MIZUTANI INTERNATIONAL SYMPOSIUM (6TH INTL. SYMP. ON SCIENCE OF INTELLIGENT & SUSTAINABLE ADVANCED MATERIALS (SISAM))
Editors: F. Kongoli, J. Dubois, E. Gaudry, T. Homma, V. Fournee

This SISAM 2022 symposium is about the lifetime achievements of Prof. Uichiro Mizutani. Among many other breakthroughs, Mizutani and his collaborators were able to define in an unambiguous way the so-called e/a ratio [1], which is a measure of the number of electrons an atom shares with the Fermi sea in an intermetallic to achieve structural stability of a given crystal architecture. Although computation of this number requires periodicity of the lattice, the concept can be extended to aperiodic metallic systems such as quasicrystals [2]. It turns out that the e/a ratio found for truly aperiodic quasicrystals as well as weakly periodic crystals of giant unit cell (the so-called approximants) corresponds to a very specific value: e/a=2.2 ± 0.1 e-/at [3]. This way, the basic assumption of An Pang Tsai [4], who discovered most of the thermodynamically stable quasicrystals using e/a, was confirmed, yet with e/a defined with no questionable assumption and a clearly assessed mechanism for the contribution of the individual atoms to the valence band.
The formation of a pseudo-gap at the Fermi energy was discovered and documented using soft X-ray spectroscopy by my late colleague, Esther Belin-Ferré [5,6]. It was well illustrated in a family of Al-based intermetallics spanning a broad range of e/a values. The deepening of the pseudo-gap around the e/a=2.2 e-/at value is clearly observable for stable compounds. The talk will report how this data helped us to understand two properties of practical interest of quasicrystals and related compounds. The first is the reduced wetting observed against polar liquids (like water) deposited on the polished surface of a quasicrystal equipped with its layer of native oxide in air [7]. The second is friction or solid-solid adhesion measured in vacuum against metallic antagonists like hard-Cr steel [8]. Both properties emphasize the role of the reduced density of free electrons in the material and indeed correlate with the electronic conductivity of these specific materials.

This SISAM 2022 symposium is about the lifetime achievements of Prof. Uichiro Mizutani. Among many other breakthroughs, Mizutani and his collaborators were able to define in an unambiguous way the so-called e/a ratio [1], which is a measure of the number of electrons an atom shares with the Fermi sea in an intermetallic to achieve structural stability of a given crystal architecture. Although computation of this number requires periodicity of the lattice, the concept can be extended to aperiodic metallic systems such as quasicrystals [2]. It turns out that the e/a ratio found for truly aperiodic quasicrystals as well as weakly periodic crystals of giant unit cell (the so-called approximants) corresponds to a very specific value: e/a=2.2 ± 0.1 e-/at [3]. This way, the basic assumption of An Pang Tsai [4], who discovered most of the thermodynamically stable quasicrystals using e/a, was confirmed, yet with e/a defined with no questionable assumption and a clearly assessed mechanism for the contribution of the individual atoms to the valence band.
The formation of a pseudo-gap at the Fermi energy was discovered and documented using soft X-ray spectroscopy by my late colleague, Esther Belin-Ferré [5,6]. It was well illustrated in a family of Al-based intermetallics spanning a broad range of e/a values. The deepening of the pseudo-gap around the e/a=2.2 e-/at value is clearly observable for stable compounds. The talk will report how this data helped us to understand two properties of practical interest of quasicrystals and related compounds. The first is the reduced wetting observed against polar liquids (like water) deposited on the polished surface of a quasicrystal equipped with its layer of native oxide in air [7]. The second is friction or solid-solid adhesion measured in vacuum against metallic antagonists like hard-Cr steel [8]. Both properties emphasize the role of the reduced density of free electrons in the material and indeed correlate with the electronic conductivity of these specific materials.

The first-principles calculations based on density functional theory (DFT) have succeeded in a broad range of systems thanks to accurate description of electronic structure and their transferability. Here we present some studies on alloys using the first-principles calculations to understand deductively mechanism of properties such as stability and superelasticity. Regarding the stability of the gamma-phase alloys, the Hume-Rother electron concentration rule was revisited in terms of the first-principles calculations. The detailed analysis elucidates an interaction between the Fermi surface and the Brillouin zone that results in pseudogap formation and stability of the system with a certain electron density [1]. The electron density also plays a significant role in Ti-Nb-Ta-Zr-O alloys called “gum metal” which shows high strength, low Young's modulus and high elastic deformability, simultaneously. These unusual properties can be understood by softening with a particular electron concentration and Zr-O nano-clusters to be obstacles for dislocation movement [2].
Despite great success of the first-principles approach, it often faces at computationally-accessible simulation size typically within 1000 atoms and 100 ps. In recent year, machine learning potential (MLP) approach has been developed. Here the use of the first-principles calculations is extremely effective for data generation to construct MLP inductively. We demonstrate the design of RhAu alloy nanoparticles for NO decomposition catalysis using machine-learning approach [3]. A local similarity kernel based on the local atomic configuration is employed as descriptors which allow interrogation of catalytic activities. With data of the first-principles calculations on single crystals and their surfaces, MLP provides size- and composition-dependent catalytic activities of the nanoparticles.

One of the iron aluminides, usually denoted as Fe₂Al₅, is the major constituent phase of the coating layer in hot-dip aluminized steel sheets and has an orthorhombic crystal structure consisting of a tunnel-like framework and guest aluminum atoms encapsulated in the framework [1,2]. Fe₂Al₅ can be categorized as inclusion compounds like clathrate and skutterudite compounds, in which guest atoms are rattling inside a cage framework [3,4]. Since it exhibits very low lattice thermal conductivity and relatively large Seebeck coefficient [5], Fe₂Al₅ is considered as a potential thermoelectric material. In this study, to elucidate the origin of the low lattice thermal conductivity, crystal orientation dependence of the transport properties of Fe₂Al₅ was investigated by using single crystals grown by the Bridgman method. Seebeck coefficient, electrical resistivity and thermal diffusivity were measured along the a-, b- and c-axes of single-crystal samples. The lattice thermal conductivity was estimated with the Wiedemann-Franz law and the Lorenz number of 2.44×10^-8 (V²/K²) [6]. The experimental lattice thermal conductivity along the c-axis, which is the principal axis of the tunnel framework, is exceptionally lower than that estimated with the phonon dispersion relationships deduced by first-principles calculations under harmonic approximation. This implies that the anharmonicity of guest vibration along the c-axis plays a dominant role in reducing the lattice thermal conductivity. Such anharmonicity of the guest vibration was confirmed not only by the calculation of the potential energy surface around the guest site but also by internal friction measurement, which suggested frequent atomic jump of guest atoms along the c-axis within the tunnel framework. Besides, Fe₂Al₅ exhibits n-type conduction along the b-axis while p-type conduction along the a- and c-axes at room temperature. Such largely anisotropic electron/hole transport properties were consistently explained in terms of the anisotropic electronic band structure but do not correspond to the anisotropic crystal structure unlike in the case of lattice thermal conductivity.

In this talk we shed a light on hidden quantum properties in magnetite, the oldest magnetic material known to mankind. The study reveals the existence of low-energy waves that indicate the important role of electronic interactions with the crystal lattice as well as the lattice vibrations in both high-temperature cubic as well low-temperature monoclinic phases. This is another step to fully understand the metal-insulator phase transition mechanism in
magnetite, and in particular to learn about the dynamical properties and critical behavior of this material in the vicinity of the transition temperature. The attentions of physicists in magnetite was attracted by a fact that at temperature of 125 K it shows an exotic phase transition, named after the Dutch chemist Verwey. This Verwey transition was also the first phase metal-to-insulator transformation observed historically. During this extremely complex process, the electrical conductivity changes by as much as two orders of magnitude and a rearrangement of the crystal structure takes place. Verwey proposed a transformation mechanism based on the location of electrons on iron ions, which leads to the appearance of a periodic spatial distribution of Fe2+ and Fe3+ charges at low temperatures as well as the orbital order. In this talk we confirm the fundamental components of this charge-orbital ordering are polarons – quasiparticles formed as a result of a local deformation of the crystal lattice caused by the electrostatic interaction of a charged particle (electron or hole) moving in the crystal based on the quantum-mechanical (density functional method) calculations. In the case of magnetite, the polarons take the form of trimerons, complexes made of three iron ions, where the inner atom has more electrons than the two outer atoms. Our study reveals a very accurate model of lattice vibrations for the high temperature phase as well as confirm the effect of the charge-orbital (trimeron) order on phonon energies and mean square displacements in the monoclinic(low-temperature) phase and hence to contribute to shed a light at the complexity of the Verwey transition. The work was published in [1-3].

The fluorine atom, the second smallest after the hydrogen atom, is characterized by its large electronegativity and small polarizability [1]. Thus, it has little effect on the crystal structure, even though it causes a large electron bias in materials. Because of these unique properties, the fluorine atom is called as ‘magic element’. Fluorine has brought tremendous benefits to our lives through heat-resistant plastics, pharmaceuticals, and pesticides.
The oxidation reaction of fluoride ions with a high redox potential is also promising as fluoride-ion batteries. If a solid electrolyte with a sufficient high fluoride-ion conductivity is applied to all-solid-state FIBs, operation at room temperature would become possible. PbSnF₄ with a layered structure exhibits a superionic conductivity (> 10^-3 Scm^-1) at room temperature [2]. Besides it contains harmful lead in the crystal, however, it has a poor reduction resistance and there have been few reports of its incorporation into batteries. Recently, single crystals of fluorinated hexagonal BN were reported to exhibit a high in-plane fluoride-ion conductivity of 0.2 Scm^-1 at room temperature [3]. These reports propose that two-dimensional fluoride-ions diffusion is effective to enhance fluoride-ion conduction. In this lecture, we survey the core design principles that guide a high fluoride-ion conductivity. We conclude with a forward-looking discussion of the exciting link between fluoride-ions diffusion and layered structures in fluoride materials.

Compton-scattered X-ray spectra correspond to the electron momentum density in matter and reflect the wave function in the ground state [1]. Therefore, it is relatively easy to interpret the observed Compton-scattered X-ray spectrum by ab initio electronic structure calculations. The observed information is bulk-sensitive because prover X-rays have energies above 100 keV and are highly penetrating through materials.
This research focuses on lithium-ion secondary battery materials. In green technologies such as electric vehicles, improvement of rechargeable battery materials is a key to enhance energy density and charge-discharge stability. In practical batteries, it is important to understand redox reactions and their spatial distribution. From a view point of redox reactions, we measured spinel LixMn2O4, a Li-ion battery cathode material. We found that the redox orbital in the lithium insertion and extraction process is mainly the oxygen 2p orbital [2], although the redox orbital has been considered to be manganese 3d states [3,4]. Furthermore, analysis of the shape of Compton-scattered X-ray spectra can be used as a new nondestructive testing (NDT) technique. We proposed S-parameter analysis to observe the spatial distribution of redox reactions in commercial batteries [5].
Our research shows that Compton scattering measurements can provide insight into the mechanism of lithium batteries and point the way to improved battery materials and new battery designs.

Recent successful alloy-design showed that Mg alloys with addition of a small amount of Zn and Y (or rare-earth elements) reveal excellent mechanical properties including remarkably improved strength with a reasonable ductility [1]. One of the prominent microstructural features, which are believed to contribute for these excellent properties, is formation of a novel type of long-period structures [2-6]. The structures are fundamentally long-period stacking derivatives of a hexagonal close-packed structure (hcp-Mg), and the resultant stacking polytypes accompany a unique chemical order that occurs to synchronize with the corresponding stacking order; i.e., the synchronized long-period stacking/order (LPSO) structure [3, 6]. We have attempted to evaluate phase stability [7] as well as to construct model structures of the complex LPSO crystals, based on electron microscopy observations and first-principles calculations [4]. Structural characteristics are well represented by the TM₆RE₈ clusters with a L1₂-type short-range order (SRO) configuration, embedded in the local fcc-Mg layer of the LPSO [4, 5]. Interestingly, it turns out that the local electronic structures as well as relaxation behaviors of the SRO clusters significantly contribute to a phase stability. In the talk, I will describe a unique SRO cluster-induced phase stabilization, providing an important clue that leads to a universal concept on how we choose proper elements during alloy design.

Because the typical length scale of their atomic structures can be large, quasicrystals and related phases are rightfully considered to be the most complex compounds in the crystal chemistry of inorganic structures. This complexity extends to the surface, thus leading to unique surface properties – at least when compared to those of conventional alloys. Examples include the non-wetting behavior [1] and the catalytic activities and selectivities [2] of Al-based quasicrystalline approximants.
The surface properties of quasicrystal approximants and related phases are inherently tied to the peculiar atomic and electronic structures of the bulk crystals [3], which are best described by a stacking of highly symmetric polyhedra held by a network of bonds with a iono-covalent character. The detailed knowledge of the surface structures is a necessary prerequisite for further studies of surface properties. In this lecture, I will first show how methods based on the Density Functional Theory can help to determine surface structures, in combination with experimental measurements if applicable. I will then present a few examples to show how surface properties are controlled by their geometric and electronic structures.

Higher Manganese Silicides (HMSs) consist of two tetragonal subsystems (sublattices) of [Mn] and [Si] with an irrational c-axis length ratio γ = c_Mn/c_Si, forming an incommensurate Nowotny chimney-ladder (NCL) structure. The [Mn] subsystem has less displacive modulation of atomic sites and 3d electrons of Mn are responsible for the electronic conduction of this family. In contrast, significant displacive modulation of Si atoms in the [Si] subsystem effectively blocks the propagation of phonons and hence to reduce lattice thermal conductivity. A good thermoelectric (TE) material must have a high Seebeck coefficient S and electrical conductivity σ as well as a low thermal conductivity κ and HMSs can be thus regarded as potential TE materials. Using γ, the structure formula of HMSs is represented as MnSi_γ (γ~ 1.73) (Miyazaki et al, 2008).
To comprehend the electronic structure of such complicated composite crystals and their solid solutions, we adopted the concept of valence electron counts, VEC. Based on the VEC concept, HMSs should exhibit a good p-type TE property as the VEC value is slightly smaller than 14. To further enhance p-type performance, a small amount of hole-doping, by a partial substitution of Cr, V, etc. for Mn, is necessary. In contrast, n-type materials can be synthesised by a partial substitution of Fe or Ru.
The incommensurate nature of the present HMS family causes variety of nano/micro structures which enrich physico-chemical properties of the present silicide system. HMSs had a serious problem to form MnSi (monosilicide) striations during the solidification. We have discovered that the formation of such monosilicide striations originates from the temperature dependence of the γ-value, gradually increases from ~1.72 just below the solidification temperature to ~1.74 at around 800 K, with decreasing temperature. Such a change in γ is unfavorable for the practical use because it would easily cause mechanical cracks during heat cycles. We confirmed that the partial substitution of transition elements, e.g., Cr, Co and V for Mn sites effectively dissipates such striations as well as a moderate hole-doping which raises the TE power factor S²σ almost doubled at 800 K. For the Co and V-solid solutions, the γ-value is around 1.72 and less temperature-dependence and it would be thus ideal for the crack-free HMS-based TE materials.

Recently, a huge magnitude of Seebeck coefficient was observed for metallic Cu₂Se under an unusual temperature gradient produced by an experimental set up consisting of the two-heaters. This material is characterized by a structure phase transition at about 400 K. Two heaters placed at the bottom and one side of sample produced a layered composite consisting of the low temperature phase (LTP) at the top surface and the high temperature phase (HTP) in the bottom. The composition of LTP varied with varying temperature during the phase transition, and eventually it became an insulator only in a very narrow temperature range. The insulating LTP staying on the metallic HTP allowed us to observe a large magnitude of Seebeck coefficient S exceeding a few mVK^-1 and rather small magnitude of electrical resistivity ρ as low as 1 mΩcm. These numbers led to a huge value of power factor PF = S²σ exceeding a few mWm^-1K^-2. Together with the small lattice thermal conductivity in association with the anharmonic lattice vibration, the dimensionless figure of merit ZT were increased to a surprisingly large value exceeding 470. [1]
The variation of composition with varying temperature in the Cu₂Se LTP limits the large ZT-value only in a very narrow temperature range of a few K in width near 350 K, and this condition has prohibited us from utilizing it in practical applications. The problem about the narrow temperature range was eliminated by employing Ag₂S that also possess a structure phase transition between insulating low temperature phase and metallic high temperature phase. Despite that the magnitude of ZT was reduced to 20, the temperature width of the large ZT-value was extended to 40 K (390 K ≤ T ≤ 430 K). [2]
The power generation from Ag₂S was also confirmed in the steady state condition, and the enhancement of power generation was found to appear above 390 K where ZT-value was strongly increased.
The new phenomena introduced in this presentation provides us with a breakthrough in the technologies of thermoelectric power generation to contribute the construction of a low-energy-consuming, sustainable carbon neutral society.

Half-Heusler NiZrSn alloys have excellent thermoelectric properties [1], mechanical strength [2], and oxidation resistance [3], and are being commercialized for the development of thermoelectric power generation devices that operate in high temperature environments. The excellent thermoelectric conversion properties of half-Heusler NiZrSn alloys are attributed to their semiconducting electronic structure with a narrow band gap near the Fermi level and low thermal conductivity. Although the half-Heusler structure with high crystal symmetry inherently results in high thermal conductivity, it has been confirmed by synchrotron powder diffraction [4] and X-ray absorption fine structure measurements [5] that in NiZrSn alloys, interstitial atomic defects exist in the vacancy sites and the surrounding atoms are distorted. This has been found to contribute to a significant decrease in thermal conductivity. In this presentation, we will show that high thermal conversion properties can be realized by utilizing the defect structure at the vacancy site, together with the latest research results.

The FLAPW (full-potential linearized augmented plane wave)-Fourier (FF) theory has been developed by Mizutani and Sato and accomplished the development in 2021 [1]. This method can elucidate interaction between the Fermi surface and Brillouin zones when phase stabilities of compounds are discussed based on the extended zone scheme. We have examined compounds having cP12 structures using the FF theory and selected pyrite-type FeS₂ as a candidate of a thermoelectric material so that (1) it has a band gap at the Fermi energy (E_F) as an insulator, (2) itinerant electrons slightly remain near E_F and (3) the conduction and valence band structures at Γ show free electron and tight-binding like behavior, respectively [2].
　The thermoelectric properties of FeS₂ have been reported in some literatures. Nevertheless, while the electrical conductivity reveals semiconductor-like behavior; that is, it monotonically increases as the temperature increases, the Seebeck coefficient sometimes shows positive values only at low temperatures or exhibits just positive values in all the measured temperatures. Thus, the transport mechanism in FeS₂ is indeed unclear particularly for the bulk state. Thus, we used plain Fe and S powders and spark plasma sintering to fabricate the FeS₂ compounds and then measured the thermoelectric properties. The results of temperature dependence are compared with those calculated by the Boltzmann transport equation and electronic structure calculations.
Fe and S powders were encapsulated in a Pyrex tube, mixed and heat treated at 625 K for 4 h in Ar atmosphere. However, due to the evaporation of S, the FeS₂ single phase could not be obtained. Then, the heat treatments were subjected to the mixtures several times, and finally pyrite-type FeS₂ had been acquired. The electrical conductivity shows 2 S/cm at room temperature and monotonically increases with increasing temperature. Though the Seebeck coefficient shows positive values at low temperatures below 500 K, it turns back negative values at high temperatures. When the Seebeck coefficient is calculated within a frame work of a constant relaxation time approximation using WIEN2k, all the Seebeck coefficient in the used temperature range gives rise to negative values. The discrepancies between the experimental and theoretical results will be discussed in view of the material preparation method , defects or effects of electron-phonon interactions.

Thermoelectrics enable direct conversion of waste heat into useful electricity; therefore, they can play a crucial role in reducing carbon dioxide emissions and improving thermal management to create a sustainable society. There have been several important breakthroughs in enhancing the figure of merit (zT) of thermoelectric materials in this century. However, thermoelectric modules and technologies are used only in niche applications. The advanced thermoelectric materials have not yet been fully explored for module development, making a big technological valley between materials and module development. This talk focuses on recent challenges in bridging the technological valley between materials development, module fabrication, and evaluation methods for high-temperature thermoelectric power generation.
In PbTe and colusites (Cu and S-based systems), we have demonstrated high zT in the materials and corresponding high conversion efficiency in the modules [1,2,3,4]. For PbTe, the material’s zT was dramatically enhanced through nanostructuring and controlled doping. For colusites, material’s zT was dramatically enhanced by chemical composition tuning. In both systems, the improved electrical and thermal contact resistances between thermoelectric materials and electrodes, enhanced mechanical strength, and the optimized configuration of thermoelectric elements and modules led to high conversion efficiency and improved reliability of high-temperature power generation in the modules.
It is also important to develop technologies for reliably and accurately evaluating the power generation characteristics of the modules. In this work, interlaboratory testing was carried out using a mechanically durable Ni-based alloy module in characterization facilities developed the National Institute of Advanced Industrial Science and Technology (AIST), the German Aerospace Center (DLR), and so on to understand the differences in the evaluation methods from each other [5].
The PbTe-based materials and module were developed together with Prof. M. G. Kanatzidis of Northwestern University and Argonne National Laboratory. The colusites-based materials and module were developed together with Dr. K. Suekuni of Kyushu University, Dr. Y. Bouyrie of AIST, Dr. R. Chetty of AIST, and Dr. E. Guilmeau of CRISMAT. Interlaboratory testing performed together with P. Ziolkowski of DLR, Prof. E. Muller of DLR, Dr. R. Chetty of AIST, Dr. K. Okawa of AIST, Dr. Y. Amagai of AIST, and Dr. R. Funahashi.

The Heusler compound Fe₂VAl is a potential candidate for thermoelectric applications because of the possession of a deep pseudogap across the Fermi level. Since the Seebeck coefficient varies systematically with the valence electron concentration (VEC), irrespective of doping elements, the net effect of doping is most likely to cause a rigid-band-like shift of the Fermi level from the central region in the pseudogap. Further increase in the Seebeck coefficient can be achieved by the V/Al off-stoichiometric composition change, so that Fe₂V_1+xAl_1-x alloys exhibit a large value of -160 μV/K for the n-type V-rich alloy (x=0.03) and 100 μV/K for the p-type Al-rich alloy (x=-0.03), coupled with a significant decrease in the electrical resistivity. Thus Fe₂V_1.05Al_0.95 achieves a large increase in the power factor up to 6.8x10^-3 W/mK², which is superior to that for half-Heusler compounds, skutterudites and Mg₂Si [1].
We believe that the large Seebeck coefficient for the V-rich alloys could be caused by an electronic structure modification of the pseudogap due to the V/Al off-stoichiometry effect. Improvement of the p-type thermoelectric performance has been investigated for Fe₂V_1.08-yTi_yAl_0.92 alloys, where the Seebeck coefficient changes in its sign from negative to positive at around VEC = 6.0 due to the Ti doping, and the peak value reaches approximately 120 μV/K at 350 K for y=0.22 [2]. As a result of a drastic reduction in the electrical resistivity, the power factor enhances to 3.7×10^-3 W/mK² at 300 K for y=0.30. The thermal conductivity increases with the Ti doping to 15.5 W/mK at 350 K for y=0.16, because of an increased stability of the L2₁ structure for VEC closer to 6.0, but then turns to decrease to approximately 12 W/mK for y=0.34.
One of the issues for thermoelectric Fe₂VAl‐based compounds is to reduce the thermal conductivity as much as possible, while maintaining a high power factor. Heavy‐element Ta doping for the V/Al off‐stoichiometric alloys causes a drastic decrease in the thermal conductivity, leading to a large increase in the figure of merit ZT up to 0.29 at 400 K for Fe₂V_0.98Ta_0.05Al_0.92. High-pressure torsion (HPT) processing further reduces the thermal conductivity because of the production of ultrafine-grained structures with grain sizes less than 100 nm, which can be obtained through the suppression of grain coarsening due to the segregation of Ta during annealing [3]. Thus, a reduced thermal conductivity of 3.5 W/mK for Fe₂V_0.98Ta_0.10Al_0.92, combined with a large power factor, leads to ZT = 0.37 around 400 K, one of the highest values ever achieved for bulk Fe₂VAl-based thermoelectric materials.

Quasiperiodic structures exhibit long-range order like normal crystals but they lack translational symmetry. Quasicrystals were first discovered as a new class of intermetallic compounds, now comprising hundreds of members in binary and ternary systems. They usually adopt either the icosahedral or the decagonal point group symmetry. The discovery of quasicrystals has led to a paradigm shift in crystallography and has attracted a large interest in the material science community, motivated by unexpected physical properties that could be linked to quasiperiodicity. This remarkable class of materials has also challenged our understanding of metal surfaces. An atomic scale description of their surfaces is especially important, as it forms the basis for understanding and predicting phenomena such as gas adsorption, metal epitaxy, and friction.
Of interest also are studies of nucleation and growth of metal thin films on quasicrystalline surfaces, demonstrating that local pseudomorphic growth can occur due to preferred adsorption of the metal ad-species at specific sites of the surface quasilattice. The idea is that the complex potential energy surface of quasicrystalline surfaces could serve as a template to grow new 2D quasicrystalline systems.
Here, we will review the different results obtained along this direction, from local peudomorphic growth of Al starfish islands on the 5-fold surface of the icosahedral i-Al-Cu-Fe quasicrystal [1] to pseudomorphic single layer high islands in the case of Ag/5f-Al-Pd-Mn [2] and up to the formation of complete 2D quasiperiodic metal layers (Pb, Bi or Sn) templated on various quasicrystalline surfaces [3]. Self-organized molecular films with long-range quasiperiodic order could also been grown by using the complex potential energy landscape of quasicrystalline surfaces as templates. The long-range order arises from a specific subset of quasilattice sites acting as preferred adsorption sites for the molecules, thus enforcing a quasiperiodic structure in the film [4]. Finally we will show some recent examples of 2D quasicrystalline oxide layers obtained by reduction of ABO3 perovskite thin films grown on Pt(111) [5,6].

In materials science, crystal growth technology is indispensable to maximize functionalities of materials. A practical method is the epitaxial growth technique such as melt-solidification using seed crystals and thin film growth on single-crystalline templates.
Our group focuses on tri-axial grain-orientation using by a modulated rotating magnetic field (MRF)[1,2] as a room-temperature process. Recently, equipment that can generate a linear drive type of MRF [3] applicable to a continuous production process was developed. It can generate a kind of MRF by reciprocating an arrayed permanent magnet unit. The unit has two different portions of bending magnetic field and uniform magnetic field, and can generate MRF with static and rotating magnetic fields with 0.9 T. In this presentation, tri-axial (or biaxial) alignment of orthorhombic cuprate superconductor powders and simulation research on the design of the magnet arrays will be reported.

We shall be happy to convene in Phuket on the occasion of the 2022 Sustainable Industrial Processes Summit to celebrate the lifetime achievements of Prof. Dr Uichiro Mizutani from University of Nagoya, Japan. Uichiro received his higher education in this university and then moved to the United States for a post-doc under the supervision of Prof. Massalski at the Mellon Institute in Pittsburg. When back to Japan, he returned to Nagoya where he took a position first as a research fellow and then as an associate professor. This took him to become a full professor and head of a laboratory for the rest of his career until he retired from public education in Japan. He then became a fellow of the famous Toyota Physical and Chemical Research Institute where he still serves as a senior fellow.
The career of Uichiro Mizutani is a magnificent example of a full dedication to one key topic in solid-state physics, i.e. the understanding of the behaviour of electrons in metals [1]. This behaviour explains the stability of solid and liquid metals, and provides definite clues to understand why Nature selects specific atomic architectures among the infinite number of possible configurations. It was a matter of interest already before the invention of quantum mechanics in the early 2Oth century, but became a central aspect of solid-state physics when the principles of quantum mechanics were applied to this subject by Fermi, Born, and many others. The invention of quantum mechanical computing techniques made it fully operational in more recent years. Mizutani and his collaborators pioneered the application of this approach to a huge variety of metallic crystals, including complex ones like quasicrystals, their periodic counterparts, and amorphous systems, thus rising a unique body of knowledge and understanding of those systems [2]. Of special relevance is their complete description of the so-called Hume-Rothery rules that explain the formation and stability of many complex crystals and which before them was more a matter of experimental discovery rather than a deeper theoretical insight. Quite a few more fields have benefitted from Mizutani’s work, such as e.g. metallic glasses, or thermoelectric, or superconducting materials. In the end, Mizutani is to be considered as the living key figure in the field of metals and alloys, to be compared with his very few predecessors who like him where honoured by the Hume-Rothery award of the TMS in preceding decades (e.g. Jacques Friedel in France or Sir Nevill Mott in the U.K.). A summary of the many prizes and awards, which were presented to Prof. Mizutani over the years can be found on the SIPS 2022 website [3].
The symposium that is dedicated to honour the achievements of Uichiro Mizutani will focus on a short list of his many pioneer results and will provide an insight into few future developments of his work.

The atomistic mechanisms governing aging and rejuvenation in metallic glasses are still unclear. In-situ X-ray diffraction allows to investigate the structural rearrangements during annealing from 77 K up to the crystallization temperature of CuZrAlHfCo bulk metallic glass rejuvenated by high pressure torsion performed at cryogenic temperatures and at room temperature.
The structural evolution was evaluated by dynamic mechanical analysis as well as by differential scanning calorimetry to determine relaxation dynamics and crystallization behavior. Using a measure of the configurational entropy calculated from the x-ray pair correlation function the structural footprint of the deformation-induced rejuvenation in bulk metallic glass is revealed. With synchrotron radiation temperature and time resolutions comparable to calorimetric experiments are possible. This opens new experimental possibilities allowing to unambiguously correlate changes in atomic configuration and structure to calorimetrically observed signals and can attribute those to changes of the dynamic and vibrational relaxations in glassy materials.
The results suggest that the structural footprint of the β-transition is related to entropic relaxation with characteristics of a first-order transition. The DMA data shows that in the range of the β-transition non-reversible structural rearrangements are preferentially activated. The low temperature γ-transition is mostly triggering reversible deformations and shows a change of slope in the entropic footprint suggesting second order characteristics.

The lecture will address one of the key aspects of the behavior of electrons in metallic systems, which explains why certain specific atomic architectures form in so-called intermetallics. This mechanism is known after the name of its discoverer, William Hume-Rothery (1899-1968), a most famous British metallurgist.
The Hume-Rothery electron concentration rule was empirically established by Hume-Rothery (1926) almost a century ago [1] and has significantly affected subsequent tremendous developments in the field of metal physics. Academic aspirations have been revived in the late 1980s to early 1990s, when stable quasicrystals were synthesized by using the empirical Hume-Rothery rule as a guide [2]. We have soon realized that a pseudogap at the Fermi level plays a key role in stabilizing these complex compounds. Mizutani and Sato developed a unique electron theory of metals, which allows us to link the Hume-Rothery rule with the formation of a pseudogap [3-5]. It fully relies on the interference phenomena of itinerant electrons with the set of lattice planes, regardless of the degree of orbital hybridization effects involved, and the theoretical Hume-Rothery rule thus established have been extended to alloys and compounds with bonding types of metallic, ionic, or covalent, or a changing mixture of these, unless the number of itinerant electrons in the valence band is too low.
The original Hume-Rothery rule was claimed to hold in randomly substituted alloys. More recently, we have confirmed that the theoretical Hume-Rothery rule is extendable to randomly substituted alloys beyond first-principles electronic structure calculations. It has therefore direct relevance to a huge variety of compounds that show electronic conductivity. Examples are quasicrystals Al₈₆Mn₁₄ [6], Al₆₅Cu₂₀Fe₁₅ [2], Samson compound Al₃Mg₂ containing 1178 atoms per unit cell [7], amorphous alloys V_xSi_100-x (x>20) [8], marginal conductor FeS₂ [9] and so on.

The lecture will address one of the key aspects of the behavior of electrons in metallic systems, which explains why certain specific atomic architectures form in so-called intermetallics. This mechanism is known after the name of its discoverer, William Hume-Rothery (1899-1968), a most famous British metallurgist.
The Hume-Rothery electron concentration rule was empirically established by Hume-Rothery (1926) almost a century ago [1] and has significantly affected subsequent tremendous developments in the field of metal physics. Academic aspirations have been revived in the late 1980s to early 1990s, when stable quasicrystals were synthesized by using the empirical Hume-Rothery rule as a guide [2]. We have soon realized that a pseudogap at the Fermi level plays a key role in stabilizing these complex compounds. Mizutani and Sato developed a unique electron theory of metals, which allows us to link the Hume-Rothery rule with the formation of a pseudogap [3-5]. It fully relies on the interference phenomena of itinerant electrons with the set of lattice planes, regardless of the degree of orbital hybridization effects involved, and the theoretical Hume-Rothery rule thus established have been extended to alloys and compounds with bonding types of metallic, ionic, or covalent, or a changing mixture of these, unless the number of itinerant electrons in the valence band is too low.
The original Hume-Rothery rule was claimed to hold in randomly substituted alloys. More recently, we have confirmed that the theoretical Hume-Rothery rule is extendable to randomly substituted alloys beyond first-principles electronic structure calculations. It has therefore direct relevance to a huge variety of compounds that show electronic conductivity. Examples are quasicrystals Al86Mn14 [6], Al65Cu20Fe15 [2], Samson compound Al3Mg2 containing 1178 atoms per unit cell [7], amorphous alloys VxSi100-x (x>20) [8], marginal conductor FeS2 [9] and so on.

Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) is the most interesting CPs; it has the highest electrical conductivity when compared to other CPs [1]. Moreover, it possesses many useful properties such as a low band gap energy, superior electrochemical and thermal stabilities, and high transparency [2]. In this work, PEDOT: PSS nanoparticles in powder form with high electrical conductivity was synthesized by chemical oxidative polymerization. In addition, the effects of acid types and EDOT: PSS weight ratio were investigated. For the effect of acid types, at the 0.5 EDOT: 5.5 PSS weight ratio in 0.1 M HClO4 was the best condition to obtain 1.04 x 104 ± 188 Scm-1 due to the multiple dopants (ClO4-, PSS-, SO42-). For the effect of EDOT: PSS weight ratio, at the 0.5 EDOT: 5.5 PSS weight ratio in 0.1 M HClO4 was the proper condition as it provided the high amount of dopant (ClO4-, PSS-, SO42- ) available to interact with PEDOT chain. These results were verified by Fourier transformed infrared spectroscopy, UV-VIS spectrometry, X-ray photoelectron spectrometry, and thermogravimetric analysis. The particle shapes of PEDOT: PSS synthesized in all conditions were spherical. The particle size of PEDOT: PSS varied from 21.15 ± 2.60 to 33.79 ± 2.27 nm.

The detailed analysis of ternary systems that form the quinary Ag-Au-Cu-Ni-Sn has been performed to assemble 3D computer models of T-x-y diagrams. The usual 3 steps were followed [1]: (1) scheme of mono- and non-variant states in table and space (3D) forms, (2) phase diagram (PD) prototype and (3) T-x-y diagram of the real system. E.g., there are 14 invariant transformations within the system Ag-Cu-Sn (6 of them with the liquid phase participation). As a result, T-x-y diagram, Ag-Cu-Sn includes 56 horizontal (isothermal) planes and 111 ruled surfaces. Besides, it is formed by 8 pairs of liquidus and solidus surfaces, 4 surfaces of transus and 54 surfaces of solvus (33 of them is degenerated into the vertical edges of the prism). In total, PD consists of 241surfaces and 88 phase regions. Space (3D) computer model was tested by 3 isothermal and 5 polythermal cuts in the Atlas [2]. Errors were found: on isothermal cut 221^оC in [2, p. 179] which is pictured an extra phase region L+C+R2, and on the isopleths via point Е an extra phase region L+R2+R8 is depicted. An error, that violates the rule of contacting state spaces (two two- phase regions are adjacent), and three more inaccuracies are found [2, c. 181] on the isopleth А-S (0, 0.82, 0.18). Other 3 isopleths don’t contain the contradictions between the [2] and model variants. Analysis of all four ternary systems, forming the Ag-Cu-Ni-Sn quaternary system (A- B-C-D), led to a scheme of di-, mono and invariant states, formally describing the geometric structure of the T-x-y-z diagram. According to this scheme, it’s possible to say, that T-x-y-z diagram contains 11 hypersurfaces of liquidus and the region of liquid immiscibility. In addition to Ag (A), Sn (D) and Cu (Ni) or B (C) solid solution, as well as seven compounds, including the R3 (R9) solid solution, there is an internal liquidus surfaces of the R11 compound and a low- temperature polymorphic modification of the R9 (Ni 3 Sn) compound. Seven invariant transformations are expected, including five of quasiperitectical type, one - euthetic and one of polymorphic transformation between allotropic forms of Ni3Sn2. Partial validation of the geometric structure forecast of the quaternary system liquidus can be carried out based on the experiments [3-4] with alloys, rich in Sn (80, 90, 95 and 97 at. %) at 210^oC and at 250^oC. This work was been performed under the program of fundamental research SB RAS (project 0336- 2019-0008), and it was partially supported by the RFBR project 19-38-90035.

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