Sc Substitution Research Articles

Non-magnetic impurity effect on suppression of Tc and gap evolution in the two-gap superconductor Lu2Fe3Si5

We report the suppression of Tc and the evolution of amplitudes of the two gaps with the introduction of non-magnetic impurities in a two-gap superconductor Lu2Fe3Si5. While Tc rapidly decreases by a small amount of substitution of Sc for Lu, the suppression of Tc is more than ten times slower than that expected from the Abrikosov–Gor’kov equation describing the reduction of Tc in a superconductor with sign reversal in the gap function. The evolution of two distinct gaps by the introduction of non-magnetic impurities does not show merging the amplitude of two gaps, which is strikingly different from the typical two-gap superconductor MgB2.

Effects of substitution on low-temperature physical properties of LuFe2Ge2

The low-temperature magnetic phase transition in LuFe2Ge2 is thought to be associated with itinerant magnetism. The effects of Y and Sc substitutions on the Lu site, as well as Ru and Co substitutions on the Fe site, on the low-temperature magnetic phase transition of the LuFe2Ge2 compound have been studied in single crystals via microscopic, thermodynamic and transport measurements. On one hand, Co substitution suppresses the transition below our base temperature of 2 K even at our lowest substitution level. On the other hand, Sc substitution enhances the transition temperature, and Y or Ru substitution suppresses the transition to lower temperature. Phase diagrams for Y, Sc and Ru substitutions have been constructed and the possibility of a unifying, composite diagram is discussed.

Thermoelectric properties and electronic structure of substituted Heusler compounds: NiTi0.3−xScxZr0.35Hf0.35Sn

The effect of Ti substitution by Sc on the thermoelectric properties of the Heusler compounds NiTi0.3−xScxZr0.35Hf0.35Sn (where 0<x≤0.05) was studied. The thermoelectric properties were investigated by measuring the electrical conductivity, Seebeck coefficient, and thermal conductivity. A reduction of the thermal conductivity by a factor of 2 was obtained by substitution of Ti by Sc. The pure compound NiTi0.3Zr0.35Hf0.35Sn showed n-type conductivity with a Seebeck coefficient of −288 μV/K at 350 K, while under Sc substitution the system switched to p-type behavior. A maximum Seebeck coefficient of +230 μV/K (350 K) was obtained by 4% Sc substitution, which is the highest value for p-type thermoelectric compounds based on Heusler alloys. The electronic structure was studied by photoelectron spectroscopy excited by hard x-ray synchrotron radiation. Massive in gap states are observed for the parent compound. This proves that the electronic states close to the Fermi energy play a key role on the behavior of the transport properties. Especially, they are responsible for the high, negative Seebeck coefficient of the parent compound.

Multiferroic properties and temperature-dependent leakage mechanism of Sc-substituted bismuth ferrite–lead titanate thin films

Bi(Fe 0.5 Sc 0.5 )O 3 –PbTiO 3 (BSFPT) films have been fabricated on Pt/TiO 2 /SiO 2 /Si substrates by pulsed laser deposition. The microstructure, chemical state, ferroelectric and magnetic properties were investigated. The leakage mechanism of the BSFPT thin film showed bulk limited, space charge limited current characteristics from 200 to 220 K, whereas bulk limited Poole–Frenkel emission and interface limited Fowler–Nordheim tunneling coexisted at temperatures between 250 and 300 K. The substitution of Sc 3+ for Fe 3+ ions was considered to improve the valence stability and, therefore, decrease the overall leakage current.

ELECTRONIC AND THERMOELECTRIC PROPERTIES OF PURE AND ALLOYS In2O3 TRANSPARENT CONDUCTORS

Electronic and thermoelectric properties of pure In 2 O 3 and In 1.5 T 0.5 O 3 ( T = Sc , Y ) alloys including the band gap, the electrical and thermal conductivity, Seebeck coefficient and figure of merit have been investigated using semi-classical Boltzmann transport theory. The calculated results indicated that substituting indium atoms by these dopants have a significant influence on the electronic properties of alloyed In 2 O 3 crystals. Substitution of Sc and Y atoms for In atoms increases the band gaps and Seebeck coefficient. The intrinsic relations between electronic structures and the transport performances of In 2 O 3 and its alloys with Sc and Y are also discussed.

Electronic transport properties of electron- and hole-doped semiconductingC1bHeusler compounds:NiTi1−xMxSn(M=Sc,V)

The substitutional series of Heusler compounds ${\text{NiTi}}_{1\ensuremath{-}x}{M}_{x}\text{Sn}$ (where $M=\text{Sc},\text{V}$ and $0lx\ensuremath{\le}0.2$) were synthesized and investigated with respect to their electronic structure and transport properties. The results show the possibility to create $n$-type and $p$-type thermoelectrics within one Heusler compound. The electronic structure and transport properties were calculated by all-electron ab initio methods and compared to the measurements. Hard x-ray photoelectron spectroscopy was carried out and the results are compared to the calculated electronic structure. Pure NiTiSn exhibits massive ``in gap'' states containing about 0.1 electrons per cell. The comparison of calculations, x-ray diffraction, and photoemission reveals that Ti atoms swapped into the vacant site are responsible for these states. The carrier concentration and temperature dependence of electrical conductivity, Seebeck coefficient, and thermal conductivity were investigated in the range from 10 to 300 K. The experimentally determined electronic structure and transport measurements agree well with the calculations. The sign of the Seebeck coefficient changes from negative for V to positive for Sc substitution. The high $n$-type and low $p$-type power factors are explained by differences in the chemical-disorder scattering-induced electric resistivity. Major differences appear because $p$-type doping (Sc) creates holes in the triply degenerate valence band at $\ensuremath{\Gamma}$ whereas $n$-type doping (V) fills electrons in the single conduction band above the indirect gap at $X$ what is typical for all semiconducting transition-metal-based Heusler compounds with $C{1}_{b}$ structure.

Structural effects of Sc doping on the multiferroicTbMnO3

The new ${\text{TbMn}}_{1\ensuremath{-}\text{x}}{\text{Sc}}_{\text{x}}{\text{O}}_{3}$ series has been synthesized and the structural properties have been characterized by x-ray diffraction, neutron diffraction, and x-ray absorption spectroscopy. The whole series belongs to the family of $AB{\text{O}}_{3}$ perovskites. All of the samples are isostructural to the parent compound ${\text{TbMnO}}_{3}$, crystallizing in an orthorhombic cell with space-group $Pbnm$ symmetry. The homovalent substitution of ${\text{Mn}}^{3+}$ with the larger ${\text{Sc}}^{3+}$ ion leads to an increase in both the unit-cell volume and the $B{\text{O}}_{6}$ octahedra tilting. The analysis of neutron and x-ray diffraction patterns suggest a continuous evolution from a Jahn-Teller distorted $B{\text{O}}_{6}$ octahedron in ${\text{TbMnO}}_{3}$ into a nearly regular one in ${\text{TbScO}}_{3}$. However, x-ray absorption measurements at the $\text{Mn}\text{ }K$ edge reveal that the local geometry around the ${\text{Mn}}^{3+}$ cation remains distorted in the series even for high values of $x$. This result is in opposition to previous findings in similar compounds such as ${\text{LaMn}}_{1\ensuremath{-}\text{x}}{(\text{Ga}/\text{Sc})}_{\text{x}}{\text{O}}_{3}$ and suggests that the strong orthorhombic distortion of the unit cell due to the small ${\text{Tb}}^{3+}$ cation size favors the stability of the distorted ${\text{MnO}}_{6}$ octahedron in diluted systems. Long-range magnetic ordering is not found for $x\ensuremath{\ge}0.3$ samples and there is not sign of ferromagnetism for $x=0.5$ in opposite to the behavior observed in the La-based compounds. Since Sc substitution induces a minor perturbation on the local structure of the Mn sublattice but magnetic ordering of both Mn and Tb sublattices disappear for a small degree of substitution, we conclude that the involved magnetic interactions should have a strong directional anisotropy and the Tb magnetic ordering strongly depends on the existence of a long-range coherent Mn ordering.

Surface and impedance spectroscopy studies of Li2.8Sc1.8−yYyZr0.2(PO4)3 (where y=0, 0.1) solid electrolyte ceramics

Abstract The solid electrolyte Li2.8Sc1.8−yYyZr0.2(PO4)3 (where y = 0, 0.1) compounds were synthesized by a solid state reaction and studied by X-ray diffraction. At room temperature the compounds belong to orthorhombic symmetry (space group Pbcn) with four formula units in the unit cell. Elemental compositions and binding energies of Zr 3d, Sc 2p, Y 3d, P 2p, O 1s, and Li 1s core level at Li2.8Sc1.8Zr0.2(PO4)3 and Li2.8Sc1.7Y0.1Zr0.2(PO4)3 ceramics’ surfaces have been determined by XPS. Impedance spectroscopy of the ceramics has been performed in the frequency range 10–3 × 109 Hz in the temperature interval 300–600 K. The substitution of Sc by Zr and Y in the host compound Li3Sc2(PO4)3 leads to the increase of ionic conductivity of the new ceramics.

Multiferroic properties of Bi(Fe0.5Sc0.5)O3–PbTiO3 thin films

Bi(Fe0.5Sc0.5)O3–PbTiO3 (BSF-PT) thin films were grown on LaNiO3/Si and Pt/TiO2/SiO2/Si substrates by pulsed laser deposition. The structure–microstructure–property relations of the films were the investigated using x-ray diffraction and scanning electron microscopy in conjunction with ferroelectric and magnetic measurements. BSF–PT films grown on Pt/TiO2/SiO2/Si substrates show a remnant polarization, Pr>40 μC cm−2, and a coercive field, Ec=1000 kV cm–1. In contrast, films grown under the same deposition conditions on LaNiO3/Si substrates have Pr=20 μC cm−2 and Ec=200 kV cm−2. Moreover, the leakage current density of the film on Pt is reduced by two orders of magnitude from 2×10−4 to 1×10−6 A cm−2. A commensurate improvement in ferromagnetic properties is also observed. Overall, the substitution of Sc for Fe improves the ferroelectric switching behavior and properties and enhances the magnetic moment with respect to BiFeO3–PbTiO3.

Impurity effects in two-gap superconductor Lu2Fe3Si5

Nonmagnetic-impurity effect is studies in a canonical two-gap superconductor Lu2Fe3Si5 by means of specific heat measurements. In contrast to the case of single-band s-wave superconductor, only 2% substitution of nonmagnetic Sc for Lu resulted in 30% reduction of Tc in agreement with previous studies on polycrystalline samples. Two-gap fit to the specific heat data shows that both the large and small gaps are suppressed in contrast to a theoretical prediction where the small gap is enhanced with the expense of suppression of the large gap.

Non-magnetic impurity effect in two-gap superconductor Lu 2Fe 3Si 5

We report detailed study of non-magnetic impurity effects in a two-gap superconductor Lu 2Fe 3Si 5 by replacing Lu with Sc. We find that the superconducting transition temperature T c is drastically suppressed by slight substitution of Sc, while lattice constants change linearly with the substitution. These results strongly indicate that a slight substitution of Sc increases the inter-band scattering and causes averaging the amplitude of two gaps, which leads to the drastic suppression of T c.

Investigation on scandium-doped manganate La 0.8Sr 0.2Mn 1− xSc xO 3− δ cathode for intermediate temperaturesolid oxide fuel cells

Scandium-doped lanthanum strontium manganate La 0.8Sr 0.2Mn 1− x Sc x O 3− δ (LSMS) combined with YSZ as composite cathode for anode-supported solid oxide fuel cell is investigated. The LSMS powders are prepared using the modified Pechini method. The XRD and H 2-TPR results reveal that non-stoichiometric defects are introduced into the perovskite lattice of LSMS samples as a result of Sc substitution, which leads to increased oxygen ion mobility in the Sc containing samples. But high level doping of Sc may results in the segregation of the Sc 2O 3 secondary phase at elevated temperature. The cells with the LSMS-containing cathodes exhibit higher performances, especially at lower temperatures, which can be ascribed to the increased oxygen anionic vacancies in the LSMS.

Effect of Sc Substitution for Al on the Optical Properties of Transparent Ce:YSAG Ceramics

Transparent Ce:YAG (Ce:Y3Al5O12) and Ce:YSAG (Ce:Y3ScxAl5−xO12) ceramics have been successfully fabricated using Sc3+ to substitute for Al3+ in Ce:YAG. The effect of Sc substitution on the luminescent properties of Ce:YAG has been investigated. At the substitution level of 20 at.% of Sc3+ for Al3+, the emission intensity of Ce:YSAG is the highest. Meanwhile, the doping of Sc into Ce:YAG lattice broadened both the absorption and emission bands, which is believed to be due to the inhomogeneous broadening of the 5d energy level of Ce3+ caused by the Sc3+ substitution.

Effect of Sc substitution on the structure, electrical, and magnetic properties of multiferroic BiFeO 3 thin films grown by a sol–gel process

Multiferroic BiFeO 3 (BFO), Bi 1− x Sc x FeO 3 (BSF), and BiFe 1− x Sc x O 3 (BFS) ( x=0.3 mol%) thin films are prepared on Pt/Ti/SiO 2/Si substrates using a sol–gel technique. The effect of Sc substitution along with the annealing ambient (N 2 and O 2) on the structure, electrical, and magnetic properties of the films are reported. X-ray diffraction (XRD) analysis reveals that the films can be prepared with the single-phase perovskite structure by annealing at 700 °C for 10 min either in O 2 or N 2 ambient. The unit cell volume increases on the substitution of Sc, which are 61.39, 62.50, and 62.57 (Å) 3 for BFO, BSF, and BFS, respectively. X-ray photoelectron spectroscopy (XPS) study reveals that the chemical environments of Bi and Fe are different in BFO, BSF, BFS films. Similarly, XPS spectra for Sc2p lines in BSF and BFS also have different peak positions; this indicates Sc doping has certain chemical impact on BSF and BFS films. Systematic studies of Sc substitution along with the effect of annealing ambient on the dielectric constant ( ε) and dielectric loss (tan δ), leakage current, remnant polarization ( P r), coercive field ( E c), and magnetic properties of the films are carried out. The room temperature values of ε and tan δ at 1 kHz for BFO and BFS films annealed in N 2 ambient are (∼208; 0.035) and (∼235; 0.023), respectively. The comparative value of leakage current for the BFO and BFS films at an applied field strength of 50 kV/cm are 2.997×10 −4 and 1.87×10 −5 A/cm 2, respectively. Room temperature value of coercive magnetization for BFS films has one order small compared to that of the BFO films; this indicates BFS films are magnetically soft and more suitable for potential device applications. Finally, among the studied compositions, the BFS films annealed in N 2 ambient show the best property.

Large-scale chemical synthesis of shape and size controlled BaFe12−xScxO19 platelets for in-plane oriented thick screen printed films

Scandium (Sc) doped, single phase BaFe12−xScxO19 (x=0.3 and 0.8) were prepared at large scale (10g) by a modified chemical coprecipitation technique. The scanning electron micrograph analysis shows the formation of nearly uniform hexagonal platelets with an average size of <1μm. The sizes of the platelets were controlled by sintering temperature. The screen printed, in-plane oriented films were annealed at different temperatures to produce a dense and thick ferrite film. The hysteresis loops for x=0.3 show a squareness ratio of 0.9 and the saturation magnetic moment of 3700G and the coercivity of 250Oe. The saturation magnetic moment was decreased with increase of Sc substitution. Ferromagnetic resonance measurements exhibited a peak-to-peak derivative linewidth (ΔH) of ∼800Oe at 34GHz for x=0.3 and at 37GHz for the x=0.8 film. The Lande spectroscopic splitting factor (g) value for the screen printed films was found to be 1.92 for x=0.3 and 2.01 for x=0.8.

Effects on transition temperature and Raman spectra of substitution of Cr and Al for Mg in MgB2

AbstractMg1−x Mx B2 (M = Cr, Al) polycrystalline bulk samples with 0 ≤ x ≤ 5% have been synthesized by a solid state reaction and studied by X‐ray diffraction, SEM and Raman spectroscopy. By comparing with the results of Sc‐substituted MgB2, it is found that all these atomic substitutions for Mg depress Tc, and Cr and Sc substitutions depress Tc even more quickly than the one of Al doping. It is suggested that the Tc changes of the M‐substituted MgB2 can be understood by the competing/cooperating effects of the hole‐filling and the disorder. The Raman peak linewidth decreases for Al‐substituted MgB2, which represents an opposite trend to the linewidth change of Mg1−x Crx B2 and shows an evidence of the disorder caused by the atomic substitution and the different arrangement of the substituted atoms in the lattice. Meanwhile, different frequency changes of the Raman peak for the Cr‐ and Al‐substitute MgB2 are discovered and understood by the competing/cooperating effects of the electron‐phonon coupling, the grain size, and the lattice contraction. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of Isovalent Substitution in the Manganese Sublattice on Magnetic, Thermal, and Structural Properties of BiMnO3: BiMn1-xMxO3 (M = Al, Sc, Cr, Fe, Ga; 0 ≤ x ≤ 0.2)

Solid solutions BiMn1-xMxO3 with M=Al, Sc, Cr, Fe, and Ga and 0<or=x<or=0.2 were prepared at a high pressure of 6 GPa and 1333-1453 K, and their magnetic, thermal, and structural properties were investigated. The orbital-ordered monoclinic phase of BiMnO3 (phase I) is destroyed by a small percentage of substitution. The M elements can be classified by their ability to destroy phase I in the sequence Ga (x approximately 0.08) approximately Fe (x approximately 0.08)<Cr (x approximately 0.04) approximately Al (x approximately 0.04)<Sc (x approximately 0.02), where phase I is most stable for Ga substitution (up to x approximately 0.08) and less stable for Sc substitution (up to x approximately 0.02). The orbital-disordered high-temperature monoclinic phase of BiMnO3 (phase II) is stabilized with larger x. In all cases, a compositional range was found where phases I and II coexist at room temperature. In phase I, the effect of substitution on the ferromagnetic transition temperature is weak (e.g., TC=102 K for BiMnO3 and TC=99 K for BiMn0.95Ga0.05O3), but there is a drastic effect on the orbital ordering temperature (e.g., TOO=474 K for BiMnO3 and TOO=412 K for BiMn0.95Ga0.05O3). Magnetic susceptibilities of phase I are typical for ferromagnets while, in phase II, ferromagnetic cluster-glass-like behavior is observed. The magnetic transition temperature of phase II (e.g., TC=70 K for BiMn0.8Ga0.2O3) exhibits a sudden drop compared with that of phase I. The effect of substitution on the structural monoclinic-to-orthorhombic transition is different depending on M (e.g., Tstr=768 K for BiMnO3, Tstr=800 K for BiMn0.95Ga0.05O3, and Tstr=738 K for BiMn0.85Cr0.15O3).

The loss of anisotropy in MgB2 with Sc substitution and its relation with the critical temperature

The electrical conductivity anisotropy of theσ-bands iscalculated for the (Mg,Sc)B2 system using a virtual crystal model. Our results reveal thatthe anisotropy drops with relatively little scandium content(<30%); this behaviour coincides with the lowering ofTc and the reduction of the Kohn anomaly. This anisotropy loss is also found in the Al and Cdoped systems. In this work it is argued that the anisotropy, or 2D-character, of theσ-bands is an important parameter for the understanding of the highTc foundin MgB2.

The influence of Sc substitution on some physical properties of ScxHo1–xNi2 solid solutions

AbstractResults of X‐ray diffraction analysis, magnetization measurements, magnetic susceptibility, electrical resistivity, and heat capacity performed on polycrystalline ScxHo1–xNi2 (0 ≤ x ≤ 1) solid solutions are reported. It was found that they crystallize with the formation of the C15 type Laves‐phase superstructure. At low temperatures (below 20 K), the ScxHo1–xNi2 solid solutions with 0 ≤ x ≤ 0.6 are ferromagnets. At higher temperatures, all solid solutions are Curie–Weiss paramagnets. Temperature dependences of the electrical resistivity exhibit the typical behaviour of metals. The heat capacity measurements allowed us to determine the Debye temperature. The magnetocaloric effect was estimated from measurements performed in a low magnetic field of 0.42 T. (© 2005 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Chemical Pressure Effect for the SDW Phase in Heavy Fermion Ce(Ru0.85Rh0.15)2Si2Compound

Susceptibility measurements have been performed on polycrystalline samples Ce 1- y R y (Ru 0.85 Rh 0.15 ) 2 Si 2 ( R = Sc, La) in order to clarify the chemical pressure effect for the SDW in the heavy fermion Ce(Ru 0.85 Rh 0.15 ) 2 Si 2 . Lattice parameters a and c both decrease with increasing Sc concentration and increase with increasing La concentration. For Ce 1- y Sc y (Ru 0.85 Rh 0.15 ) 2 Si 2 system, the Néel temperature T N decreases with increasing Sc concentration and disappears for y ≥0.2. We observed the Curie–Weiss law in the susceptibility at high temperature and a tendency of the saturation in the low temperature susceptibility. The tendency of the saturation and the Weiss temperature Θ determined from the high temperature susceptibility increase with increasing Sc concentration. These facts can be explained through the increase of the c – f hybridization and itinerancy of the f electron. For Ce 1- y La y (Ru 0.85 Rh 0.15 ) 2 Si 2 system, the T N slightly decreases with increasing La concentration and the tendency of the saturation becomes weaker with increasing y and is no more observed down to T N for y > 0.15. The Θ rapidly decreases with increasing La concentration and becomes almost zero for y > 0.15. These facts suggest that the c – f hybridization becomes weak with increasing y and that the itinerant AF phase for y < 0.15 is replaced by the AF phase with the localized moment for y > 0.15. The Kondo temperature T K estimated from Θ is scaled by a single proportional function of the lattice parameter c in both cases for the Sc and La substitution.