiting a miscibility gap, as well as a small solubility of Al2O3 in wustite are quantitatively described by a simple Bragg-Williams model.

Physical-Chemical Properties of the Naf-AlF3-Sc2O3-Al2O3 Molten System

The Al-Sc alloys are typically obtained by aluminothermy method. However, the high alloy’s price is defined by the cost of a scandium-containing substance (such as ScF3 or Sc, etc.) prepared from its raw material (Sc2O3) for the reaction with aluminum. Expenses for a multistage scandium extraction process are also substantial. Another way for producing the Al-Sc alloys can be the electrochemical co-reduction of Al and Sc from their oxides dissolved in a cryolite (NaF-AlF3) melt. To develop the electrolysis process and to determine its operating parameters it is necessary to know some basic physical-chemical properties of the NaF-AlF3-Sc2O3-Al2O3 molten system, such as liquidus temperature, Sc2O3 solubility in cryolite including a cross impact of both Sc2O3 and Al2O3 oxides on their solubility and electrical conductivity of molten mixture. A thermo analysis (TA) was used for liquidus temperature measurements. An oxide solubility was determined by the TA along with isothermic saturation method. An electrical conductivity was measured in the capillary (BN) cell and in the cell with parallel Mo-electrodes using an impedance technique. The obtained results testified that the Sc2O3 behaved similar to the Al2O3. Its additions to the molten cryolite decreased the liquidus temperature and the electrical conductivity. The Sc2O3 solubility in the NaF-AlF3 melt with molar ratio of NaF/AlF3=2.3 was found to be about 10 wt% at 980 ᵒC. The Al2O3 solubility in the scandium-containing cryolite decreased with the Sc2O3 concentration rise. The total solubility of both oxides, in controversial to known data, was determined to be slightly higher than the solubility of each separate oxide in the NaF-AlF3 melt.

The Behavior of KBF4 in Potassium-Cryolite-Based Melts

The KBF4 impact on the physical-chemical properties of the KF-AlF3 and KF-NaF(10 wt%)-AlF3 melts with cryolite ratio (CR) 1.3–1.5 was studied at temperatures 700–800°C. The KBF4 additions (up to 15 mol%) to the potassium-cryolite-based electrolytes increase the liquidus temperature, however, the KBF4 presence in the cryolite-alumina melt improves the Al2O3 solubility and enlarges the range of homogeneity in the (cryolite-KBF4)-Al2O3 system. The KBF4 additions (within a concentration range of 0–10 mol%) do not noticeably impact the electrical conductivity of the KF-AlF3-KBF4 melt (CR = 1.3). The mass loss of the KF-AlF3-KBF4 samples with low CR determined by thermogravimetry analysis over two hours is not higher than 3% at temperature 800°C.

Determination of Vanadium Solubility in the Al2O3-CaO(30 Mass Pct)-SiO2 and Al2O3-CaO(35 Mass Pct)-SiO2 System

The solubility of vanadium oxide in the Al2O3-CaO(30 mass pct)-SiO2 system and Al2O3-CaO(35 mass pct)-SiO2 system was determined experimentally at 1873 K (1600 °C) and at a fixed oxygen potential of 9.37 × 10−11 bar. EPMA microanalyses were employed to identify the phases and their compositions in the quenched samples. The solubility of vanadium oxide in the liquid phase was found to decrease with increasing CaO content in the liquid. The vanadium oxide solubility was especially low when both CaO and Al2O3 contents were high in the liquid phase. The maximum solubility of vanadium oxide was up to 7 mass pct (as V). Two solid phases were found, a solid solution of Al2O3 and vanadium oxide and an Al2O3-rich solid phase with 16.7 mass pct V2O3. The Al2O3 solubility in the solid solution was found to increase with increasing Al2O3 content in the liquid, the impact of the CaO content in the liquid on the solubility of Al2O3 in V2O3 was found to be small. The Al2O3-rich solid phase was identified as the mineral hibonite with fractionation of V into the crystal structure.

Determination of the vanadium solubility in the Al2O3–CaO (25 mass%)–SiO2 system

Vanadium (V) solubility in the Al2O3–CaO (25mass%)–SiO2 system was determined experimentally at 1873K and at a fixed oxygen potential of 9.37×10−11 bar. EPMA microanalyses were employed to identify the phases and their compositions in the quenched samples. It showed that the solubility of V-oxide increased slightly with decreasing Al2O3-content in the interval from 3mass% to 53mass%. The maximum V-solubility was up to 7mass% (as V). A solid solution rich in V-oxide was detected. The Al2O3 solubility in this solid solution was found to increase with increasing Al2O3-content in the liquid.