Spinodal decomposition and nucleation and growth as a means to bulk nanostructured thermoelectrics: enhanced performance in Pb(1-x)Sn(x)Te-PbS

The solid-state transformation phenomena of spinodal decomposition and nucleation and growth are presented as tools to create nanostructured thermoelectric materials with very low thermal conductivity and greatly enhanced figure of merit. The systems (PbTe)(1-x)(PbS)(x) and (Pb(0.95)Sn(0.05)Te)(1-x)(PbS)(x) are not solid solutions but phase separate into PbTe-rich and PbS-rich regions to produce coherent nanoscale heterogeneities that severely depress the lattice thermal conductivity. For x > approximately 0.03 the materials are ordered on three submicrometer length scales. Transmission electron microscopy reveals both spinodal decomposition and nucleation and growth phenomena the relative magnitude of which varies with x. We show that the (Pb(0.95)Sn(0.05)Te)(1-x)(PbS)(x) system, despite its nanostructured nature, maintains a high electron mobility (>100 cm(2)/V x s at 700 K). At x approximately 0.08 the material achieves a very low room-temperature lattice thermal conductivity of approximately 0.4 W/m x K. This value is only 28% of the PbTe lattice thermal conductivity at room temperature. The inhibition of heat flow in this system is caused by nanostructure-induced acoustic impedance mismatch between the PbTe-rich and PbS-rich regions. As a result the thermoelectric properties of (Pb(0.95)Sn(0.05)Te)(1-x)(PbS)(x) at x = 0.04, 0.08, and 0.16 were found to be superior to those of PbTe by almost a factor of 2. The relative importance of the two observed modes of nanostructuring, spinodal decomposition and nucleation and growth, in suppressing the thermal conductivity was assessed in this work, and we can conclude that the latter mode seems more effective in doing so. The promise of such a system for high efficiency is highlighted by a ZT approximately 1.50 at 642 K for x approximately 0.08.     

Cubic aluminum silicides RE8Ru12Al49Si9(Al(x)Si12-x) (RE = Pr, Sm) from liquid aluminum. Empty (Si,Al)12 cuboctahedral clusters and assignment of the Al/Si distribution with neutron diffraction.

Two new quaternary aluminum silicides, RE8Ru12Al49Si9(Al(x)Si12-x) (x approximately 4; RE = Pr, Sm), have been synthesized from Sm (or Sm2O3), Pr, Ru, and Si in molten aluminum between 800 and 1000 degrees C in sealed fused silica tubes. Both compounds form black shiny crystals that are stable in air and NaOH. The Nd analog is also stable. The compounds crystallize in a new structural type. The structure, determined by single-crystal X-ray diffraction, is cubic, space group Pm3m with Z = 1, and has lattice parameters of a = 11.510(1) A for Sm8Ru12Al49Si9(Al(x)Si12-x) and a = 11.553(2) A for Pr8Ru12Al49Si9(Al(x)Si12-x) (x approximately 4). The structure consists of octahedral units of AlSi6, at the cell center, Si2Ru4Al8 clusters, at each face center, SiAl8 cubes, at the middle of the cell edges, and unique (Al,Si)12 cuboctohedral clusters, at the cell corners. These different structural units are connected to each other either by shared atoms, Al-Al bonds, or Al-Ru bonds. The rare earth metal atoms fill the space between various structural units. The Al/Si distribution was verified by single-crystal neutron diffraction studies conducted on Pr8Ru12Al49Si9(Al(x)Si12-x). Sm8Ru12Al49Si9(Al(x)Si12-x) and Pr8Ru12Al49Si9(Al(x)Si12-x) show ferromagnetic ordering at Tc approximately 10 and approximately 20 K, respectively. A charge of 3+ can be assigned to the rare earth atoms while the Ru atoms are diamagnetic.     

Structural characterization and oxidative dehydrogenation activity of V2O5/Ce(x)Zr(1-x)O2/SiO2 catalysts

The thermal stability of a nanosized Ce(x)Zr(1-x)O2 solid solution on a silica surface and the dispersion behavior of V2O5 over Ce(x)Zr(1-x)O2/SiO2 have been investigated using XRD, Raman spectroscopy, XPS, HREM, and BET surface area techniques. Oxidative dehydrogenation of ethylbenzene to styrene was performed as a test reaction to assess the usefulness of the VOx/Ce(x)Zr(1-x)O2/SiO2 catalyst. Ce(x)Zr(1-x)O2/SiO2 (1:1:2 mol ratio based on oxides) was synthesized through a soft-chemical route from ultrahigh dilute solutions by adopting a deposition coprecipitation technique. A theoretical monolayer equivalent to 10 wt % V2O5 was impregnated over the calcined Ce(x)Zr(1-x)O2/SiO2 sample (773 K) by an aqueous wet impregnation technique. The prepared V2O5/Ce(x)Zr(1-x)O2/SiO2 sample was subjected to thermal treatments from 773 to 1073 K. The XRD measurements indicate the presence of cubic Ce0.75Zr0.25O2 in the case of Ce(x)Zr(1-x)O2/SiO2, while cubic Ce0.5Zr0.5O2 and tetragonal Ce0.16Zr0.84O2 in the case of V2O5/Ce(x)Zr(1-x)O2/SiO2 when calcined at various temperatures. Dispersed vanadium oxide induces more incorporation of zirconium into the ceria lattice, thereby decreasing its lattice size and also accelerating the crystallization of Ce-Zr-O solid solutions at higher calcination temperatures. Further, it interacts selectively with the ceria portion of the composite oxide to form CeVO4. The RS measurements provide good evidence about the dispersed form of vanadium oxide and the CeVO4 compound. The HREM studies show the presence of small Ce-Zr-oxide particles of approximately 5 nm size over the surface of amorphous silica and corroborate with the results obtained from other techniques. The catalytic activity studies reveal the ability of vanadium oxide supported on Ce(x)Zr(1-x)O2/SiO2 to efficiently catalyze the ODH of ethylbenzene at normal atmospheric pressure. The remarkable ability of Ce(x)Zr(1-x)O2 to prevent the deactivation of supported vanadium oxide leading to stable activity in the time-on-stream experiments and high selectivity to styrene are other important observations.     

Structural, optical, and magnetic properties of Mn-doped ZnO thin film

The Zn(1-x)Mn(x)O (x = 0, 0.16, and 0.25) thin films were grown on fused quartz substrates by reactive magnetron cosputtering. X-ray-diffraction measurement revealed that all the films were single phase and had wurtzite structure with c-axis orientation. As Mn concentration increased in the Zn(1-x)Mn(x)O films, the c-axis lattice constant and band-gap energy increased gradually. In Raman-scattering studies, an additional Mn-related vibration mode appeared at 520 cm(-1). E(2H) phonon line of Zn(1-x)Mn(x)O alloy was broadened asymmetrically and redshifted as a result of microscopic structural disorder induced by Mn(2+) random substitution. The Zn(0.84)Mn(0.16)O film exhibited a ferromagnetic characteristic with a Curie temperature of approximately 62 K. However, with increasing Mn concentration to 25 at. %, ferromagnetism disappeared due to the enhanced antiferromagnetic superexchange interactions between neighboring Mn(2+) ions.     

Perovskite, LiNbO3, corundum, and hexagonal polymorphs of (In(1-x)M(x))MO3

LiNbO(3) (LN), corundum (cor), and hexagonal (hex) phases of (In(1-x)M(x))MO(3) (x = 0.143; M = Fe(0.5)Mn(0.5)) were prepared. Their crystal structures were investigated with synchrotron X-ray powder diffraction, and their properties were studied by differential thermal analysis, magnetic measurements, and M?ssbauer spectroscopy. The LN-phase was prepared at high pressure of 6 GPa and 1770 K; it crystallizes in space group R3c with a = 5.25054(7) ?, c = 13.96084(17) ?, and has a long-range antiferromagnetic ordering near T(N) = 270 K. The cor- and hex-phases were obtained at ambient pressure by heating the LN-phase in air up to 870 and 1220 K, respectively. The cor-phase crystallizes in space group R-3c with a = 5.25047(10) ?, c = 14.0750(2) ?, and the hex-phase in space group P6(3)/mmc with a = 3.34340(18) ?, c = 11.8734(5) ?. T(N) of the cor-phase is about 200 K, and T(N) of the hex-phase is about 140 K. During irreversible transformations of LN-(In(1-x)M(x))MO(3) with the (partial) cation ordering, the In(3+), Mn(3+), and Fe(3+) cations become completely disordered in one crystallographic site of the corundum structure, and then they are (partially) ordered again in the hex-phase. LN-(In(1-x)M(x))MO(3) exhibits a reversible transformation to a perovskite GdFeO(3)-type structure (space group Pnma; a = 5.2946(3) ?, b = 7.5339(4) ?, c = 5.0739(2) ? at 10.3 GPa) at room temperature and pressure of about 5 GPa.     

Magnetization, Mössbauer and isothermal dilatometric behavior of oxidized YBa(Co,Fe)4O(7+δ)

M?ssbauer spectroscopy and magnetization studies of YBaCo(4-x)Fe(x)O(7+δ) (x = 0-0.8) oxidized at 0.21 and 100 atm O(2), indicate an increasing role of penta-coordinated Co(3+) states when the oxygen content approaches 8-8.5 atoms per formula unit. Strong magnetic correlations are observed in YBaCo(4-x)Fe(x)O(8.5) from 2 K up to 55-70 K, whilst the average magnetic moment of Co(3+) is lower than that for δ ≤ 0.2, in correlation with the lower (57)Fe(3+) isomer shifts determined from M?ssbauer spectra. The hypothesis on dominant five-fold coordination of cobalt cations was validated by molecular dynamics modeling of YBaCo(4)O(8.5). The iron solubility limit in YBaCo(4-x)Fe(x)O(7+δ) corresponds to approximately x ≈ 0.7. The oxygen intercalation processes in YBaCo(4)O(7+δ) at 470-700 K, analyzed by X-ray diffraction, thermogravimetry and controlled-atmosphere dilatometry, lead to unusual volume expansion opposing to the cobalt cation radius variations. This behavior is associated with increasing cobalt coordination numbers and with rising local distortions and disorder in the crystal lattice on oxidation, predicted by the computer simulations. When the oxygen partial pressure increases from 4 × 10(-5) to 1 atm, the linear strain in YBaCo(4)O(7+δ) ceramics at 598 K is as high as 0.33%.     

Overall water splitting on (Ga(1-x)Zn(x))(N(1-x)O(x)) solid solution photocatalyst: relationship between physical properties and photocatalytic activity

The physical and photocatalytic properties of a novel solid solution between GaN and ZnO, (Ga(1-x)Zn(x))(N(1-x)O(x)), are investigated. Nitridation of a mixture of Ga(2)O(3) and ZnO at 1123 K for 5-30 h under NH(3) flow results in the formation of a (Ga(1-x)Zn(x))(N(1-x)O(x)) solid solution with x = 0.05-0.22. With increasing nitridation time, the zinc and oxygen concentrations decrease due to reduction of ZnO and volatilization of zinc, and the crystallinity and band gap energy of the product increase. The highest activity for overall water splitting is obtained for (Ga(1-x)Zn(x))(N(1-x)O(x)) with x = 0.12 after nitridation for 15 h. The crystallinity of the catalyst is also found to increase with increasing the ratio of ZnO to Ga(2)O(3) in the starting material, resulting in an increase in activity.     

Solubility of hydrogen in PdAg and PdAu binary alloys using density functional theory

The present work deals with the study of palladium-silver (PdAg) and palladium-gold (PdAu) binary alloys over a broad range of temperatures and alloy compositions using density functional theory (DFT) to find possible conditions where the solubility of hydrogen (H) is significantly higher than that of pure palladium (Pd). Several alloy structures, such as Pd(100-x)Ag(x) with x = 14.81, 25.93, 37.04, and 48.51, Pd(100-x)Aux with x = 14.81, 25.93, and 37.04, and Pd(100-x)Cu(x) with x = 25.93 and 48.51 were considered. The lattice constants of these structures were optimized using DFT, and relaxed structures were used for the estimation of binding energy. It was found that the solubility of H in PdAg is higher than pure Pd with a maximum at approximately 30% Ag at 456 K. Also, the solubility of PdAu alloys was higher than pure Pd with a maximum at about 20% Au with a solubility 12 times higher than that of pure Pd. It was found that for a 3.7% H concentration in a PdAg alloy, a cell expansion of 0.15-0.2% occurs, which if ignored may affect the individual binding energy of the O-site by approximately 3.56% and may affect the predicted solubility by approximately 11.8%.     

Synthesis, structure, chemical stability, and electrical properties of Nb-, Zr-, and Nb-codoped BaCeO3 perovskites

We report the effect of donor-doped perovskite-type BaCeO(3) on the chemical stability in CO(2) and boiling H(2)O and electrical transport properties in various gas atmospheres that include ambient air, N(2), H(2), and wet and dry H(2). Formation of perovskite-like BaCe(1-x)Nb(x)O(3±δ) and BaCe(0.9-x)Zr(x)Nb(0.1)O(3±δ) (x = 0.1; 0.2) was confirmed using powder X-ray diffraction (XRD) and electron diffraction (ED). The lattice constant was found to decrease with increasing Nb in BaCe(1-x)Nb(x)O(3±δ), which is consistent with Shannon's ionic radius trend. Like BaCeO(3), BaCe(1-x)Nb(x)O(3±δ) was found to be chemically unstable in 50% CO(2) at 700 °C, while Zr doping for Ce improves the structural stability of BaCe(1-x)Nb(x)O(3±δ). AC impedance spectroscopy was used to estimate electrical conductivity, and it was found to vary with the atmospheric conditions and showed mixed ionic and electronic conduction in H(2)-containing atmosphere. Arrhenius-like behavior was observed for BaCe(0.9-x)Zr(x)Nb(0.1)O(3±δ) at 400-700 °C, while Zr-free BaCe(1-x)Nb(x)O(3±δ) exhibits non-Arrhenius behavior at the same temperature range. Among the perovskite-type oxides investigated in the present work, BaCe(0.8)Zr(0.1)Nb(0.1)O(3±δ) showed the highest bulk electrical conductivity of 1.3 × 10(-3) S cm(-1) in wet H(2) at 500 °C, which is comparable to CO(2) and H(2)O unstable high-temperature Y-doped BaCeO(3) proton conductors.     

Structure and thermoelectric properties of the new quaternary bismuth selenides A(1-x)M(4-x)Bi(11+x)Se21 (A = K and Rb and Cs; M = Sn and Pb)--members of the grand homologous series Km(M6Se8)m(M(5+n)Se(9+n))

Several members of the new family A(1-x)M(4-x)Bi(11+x)Se21 (A = K, Rb, Cs; M = Sn, Pb) were prepared by direct combination of A2Se, Bi2Se3, Sn (or Pb), and Se at 800 degrees C. The single-crystal structures of K(0.54)Sn(3.54)Bi(11.46)Se21, K(1.46)Pb(3.08)Bi(11.46)Se21, Rb(0.69)Pb(3.69)Bi(11.31)Se21, and Cs(0.65)Pb(3.65)Bi(11.35)Se21 were determined. The compounds A(1-x)M(4-x)Bi(11+x) Se21 crystallize in a new structure type with the monoclinic space group C2/m, in which building units of the Bi2Te3 and NaCl structure type join to give rise to a novel kind of three-dimensional anionic framework with alkali-ion-filled tunnels. The building units are assembled from distorted, edge-sharing (Bi,Sn)Se6 octahedra. Bi and Sn/Pb atoms are disordered over the metal sites of the chalcogenide network, while the alkali site is not fully occupied. A grand homologous series Km(M6Se8)m(M(5+n)Se(9+n)) has been identified of which the compounds A(1-x)M(4-x)Bi(11+x)Se21 are members. We discuss here the crystal structure, charge-transport properties, and very low thermal conductivity of A(1-x)M(4-x)Bi(11+x)Se21.     

Dependence of electron transfer among alpha cages on the chemical compositions of zeolite LTAs including K clusters

K atoms are loaded in diluted amount into K-form LTA zeolites whose framework compositions are Al(x)Si(24-x)O(48) (6相似文献   

La4Cu(3-x)Zn(x)MoO12: zinc-doped cuprates with Kagomé lattices

Two solid solutions, La4Cu(3-x)Zn(x)MoO12 (0.05 < or = x < or = 0.20, SS1) and La4Cu(3-x)Zn(x)MoO12 (0.30 < or = x < or = 2.40, SS2), were synthesized at ambient pressure and at temperatures from 1025 to 1200 degrees C by traditional solid-state reactions. Their structures were determined from X-ray powder diffraction with the help of electron and neutron diffraction. The atomic arrangements of SS1 and SS2 are similar, but their space groups are different, Pmnm for SS1 and P-1 for SS2, respectively. The copper, zinc, and molybdenum are coordinated by oxygen in corner-sharing trigonal bipyramids that are sandwiched between layers of lanthanum cations. In the transition metal cations layer of SS2, the copper and zinc cations order into a Kagomé-like lattice of triangular clusters. The magnetism has been measured from 2 to 300 K and is highly influenced by the geometric arrangement of the Cu(II) and Zn(II) cations. The number of free electrons per three Cu atoms is close to one for all samples in SS1 and SS2 indicating that the system can be well expressed by independent Cu(II)3 clusters. Spontaneous magnetization was observed in the system.     

对二甲苯＋环己烷及对二甲苯＋二甲基亚砜的固液相平衡和过量吉布斯自由能

测定了对二甲苯＋环己烷及对二甲苯＋二甲基亚砜体系（均为简单低共熔混合物）的固液平衡相图，计算出它们在３１３．１５Ｋ的过量吉布斯自由能。结果表明两体系对理想溶液均产生正偏差。     

Thermal Properties of K（Y1-xYbx）（WO4）2（x=0.098,0.196,0.294） Crystal

Thermal properties of pure KY(WO4)2 and K(Y1-xYbx)(WO4)2(x=0.098,0.196,0.294) crystals were investigated.The specific heat and thermal diffusivity of crystals were calculated at a range of 50～300 ℃.The calculated result shows that the specific heat and thermal diffusivity of K(Y1-xYbx)(WO4)2(x=0.098,0.196,0.294) crystals were slightly affected by the Yb3+ concentration.The thermal expansion coefficient of K(Y0.804Yb0.196)(WO4)2 crystals along x,y and z axes were determined to be 13.51,4.474 and 16.60×10-6 K-1,respectively.These results suggest the K(Y1-xYbx)(WO4)2(x=0.098,0.196,0.294) crystal as a laser crystal of low-middle power.     

Photoluminescence and Raman scattering from catalytically grown Zn(x)Cd(1-x)Se alloy nanowires

Zn(x)Cd(1-x)Se alloy nanowires, with composition x = 0, 0.2, 0.5, 0.7, and 1, have been successfully synthesized by a chemical vapor deposition (CVD) method assisted with laser ablation. The as-synthesized alloy nanowires, 60-150 nm in diameter and several tens of micrometers in length, complied with a typical vapor-liquid-solid (VLS) growth mechanism. The Zn(x)Cd(1-x)Se nanowires are single crystalline revealed from high-resolution transmission electron microscopic (HRTEM) images, selected area electron diffraction (SAED) patterns, and X-ray diffraction (XRD) measurement. Compositions of the alloy nanowires can be adjusted by varying the precursor ratios of the laser ablated target and the CVD deposition temperature. Crystalline structures of the Zn(x)Cd(1-x)Se nanowires are hexagonal wurtzite at x = 0, 0.2, and 0.5 with the [0 1 -1 0] growth direction and zinc blende at x = 0.7 and 1 with the [1 -1 1] growth direction. Energy gaps of the Zn(x)Cd(1-x)Se nanowires, determined from micro-photoluminescence (PL) measurements, change nonlinearly as a quadratic function of x with a bowing parameter of approximately 0.45 eV. Strong PL from the Zn(x)Cd(1-x)Se nanowires can be tuned from red (712 nm) to blue (463 nm) with x varying from 0 to 1 and has demonstrated that the alloy nanowires have potential applications in optical and sensory nanotechnology. Micro-Raman shifts of the longitudinal optical (LO) phonon mode observed in the Zn(x)Cd(1-x)Se nanowires show a one-mode behavior pattern following the prediction of a modified random element isodisplacement (MREI) model.     

混合溶剂中混合电解质活度系数的研究——HCl+NaCl+PrOH+H2O体系, 298.15 K

This paper reports our studies on HCl+NaCl+PrOH+H_2O system by mesns of emf measurements of the cell without liquid junction as type (A) Pt, H_2 (latm) |HCI (m_A), NaCl (m_B), PrOH(x), H_2O(1-x)| AgCl-Ag (A) at constant total ionic strengths I=0.1, 0.5, 1.0, 2.0 and 3.0 mol kg~(-1), at 298.15 K, where m_A and m_B are the molalities of HCl and NaCl, respectively, x is the molar fraction of PrOH in mixed solvents, x=0.05. The results show that HCI approximately follows Harned's Rule from I=0.1 to 3.0 mole kg~(-1)...     

Structural evolution and properties of solid solutions of hexagonal InMnO3 and InGaO3

Solid solutions InMn(1-x)Ga(x)O(3) (0 ≤ x ≤ 1) have been investigated using magnetic, dielectric, specific heat, differential scanning calorimetry (DSC), and high-temperature powder synchrotron X-ray diffraction (HT-SXRD) measurements. It was found that samples with 0.5 ≤ x ≤ 1 crystallize in space group P6(3)/mmc with a ~ 3.32 ? and c ~ 11.9 ?, and samples with 0.0 ≤ x ≤ 0.4 crystallize in space group P6(3)cm with a ~ 5.8 ? and c ~ 11.6 ? at room temperature. HT-SXRD data revealed the existence of a P6(3)cm-to-P6(3)/mmc phase transition at about 480 K in InMn(0.6)Ga(0.4)O(3) and at 950 K in InMn(0.7)Ga(0.3)O(3). However, no dielectric, phonon, second-harmonic-generation, or DSC anomalies were found to be associated with these phase transitions. The phase transition should be improper ferroelectric from the symmetry point of view, but the above-mentioned experimental facts, together with the absence of ferroelectric hysteresis loops, revealed no evidence for ferroelectricity in the low-temperature P6(3)cm structure. We suggest that InMn(1-x)Ga(x)O(3) corresponds to a nonferroelectric phase of hexagonal RMnO(3) with P6(3)cm symmetry. The antiferromagnetic phase-transition temperature decreases from 118 K for x = 0 to 105 K for x = 0.1 and 73 K for x = 0.2, and no long-range magnetic ordering could be found for x ≥ 0.3. Specific heat anomalies associated with short-range magnetic ordering were observed for 0.0 ≤ x ≤ 0.5. InMn(1-x)Ga(x)O(3) with small Mn contents (0.8 ≤ x ≤ 0.98) has a bright-blue color.     

Low-spin→high-spin relaxation dynamics in the highly diluted spin-crossover system [Fe(x)Zn(1-x)(bbtr)3](ClO4)2

Whereas the neat polymeric iron(II) compound [Fe(bbtr)(3)](ClO(4))(2), bbtr = 1,4-di(1,2,3-triazol-1-yl)butane, shows a quantitative spin transition triggered by a crystallographic phase transition centered at 107 K with a 13 K wide hysteresis, the iron(II) complexes in the diluted mixed crystals [Fe(x)Zn(1-x)(bbtr)(3)](ClO(4))(2), x = 0.02 and 0.1, stay predominantly in the (5)T(2) high-spin state down to cryogenic temperatures. However, the (1)A(1) low-spin state can be populated as metastable state via irradiation into the spin-allowed (5)T(2)→(5)E ligand-field transition of the high-spin species in the near-infrared. The quantum efficiency of the light-induced conversion is approximately 10% at low temperatures and decreases rapidly above 160 K. The lifetime of the light-induced low-spin state decreases from 15 days at 40 K to 30 ns at 220 K, that is, by 14 orders of magnitude. In the high-temperature regime the activation energy for the low-spin→high-spin relaxation is 1840(20) cm(-1).     

Molecular alloy with diluted magnetic moments-molecular Kondo system

[Ni(1-x)Cu(x)(tmdt)(2)] (tmdt = trimethylenetetrathiafulvalenedithiolate) was prepared for realizing molecular Kondo systems. Magnetic moments (S = (1)/(2)) are considered to exist at the central {CuS(4)} parts of Cu(tmdt)(2) molecules. The χT-versus-T curve of the system with x ≈ 0.15 showed a broad peak at ~10 K. The decrease in the χT value below 10 K is consistent with a singlet ground state, as expected for a Kondo system. However, in the system with x ≈ 0.27, the χT value decreased when the temperature was lowered to 2 K, indicating antiferromagnetic interactions between magnetic moments through π-d interactions. Although the susceptibility anomaly suggested that the π-d interactions become important at T < 20 K, the observed resistivity (ρ(obs)) showed no resistivity minimum characteristic of a Kondo system down to 4.2 K. However, the differential resistivity Δρ(T) = ρ(obs) - ρ(L)(T) showed a logarithmic resistivity increase at 8-20 K with decreasing temperature, where ρ(L)(T) is a fitted function of ρ(obs) obtained at T > 50 K that is considered to represent approximately the temperature dependence of the resistivity without spin scattering of the conduction electrons.     

Imaging water dissociation on TiO2(110): Evidence for inequivalent geminate OH groups

Identical regions of partially reduced TiO2(110) surfaces with bridge-bonded oxygen vacancy (BBO(V)) concentrations of approximately 10% ML (1 ML = 5.2 x 10(14) cm(-2)) were imaged using scanning tunneling microscopy (STM) before and after dosing H2O at ambient temperature (approximately 300 K). Atomically resolved images confirm that H2O adsorbs dissociatively on the BBO(V) sites, producing two hydroxyl species, one positioned at BBO(V) and denoted OH(V) and the other, denoted OH(B), formed by protonation at either of the two nearest-neighbor bridge-bonded oxygen atoms. Hydrogen hopping along the [001] direction is observed at ambient temperature, with a strong preference for OH(B) (approximately 10x) hydrogen motion. This powerful imbalance demonstrates the inequality of OH(V) and OH(B) and suggests differences in their charge and/or binding configuration.