Pseudobinary Series Research Articles

Optimizing Thermoelectric Performance of Hybrid Crystals Bi2O2Se1-xTex in the Bi2O2X System.

In addressing the global need for sustainable energy conversion, this study presents a breakthrough in thermoelectric materials research by optimizing the Bi2O2Se1-xTex system in the Bi2O2Se/Bi2O2Te pseudobinary series. Leveraging the principles of innovative transport mechanisms and defect engineering, we introduce tellurium (Te) doping into Bi2O2Se to enhance its thermoelectric properties synergistically. With the help of various advanced characterization tools such as XRD, SEM, TEM, XPS, FTIR, TGA, LFA, and DSC, combined with relevant resistance and density measurement techniques, we conducted an in-depth exploration of the complex interactions between various factors within thermoelectric materials. We recognize that the balance and synergy of these factors in the thermoelectric conversion process are crucial to achieving efficient energy conversion. Through systematic research, we are committed to revealing the mechanisms of these interactions and providing a solid scientific foundation for the optimal design and performance enhancement of thermoelectric materials. Finally, the advantage coefficient (ZT) of the thermoelectric material has been significantly improved. The crystallographic analysis confirms the formation of a continuous series of mixed crystals with varying Te concentrations, adhering to Vegard's law and exhibiting significant improvements in electrical and thermal conductivities. The Bi2O2Se1-xTex crystals, particularly the Bi2O2Se0.6Te0.4 composition, demonstrate a peak ZT of 0.86 at 373 K. This achievement aligns with recent advancements in defect-enabled mechanisms and band convergence and sets a new standard for high-performance thermoelectrics. The study's findings contribute significantly to the ongoing quest for efficient thermal-to-electrical energy conversion, offering a promising avenue for future sustainable energy technologies.

The unusual magnetic properties of kuramite–stannite pseudobinary series: a SQUID and EPR survey

The magnetic properties of the synthetic Cu3SnS4 (kuramite)–Cu2FeSnS4 (stannite) pseudobinary series were investigated by means of electron paramagnetic resonance (EPR) spectroscopy, at room temperature, and by magnetometry, in the range 2–300 K. The system is particularly complex, from both chemical and crystal chemical points of view, in particular with respect to the metal valence states and the local ordering in the different terms of the series. Nevertheless, recent successes in synthesising nanostructured kuramite foster the interest to ascertain the bulk magnetic properties of these important semiconducting phases. The obtained results allowed to ascertain that a variable lack of local ordering in the Cu3–x Fe x SnS4 (x < 0.85) samples induce the raise of strong metal–sulphur–metal superexchange interactions, that result in the appearance of marked deviations from the single-ion behaviour, typical for pure stannite. Ferro- and antiferromagnetic interactions are in fact observed at relatively high temperatures (~150 K). A possible role played by Cu(I)–Fe(III) was revealed by the EPR measurements. The Cu-rich terms of the series (x < 0.1) are characterised by dynamic resonant disorder (i.e. time-evolving delocalisation of the formally divalent valence state for Cu among the nearest neighbouring Cu-sites), in addition to the Cu–Fe–Sn static disorder verified along the whole series. Both factors concurring to a non-periodic arrangement of paramagnetic ions in the lattice have the main effect to drastically broaden the EPR lines.

Magnetic properties of the CeGe 1− xSi x series studied by powder neutron diffraction and μSR-measurements

The antiferromagnetic ordering in orthorhombic (Pnma) CeGe 1− x Si x pseudobinary series was studied by powder neutron diffraction and μSR measurements. The ordering temperature varies linearly between 10.4 K for CeGe and 6.1 K for CeSi. The magnetic phase diagram comprises two distinct regions of magnetic ordering as a function of Si concentration x, which are characterized by the wave vectors q 1=(0, 1 2 ,0) r.l.u. , for 0⩽ x⩽0.8 and q 2=(0, 1 2 , 1 16 ) r.l.u. for CeSi. Both structures correspond to collinear arrangements of the Ce moments within the ( a, b) plane. The ordered Ce 3+ moment value of 1.0(1)μ B/atom at 1.5 K of the commensurate q 1 phases as well as the amplitude of the wave of the modulated q 2 phase (1.56(4)μ B/atom) are strongly reduced compared to the free Ce 3+ ion value gJμ B=2.14μ B. A narrow field distribution observed with μSR suggests that CeSi has a commensurate square wave magnetic structure, which possibility could not be tested in the neutron work due the unobservability of the expected weak higher harmonics. The temperature dependence of the internal field detected by μSR suggests that the spin interactions are long range in CeSi, but short ranged in CeGe. These results point towards a localized non-Kondo behavior for CeSi and strong hybridization of the 4f electrons with the conduction band for CeGe.

Application of Doniach Diagram on Valence Transition in EuCu2(SixGe1-x)2

To investigate the valence transition of Eu in the pseudo-binary compounds series, EuCu 2 (Si x Ge 1- x ) 2 , measurements of the lattice constants, the X-ray absorption spectroscopy (XAS), the mag...

On the magnetic phase transition in Fe xMn 1 −xSi

The pseudobinary series Fe x Mn 1− x Si shows a transition from an insulator for x=1 to a metallic state with long range magnetic order at the Mn-rich side. In order to understand the mechanism of the magnetic phase transition, we perform ab initio calculations for the electronic band structure and the magnetic properties of Fe x Mn 1− x Si. The calculations are based on density-functional theory with the local-spin-density approximation. The pressure effect on the magnetic properties of MnSi are calculated. It is found that the magnetic phase transition can be attributed to the hybridization among Mn 3d, Fe 3d and Si 3p orbitals.

Evolution of Magnetism and Its Interplay with Superconductivity in Heavy‐fermion UPt3 Doped with Pd

AbstractFor Abstract see ChemInform Abstract in Full Text.

Hardness behaviour in B2 pseudo-binary systems

Room-temperature hardness data and lattice constants were assembled for a number of Ru and Ir-based ternary systems exhibiting continuous B2 (CsCl) phase fields between the binary compounds. Near-linear relationships were found to exist in the hardness profiles and lattice constants of the RuAlRuTi, RuAlCoAl, RuAlIrAl, IrAlNiAl and RuAlRu 2NbAl (L2 1) pseudo-binary series, suggesting a strong correlation of hardness with just one parameter. Pronounced solution hardening is reported for the RuAlNiAl, RuTiNiTi and RuZrPdZr series. In these cases, no clear correlations with the lattice parameters could be found, indicative of constitutional effects such as defects and ternary ordering. Volume size factors were examined as a basis for predicting lattice constants in these systems. Where such data exist, it was generally found that quantitative size factors yield errors commensurate with the precision of the available data.

Evolution of magnetism and its interplay with superconductivity in heavy-fermion UPt 3 doped with Pd

The pseudobinary series U(Pt 1− x Pd x ) 3 demonstrates a wealth of magnetic and superconducting properties that are exemplary for heavy-fermion physics. In this paper, I present a survey of recent neutron-diffraction and μSR experiments, conducted to study the evolution of magnetism, and its interplay with superconductivity, in UPt 3 doped with Pd. The small-moment antiferromagnetic order (SMAF) with T N∼6 K reported for pure UPt 3, is robust upon alloying till at least x=0.005. The small ordered moment m( x) grows from 0.018 μ B/U-atom for x=0.00 to 0.048 μ B/U-atom for x=0.005. T N of the SMAF phase does not vary with Pd content. The increase of m( x) correlates with the splitting Δ T c of the superconducting transition and provides evidence for a Ginzburg–Landau scenario for unconventional superconductivity with magnetism as symmetry-breaking field. The absence of a signal of the SMAF phase in zero-field μSR spectra provides strong evidence for a moment fluctuating at a rate >10 MHz. A second large-moment antiferromagnetic phase (LMAF) is found at higher Pd concentrations. For this phase, at optimum doping ( x=0.05) T N,max=5.8 K and m=0.62 μ B/U-atom. The critical Pd concentration for the emergence of the LMAF phase is x c,af∼0.006. At the same Pd content, superconductivity is completely suppressed. The existence of a magnetic quantum critical point in the phase diagram, which coincides with the critical point for superconductivity ( x c,af= x c,sc≈0.006), yields evidence for odd-parity superconductivity mediated by ferromagnetic spin-fluctuations.

The magnetic state of the Co-sublattice in Tb 1− xY xCo 2

The Tb 1− x Y x Co 2 pseudobinary series has been studied by means of resistivity, magnetic susceptibility and neutron diffraction measurements. According to the neutron diffraction a long-range magnetic order in this system exists only for x<0.8. In compounds with the yttrium concentration near x c≈0.8 a short-range magnetic order and anomalies in the transport properties: maximal value of the residual resistivity and large magnetoresistance effect (about −30%) were observed. We have found that the concentration dependence of the residual resistivity ρ res for Tb 1− x Y x Co 2 (as well as for other (R 1− x Y x )Co 2 compounds) correlates with the variation of the coefficient γ (linear term of the low-temperature specific heat). In vicinity of x c where the Co-magnetic moment is unstable the maximums of ρ res and γ can be associated with the large contribution from localized spin density fluctuations of d-electrons to both electrical resistivity and specific heat.

Quadrupolar Kondo effect in U 3Ni 3Sb 4− xSn x alloys

In the pseudobinary series U 3Ni 3Sb 4− x Sn x there is a cross-over from a localised non-magnetic state to a many-body Kondo singlet state, accompanied by a transition from semiconducting to metallic behaviour. Our analysis of the crystal field spectra of U 3Ni 3Sb 4 has shown that its non-magnetic ground state is a doublet, so that the system meets the criteria for the quadrupolar Kondo effect. For intermediate compositions the susceptibility shows weak power law divergences at low temperature, consistent with non-Fermi liquid behaviour.

Magnetic Phase Diagram of Ce(Ni1-xPdx)2Ge2

We have measured the temperature dependence of the magnetic susceptibility, the electrical resistivity, the specific heat and the Hall coefficient on the pseudo-binary series Ce(Ni 1- x Pd x ) 2 Ge 2 (1.0≥ x ≥0.0). The Neel temperature decreases monotonously from 5.1 K for CePd 2 Ge 2 to 2.8 K for Ce(Ni 0.8 Pd 0.2 ) 2 Ge 2 with decreasing Pd concentration. For x ≤0.1, the ground state is paramagnetic.

ROLE OF AN INTERGRANULAR PHASE IN RuAl WITH SUBSTITUTIONAL ADDITIONS

The unusual room-temperature ductility of the binary RuAl (B2) phase is extended by the occurrence of an intergranular eutectic film in a manner seemingly akin to a compliant layer effect. The premise that the controlled deployment of such a film might extend the favourable mechanical properties of RuAl to ternary formulations was examined for substitutional additions of Ni, Co and Ti in RuAl. Whereas single-phase ternary formulations invariably resulted in a sharp loss of ductility, dual-phase alloys in the pseudo-binary series Ru50Al50-Co70Al30 and Ru52Al48-Ru52Ti48 were found to support significant plasticity, as determined by room-temperature compression tests, up to alloying additions of the order of 40 at.%. Alloys based on the series Ru50Al50-Ni65Al35 however, exhibited limited ductility, commensurate with strong solution strengthening effects and only a partially developed intergranular film. © 1997 Acta Metallurgica Inc.

μSR study of antiferromagnetic order in UPt 3 alloyed with Pd

We report on a μSR study of the evolution of antiferromagnetism in the heavy-fermion pseudobinary series U(Pt, Pd) 3. For pure UPt 3 adn U(Pt 0.998Pd 0.002) 3 no small-moment antiferromagnetism has been observed in the present experiment: the zero-field μSR data yield a temperature-independent Kubo-Toyabe line width σ KT = 0.06 ± 0.01 μs −1 ( T ⩽ 8 K). As recent neutron-diffraction experiments on UPt 3 and U(Pt 0.998Pd 0.002) 3 do reveal magnetic order, we suggest that the muons stop at high symmetry sites where the dipole fields cancel. However, for the large-moment compound U(Pt 0.95Pd 0.05) 3), the μSR data unambiguously show magnetic signals: below T N two frequencies appear ( ν 1 ⋍ 8.0 MHz and ν 2 ⋍ 2.0 MHz, for T → 0 ), indicating two magnetically inequivalent muon stopping sites.

(Fe,Mn) Si: Transitions from a magnetic to a nonmagnetic state and from metallic to semiconducting behaviour

The pseudobinary series (FexMn1-x)Si shows a transition from an insulator for x = 1 to a metallic state with long range magnetic order at the Mn-rich side. This behaviour can be attributed to the shift of the Fermi energy across a narrow gap into a region of high density of states.

First-order valence phase transition in CeNi1-xCoxSn alloys.

Alloys in the pseudobinary series ${\mathrm{CeNi}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Co}}_{\mathit{x}}$Sn (x=0--0.5) have been investigated using a wide variety of experimental techniques. The gap in the electronic density of states, found in the Kondo compound CeNiSn at low temperatures, was found to decrease rapidly with Co concentration. The temperature dependence of the susceptibility shows a dramatic change with Co concentration. In alloys with 0\ensuremath{\le}x\ensuremath{\le}0.34, \ensuremath{\chi}(T) has a form which shows an increasing trend towards intermediate valence behavior with increasing x: for x=0.34 \ensuremath{\chi}(T) exhibits a broad maximum at 95 K. For x in the range 0.35--0.4 the susceptibility exhibits a sharp drop at temperatures between 40 and 75 K (dependent on composition). The unit-cell volume for the x=0.38 alloy, measured by neutron diffraction and linear thermal expansion, shows a 0.3% contraction, and the volume and anisotropic magnetostrictions exhibit large anomalies at the same temperature. We attribute these anomalies to a first-order valence phase transition. Inelastic-neutron-scattering measurements on the x=0.38 alloy above the phase transition temperature ${\mathit{T}}_{\mathit{v}}$ show a quasielastic line and two crystal-field excitations at 26 and 42 meV, while below ${\mathit{T}}_{\mathit{v}}$ the quasielastic peak disappears, and a gap opens up the response, extending up to 20 meV. This type of response is characteristic of intermediate valence systems. All the measurements are consistent with a first-order valence transition, like that observed in the compound ${\mathrm{YbInCu}}_{4}$.

Thermal expansion in the pseudobinary Y(Mn1−xNix)2 intermetallics

Thermal expansion measurements have been performed in the pseudobinary series Y(Mn1−xNix)2 for x=0, 0.01, 0.025, 0.05 and 0.1 in the range of temperature of 4.2<T<300K. The substitution of Mn by Ni has a very drastic influence on the magnetic and structural properties of YMn2. For concentration higher than 5% of Ni the first order magnetic phase transition as observed in the thermal expansion of YMn2 is completely suppressed. This transition is not affected by an applied magnetic field up to 12 Tesla.

Single-ion competing magnetic anisotropies in PrxNd1-xCo5 intermetallic compounds.

Competing single-ion 4f magnetic anisotropies have been studied within a noncollinear three-sublattice mean-field crystal-electric-field model in order to explain the observed complex magnetic behavior in the pseudobinary series ${\mathrm{Pr}}_{\mathit{x}}$${\mathrm{Nd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Co}}_{5}$. The interplay of different magnetic anisotropies gives rise to a contribution in the spontaneous free energy which turns out to have a minimum for the direction of the magnetization along a non-major-symmetry direction. A comparison with the experimental data of the spin-reorientation temperature and also with the thermal evolution of the spontaneous-spin-reorientation angle has allowed the determination of a reliable set of crystalline-electric-field parameters for the ${\mathrm{Pr}}^{3+}$ and ${\mathrm{Nd}}^{3+}$ ions. A calculation of the theoretical magnetization isotherms has been undertaken using these crystalline-electric-field parameters, in order to determine the theoretical magnetic anisotropy field, which has been compared for different temperatures and concentrations with experimental results obtained from singular-point-detection measurements.

Magnetic anisotropy of the Y(Co 1-xFe x) 3 pseudobinary compounds

The anisotropy energy of the Y(Co 1 - x Fe x ) 3 compounds has been determined between 4.2 and 250 K. The concentration dependence of the anisotropy energy behaves anomalously in this pseudo-binary series. Upon increasing the iron content, the anisotropy energy increases up to x = 0.25, then decreases, changes sign around x = 0.45 and reaches a flat minimum at the iron-rich side. This anomaly can satisfactorily be explained in terms of the individual site anisotropy model by considering the different occupancy factors of iron and cobalt for the 3d sites.

Influence of Cu and Ni substitution on the Kondo compound CeAl 2

Measurements of the electrical resistivity, thermopower and of the specific heat of the pseudobinary series Ce(Al xM 1−x) 2 (M = Cu, Ni) show that due to this substitution the Kondo properties of CeAl 2 diminish continuously. Additionally the substitution suppresses the long range magnetic order while spin freezing phenomena develop.

The magneto crystalline anisotropy of Y 2(Co xFe 1− x) 17

The results of neutron diffraction studies on the preferential occupation of iron and cobalt atoms in the pseudobinary series Nd 2(Fe 1− x Co x ) 17 are used to evaluate the differences in the contribution of iron and cobalt atoms to the magnetic anisotropy of the four inequivalent crystallographic sites. With these four parameters an almost perfect fit to the experimental anisotropy data for the pseudobinary series Y 2(Fe 1− x Co x ) 17 is achieved.