High-temperature Solid Solution Research Articles

Grain refining mechanism and strength-ductility trade-off of NbC-reinforced FeCoNiCrMn HEA

The strength-ductility trade-off has long challenged FCC-typed HEAs. This paper presents a NbC-reinforced FeCoNiCrMn HEA with ultra-fine grain and nano NbC particle. Its ultimate tensile strength and elongation are 853.7 ± 7.3 MPa and 57.8 ± 1.9 %, respectively. The combination of high temperature solid solution at 1180 °C, cold rolling, and low temperature annealing at 1050 °C contributes to the generation of nano-sized NbC particles on the high-density grain boundary (GB) and sub-GB of rolled microstructure. The almost uniformly distributed nano-sized NbC particles deeply hinders the grain growth and contributes to the ultra-fine grain of NbC-reinforced HEA. It sheds new insights into understanding the way to refine grain and precipitate of NbC-reinforced FCC-typed HEA and its effect on strength-ductility trade-off.

The role of zinc addition on the microstructural evolution and mechanical properties of wire-arc directed energy deposited Mg-Gd-Y-(Zn)-Zr alloys

Wire-arc directed energy deposition (WA-DED) demonstrates significant potential in the rapid and free forming of high-strength magnesium rare-earth (Mg-RE) alloys. This highlights a growing demand for tailored wire alloy compositions to promote engineering applications of this technology. In this work, the role of zinc addition on WA-DED processed Mg-Gd-Y based alloys has been thoroughly investigated by utilizing Mg-6Gd-3Y-0.5Zr (wt.%, GW63K) and Mg-6Gd-3Y-0.5Zn-0.5Zr (wt.%, GWZ631K) alloy wires as model materials. The microstructure evolution of these two alloys during deposition and heat treatment is revealed by multi-scale microstructure characterization techniques. The influences of Zn addition on mechanical properties of these deposited alloys are investigated comparatively. Obtained results indicate that addition of Zn element into Mg-Gd-Y based alloys promotes phase transformation between eutectic phases and long period stacking order (LPSO) phases during the WA-DED deposition process owing to the multiple thermal cycling. More importantly, the addition of Zn element increases the tendency of solidification shrinkage of the deposited metal. During high-temperature solid solution treatment, the presence of Zn is conducive to improving the thermal stability of the as-deposited grain boundaries and thus suppressing grain coarsening. After optimized T6 treatments, the strength of GW63K alloys increases to 374±7MPa, and is obviously higher than that (315±6MPa) of GWZ631K alloys. The addition of Zn element weakens the precipitation strengthening effect. This can be attributed to the formation of LPSO phases, which consumes a substantial amount of RE elements, and in turn decreases the density of aging precipitated nanoscale β´ phases. This work promotes the understanding of the non-equilibrium solidified microstructure evolution of multi-component Mg-RE alloys and guides the optimization of alloy composition of WA-DED specific wire materials.

Fully equiaxed grain structure and isotropic mechanical properties in wire arc additive manufactured Mg–Al-RE alloy

Wire arc additive manufacturing (WAAM) of Mg–Al-RE alloy is an essential technology for producing high-quality large-scale components with high manufacturing flexibility. In this study, WAAM was utilized to fabricate a thin-wall component made of Mg-8.2Al-0.6Y-0.4Ce (AE81) alloy. The microstructure and tensile properties of the fabricated component were investigated. The results showed that the as-built AE81 alloy exhibits superior isotropic tensile strengths and a homogeneous equiaxed α-Mg grains structure. Additionally, the alloy demonstrated a minimal growth in grain size after high-temperature solid solution treatment due to the presence of thermally stable Al11/rare earth (RE)3 phases at grain boundaries. Further ageing treatment induces the formation of high-density of β-Mg17Al12 precipitates within the α-Mg grains, resulting in a considerable precipitation strengthening effect. Consequently, the heat-treated AE81 alloy demonstrated significantly enhanced tensile strength of 280 MPa and acceptable ductility of 4.6%. The results also revealed that the formation of equiaxed grains during WAAM contributed to the isotropic mechanical properties. These findings can facilitate advancements in AM processes and the development of high-performance Mg alloys.

Influence of cooling rate during the heat treatment process on the precipitates and ductility behavior of inconel 718 superalloy fabricated by selective laser melting

IN718 superalloy by elective laser melting (SLM) has shown great application prospects in the aerospace engine key parts. Different phases are precipitated during the SLM forming process. Although the Laves phase could be dissolved in dendrites by heat treatment, the specific evolution of the second phase particles is still unclear. In this work, the influences of solution and aging heat treatment, as well as cooling rate on the precipitates and ductility behavior of IN718 superalloy fabricated by SLM were systematically investigated. The medium temperature (980 °C) solution treatment regimes included three different colling rates and the control group only underwent aging treatment were studied. The results indicated that high temperature solid solution treatment effectively improved compositional segregation and significantly enhanced homogeneity of microstructure. The reduce of cooling rate at 980 °C was beneficial to the extension time and increased the number of δ phase precipitation. An appropriate number of δ phase improves the notch sensitivity and nails grain boundaries. In addition, the complex dislocations and second phase particles retards the migration of slip dislocations during ductility deformation process, which enhances the strength of SLM-ed IN718. The yield strength of specimens increases from 680 MPa to 1205 MPa. The microhardness is greatly improved as compared with as-deposited IN718, and the highest microhardness reaches 485 HV. The results provide a technical support and reference for formulating the heat treatment schedule of IN718 prepared by SLM.

In situ self-adaptive growth of graphene coatings on hard substrates via competitive NiCo catalysis reaction

Graphene coatings have sprung up as promising solid lubrication materials due to their intriguing mechanical properties. Achieving in situ deposition of a conformally encapsulated, high-quality graphene coating on hard substrates holds immense potential for industrial antifriction applications. However, the challenge persists in ensuring robust adhesion between graphene coatings and hard substrates (WC-Co), while minimizing excessive interfacial bonding to reduce growth energy consumption and friction. To tackle this problem, NiCo solid solution and competitive reaction strategies have been employed to achieve the in situ self-adaptive growth of graphene coating on WC-Co substrates with intimate interfaces. The high-temperature solid solution breaks through the physical diffusion barriers of the Co binding phase within the substrate to the Ni layer, facilitating the strong coupling effect at the NiCo-WC substrates. Experiments and density functional theory demonstrated that the accumulated Co atoms induce competitive reactions to inhibit the overlap of the electron cloud in Ni-C bonds, providing C atoms with sufficient energy to in situ segregate and diffuse laterally. Benefiting from the weakened interfacial covalent interaction and lower sliding energy barrier, graphene coating in situ deposited on substrates with deeper NiCo solid solution demonstrates superior macroscale low-friction and durability. Drawing on this design strategy, it is highly expected that hard substrate can be extended to diverse industrial surfaces composed of competitive metals for engineered graphene anti-friction applications.

SURFACES OF CRYSTALLIZATION AND PHASE RELATIONS IN THE 6Ag2Se+Ag8SiTe66Ag2Te+Ag8SiSe6 RECIPROCAL SYSTEM

The paper presents the results of a study of phase equilibria in the 6Ag2Se+Ag8SiTe6 6Ag2Te+Ag8SiSe6 reciprocal system by DTA and XRD methods. The projection of the liquidus surface, isothermal sections at 300, 500, 1150 K, and some polythermal sections of the phase diagram are constructed. It is shown that the system is reversible-reciprocal. It is characterized by the formation of continuous high-temperature solid solutions along the Ag8SiSe6-Ag8SiTe6 () and Ag2Se-Ag2Te () boundary systems. It has been established that the liquidus surface of the reciprocal system consists of two fields of primary crystallization - and -phases. These surfaces are delimited by a eutectic curve with monovariant equilibrium L+. In the subsolidus part of the system, a complex interaction is observed associated with the polymorphism of the initial compounds and phases based on them

Study on surface nitriding treatment of the sintered SUS430 ferritic stainless steel

Ferritic stainless steels with the advantages of high thermal conductivity, low expansion coefficient, excellent oxidation resistance, resistance to stress corrosion capacity, and low cost are widely applied. The parts are prepared by powder metallurgy with SUS430 ferritic stainless steel. Under an H2 protective atmosphere, the compactions are sintered at 1300 °C, and the density of the as-sintered sample achieves 7.4 g/cm3. Then, high-temperature solid solution nitriding treatment is carried out at 1110 °C under an N2/H2 mixed atmosphere. The nitride layers are formed on the surface of the samples. The thickness of nitride layers is about 130–150 μm, and its microhardness is 490 HV. Moreover, it suggests that gas nitriding treatment can effectively improve surface hardness and wear resistance. Still, the core matrix with ferritic microstructure maintains good plasticities and ductilities, and its hardness is about 126 HV.

PHASE EQUILIBRA IN THE Ag2Se–Ag8GeSe6–Ag8SiSe6 SYSTEM AND CHARACTERIZATION Of the Ag8Si1-xGexSe6 SOLID SOLUTIONS

Phase equilibria in the Ag2Se–Ag8SiSe6–Ag8GeSe6 system were studied by differential thermal analysis and X-ray diffraction thechnique. Based on the experimental results and literature data, the projection of the liquidus surface of the Ag2Se–Ag8SiSe6–Ag8GeSe6 system, the isothermal section at 300 K and some polythermal sections of the phase diagram were constructed. It was determined that continuous series of solid solution are formed based on high-temperature cubic modification and limited solid solution areas are formed based on low-temperature modification of initial compounds on the Ag8SiSe6–Ag8GeSe6 side of concentration triangle. The formation of solid solutions leads to a sharp decreasing of polymorphic transition temperatures of ternary compounds and stabilization of high-temperature phases at room temperature. The liquidus surface of the Ag2Se–Ag8SiSe6–Ag8GeSe6 system consists of 2 areas reflecting the initial crystallization of α'-phase based on HT-Ag2Se and HT-Ag8Si1-xGexSe6 solid solutions. The obtained new phases are of interest as environmentally safe materials with thermoelectric properties and mixed ion-electron conductivity.

Formation of Noble Metal Phases (Pt, Pd, Rh, Ru, Ir, Au, Ag) in the Process of Fractional Crystallization of the CuFeS2 Melt

The quasi-equilibrium directional crystallization of the melt composition (at. %): Cu 24.998, Fe 25.001, S 49.983, with Ag 0.002, Pd 0.003, Ru 0.004, Rh 0.006, and Au, Pt, Ir (each as 0.001) was carried out. The crystallized cylindrical ingot consisted of two primary zones and three secondary zones with different chemical and phase compositions. The compositions of the primary zones corresponded to high-temperature intermediate solid solution (zone I) and liquid enriched in sulfur (zone II). The compositions of the secondary zones corresponded to low-temperature intermediate solid solution and chalcopyrite (zone Ia), the same intermediate solid solution with chalcopyrite and bornite (zone Ib), and again with bornite, chalcocite, and idaite (zone II). We plotted the distribution curves of Fe, Cu, and S along the ingot, calculated the distribution coefficients of the components during directional crystallization, and clearly showed that, from the initial stoichiometric composition CuFeS2, the intermediate solid solution enriched in Fe and depleted in S is crystallized. Based on the data of directional crystallization and thermal analysis, a cross section was constructed in the intermediate solid solution-sulfide melt region of the Cu-Fe-S system. With solubility in the solid Cu-Fe sulfides lying below detection limit of scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM/EDS), noble elements occurred as individual phases of a size more often <10 µm. They were identified as Ag, RuS2, PdS, Au* (an Au based alloy), (Rh, Ir, Ru)3S8, (Rh, Ir)3S8, Rh3S8, and (Cu, Fe)~2(Pt, Rh)1S~5 phases by electron microprobe. Based on ab initio calculations of crystal structure, electronic band structure, and lattice dynamics of idealized laurite RuS2 phase and the idealized Ir3S8, Rh3S8, and Ru3S8 phases, the interpretation of Raman spectrum of the cation-mixed (Ru, Rh, Ir)S2 sulfide was presented for the first time.

The thermal activation of MnOx-Al2O3 catalysts: Effect of gallium doping

In this study, the effect produced by the gallium oxides intercalation into MnOx-Al2O3 catalysts on their catalytic properties and structural aspects of the active component formation was investigated. Three series of the catalysts, Mn–Al, Mn–Ga, and Mn–Al-Ga, having a similar Mn content but different Al/Ga ratio, were synthesized by coprecipitation and subsequent calcination at temperatures from 600 to 1200°С°. The catalysts were tested in CO oxidation. For the Mn–Al series of catalysts, a thermal activation effect is observed, defined as an increase in catalytic activity after high-temperature treatment at 900-1000°С. The increase in the activity after calcination is related to the formation of the Mn3-xAlxO4 solid solution at the synthesis temperature and its segregation upon cooling. Segregation of the solid solution leads to the formation of the Mn3O4+δ defect oxide and an amorphous aluminum-containing component. The addition of 5%Ga to the Mn–Al catalyst changes the phase transformation route during thermal activation. The in situ XRD data has showed that at 1000°С the high-temperature solid solution (MnGaAl)3O4 with the cubic spinel structure is formed; however, its further segregation upon cooling is hindered. The introduction of gallium stabilizes the structure of the (MnGaAl)3O4 mixed oxide, the parent oxide is partially decomposed after cooling with Mn3O4 nanoparticles formation. However the amount of produced active Mn3O4 particles and/or weakly bound oxygen is much lower, which in turn adversely affects the catalytic properties.

β-Si4Al2O2N6 supported Ni catalyst for enhanced ethanol steam reforming: Tuning metal-support interaction by high-temperature solution of Si3N4 with Al2O3

Developing a high-performance Ni-based catalyst for ethanol steam reforming (ESR) reaction is desirable for sustainable hydrogen production. In this work, β-Si4Al2O2N6, the high-temperature solid solution of Si3N4 and Al2O3, was utilized as support to fabricate Ni catalyst (Ni/Si4Al2O2N6) for ESR reaction to enhance hydrogen-production efficiency. The catalytic experiments demonstrated that Ni/Si4Al2O2N6 catalyst exhibited higher C–C bond cleavage capacity, hydrogen-production efficiency, catalytic durability and better anti-coke performance as compared with Ni/Si3N4 and Ni/Al2O3 catalysts. H2-TPR, XPS and NH3-TPD studies revealed that the stronger metal-support interaction (MSI) in Ni/Si4Al2O2N6 catalysts induced more distinct charge transfer from Ni species to Si4Al2O2N6 support, fabricating Ni active sites with higher oxidation state and achieving higher catalytic activity and durability for ESR reaction.

Unit cell volumes of the silicon- and germanium-containing solid solutions based on the 3d bcc transition metals

Abstract The unit cell parameters and the unit cell volumes were investigated for Si- and Ge-containing solid solutions based on the 3d body-centred cubic transition metals. Excepting the high-temperature solid solution δ-Mn(Si), the solubility of Si increases with increasing number of 3d electrons. In contradiction to the large atomic volume of Si, which is substantially larger than that of the 3d transition metals, the unit cell volume of the terminal solid solutions decreases with increasing Si content. For solid solutions showing a large homogeneity range – α-Fe(Si) and α-Fe(Ge) –, the partial atomic volumes of Si and Ge were evaluated. Comparing the quasihomological Al- and Si-containing solid solutions α-Fe(Al) and α-Fe(Si), the higher bond energy occurs between atoms of Si and Fe than between Al and Fe atoms. Taking into consideration the homology of metalloids in the solid solutions α-Fe(Si) and α-Fe(Ge), the higher bond energy can also be expected between Si and Fe than between Ge and Fe atoms.

Pyroxenite-hosted chalcopyrites from Sung Valley, Meghalaya, NE India: implications for the formation of both high- and low-temperature sulfides in plume-derived magma

Abstract Sulfides play a crucial role in the distribution of chalcophile elements in the Earth's mantle. In this work, combined petrography and mineral chemistry of sulfide and diopside in a pyroxenite from an ultramafic–alkaline–carbonatite complex of NE India, related to the Kerguelen plume, was carried out and a considerably high sulfur concentration in the parental melt of the pyroxenite was obtained. Two types of sulfide, with similar compositions, were detected in pyroxenite: Type A are multifaceted polygons, elliptical and spherical in shape, occurring as poikilitic inclusions in diopside; and Type B are intergranular sulfides of irregular shapes in silicate grains. These sulfides are often partially replaced by magnetite. Mineral chemistry suggests that both types of sulfide are products of re-equilibration of high-temperature monosulfide solid solution and represent a low-temperature ( c. 400°C) mineral phase of the Cu–Fe–S system. Petrographical features suggest that the sulfides were separated as immiscible melt droplets at the time of sulfur saturation and fractionation of diopside in the coexisting silicate magma. Our study implicates that both high- and low-temperature sulfides can form in the plume-associated ultramafic rocks.

Theoretical prediction of solution in Sc<sub><i>x</i></sub>Y<sub>1–<i>x</i></sub> Fe<sub>2</sub> and order-disorder transitions in V<sub>2<i>x</i></sub> Fe<sub>2(1–<i>x</i>)</sub>Zr

Alloying is an important way to increase the diversity of material structure and properties. In this paper, we start from Ising model considering nearest neighbor interaction, in which a ferromagnetic system corresponds to a low temperature phase separation and high temperature solid solution of binary alloy, while antiferromagnetic system corresponds to a low temperature ordered solid solution and a high temperature disorder. The high-throughput first-principles calculation based on the structure recognition is realized by the program SAGAR (structures of alloy generation and recognition) developed by our research group. By considering the contribution of structural degeneracy to the partition function, theoretical prediction of alloy materials can be carried out at finite temperature. Taking hydrogen storage alloy (Sc<sub><i>x</i></sub>Y<sub>1–<i>x</i></sub> Fe<sub>2</sub> and V<sub>2<i>x</i></sub> Fe<sub>2(1–<i>x</i>)</sub>Zr) for example, the formation energy of ground state (at zero temperature) can be obtained by the first-principles calculations. It is found that the formation energy of Sc<sub><i>x</i></sub>Y<sub>1–<i>x</i></sub> Fe<sub>2</sub> is greater than zero, thereby inducing the phase separation at low temperature. The free energy will decrease with the temperature and concentration increasing, where the critical temperature of solid solution of alloy is determined according to the zero point of free energy. The formation energies of V<sub>2<i>x</i></sub> Fe<sub>2(1–<i>x</i>)</sub>Zr are all lower than zero, and the ordered phase occurs at low temperature. The order-disorder transition temperature of V<sub>0.5</sub>Fe<sub>1.5</sub>Zr and V<sub>1.5</sub>Fe<sub>0.5</sub>Zr are both about 100 K, while the transition temperature of VFeZr is nearly 50 K. The calculation process will effectively improve the high throughput screening efficiency of alloy, and also provide relevant theoretical reference for experimental research.

Phase Equilibria in the Ag2Te-PbTe-Sb2Te3 System and Thermodynamic Properties of the (2PbTe)1-x(AgSbTe2)x Solid Solutions

Phase equilibria in the Ag2Te-PbTe-Sb2Te3 system were experimentally investigated by means of differential thermal analysis, powder X-ray diffraction techniques and electromotive force (EMF) measurement method. A liquidus surface projection of the system, 750 K and 300 K isothermal sections, as well as five vertical sections of the phase diagram, were constructed. The primary crystallization fields of phases and homogeneity range of phases were also determined. The character and temperature of the various nonvariant and monovariant equilibria were identified. The studied sys-tem is characterized by the formation of a wide continuous band of a high-temperature cubic structured solid solution (?-phase) between PbTe and Ag1-xSb1 + xTe2 + x intermediate phase. The partial molar thermodynamic functions of lead telluride in alloys and standard integral thermodynamic functions of the ?-solid solutions along the 2PbTe-AgSbTe2 section were calculated based on the EMF measurements results.

Menshikovite Pd<sub>3</sub>Ni<sub>2</sub>As<sub>3</sub> and associated minerals of sulphide ores within the Eastern flank of the Oktyabrsky deposit (Norilsk ore field)

Significant amount of menshikovite (rare palladium and nickel arsenide) Pd3Ni2As3was found on the Eastern flank of the Oktyabrsky deposit (Norilsk ore field), near the contact of solid and impregnation sulfide Co-Ni-Cu ores among magnetite-plagioclase-fassaite skarns. Sulfide material of both ores consists of chalcopyrite, pentlandite, pyrrhotite and cubanite aggregates, which are the products of subsolidus transformations of high-temperature solid solutions Iss3, Iss4 and subordinate Mss; with interpositions of later Se-galenite. Menshikovite in association with mertieite-II, silver-gold (fineness 756–706), golden-electrum (fineness 694–672), kotulskite, moncheite, rare altaite, hessite, naldrettite and melonite forms small (up to 30 microns) metasomatic growths on the contact of silicate matrix and magmatogenic sulfide aggregates. The average composition of menshikovite is close to theoretical data: (Pd2,98Ru0,03)3,01(Ni1,89Fe0,-08Co0,01)1,98(As2,94Se0,04Bi0,02Sn0,01)3,01. Sperrylite metacrystals cut the borders of menshikovite accretions as well as other minerals of precious metals and contain “corroded” inclusions. This association of minerals of noble metals has arisen under the increased activity of As, Te, Sb, Bi and low activity of Sn in fluids. Menshikovite is typical for Pd-rich ores of the Oktyabrsky Deposit, while mayakite PdNiAs (another palladium and nickel arsenide) is relatively widely developed in ores of the Talnakh Deposit (Mayak mine and partly Komsomolsky mine) and the Norilsk-I. Perhaps, such a distribution of palladium-nickel arsenides is an element of mineral zonality of the Norilsk ore field.

The Occurrence and Origin of Pentlandite-Chalcopyrite-Pyrrhotite Loop Textures in Magmatic Ni-Cu Sulfide Ores

Abstract Pentlandite is the dominant Ni-hosting ore mineral in most magmatic sulfide deposits and has conventionally been interpreted as being entirely generated by solid-state exsolution from the high-temperature monosulfide solid solution (MSS) (Fe,Ni)1–xS. This process gives rise to the development of loops of pentlandite surrounding pyrrhotite grains. Recently it has been recognized that not all pentlandite forms by exsolution. Some may form as the result of peritectic reaction between early formed MSS and residual Ni-Cu–rich sulfide liquid during differentiation of the sulfide melt, such that at least some loop textures may be genuinely magmatic in origin. Testing this hypothesis involved microbeam X-ray fluorescence mapping to image pentlandite-pyrrhotite-chalcopyrite intergrowths from a range of different deposits. These deposits exemplify slowly cooled magmatic environments (Nova, Western Australia; Sudbury, Canada), globular ores from shallow-level intrusions (Norilsk, Siberia), extrusive komatiite-hosted ores from low and high metamorphic-grade terranes, and a number of other deposits. Our approach was complemented by laser ablation-inductively coupled plasma-mass spectrometry analysis of palladium in varying textural types of pentlandite within these deposits. Pentlandite forming coarse granular aggregates, together with loop-textured pentlandite where chalcopyrite also forms part of the loop framework, consistently has the highest Pd content compared with pentlandite clearly exsolved as lamellae from MSS or pyrrhotite. This is consistent with much of granular and loop pentlandite being formed by peritectic reaction between Pd-rich residual sulfide liquid and early crystallized MSS, rather than forming entirely by subsolidus grain boundary exsolution from MSS, as has hitherto been assumed. The wide range of Pd contents in pentlandite in individual samples reflects a continuum of processes between peritectic reaction and grain boundary exsolution. Textures in metamorphically recrystallized ores are distinctly different from loop-textured ores, implying that loop textures cannot be regenerated (except in special circumstances) by metamorphic recrystallization of original magmatic-textured ores. The presence of loop textures can therefore be taken as evidence of a lack of penetrative deformation and remobilization at submagmatic temperatures, a conclusion of particular significance to the interpretation of the Nova deposit as having formed synchronously with the peak of regional deformation at temperatures within the sulfide melting range.

Phase diagram studies on ternary Bi–Mo–O system

The ternary Bi–Mo–O system was investigated by long term equilibration studies followed by XRD analysis of the equilibrium phases. Existence of ten ternary compounds and a high temperature solid solution in the system were confirmed. Combining the partial phase diagrams of the system reported earlier, isothermal sections of Bi–Mo–O system at 773, 873 and 1023 ​K have been constructed and reported.

A Mineralogical Investigation of Sintering in Cu-Rich Polymetallic Concentrates During Roasting in Inert Atmosphere

Four different Cu-rich polymetallic concentrates (additionally comprising Zn, Pb and impurity elements As, Sb) from various deposits in Sweden are examined, in particular for the sintering tendency during roasting in inert atmosphere. Experiments performed in a laboratory-scale roasting setup between 200 °C and 700 °C in intervals of 100 °C revealed that significant sintering initiates from 500 °C for all four concentrates. Two sintering mechanisms are determined from the examination of the sintered calcines: (1) solid-state assimilation of Cu-, Zn- and Fe-bearing main sulphide minerals to form a high-temperature solid solution, the iss phase belonging to the Cu-Fe-Zn-S system; (2) low-melting liquid phase formation due to partial melting of galena facilitated by the presence of impurity-bearing minerals, mainly the arsenopyrite and Sb sulphosalts such as tetrahedrite. Galena also forms a melt below 700 °C with the iss phase. Therefore, the presence of galena in polymetallic concentrates generally increases the susceptibility to early sintering. These experiments in inert atmosphere facilitate a fundamental study with practical relevance to the roasting in low oxidation potential environments, favourable for volatilization of impurity elements such as As and Sb.

Dielectric and transport properties of ‘Sr’ modified lead free double perovskite

The polycrystalline sample Ba0.5Sr1.5FeVO6 is prepared by high temperature solid solution route. The real (ε') and imaginary (ε'') part of complex dielectric constant of the sample was recorded over wide range of frequency (100 Hz–5 MHz) and temperature (30–500 °C). The frequency dependent ac conductivity (σac = ωε0ε'') obtained by using dielectric data was consistent with Jonscher’s power law. Temperature dependent conductivity give a typical texture of ionic conduction. I-V characteristics suggest semiconducting nature in the material.