Electrical conductivity and chemical diffusion coefficient measurements in single crystalline nickel oxide at high temperatures

Electrical conductivity measurements on nickel oxide have been performed at high temperatures (1273 K<T< 1673 K) and in partial pressures of oxygen ranging from Po₂ = 1.89 × 10^?4 atm to Po₂ = 1 atm. The $\text{po}{}_2{}^{\mathrm{<mtext>1</mtext><mtext>n</mtext>}}$ dependence of the conductivity decreases from about $\text{1}\text{4}$ for Po₂ = 1 atm to smaller values for lower partial pressures of oxygen. The activation enthalpy for conduction increases for decreasing oxygen partial pressures (from 22.5 kcal mol^?1 at Po₂ = 1 atm to 26.0 kcal mol^?1 for Po₂ = 1.89 × 10^?4 atm). This behaviour can be explained by the simultaneous presence of singly and doubly ionized nickel vacancies, with different energies of formation.Furthermore, chemical diffusion coefficient measurements have been performed in the same temperature range, using the conductivity technique, and leading to the result:

$\text{D}\text{?}\text{= 0.244 exp (?}\text{36,600}\text{RT}\text{) cm}{}^2\text{s}{}^{\mathrm{?1}}$

.     

Thermodynamics and mobility of copper in bornite (Cu5FeS4)

The thermodynamics and kinetics of copper transport in bornite (Cu₅FeS₄) have been investigated. Coulometric titration experiments on single-crystal and hot-pressed polycrystalline materials indicated a restricted range of composition for substoichiometric single-phase bornite, with materials of copper contents less than Cu_4.95FeS₄ existing as a two-phase mixture of bornite and a chalcopyrite-type phase (Cu₃FeS₄). For the polycrystalline material the van der Pauw technique was used to obtain the electronic conductivity (σ_e) as a function of temperature and a six-point cell was used to measure the ionic conductivity (σ_i) as a function of composition. Typical results obtained at 170°C were $\text{σ}{}_{\mathrm{e}}\text{=230 Ω}{}^{\mathrm{?1}}\text{m}{}^{\mathrm{?1}}$, $\text{σ}{}_{\mathrm{i}}\text{= 11 Ω}{}^{\mathrm{?1}}\text{m}{}^{\mathrm{?1}}$, activation energy for electronic conduction = 15 kJ mol^?1. The transient behaviour of the electronic and ionic probe voltages during the six-point cell experiments have been tentatively interpreted in terms of the chemistry of the copper-iron sulphides.     

Electrical conductivity at high temperature and thermodynamic study of point defects in single crystalline cuprous oxide

In order to follow the variation of point defect interactions in relatively concentrated solutions we have studied the electrical conductivity of cuprous oxide in the range of temperature 650–1100°C and for oxygen partial pressures greater than 10^?6 atm. The P^{$\text{1}\text{π}$}_O2 dependence of the conductivity varied non linearly from about n = 8 for P_o2 close to 10^?6 atm. to lower values of n with increasing oxygen partial pressure. The activation enthalpy of conductivity determined in these ranges of temperature and oxygen partial pressure has been found to be also a function of temperature and varied between 12 and 17 kcal mol^?1.The interpretation of these results has permitted us to show that the departure from linearity of the plots of log or log $\text{σ = ?(}\text{l}\text{T}\text{)}$ excludes the existence of an ideal solution of ionized and non-ionized copper vacancies as was proposed previously in the literature. To explain these results it is possible to take into account a partially disordered distribution of these defects. It is shown that the increase of interactions and consequently the variation of the electrical conductivity as a function of the thermodynamic parameters, may be simulated by an ideal solution including new charged species of the type (V'_CuV^x_Cu).     

Diffusional transport in manganous sulphide

Using a novel diffusion-evaporation method, the self-diffusion coefficient of manganese in manganous sulphide has been determined as a function of temperature (1073–1373 K) in equilibrium with the metallic phase. It has been shown that the activation energy of this process at constant sulphur activity amounts to 269 kJ/mol and the self-diffusion coefficient is the following function of temperature and sulphur vapour pressure: . Diffusion of Mn²⁺ cations in Mn_1+yS proceeds via the interstitialcy mechanism and the activation enthalpy of successive jumps of these defects, δH_m is equal to 118 kJ/mol. It has been demonstrated that the mobility of interstitial cations in the Mn_1+yS lattice does not depend on their concentration and the diffusion coefficient of these defects has the following function of temperature: D_i=0.759 exp(-118 kJ/mol/RT).     

Autodiffusion cationique dans l'oxyde de nickel monocristallin sous pression partielle d'oxygene voisine de la pression de dissociation de l'oxyde

⁶³Ni diffusion measurements on single crystalline nickel oxide have been performed at temperatures between 1073 and 1373 K and in partial pressures of oxygen equal to the NiO dissociation pressure. In such conditions, the intrinsic defect content is very low and the preponderant defect consists in doubly ionized nickel vacancies (V″).Diffusion coefficient values lead to the result

$\text{D}{}_{\mathrm{v}}\text{(}\text{cm}{}^2\text{s}{}^{\mathrm{?1}}\text{) = 5.2510}{}^{\mathrm{?6}}\text{exp}\text{( ?}\text{154}\text{kJ mol}{}^{\mathrm{?1}}\text{RT}\text{)}$

The activation energy thus determined agrees with the value of the migration enthalpy of the doubly ionized nickel vacancy. Thus, it appears that under such experimental conditions, the vacancy content is determined by the impurity content.     

Thermochemistry of azide salts and the azide ion using direct minimisation equations to obtain the lattice energy of the univalent azide salts

The opportunity to test a new equation for the computation of the lattice energy and at the same time examine a disparity in the literature data for the enthalpy of formation of the azide ion, $\text{ΔH}{}^{\mathrm{\theta }}{}_{\mathrm{?}}\text{(}\text{N}{}_3{}^{\mathrm{?}}\text{) (}\text{g}\text{)}$ was the motivation for this study. The results confirm our earlier calculation and show the new equation to be reliable. Thermodynamic data produced in the study take values: $\text{ΔH}{}^{\mathrm{\theta }}{}_{\mathrm{?}}\text{(}\text{N}{}_3{}^{\mathrm{?}}\text{)(}\text{g}\text{) = 144}\text{kJ mor}{}^{\mathrm{?1}}$ΔH^θ_hyd(N₃^?) = ?315 KJ mol^?1 or ΔH^θ_hyd(N₃^?) = ?295 KJ mol^?1U_POT(NaN₃) = 732 kJ mol^?1U_POT(KN₃) = 659 kJ mol^?1U_POT(RbN₃) = 637 kJ mol^?1U_POT(CsN₃) = 612 kJ mol^?1U_POT(TIN₃) = 689 kJ mol^?1. The lattice energies of azides whose enthalpies of formation are documented have been calculated as well as the enthalpy of formation of the azide radical.     

Chemical diffusion in nonstoichiometric chromium sulfide,Cr2+yS3

Using the re-equilibration kinetic method the chemical diffusion coefficient in nonstoichiometric chromium sesquisulfide, Cr_2+yS₃, has been determined as a function of temperature (1073–1373 K) and sulphur vapour pressure (10?10⁴ Pa). It has been found that this coefficient is independent of sulphur pressure and can be described by the following empirical equation: $\text{D}\text{?}\text{Cr}{}_{\mathrm{2+y}}\text{S}{}_3\text{=50.86}\text{exp(-39070 cal/mole/}\text{RT)}\text{(cm}{}^2\text{s}{}^{\mathrm{?1)}}$. It has been shown that the mobility of the point defects inCr_2+yS₃ is independent of their concentration and that the self-diffusion coefficient of chromium in this sulfide has the following function of temperature and sulphur pressure: . (cm²s^?1).     

Self-diffusion of C in single crystals of NBCx

The self-diffusion coefficients of ¹⁴C in NbC_x single crystals have been measured as a function of composition in the temperature range 1900–2315 K, and can be represented by the expressions

$\text{D}{}^1{}_{\mathrm{C}}\text{(}\text{NbC}{}_{0.868}\text{) = (2.59}{}_{\mathrm{?1.07}}{}^{\mathrm{+1.82}}\text{)}\text{exp}\text{(?}\text{100.42 ± 2.2}\text{kcal}\text{mol}\text{RT}\text{)}\text{cm}{}^2\text{s}$

$\text{D}{}^1{}_{\mathrm{C}}\text{(}\text{NbC}{}_{0.834}\text{) = (7.44}{}_{\mathrm{?4.14}}{}^{\mathrm{+9.36}}\text{)}\text{exp}\text{(?}\text{105.0 ± 3.3}\text{kcal}\text{mol}\text{RT}\text{)}\text{cm}{}^2\text{s}$

$\text{D}{}^1{}_{\mathrm{C}}\text{(}\text{NbC}{}_{0.766}\text{) = (2.22}{}_{\mathrm{?1.04}}{}^{\mathrm{+1.98}}\text{) × 10}{}^{\mathrm{?2}}\text{exp}\text{(?}\text{76.02 ± 2.7}\text{kcal}\text{mol}\text{RT}\text{)}\text{cm}{}^2\text{s}$

The lower values of the activation energy and the pre-exponential term in NbC_0.766 are attributed to a change in the path of C mass transport from that of an octahedral-tetrahedral-octahedral mechanism in NbC_0.868 and NbC_0.834 involving a C-metal divacancy mechanism. The effect of lattice geometry and the electronic charge distribution on the diffusion mechanism is also discussed.     

Self-diffusion of manganese in manganous sulphide

The self-diffusion coefficient of manganese in manganous sulphide has been calculated as a function of temperature and sulphur vapour pressure. It has been shown that near the Mn/MnS phase boundary Mn self diffusion occurs by means of interstitial or interstitialcy mechanism and D_Mn is the following function of temperature and sulphur vapour pressure: . At higher sulphur pressures manganese diffuses via doubly ionized cation vacancies and analogous pressure and temperature dependence can be described by the following empirical equation: .     

The rotational analysis of the 1Π-X 1Σ+ system at 649.5 nanometers of zirconium oxide

A red-degraded band head, normally badly overlapped by the gamma system, $\text{A}{}^3\text{Φ}\text{- X′}{}^3\text{Δ}$, of zirconium oxide, appears in emission spectra of zirconium arcs and in absorption spectra of S-type stars and of frozen rare gas matrices containing zirconium. The emission band has been examined at high-resolution with the aid of separated zirconium isotopes. Identification of the band as 0-0 of a ${}^1\text{Π}\text{- X}{}^1\text{Σ}{}^{\mathrm{+}}$ system of zirconium oxide is confirmed by rotational analysis where the following constants (cm^?1) are obtained for ⁹⁰Zr¹⁶O:

$\text{B}{}_0\text{′(R,P) = 0.40142 D}{}_0\text{′(R,P) = 3.51 × 10}{}^{\mathrm{?7}}$

$\text{B}{}_0\text{′(Q) = 0.40166 D}{}_0\text{′(Q) =3.52 × 10}{}^{\mathrm{?7}}$

$\text{B}{}_0\text{″ = 0.42263 D}{}_0\text{″ =3.19 × 10}{}^{\mathrm{?7}}$

$\text{ν}{}_0\text{= 15383.81s}$

The Λ-type doubling in the ¹Π state and the question of whether $\text{X}{}^1\text{Σ}{}^{\mathrm{+}}$ or $\text{X′}{}^3\text{Δ}$ is the true ground state of ZrO are discussed.     

Diffusion of water in additively colored potassium iodide crystals

The diffusion of water into additively colored potassium iodide has been studied in the range 15–45°C. Penetration depths, measured by decrease in the F-band absorption, increase with $\text{t}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$. The diffusion coefficient, D = 0·58 exp (?6496/T) cm² sec^?1 agrees very well with that determined by other workers. The Henry's law constant, $\text{K =}\text{C}{}_0\text{p}{}_{\mathrm{w}}\text{= 1·3 × 10}{}^9\text{exp}\text{(+4882/T)}\text{cm}{}^{\mathrm{?3}}\text{torr}{}^{\mathrm{?1}}$ implies a water concentration of C₀ ? 10¹⁷ molecules per cm³ in the surface of KI crystals in equilibrium with an environment at 25°C and 35 per cent relative humidity. The large C₀ makes penetration very rapid. Diffusion occurs by interstitial migration of water molecules with an entropy of activation of 9.4 cal/mol deg and an enthalpy of activation of 12·9 kcal/mol.     

A high-precision measurement of the stark shift of the sodium D1-line

Using laser—atomic-beam spectroscopy and a special field arrangement the Stark shift of the sodium D₁-line was determined to be 48.986 (112) kHz (kV/cm)^?2. Using the literature value for the scalar polarizability of $\text{2}{}^2\text{S}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, 39.7 (8) kHz (kV/cm)^?2, the polarizability of $\text{2}{}^2\text{P}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ was derived to be 88.69 (81) kHz (kV/cm)^?2.     

Nuclear spin-lattice relaxation of Co59 in CoB

We report the result of the Co⁵⁹ nuclear spin-lattice relaxation time T₁ measurements in the diamagnetic monoboride CoB. The analysis of the data, in the 4.2–300 K temperature range, allows us to separate three contributions to the relaxation rate: first a Korringa process, (T_1KT)^?1= 0.21 sec^?1K^?1 (in good agreement with the temperature independent isotropic Knight shift) from which we deduced the Co⁵⁹ hyperfine constant A=6.2 ×10^?6eV, second an impurity contribution independent of temperature and third a quadrupolar term, $\text{T}{}^{\mathrm{?1}}{}_{\mathrm{1Q}}\text{=3560 (}\text{T}\text{θ}{}_{\mathrm{D}}\text{)}{}^2\text{E(}\text{T}\text{θ}{}_{\mathrm{D}}\text{) sec}{}^{\mathrm{?1}}$, which is predominant at high temperature and well explained by the Van Kranendonk theory. It seems that it was the first time that such a quadrupolar effect was detected in a metallic compound. A remarkable coherency between Lundquist's three bands model and our experimental results has to be noted.     

Direct evidence for W exchange in charmed meson decay

Using the ARGUS detector at DORIS II, we have observed a signal of 36.7±8.0 events in the decay channel D⁰→K_s⁰φ. In the same data sample, we have observed the well established decay D⁰→K_s⁰π⁺π^?, and find the ratio, $\text{Br(D)}{}^0\text{→}\text{K}{}_{\mathrm{<mtext>s</mtext>}}{}^0\text{φ)}\text{Br(D)}{}^0\text{→}\text{K}{}_{\mathrm{<mtext>s</mtext>}}{}^0\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{)}$, to be 0.186±0.052. The substantial value of (0.99±0.32±0.17)% then derived for the branching ratio for $\text{D}{}^0\text{→}\text{K}{}^0\text{φ}$ gives direct evidence that W exchange contributes D⁰ decay.     

Conductivite electrique totale du protoxyde de cuivre en fonction de sa composition definie par des electrodes d'alliage or-cuivre

The total electrical conductivity of cuprous oxide has been measured from 800 to 1100°K as a function of its composition, especially in the range of very low oxygen pressures up to the limit of equilibrium with copper. These measurements have been carried out by means of a new method using copper-gold alloy electrodes in order to have given activities of components.The results indicate for cuprous oxide a p semi-conduction throughout its stability range.The conductivity σ (ohm^?1. cm^?1) is given as a function of the temperature T (K) and the partial pressure P_o2 (torr) of oxygen in equilibrium with the oxide by the following equation:

     

Measurement and interpretation of the 1-0 band of 14N16O at 1900 cm−1

The wavenumbers of the vibration rotation band lines of ¹⁴N¹⁶O are reported for the ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{-}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{-}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{-}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ subbands of the 1-0 transition in the infrared. The full set of spectroscopic constants for this band has been determined by direct approach using the analysis of Zare, Schmeltekopf, Harrop, and Albritton. In addition to the band origin ν₀ and the B, D, H constants for the lower and upper vibrational levels, the following spin-orbit coupling constants have been derived: $\text{A}\text{?}{}_0\text{= 123.02772 ± 0.00011}$ and $\text{A}\text{?}{}_1\text{= 122.78248 ± 0.00011}$ (in cm^?1). Apparent centrifugal corrections to these constants have been determined and the values obtained for them are $\text{A}\text{?}{}_{\mathrm{<mtext>D</mtext><mtext>0</mtext>}}\text{= (0.347573 ± 0.00051) × 10}{}^{\mathrm{?3}}$ and $\text{A}\text{?}{}_{\mathrm{<mtext>D</mtext><mtext>1</mtext>}}\text{= (0.337135 ± 0.00050) × 10}{}^{\mathrm{?3}}\text{cm}{}^{\mathrm{?1}}$. Λ-Type doubling constants evaluated by using both grating and tunable laser data are also reported.     

Reorientational motion of the OH− ion in cubic sodium hydroxide

The rotational motion of the OH^? ion was studied in cubic NaOH at 575 K with quasielastic incoherent neutron scattering. The data are compared to two simple models yielding values for the radius of rotation R, the translational mean square displacement 〈u²〉_H, the rotational jump rate τ^?1 and the rotational diffusion coefficient D_R. The following parameter values are obtained: (a) rotational jump model: $\text{R = 0.95}\text{A}\text{?}$, $\text{〈u}{}^2\text{〉}{}_{\mathrm{H}}\text{= 0.052}\text{A}\text{?}{}^2\text{, τ}{}^{\mathrm{?1}}\text{= 2}\text{meV}$, (b) rotational diffusion model: $\text{R = 0.99}\text{A}\text{?}\text{, 〈u}{}^2\text{〉}{}_{\mathrm{H}}\text{= 0.046}\text{A}\text{?}{}^2\text{, D}{}_{\mathrm{R}}\text{= 0.72}\text{meV}$.     

SIMS,AES, work function and flash desorption measurements of the CO adsorption on NiCu alloy surfaces

The chemisorption of CO on Cu, Ni and CuNi alloy surfaces was examined by SIMS, work function measurements and desorption spectroscopy. Using a dynamic SIMS technique the M⁺, M⁺₂, MCO⁺ and M₂CO⁺ emission at different temperatures (100–400 K) was measured as a function of CO exposure. In agreement with the work function and desorption experiments an increase of M⁺ and MCO⁺ emission due to the CO adsorption on Cu was found only at low temperatures (100–190 K). On the Ni surface an increase of Ni⁺, NiCO⁺ and Ni₂CO⁺ was measured up to 400 K. The adsorption of CO on CuNi alloy surfaces — as derived from the work function measurements — can be described by the assumption of two different states of adsorbed carbon monoxide. They can be characterized by different binding energies and from sign and magnitude different work function changes. These states were interpreted as adsorption at Ni or Cu sites of the alloy surfaces, respectively. To a certain extent the SIMS results from the alloy surfaces are incompatible with the work function measurements and desorption spectroscopy and the SIMS studies on the pure metals. A Cu⁺ emission with comparable intensity to the Ni⁺ emission was found for alloys with bulk concentrations of 60 and 40 at% Cu at 300 K. The ratio $\text{Ni}{}^{\mathrm{+}}\text{Cu}{}^{\mathrm{+}}$ was nearly independent of CO pressure and temperature. The measured ratios of $\text{Cu}{}^{\mathrm{+}}{}_2\text{(}\text{Cu}{}^{\mathrm{+}}\text{+}\text{Ni}{}^{\mathrm{+}}\text{)}$, $\text{Ni}{}^{\mathrm{+}}{}_2\text{(}\text{Cu}{}^{\mathrm{+}}\text{+}\text{Ni}{}^{\mathrm{+}}\text{)}$ and $\text{CuNi}{}^{\mathrm{+}}\text{(}\text{Cu}{}^{\mathrm{+}}\text{+}\text{Ni}{}^{\mathrm{+}}\text{)}$ with values about 10^?2 can be explained the basis of a statistical arrangement of Cu and Ni atoms in the alloy surface. The intensities of the MCO⁺ emissions are 10² times smaller than the corresponding values of the pure metals. No emission of M₂CO⁺ was found on CuNi during CO adsorption.     

On the electronic spectrum of the Mo2 molecule observed after flash photolysis of Mo(CO)6

Absorption and emission spectra of Mo₂ were investigated using flash photolysis of the Mo(CO)₆ molecule. Tentative vibrational and rotational analyses of the ⁹⁸Mo₂ spectra were performed. For the ground state, ${}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ type was proposed with ω_e = 477.1 cm^?1, $\text{r}{}_{\mathrm{e}}\text{= 1.929}\text{A}\text{?}$, and D₀(Mo₂) = 95 ± 15 kcal mole^?1. The results were compared with theoretical calculations for Mo₂ and experimental results for Cr₂ obtained previously. It seems reasonable that the transition metal diatomic molecules of this type have a high bond order.     

Cation self-diffusion and the isotope effect in Fe2O3

Self-diffusion of ⁵⁹Fe parallel to the c axis in single crystals of Fe₂O₃ has been measured as a function of temperature (1150–1340°C) and oxygen partial pressure (2 × 10^?3 ? p_O2 ? 1 atm) The temperature dependence of the cation diffusivity in air is given by the expression

$\text{D}{}_{\mathrm{<mtext>Fe</mtext>}}{}^1\text{= (1.9}{}_{\mathrm{?1.4}}{}^{\mathrm{+5.2}}\text{× 10}{}^9\text{exp}\text{(?}\text{141.4 ± 4.0 kcal/mole}\text{RT}\text{)}\text{cm}{}^2\text{/}\text{s}$

.The unusually large value of D₀ is interpreted in terms of the values of the preexponential terms in the reaction constants for the creation of defects in Fe₂O₃. The oxygen-partial-pressure dependence of the diffusivity indicates that cation self-diffusion occurs by an interstitial-type mechanism The simultaneous diffusion of ⁵²Fe and ⁵⁹Fe has been measured in Fe₂O₃. The small value of the isotope effect suggests that iron ions diffuse by an noncollinear interstitialcy mechanism, which is consistent with the crystal structure of Fe₂O₃.