Stoichiometric icosahedral phase in the Zn–Mg–Y system

1997 ◽  
Vol 12 (6) ◽  
pp. 1468-1471 ◽  
Author(s):  
A. P. Tsai ◽  
A. Niikura ◽  
A. Inoue ◽  
T. Masumoto
Keyword(s):  
Formation Process ◽  
Peritectic Reaction ◽  
Stoichiometric Composition ◽  
Icosahedral Phase ◽  
Peritectic Temperature ◽  
Constant Composition ◽  
Compositional Range ◽  
Wide Compositional Range

Stoichiometric composition and formation process of the icosahedral phase in the Zn–Mg–Y system have been studied. The icosahedral phase exhibit a stoichiometric composition in the vicinity of Zn60Mg30Y10. During cooling, (Zn, Mg)5Y phase primarily crystallizes from the melt at ∼960 K and then undergoes a peritectic reaction with the residual Mg-enriched melt (∼820 K) to form the icosahedral phase. The melt with a constant composition close to Mg7Zn3 is in equilibrium with the (Zn, Mg)5Y phase above the peritectic temperature in a wide compositional range.

Thermoelectric Properties of Ru2Si3-Based Chimney-Ladder Phases

2007 ◽  
Vol 561-565 ◽  
pp. 463-466 ◽  
Author(s):  
Kyosuke Kishida ◽  
Akira Ishida ◽  
Katsushi Tanaka ◽  
Haruyuki Inui
Keyword(s):  
Crystal Structures ◽  
Thermoelectric Properties ◽  
Electron Concentration ◽  
Valence Electron ◽  
Valence Electron Concentration ◽  
Compositional Range ◽  
Wide Compositional Range ◽  
P Type ◽  
Semiconducting Behavior

The variations of the crystal structures and thermoelectric properties of the Ru1-xRexSiy chimney-ladder phases were studied as a function of the Re concentration. A series of chimney-ladder phases with a compositional formula of Ru1-xRexSi1.539+0.178x are formed in a wide compositional range, 0.14 ≤ x ≤ 0.76. The composition of the chimney-ladder phase is systematically deviated from the idealized composition satisfying the valence electron concentration rule: VEC=14. Measurements of thermoelectric properties reveal that the chimney-ladder phases exhibit n-type semiconducting behavior at low Re concentrations and p-type semiconducting behavior at high Re concentrations, which are well consistent with the prediction based on the deviation of the composition of the chimney-ladder phase from the idealized composition.

Origin of the Y2Ba1Cu1O5 free region in melt-textured Y–Ba–Cu–O oxides

1995 ◽  
Vol 10 (9) ◽  
pp. 2235-2240 ◽  
Author(s):  
Chan-Joong Kim ◽  
Hee-Gyoun Lee ◽  
Ki-Baik Kim ◽  
Gye-Won Hong
Keyword(s):  
Liquid Phase ◽  
Formation Mechanism ◽  
Peritectic Reaction ◽  
Peritectic Temperature ◽  
Incongruent Melting ◽  
Slow Cooling ◽  
Free Region

In order to understand the formation mechanism of the Y2BaCuO5 free region, microstructures concerning incongraent mehing and peritectic reaction were studied in melt-textured Y–Ba–Cu–O oxides. It is found that spherical pores form during incongruent melting of the YBa2Cu3O7−y phase into Y2BaCuO3 and a Ba–Cu–O liquid phase. As the melting goes on, liquid phase flows into the pores and then produces spherical liquid pockets containing a few Y2BaCuO5 particles. During slow cooling of the sample from the peritectic temperature to the temperature where YBa2Cu3O7−y phase is formed, the liquid pockets are converted into YBa2Cu3O7−y phase containing a few Y2BaCuO5 particles. Sometimes, remnant Ba–Cu–O liquid phase is present at the center part of the Y2BaCuO5 free regions due to the incomplete peritectic reaction. It is concluded that formation of spherical pores during incongruent melting of YBa2Cu3O7−y is responsible for the formation of the Y2BaCuO5 free regions.

scholarly journals THE ICOSAHEDRAL PHASE OF Al63Cu25Fe12 SYSTEM

2019 ◽  
Vol 28 (1) ◽  
pp. 51-56
Author(s):  
Anastazia Melnik ◽  
Luciano Nascimento
Keyword(s):  
Chemical Elements ◽  
Stoichiometric Composition ◽  
Icosahedral Phase ◽  
Quasicrystalline Phase ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ideal Composition ◽  
Diffraction Patterns

The present work aimed to characterize the microstructure of the icosahedral phase (quasicrystalline phase-ϕ) of the system with stoichiometric composition of the quasicrystal Al63Cu25Fe12. The ternary alloy with nominal composition of Al63Cu25Fe12 was processed by mechanical alloying (MA) as a viable solid state processing method for producing various metastable and stable quasicrystalline phases. The structural characterization of the obtained samples was performed by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), while the elemental composition of the chemical elements Al, Fe and Cu were determined by X-ray spectroscopy technique of dispersive energy (EDS). According to the results of XRD, the diffraction patterns of Al63Cu25Fe12 showed the presence of β-Al(Fe, Cu) and λ-Al13Fe4 phases coexist with the thermodynamic ϕ-phase quasicrystalline. Finally, elemental analysis indicates that during alloy synthesis there is little variation of the ideal composition. The results indicate that alloys with high percentage of icosahedral phase can be obtained by casting in the air.

Crystal Structure and Thermoelectric Properties of Mn-Substituted Ru2Si3 with the Chimney-Ladder Structure

2008 ◽  
Vol 1128 ◽  
Author(s):  
Tatsuya Koyama ◽  
Norihiko L. Okamoto ◽  
Kyosuke Kishida ◽  
Katsushi Tanaka ◽  
Haruyuki Inui
Keyword(s):  
Thermoelectric Properties ◽  
Solid Solubility ◽  
Solubility Limit ◽  
Ladder Structure ◽  
Thermoelectric Power Factor ◽  
Compositional Range ◽  
General Chemical ◽  
Ternary Element ◽  
Wide Compositional Range ◽  
Mn Content

AbstractChimney-ladder compounds with the general chemical formula of Mn X2n-m (n, m: integers) possess tetragonal crystal structures which consist of two types of subcells; one composed of transition metal atoms (M) with the γÀ-Sn structure and the other composed of group 13 or 14 atoms (X) with a helical arrangement along the tetragonal c-axis. Since the chimney-ladder compounds generally exhibit very low thermal conductivity, presumably due to its long periodicity along the c-axis, they have been extensively investigated as promising thermoelectric materials. The high-temperature (HT) phase of Ru2Si3 is one of the chimney-ladder compounds with n=2 and m=1. Recently we have found that the HT-Ru2Si3 phase is stabilized by substituting Ru with Re so as to exist even at low temperatures in a wide compositional range of the Re content (Re: 14 to 73%), and that the thermoelectric power factor for alloys with high Re contents increases with the Re content and the highest value was obtained for the alloy with the highest Re content (73%), which is the solubility limit of Re in the chimney-ladder phase. In order to further enhance the thermoelectric properties, another ternary element which extends the solid solubility region of the HT-Ru2Si3 phase is favorable. We have chosen Mn as the ternary element because Mn4Si7 with the chimney-ladder structure exists as a counterpart of HT-Ru2Si3 in the Ru2Si3 -Mn4Si7 pseudo-binary system so that the solid solubility region of the chimney-ladder phase is anticipated to extend in a wider composition range than the Re case. Our study, in fact, shows that the Mn-substitution stabilizes the HT-Ru2Si3 phase in a wide compositional range of the Mn content; 12 to 100%. Compositional analyses indicate that the Si/M ratio gradually increases as the Mn content increases. This is considered to be due to the addition of Si atoms in the Si subcell in order to compensate the decrease in the valence electron concentrations (VEC) per M atom by the substitution of Ru (group 8) with Mn (group 7) with fewer valence electrons. The Seebeck coefficient and electrical resistivity of the Mn-substituted Ru2Si3 are explained in terms of the VEC deviation from the idealized value, 14, which is expected for intrinsic semiconductors with the chimney-ladder structure. The highest dimensionless thermoelectric figure of merit (ZT=0.76) is obtained for 90%Mn-substituted alloy. The relationships between the microstructure and thermoelectric properties will be discussed.

scholarly journals ICOSAHEDRAL PHASE OF Al65Cu25Fe15

2020 ◽  
Vol 4 (01) ◽  
pp. 1-14
Author(s):  
Luciano Nascimento
Keyword(s):  
Stoichiometric Composition ◽  
Icosahedral Phase ◽  
Quasicrystalline Phase ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
Ideal Composition ◽  
Diffraction Patterns ◽  
State Processing ◽  
The Ideal

The present work aimed to characterize the microstructure of the icosahedral phase (quasicrystalline phase-ϕ) of the system with stoichiometric composition of the quasicrystal Al65Cu25Fe15 . The ternary alloy with nominal composition of Al63Cu25Fe12 was processed by mechanical alloying (MA) as a viable solid state processing method for producing various metastable and stable quasicrystalline phases. The structural characterization of the obtained samples was performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), while the elemental composition was determined by dispersive energy spectroscopy (DES). The diffraction patterns of Al65Cu25Fe15 showed the presence of ω-Al7Cu2Fe , β-Al(Fe, Cu) and λ-Al13Fe4 phases that coexist with the thermodynamic quasicrystalline phase-ϕ. Finally, elemental analysis indicates that during alloy synthesis there is little variation of the ideal composition. The results indicate that alloys with high percentage of icosahedral phase can be obtained by casting in the air.

scholarly journals Brønsted acids in ionic liquids: how acidity depends on the liquid structure

2014 ◽  
Vol 16 (42) ◽  
pp. 23233-23243 ◽  
Author(s):  
Jade A. McCune ◽  
Peizhao He ◽  
Marina Petkovic ◽  
Fergal Coleman ◽  
Julien Estager ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Liquid Structure ◽  
Liquid Mixtures ◽  
Bronsted Acids ◽  
Bronsted Acid ◽  
Acceptor Number ◽  
Compositional Range ◽  
Brönsted Acid ◽  
Wide Compositional Range

Gutmann Acceptor Number (AN) values have been determined for Brønsted acid–ionic liquid mixtures, over a wide compositional range.

scholarly journals The Petrology and  Genesis of Silicic  Magmas in the  Kermadec Arc

2021 ◽  
Author(s):  
◽  
Simon James Barker
Keyword(s):  
Subduction Zone ◽  
Structural Changes ◽  
Mineral Chemistry ◽  
Silicic Magma ◽  
Small Scale ◽  
Mafic Enclaves ◽  
Compositional Range ◽  
Dominant Process ◽  
Wide Compositional Range ◽  
Silicic Magmas

<p>Recent work has shown that silicic volcanism can be abundant in intra-oceanic subduction settings, and is often associated with large explosive caldera-forming eruptions. Several major petrogenetic questions arise over the origin and eruption of large amounts of silicic magma at these relatively simple subduction settings. This study has investigated the geochemistry of pyroclasts collected from four volcanoes along the Kermadec arc, a young (<2 Myr) oceanic subduction zone in the southwest Pacific. Raoul, Macauley and a newly discovered volcano (here informally named 'New volcano') in the northern Kermadec arc, and Healy volcano in the southern Kermadec arc have all erupted dacitic to rhyolitic pumice within the last 10 kyr. For Raoul, New volcano and Healy, whole rock major element compositions fall with a limited compositional range. In contrast, pumice dredged from around Macauley caldera covers a wide compositional range indicating that there have been multiple silicic eruptions, not just the Sandy Bay Tephra exposed on Macauley Island. Distinctive crystal populations in both pumice samples and plutonic xenoliths suggest that many of the crystals did not grow in the evolved magmas, but were mixed in from other sources including gabbros and tonalites. Such open system mixing is ubiquitous in magmas from the four Kermadec volcanoes studied here. Silicic magmas, co-eruptive mafic enclaves and previously erupted basalts show sub-parallel REE patterns, and crystal composition and zonation suggests that mafic and silicic magmas have a strong genetic affiliation. Examination of whole rock, glass and mineral chemistry reveals that evolved magmas can be generated at each volcano through 60-75% crystal fractionation of a basaltic parent. These findings are not consistent with silicic magma generation via crustal anatexis, as previously suggested for the Kermadec arc. Although crystallisation is the dominant process driving melt evolution in the Kermadec volcanoes, the magmatic systems are open to contributions from both newly arriving melts and wholly crystalline plutonic bodies. Such processes occur in variable proportions between magma batches, and are largely reflected by small scale chemical variations between eruption units. Larger scale chemical trends reflect the position of the volcanoes along the arc, which in turn may reflect structural changes in the subduction zone and variations in sediment influx.</p>

scholarly journals The Petrology and  Genesis of Silicic  Magmas in the  Kermadec Arc

2021 ◽  
Author(s):  
◽  
Simon James Barker
Keyword(s):  
Subduction Zone ◽  
Structural Changes ◽  
Mineral Chemistry ◽  
Silicic Magma ◽  
Small Scale ◽  
Mafic Enclaves ◽  
Compositional Range ◽  
Dominant Process ◽  
Wide Compositional Range ◽  
Silicic Magmas

<p>Recent work has shown that silicic volcanism can be abundant in intra-oceanic subduction settings, and is often associated with large explosive caldera-forming eruptions. Several major petrogenetic questions arise over the origin and eruption of large amounts of silicic magma at these relatively simple subduction settings. This study has investigated the geochemistry of pyroclasts collected from four volcanoes along the Kermadec arc, a young (<2 Myr) oceanic subduction zone in the southwest Pacific. Raoul, Macauley and a newly discovered volcano (here informally named 'New volcano') in the northern Kermadec arc, and Healy volcano in the southern Kermadec arc have all erupted dacitic to rhyolitic pumice within the last 10 kyr. For Raoul, New volcano and Healy, whole rock major element compositions fall with a limited compositional range. In contrast, pumice dredged from around Macauley caldera covers a wide compositional range indicating that there have been multiple silicic eruptions, not just the Sandy Bay Tephra exposed on Macauley Island. Distinctive crystal populations in both pumice samples and plutonic xenoliths suggest that many of the crystals did not grow in the evolved magmas, but were mixed in from other sources including gabbros and tonalites. Such open system mixing is ubiquitous in magmas from the four Kermadec volcanoes studied here. Silicic magmas, co-eruptive mafic enclaves and previously erupted basalts show sub-parallel REE patterns, and crystal composition and zonation suggests that mafic and silicic magmas have a strong genetic affiliation. Examination of whole rock, glass and mineral chemistry reveals that evolved magmas can be generated at each volcano through 60-75% crystal fractionation of a basaltic parent. These findings are not consistent with silicic magma generation via crustal anatexis, as previously suggested for the Kermadec arc. Although crystallisation is the dominant process driving melt evolution in the Kermadec volcanoes, the magmatic systems are open to contributions from both newly arriving melts and wholly crystalline plutonic bodies. Such processes occur in variable proportions between magma batches, and are largely reflected by small scale chemical variations between eruption units. Larger scale chemical trends reflect the position of the volcanoes along the arc, which in turn may reflect structural changes in the subduction zone and variations in sediment influx.</p>

scholarly journals Mineralogical Study of the Advanced Argillic Alteration Zone at the Konos Hill Mo–Cu–Re–Au Porphyry Prospect, NE Greece

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 479 ◽  
Author(s):  
Constantinos Mavrogonatos ◽  
Panagiotis Voudouris ◽  
Paul G. Spry ◽  
Vasilios Melfos ◽  
Stephan Klemme ◽  
...  
Keyword(s):  
Deep Level ◽  
Stoichiometric Composition ◽  
Aluminum Phosphate ◽  
Alteration Zone ◽  
High Sulfidation ◽  
Argillic Alteration ◽  
Ore Minerals ◽  
Mineralogical Study ◽  
Wide Compositional Range ◽  
Advanced Argillic Alteration

The Konos Hill prospect in NE Greece represents a telescoped Mo–Cu–Re–Au porphyry occurrence overprinted by deep-level high-sulfidation mineralization. Porphyry-style mineralization is exposed in the deeper parts of the system and comprises quartz stockwork veins hosted in subvolcanic intrusions of granodioritic composition. Ore minerals include pyrite, molybdenite, chalcopyrite, and rheniite. In the upper part of the system, intense hydrothermal alteration resulted in the formation of a silicified zone and the development of various advanced argillic alteration assemblages, which are spatially related to N–S, NNW–SSE, and E–W trending faults. More distal and downwards, advanced argillic alteration gradually evolves into phyllic assemblages dominated by quartz and sericite. Zunyite, along with various amounts of quartz, alunite, aluminum phosphate–sulfate minerals (APS), diaspore, kaolinite, and minor pyrophyllite, are the main minerals in the advanced argillic alteration. Mineral-chemical analyses reveal significant variance in the SiO2, F, and Cl content of zunyite. Alunite supergroup minerals display a wide compositional range corresponding to members of the alunite, beudantite, and plumbogummite subgroups. Diaspore displays an almost stoichiometric composition. Mineralization in the lithocap consists of pyrite, enargite, tetrahedrite/tennantite, and colusite. Bulk ore analyses of mineralized samples show a relative enrichment in elements such as Se, Mo, and Bi, which supports a genetic link between the studied lithocap and the underlying Konos Hill porphyry-style mineralization. The occurrence of advanced argillic alteration assemblages along the N–S, NNW–SSE, and E–W trending faults suggests that highly acidic hydrothermal fluids were ascending into the lithocap environment. Zunyite, along with diaspore, pyrophyllite, and Sr- and Rare Earth Elements-bearing APS minerals, mark the proximity of the hypogene advanced argillic alteration zone to the porphyry environment.

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