Magnetic and Electronic Properties of Nitrogen-Doped Lanthanum Sesquioxide La<Subscript>2</Subscript>O<Subscript>3</Subscript> as Predicted from First Principles

Using the ab initio FLAPW-GGA method, we examine the electronic and magnetic properties of nitrogen-doped non-magnetic sesquioxide La₂O₃ emphasizing the role of doping sites in the occurrence of d ⁰-magnetism. We predict the magnetization of La₂O₃ induced by nitrogen impurity in both octahedral and tetrahedral sites of the oxygen sublattice. The most interesting results are that (i) the total magnetic moments (about 1 μ _B per supercells) are independent of the doping site, whereas (ii) the electronic spectra of these systems differ drastically: La₂O₃:N with six-fold coordinated nitrogen behaves as a narrow-band-gap magnetic semiconductor, whereas with four-fold coordinated nitrogen is predicted to be a magnetic half-metal. This effect is explained taking into account the differences in N-2p_z^{ˉ -}2p_{z}^{\downarrow \uparrow} versus N-2p_x,y^{ˉ -}2p_{x,y}^{\downarrow \uparrow} orbital splitting for various doping sites. Thus, the type of the doping site is one of the essential factors for designing of new d ⁰-magnetic materials with promising properties.     

High-field ESR on Light-Induced Transition of Spin Multiplicity in FeCo Complex

Cyanide-bridged Fe-Co complex [Fe(Tp)(CN)₃]₂Co(bpe)?5H₂O (1?5H₂O; Tp = hydro-tris(pyrazolyl)borate; bpe = 1,2-bis(4-pyridyl)ethane) shows temperature- and light- induced metal-to-metal charge transfer (MMCT) involving spin state changes between magnetic $\mathrm{Fe}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{HS}}$ (HS = high spin, LS = low spin) state and nonmagnetic $\mathrm{Fe}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}$ state, while the dehydrated material 1 does not show any MMCT and holds $\mathrm{Fe}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{HS}}$ state. We have investigated the magnetic properties of each spin state in 1 and 1?5H₂O by means of magnetization and ESR measurement under pulsed high magnetic field. At low temperature below T _N, in both 1 and 1?5H₂O, the saturation magnetization in the induced ferromagnetic phase is well explained by S and g values derived from the magnetic susceptibility study. In the ESR of 1, we observed characteristic modes corresponding to a spin excitation in the induced ferromagnetic phase where its temperature dependence shows an evolution of spin correlation in the $\mathrm{Fe}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{HS}}$ state at low temperature. We further found that the similar ESR modes grow in the light-induced state of 1?5H₂O. The results strongly suggest that the light-induced magnetization in 1?5H₂O is driven by a light-induced MMCT, which involves transition of spin multiplicity from the nonmagnetic $\mathrm{Fe}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}$ to the magnetic $\mathrm{Fe}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{II}}_{\phantom{\mathrm{\mathrm{II}}}\mathrm{HS}}$ pair.     

Characterization of Pb-doped Sr-Ferrites at Room Temperature

We report the magnetic characteristics of Pb-doped Sr-ferrites at room temperature. The polycrystalline samples of the series Sr_0.5Pb_0.5^{2 +} Fe_{12 - x}Pb_x^{3 +} O₁₉\mathrm{Sr}_{0.5}\mathrm{Pb}_{0.5}^{2 +} \mathrm{Fe}_{12 - x}\mathrm{Pb}_{x}^{3 +} \mathrm{O}_{19} (x=0, 0.2, 0.4, 0.6, 0.8, 1.0) have been prepared by the standard ceramic technique with the aim to study the magnetic properties including coercivity, remanence, and energy at room temperature. The measurements show decreasing trends in coercivity and remanence from 4682 Oe to 1783 Oe and from 1833 G to 1511 G for the sample with x-content of 0.0 to 1.0, respectively. A minute addition of Pb affects the behavior of the materials by decreasing its energy product.     

Thermal impurity reactions and structural changes in slightly carbonated hydroxyapatite

Lattice and surface impurity reactions and structural changes induced by them in slightly carbonated hydroxyapatite (SCHA) treated at 25–1100oC were comprehensively studied. The SCHA was processed by a conventional wet synthesis at a high possible temperature (96oC) using ammonium containing parent reagents. IR-spectroscopy, XRD, TG-DTA technique and mass spectrometric thermal analysis (MSTA) were employed for characterization of the samples. with in cationic- and (A- and B-positions) with in anionic sites, and H₂O, () , N _x H _y on the surface of particles were found and considered as impurity groups. Complicated changes in lattice constants of the SCHA stepwise annealed in air (for 2 h) were revealed; the changes were associated with reactions of the impurity groups. Filling the hexed sites with hydroxyl ions above 500oC was shown to happen partly due to lattice reactions but was mainly owing to hydrolysis of the SCHA by water molecules in air. Decomposition of groups proceeded through both thermal destruction and reactions with some of the impurity ions. The decarbonation in A-sites occurred at much lower temperatures (450–600oC) than in B-sites (700–950oC) and was first revealed to happen in two stages: due to an impurity reaction around 500oC, and then through thermal destruction at 570oC. A redistribution of ions, decreasing in amount on the whole, was observed upon annealing above 500oC. To avoid possible erroneous conclusions from TG-data, a sensitive method was shown to be required for monitoring gaseous decomposition products (such as the MSTA in this study), in case several impurity groups were present in a SCHA.     

The Transport Properties of Sodium Atoms and the Heat Capacity of Sodium Dimers at High Temperatures

Including the contribution of excited state atoms can improve calculations of dilute gaseous transport properties at high temperatures. For sodium, experimental and/or theoretical information is available about the potential energy curves associated with each of ten low-lying states of the sodium dimer. These include the ${{\rm X}^{1}\Sigma_{\rm g}{}^{+}}$ and ${^{3}\Sigma_{\rm u}{}{}^{+}}$ states that dissociate to two ground state ²S sodium atoms and the four ${^{3}\Sigma_{\rm g,u}{}^{+},\,^{1}\Sigma _{\rm g,u}{}^{+},\,^{1}\Pi _{\rm g,u},\,^{3}\Pi _{\rm g,u}}$ gerade/ungerade pairs of states that dissociate to a ground state ²S atom and an excited state ²P atom. Nine of these are bound states and have been fitted with the Hulburt–Hirschfelder potential, a very good general purpose atom–atom potential. The ³Π_g state is not bound and has been fitted with the exponential repulsive potential. We have used these potentials to calculate viscosity collision integrals as a function of temperature, and employed degeneracy-weighted averaging to determine the viscosity and translational contribution to the thermal conductivity of the sodium atoms. These same potentials have been used to calculate the heat capacity, ${C_{p}^{\rm o}}$ , of the sodium dimer using an approach that depends on the second virial coefficient and its first two temperature derivatives. Again, the inclusion of molecular states that dissociate to an excited state atom allows ${C_{p}^{\rm o}}$ to be determined with improved accuracy at higher temperatures. Thus, thermophysical property calculations for sodium have been extended to 25,000 K. These results are compared with previous results, including heat capacities given in the NIST-JANAF Thermochemical Tables.     

The Effect of Inhomogeneous Phase on the Critical Temperature of Smart Meta-superconductor MgB<Subscript>2</Subscript>

The critical temperature (T_C) of MgB₂, one of the key factors limiting its application, is highly desired to be improved. On the basis of the meta-material structure, we prepared a smart meta-superconductor structure consisting of MgB₂ micro-particles and inhomogeneous phases by an ex situ process. The effect of inhomogeneous phase on the T_C of smart meta-superconductor MgB₂ was investigated. Results showed that the onset temperature (\(T_{\mathrm {C}}^{\text {on}}\)) of doping samples was lower than those of pure MgB₂. However, the offset temperature (\({T}_{\mathrm {C}}^{\text {off}}\)) of the sample doped with Y₂O₃:Eu³⁺ nanosheets with a thickness of 2 ～ 3 nm which is much less than the coherence length of MgB₂ is 1.2 K higher than that of pure MgB₂. The effect of the applied electric field on the T_C of the sample was also studied. Results indicated that with the increase of current, \({T}_{\mathrm {C}}^{\text {on}}\) is slightly increased in the samples doping with different inhomogeneous phases. With increasing current, the \({T}_{\mathrm {C}}^{\text {off}}\) of the samples doped with nonluminous inhomogeneous phases was decreased. However, the \({T}_{\mathrm {C}}^{\text {off}}\) of the luminescent inhomogeneous phase doping samples increased and then decreased with increasing current.     

Kinetics of flow stress in ultra-pure tantalum single crystals in stress/temperature regime III

The temperature dependence of the critical resolved shear stress (CRSS), τ, of ultra-pure tantalum single crystals (RRR ≥ 14000) observed below 250 K for a range of shear-strain rates [(g)\dot] = 2×10 ^{- 5} - 6×10 ^{- 3}  \texts ^{- 1} \dot{\gamma } = 2\times 10^{ - 5} - 6\times 10^{ - 3} \,{\text{s}}^{ - 1} was analyzed within the framework of a kink-pair nucleation model of flow stress. The CRSS/strain-rate data follow the model formulation t ^{1/ 2} = C + D  ln[(g)\dot] \tau^{ 1/ 2} = C + D\,{ \ln }\dot{\gamma } , where C and D are positive constants, for each deformation temperature T in the range 78–250 K. Evaluation of the various slip-parameters of flow stress points to (211)[[`1]11] [\bar{1}11] slip system responsible for the yielding of ultra-pure tantalum single crystals in the so-called stress/temperature regime III (T < 250 K). The value of the pre-exponential factor [(g)\dot]_\texto \dot{\gamma }_{\text{o}} in the Arrhenius-type equation for the shear-strain rate [(g)\dot] \dot{\gamma } is found to be of the order of 10⁵ s⁻¹, which is substantially lower than that ( [(g)\dot]_\texto ~ 10⁷  \texts ^{- 1} ) \left( {\dot{\gamma }_{\text{o}} \sim 10^{7} \,{\text{s}}^{ - 1} } \right) determined in the stress/temperature regime II (250–400 K) and contradicts the assumption invariably made in most of the theoretical models of flow stress that [(g)\dot]_\texto \dot{\gamma }_{\text{o}} is a constant over a wide temperature range.     

Inhomogeneous Superconducting State and Intrinsic T c : Near Room Temperature Superconductivity in the Cuprates

Doped cuprates are inhomogeneous superconductors. The concept of an intrinsic critical temperature, T_c^intr. o T_c^*T_{c}^{\mathrm{intr.}} \equiv T_{c}^{*}, whose value greatly exceeds that for the resistive T_c^res. o T_cT_{c}^{\mathrm{res.}}\equiv T_{c}, is supported by a number of experimental studies, including those performed recently. These data are discussed in this review. The anomalous diamagnetism observed at T_c^res. < T < T_c^*T_{c}^{\mathrm{res.}} 相似文献   

Structural properties of nickel manganite Ni x Mn3−x O4 with 0.5 ⩽x ⩽ 1

Single-phase nickel manganite spinels, Ni _x Mn_3–x O₄, with 0.5 x 1, were prepared by a careful thermal processing of nickel-manganese coprecipitated oxalate precursors. Powder X-ray diffraction analysis of the spinel revealed the presence of cubic single spinel phase with parametera which decreases with nickel content. The lattice parameter variation can be explained in terms of the distribution of Ni²⁺ ions on the octahedral sites. Therefore, a fine analysis of data shows that some Ni²⁺ ions (forx>0.56) are located in tetrahedral sites. The percentage of nickel in A-sites increases with nickel content (x) following the relation % Ni²⁺ in A sites =P = – 82.1x ²+192.4x–81.5 and thus the general formula for cation distribution is

Preparation,characterization of chitosan/bamboo charcoal/poly(methacrylate) composite beads

Preparation and characterization of a low-cost, novel steam-activated bamboo charcoal (BC) and poly(methacrylate) (PMAA) bound with chitosan (CTS) to form chitosan/bamboo charcoal/poly(methacrylate) (CTS/BC/PMAA) composite beads is reported for the first time in this paper. The characteristics are revealed by techniques such as X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Brunauer Emmett Teller (BET), solution pH and pH at point of zero charge \((\hbox {pH}_{\mathrm {pzc}})\). The composite beads possessed a dominant acidic surface group of 0.663 mmol \(\hbox {g}^{\mathrm {-1}}\), as revealed by Boehm titration method. This acidity was confirmed by its solution pH of 6.46; \(\hbox {pH}_{\mathrm {pzc}}\) of 6.70 and increase in oxygen surface via XPS analysis. \(\hbox {N}_{\mathrm {2}}\) adsorption–desorption isotherms at 77 K of the beads revealed high BET surface area (SA) of 681.15 \(\hbox {m}^{\mathrm {2}}\hbox {g}^{\mathrm {-1}}\). Langmuir model affords a SA of 773.34 \(\hbox {m}^{\mathrm {2}}\hbox {g}^{\mathrm {-1}}\). SEM showed the microporous nature of the composite beads. The properties of CTS/BC/PMAA composite beads were compared to CTS/BC and neat BC. Thermal stability and successful coating of 5.1 wt% of PMAA and 6.8 wt% of CTS to CTS/BC/PMAA beads were shown by DSC and TGA analyses. The composite beads showed low carbon particle released at pH 7.4 and 6.8. Furthermore, dynamic adsorption revealed that CTS/BC/PMAA composite beads can be used to capture a polar substance, such as creatinine.     

Magnetic Properties of Nanocrystalline Nickel–Cobalt Ferrites (\mathrm{Ni}_{1/2}{\mathrm{{Co}}}_{1/2}{\mathrm{{Fe}}}_{2}{\mathrm{O}}_{4})

In this study, the nanocrystalline nickel–cobalt ferrites $(\mathrm{Ni}_{1/2}\mathrm{Co}_{1/2}\mathrm{Fe}_{2}\mathrm{O}_{4})$ were prepared via the citrate route method at $27\,^{\circ }\mathrm{C}$ . The samples were calcined at $300\,^{\circ }\mathrm{C}$ for 3 h. The crystalline structure and the single-phase formations were confirmed by X-ray diffraction (XRD) measurements. Prepared materials showed the cubic spinel structure with m3m symmetry and Fd3m space group. The analyses of XRD patterns were carried out using POWD software. It gave an estimation of lattice constant “ $a$ ” of 8.3584 Å, which was in good agreement with the results reported in JCPDS file no. 742081. The crystal size of the prepared materials calculated by Scherer’s formula was 27.6 nm and the electrical conductivity was around $10^{-5}~\mathrm{S}\,\cdot \, \mathrm{m}^{-1}$ . The permeability component variations with frequency were realized. The magnetic properties of the prepared materials were analyzed by a vibrating sample magnetometer (VSM). It showed a saturation magnetization of $27.26\,\mathrm{emu} \cdot \mathrm{m}^{-1}$ and the behavior of a hard magnet.     

Synthesis, Magnetic Properties, Magnetic Entropy and Arrot Plot of Antiferromagnetic Frustrated Er2Ti2O7 Compound

The pyrochlore $\mathrm{Er}_{2}^{3 +} \mathrm{Ti}_{2}^{4 +}\mathrm{O}_{7}^{2 -}$ was synthesized via a ceramic method using two different oxides (Er₂O₃ and TiO₂). The compound was found to crystallize in the cubic system with the $\mathrm{Fd}\overline{3}\mathrm{m}$ space group (No. 227). A magnetic study, carried out at 2 and 300 K under an applied magnetic field ?? ₀ H=0.05?T, has revealed a complex magnetic structure at low temperature. The effective paramagnetic moment $\mu_{\mathrm{eff}}^{\exp}$ , deduced from (????? ₀)^?1=f(T) curve, was found by assuming a zero moment on the transition metal atom Ti⁴⁺. The paramagnetic Curie?CWeiss temperature ?? _CW=?21.54?K, the nearest neighbor interaction J _nn =?2.30?K, the classical nearest neighbor J ^cl=?8.65?K and the dipolar D _nn =3.76?K interactions?? values have revealed an antiferromagnetic behavior for Er₂Ti₂O₇ compound at low temperature. We have also studied the effects of the magnetic field splitting of rare-earth atom Er³⁺ in the compound Er₂Ti₂O₇ curved Arrott plots.     

Extensions of access structures and their cryptographic applications

In secret sharing schemes a secret is distributed among a set of users ${\mathcal{P}}In secret sharing schemes a secret is distributed among a set of users P{\mathcal{P}} in such a way that only some sets, the authorized sets, can recover it. The family Γ of authorized sets is called the access structure. To design new cryptographic protocols, we introduce in this work the concept of extension of an access structure: given a monotone family G ì 2^P{{\it \Gamma} \subset 2^\mathcal{P}} and a larger set P^￠ = P è[(P)\tilde]{\mathcal{P}^{\prime} = \mathcal{P} \cup \tilde{\mathcal{P}}}, a monotone access structure G^￠ ì 2^P￠{{\it \Gamma}^{\prime}\subset 2^{\mathcal{P}^{\prime}}} is an extension of Γ if the following two conditions are satisfied: (1) The set P{\mathcal{P}} is a minimal subset of Γ′, i.e. P ? G^￠{\mathcal{P} \in {\it \Gamma}^{\prime}} and P - {R_i} ? G^￠{\mathcal{P} - \{R_i\}\notin {\it \Gamma}^{\prime}} for every R_i ? P{R_i \in \mathcal{P}}, (2) A subset A ì P{A \subset \mathcal{P}} is in Γ if and only if the subset A è[(P)\tilde]{A \cup \tilde{\mathcal{P}}} is in Γ′. As our first contribution, we give an explicit construction of an extension Γ′ of a vector space access structure Γ, and we prove that Γ′ is also a vector space access structure. Although the definition may seem a bit artificial at first, it is well motivated from a cryptographic point of view. Indeed, our second contribution is to show that the concept of extension of an access structure can be used to design encryption schemes with access structures that are chosen ad-hoc at the time of encryption. Specifically, we design and analyze a dynamic distributed encryption scheme and a ciphertext-policy attribute-based encryption scheme. In some cases, the new schemes enjoy better properties than existing ones.     

Cation distribution investigation of the system Li0.5Fe x Ga2.50-xO4 by X-rays,electrical conductivity and Mossbauer studies

Structural, electrical and Mossbauer studies were carried out for the system Li_0.5Fe _x Ga_2.50-xO₄. All the compounds with 0 ? x? 2.5 crystallised with cubic spinel structure. Lattice constant values calculated from XRD analysis were found to increase with increasing x. X-ray intensity calculations indicated that Li¹⁺ occupies only the octahedral site and Ga³⁺ and Fe³⁺ ions occupy both octahedral and tetrahedral sites. Activation energy and thermoelectric coefficient values decreased with increasing values of x. All the compounds studied were p-type semiconductors and possess low mobility values of 10^?7-10^?9 cm²V^?1 s^?1. Mossbauer data show the presence of iron in the Fe³⁺ state and the isomer shift values for all the compositions of the system are within the range of high spin ferric compounds. The probable ionic configuration for the system is suggested as: $${\text{Ga}}_{{\text{1 - }}\alpha }^{{\text{3 + }}} {\text{Fe}}_\alpha ^{{\text{3 + }}} [Li_{0.5}^1 {\text{Fe}}_{{\text{x - }}\alpha }^{{\text{3 + }}} {\text{Ga}}_{{\text{2}}{\text{.5 - x + }}\alpha }^{\text{3}} ] {\text{O}}_{\text{4}}^{{\text{2 - }}} $$      

Structure and properties of CaF<Subscript>2</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript> glasses

FTIR spectroscopy has been employed to investigate the structure of CaF₂–B₂O₃ glasses. It is proposed that CaF₂ partially modifies the borate network forming \textCa _{1 / 2} ²⁺ [\textBO _{3 / 2} \textF] ^- {\text{Ca}}_{ 1 / 2}^{ 2+ } [{\text{BO}}_{ 3 / 2} {\text{F]}}^{ - } units. The rest of CaF₂ is assumed to build an amorphous network formed of CaF₄ tetrahedra. Analysis of density and molar volume revealed that the volume of CaF₄ tetrahedron in the studied glasses is slightly greater than that in the crystalline form. Data of density, molar volume, and electric conductivity have been correlated with the glass structure. As far as the authors know, CaF₂–B₂O₃ glasses are investigated for the first time.     

Physicochemical Behavior of Some Amino Acids/Glycylglycine in Aqueous <Emphasis Type="SmallCaps">D</Emphasis>-Galactose Solutions at Different Temperatures

The apparent molar volumes ([`(V<sub>2</sub>)]){(\overline{V_2})} for glycine (Gly), l-alanine (Ala), phenylalanine (Phe), and glycylglycine (Gly-Gly) in 0.10 m aqueous d-galactose solutions have been determined from density measurements at (298.15, 303.15, 308.15, and 313.15) K. The data for ([`(V₂)]){(\overline{V_2})} were utilized to estimate the partial molar volume at infinite dilution ([`(V<sub>2</sub><sup>0</sup>)]){(\overline{V_2^0})} , and experimental slope (S<sub>v</sub><sup>*</sup>){(S_{\rm v}^\ast)} . The transfer volume, ([`(V₂⁰)]_(tr)){(\overline{V_{2}^0}_{\rm (tr)})} , and hydration number, (n _H) were also evaluated. The viscosity data were used to evaluate A- and B-coefficients of the Jones–Dole equation, the free energy of activation of viscous flow per mole of the solvent (Dm₁^0* ){\left(\Delta \mu_{1}^{0\ast} \right)} and the solute (Dm₂^0* ){\left(\Delta \mu _{2}^{0\ast} \right)} . The molar refractivity (R _D) was calculated from refractive index data. The results were discussed in terms of hydrophilic–ionic, hydrophilic–hydrophobic, and hydrophobic–hydrophobic interactions, and structure-making/-breaking ability of the solute (AAs/peptide) in aqueous d-galactose solutions.     

Effect of defect dipoles on the dielectric and electrical properties of Mn:K2Ti6O13 lead-free ceramics: EPR spectroscopy-cum-dielectric-spectroscopy

In this paper, we report the synthesis of Mn:K₂Ti₆O₁₃ lead-free ceramics in a monoclinic phase with microtubular surface morphology via high temperature solid-state reactions. EPR-spectroscopy, achieved at room temperature and at X-band frequencies, recognised Mn²⁺, Mn³⁺, and Mn⁴⁺ partial substitutions at Ti⁴⁺ lattice sites with dominating Mn²⁺ substitution, and identified ( \textFe_\textTi^￠ {\text{Fe}}_{\text{Ti}}^{\prime } – V_\textO ^·· V_{\text{O}}^{ \cdot \cdot } ) and ( \textMn_\textTi^￠￠ {\text{Mn}}_{\text{Ti}}^{\prime \prime } – V_\textO ^·· V_{\text{O}}^{ \cdot \cdot } ) defect associate dipoles exhibited in the low-field EPR signals which smeared with excessive doping due to augmented exchange interactions. These dipoles rendered diffusive nature to the ferroelectric-paraelectric type phase transitions recognized in the ε _r (T) plots. Space charges, dipole orientation, and electrical conduction cooperatively contributed to dielectric losses. The study also provides a select composition with x = 0.05 mol% doping, performing low loss with high dielectric permittivity useful for high-temperature applications. Conductivity data proposed a shift from electronic (hopping) conduction mechanism in the low-temperate region to ionic (intratunnel) conduction at high-temperatures. Whereas slight doping augmented a.c. conductivity due to increased spin-phonon interaction and commanding electron hopping conduction, heavy doping reduced it, attributed to shrinkage of tunnel space and trapping of conduction electrons.     

Canadian Field Soils IV: Modeling Thermal Conductivity at Dryness and Saturation

The thermal conductivity data of 40 Canadian soils at dryness \((\lambda _{\mathrm{dry}})\) and at full saturation \((\lambda _{\mathrm{sat}})\) were used to verify 13 predictive models, i.e., four mechanistic, four semi-empirical and five empirical equations. The performance of each model, for \(\lambda _{\mathrm{dry}}\) and \(\lambda _{\mathrm{sat}}\), was evaluated using a standard deviation (SD) formula. Among the mechanistic models applied to dry soils, the closest \(\lambda _{\mathrm{dry}}\) estimates were obtained by MaxRTCM \((\textit{SD} = \pm ~0.018\,\hbox { Wm}^{-1}\cdot \hbox {K}^{-1})\), followed by de Vries and a series-parallel model (\(\hbox {S-}{\vert }{\vert }\)). Among the semi-empirical equations (deVries-ave, Advanced Geometric Mean Model (A-GMM), Chaudhary and Bhandari (C–B) and Chen’s equation), the closest \(\lambda _{\mathrm{dry}}\) estimates were obtained by the C–B model \((\pm ~0.022\,\hbox { Wm}^{-1}\cdot \hbox {K}^{-1})\). Among the empirical equations, the top \(\lambda _{\mathrm{dry}}\) estimates were given by CDry-40 \((\pm ~0.021\,\hbox { Wm}^{-1}\cdot \hbox {K}^{-1}\) and \(\pm ~0.018\,\hbox { Wm}^{-1}\cdot \hbox {K}^{-1}\) for18-coarse and 22-fine soils, respectively). In addition, \(\lambda _{\mathrm{dry}}\) and \(\lambda _{\mathrm{sat}}\) models were applied to the \(\lambda _{\mathrm{sat}}\) database of 21 other soils. From all the models tested, only the maxRTCM and the CDry-40 models provided the closest \(\lambda _{\mathrm{dry}}\) estimates for the 40 Canadian soils as well as the 21 soils. The best \(\lambda _{\mathrm{sat}}\) estimates for the 40-Canadian soils and the 21 soils were given by the A-GMM and the \(\hbox {S-}{\vert }{\vert }\) model.     

Equilibration kinetics of (La,Sr)MnO3

The present work reports isothermal changes of oxygen non-stoichiometry for the perovskite-type electrode material (La_0.8Sr_0.2)MnO₃ in the temperature range 945–1255 K. A thermogravimetric method was used to monitor the rate of the gas/solid equilibration. For equilibration degrees larger than 0.5, the equilibration kinetic data can be described by a diffusion equation. The determined chemical diffusion coefficient depends essentially on the oxygen partial pressure. Its temperature dependence can be expressed by the following expressions at low and high p(O₂), respectively:

Three oxidation states and atomic-scale <Emphasis Type="Italic">p–n</Emphasis> junctions in manganese perovskite oxide from hydrothermal systems

Perovskite oxides have provided magical structural models for superconducting and colossal magnetoresistance, and the search for nano-scale and/or atomic-scale devices with particular property by specific preparations in the same systems has been extensively conducted. We present here the three oxidation states of manganese (Mn³⁺, Mn⁴⁺, Mn⁵⁺) in the perovskite oxide, La_0.66Ca_0.29K_0.05MnO₃, which most interestingly shows the rectifying effect as atomic-scale p–n junctions (namely FY-Junctions) of single crystals and films. The family of cubic perovskite oxides were synthesised by the so-called hydrothermal disproportionation reaction of MnO₂ under the condition of strong alkali media. The new concept of the atomic-scale p–n junctions, based on the ideal rectification characteristic of the p–n junctions in the single crystal, basically originates from the structural linkages of [Mn³⁺–O–Mn⁴⁺–O–Mn⁵⁺], where Mn³⁺ and Mn⁵⁺ in octahedral symmetry serve as a donor and an acceptor, respectively, corresponding to the localized Mn⁴⁺ .