Relative Partial Molar Entropy Research Articles

Electrochemical behaviour of erbium in the eutectic LiCl–KCl at W and Al electrodes

The electrochemical behaviour of Er(III) was studied in the molten LiCl–KCl eutectic for temperatures ranging from 653 to 823 K. Transient electrochemical techniques, such as cyclic voltammetry, chronopotentiometry and chronoamperometry were used in order to study the reaction mechanism and the transport parameters of electroactive species at a tungsten electrode. The results showed that in the eutectic LiCl–KCl, the reduction of Er(III) occurs in a step with a global exchange of three electrons, and that electrocrystallization plays an important role in the electrodeposition process. Chronoamperometric studies indicated instantaneous nucleation of erbium with three-dimensional growth of the nuclei whatever the applied overpotential. Mass transport towards the electrode is a simple diffusion process, and the temperature dependence of the diffusion coefficient of the electroactive specie Er(III) was written in the following equation: log D Er ( III ) = − 2.77 ( ± 0.175 ) − 1695 ( ± 121 ) T The electrode reactions of the LiCl–KCl–ErCl 3 solutions at an Al wire were also investigated by cyclic voltammetry and open circuit chronopotentiometry in the temperature range of 673–823 K. The redox potential of the Er(III)/Er couple at the Al electrode was observed at more positive potentials values than those at the inert electrode. This potential shift was thermodynamically analyzed by a lowering of activity of Er in the metal phase due to the formation of intermetallic compounds. The activities and relative partial molar Gibbs energies of Er were obtained from the open circuit chronopotentiometry measurements. The standard Gibbs energies of formation for the ErAl 3 intermetallic compound were estimated and the relative partial molar entropies and enthalpies of Er were also calculated.

The electrochemical behaviour of the Pr(III)/Pr redox system at Bi and Cd liquid electrodes in molten eutectic LiCl–KCl

The electrode reactions of LiCl–KCl–PrCl 3 solutions at the surface of liquid electrodes, i.e. Cd and Bi, were investigated by electrochemical techniques. The redox potential of the Pr(III)/Pr couple at the liquid electrodes were observed at more positive potential values than those at one inert electrode. This potential shift was thermodynamically analysed by a lowering of activity of Pr in the metal phase. Cyclic voltammetry, using Cd and Bi pools as working electrodes, was conducted in order to study the reaction mechanism. The results suggest a quasi-reversible behaviour of the Pr(III)/Pr electrochemical system at the liquid electrodes, and the values of the kinetic parameters, k 0 and α as well as the reversible half wave potential, E 1 / 2 r , have been obtained. The interdiffusion coefficients of Pr in the metal phases seem to be similar to the diffusion coefficient of Pr(III) in solution. From comparison between the equilibrium potential adopted by a praseodymium electrode immersed in a solution containing Pr(III) ions, and the calculated E 1 / 2 r of the system Pr(III)/Pr–M (being M = Cd or Bi) it has been possible to estimate the activity coefficients of Pr in the Cd and Bi phases. Open circuit chronopotentiometry using Cd or Bi film electrodes was also conducted. Electromotive force, emf, measurements for various intermetallic compounds in two-phase coexisting states were carried out in the temperature range of 673–823 K. The activities and relative partial molar Gibbs energies of Pr were obtained from the measured emf for various Pr–Cd and Pr–Bi intermetallic compounds, PrCd 11, PrCd 6, PrCd 4.46, PrBi 2 and PrBi. The relative partial molar entropies and enthalpies of Pr were also calculated from the temperature dependence of the emf. The standard Gibbs energies of formation for the Pr–Cd and Pr–Bi intermetallic compounds were calculated.

Measurements on the Thermodynamic Properties of Porewater in Sandstone by Vapor Pressure Method

The thermodynamic properties of porewater in sandstone were obtained as a function of water content and temperature by vapor pressure method. The activity, the relative partial molar Gibbs free energy (Δ HH2O), the relative partial molar enthalpy (Δ SH2O) and the relative partial molar entropy (ΔSH2O) of the porewater were determined at 298.15 K. The activity decreased with decreasing water content in the region where water content is about 1.5%, and drastically decreased in the region where water content is about 0.5%. No clear dependencies of Δ H 2O and Δ SH2O on water content were found. Synthesizing the correlations of the activity, Δ GH2O, Δ H H2O and Δ S H2O with water content and the enthalpy and entropy of fusion for ice, the porewater at the surface of the solid was found to have a low chemical potential compared with free water, and dissimilar with the structure of ice. Correlating the activity and Δ GH2 O with water content, the specific surface area of sandstone and the porosity, the porewater is deduced to be weakly affected up to a distance of approximately 3 nm from the surface of the solid. However, as the porewater approaches a distance of approximately 1.1nm from the solid surface, the effect from the solid surface abruptly becomes strong. This is deduced to be the effects of hydrogen bond at the solid surface and hydration to cations corresponding to the CEC.

Electrical Conductivity and Thermodynamic Properties of Some Alkaline Earth-Doped Lanthanum Chromites

Alkaline-earth doped lanthanum chromites are currently the interconnecting materials of choice for solid oxide fuel cells (SOFCs). Since these materials in SOFC operating conditions are under a large oxygen potential gradient and at high temperature (1273 K), a thorough knowledge of their physical and thermochemical properties is very important. In the present study, the alkaline-earth doped lanthanum chromites La1-xSr x CrO3 (x=0–0.3) and La0.7Ca0.3CrO3 were prepared from complex precursors isolated from the La(NO3)3–Cr(NO3)3–urea system. The oxide powders were characterized by means of X-ray diffraction (XRD). The DC electrical conductivities of the samples were measured in the temperature range of 295–1273 K in air. The thermodynamic properties represented by the relative partial molar free energies, enthalpies, and entropies of oxygen dissolution in the perovskite phase, as well as the partial pressures of oxygen, have been investigated by the solid electrolyte galvanic cells method coupled with the solid-state coulometric titration technique, within the temperature range of 1073–1273 K and in a reducing atmosphere (10−5 Pa). The variation of the electrical conductivities and thermodynamic properties with changing oxygen stoichiometry is discussed. The study demonstrates new correlations existing between the structural, electrical, and thermodynamic properties in the doped lanthanum chromites.

Measurements on the Thermodynamic Properties of Porewater in Sandstone by Vapor Pressure Method

The thermodynamic properties of porewater in sandstone were obtained as a function of water content and temperature by vapor pressure method. The activity, the relative partial molar Gibbs free energy (Δ HH2O), the relative partial molar enthalpy (Δ SH2O) and the relative partial molar entropy (ΔSH2O) of the porewater were determined at 298.15 K. The activity decreased with decreasing water content in the region where water content is about 1.5%, and drastically decreased in the region where water content is about 0.5%. No clear dependencies of Δ H 2O and Δ SH2O on water content were found. Synthesizing the correlations of the activity, Δ GH2O, Δ H H2O and Δ S H2O with water content and the enthalpy and entropy of fusion for ice, the porewater at the surface of the solid was found to have a low chemical potential compared with free water, and dissimilar with the structure of ice. Correlating the activity and Δ GH2 O with water content, the specific surface area of sandstone and the porosity, the porewater is deduced to be weakly affected up to a distance of approximately 3 nm from the surface of the solid. However, as the porewater approaches a distance of approximately 1.1nm from the solid surface, the effect from the solid surface abruptly becomes strong. This is deduced to be the effects of hydrogen bond at the solid surface and hydration to cations corresponding to the CEC.

Oxygen nonstoichiometry ( δ) of TiO 2−δ-revisited

Oxygen nonstoichiometry ( δ ) of “undoped” polycrystalline TiO 2− δ has been measured as a function of oxygen partial pressure in the widest ever examined range of 10 - 18 ⩽ P O 2 / atm ⩽ 10 - 1 at elevated temperatures (1073⩽ T/K⩽1473) by thermogravimetry and coulometric titrometry combined and compared with all the reported values. Isothermal variation of nonstoichiometry against P O 2 is explained with a defect model involving quadruply ionized titanium interstitials, electrons, holes, and unidentified acceptors which may be background impurity acceptors or cation vacancies. The equilibrium constants for intrinsic electronic excitation reaction and redox reaction are determined from the nonstoichiometry measured and compared exhaustively with all the reported values. The relative partial molar enthalpy and entropy of oxygen are evaluated as functions of nonstoichiometry and the inner workings of their variations discussed.

Experimental Vapor Pressures and Derived Thermodynamic Properties of Aqueous Solutions of Lithium Nitrate from 423 to 623 K

Vapor pressures of six aqueous lithium nitrate solutions with molalities of (0.181, 0.526, 0.963, 1.730, 2.990, and 5.250) mol-kg−1 have been measured in the temperature range 423.15–623.15 K with a constant-volume piezometer immersed in a precision liquid thermostat. The static method was used to measure the vapor pressure. The total uncertainty of the temperature, pressure and composition measurements were estimated to be less than 15 mK, 0.2%, and 0.014%, respectively. The vapor pressures of pure water were measured with the same apparatus and procedure to confirm the accuracy of the method used for aqueous lithium nitrate solutions. The results for pure water were compared with high-accuracy PS–TS data calculated from the IAPWS standard equation of state. Important thermodynamic functions (activities of water and lithium nitrate, partial molar volumes, osmotic coefficient, excess relative partial molar entropy, and relative partial molar enthalpy values of the solvent) were derived using the measured values of vapor pressure for the solution and pure water. The measured and derived thermodynamic properties for solutions were compared with data reported in the literature. The present results are consistent with most previous reported thermodynamic data for the pure water and H2O + LiNO3 solutions at low temperatures.

Thermodynamic Properties of Nano- and Micro-Structured Perovskite-Type Compounds

The thermodynamic properties of the ABO3 perovskite-type compounds are strongly affected by the A- and B- site substitution and the oxygen nonstoichiometry. The paper presents the thermodynamic properties of some doped nano- and microstructured lanthanum manganites of general formula La1-xMxMn1-yMeyO3 (where M=Sr, Ca; Me=Al; x=0.3;0.33, y=0;0.05) which have been studied within the temperature range of 873-1273 K in a reducing atmosphere (10-6 Pa). The relative partial molar free energies, enthalpies and entropies of oxygen dissolution in the perovskite phase and the equilibrium partial pressures of oxygen have been obtained by using a solid electrolyte galvanic cell method. The influence of the oxygen stoichiometry change on the thermodynamic properties was examined using the data obtained by a coulometric titration technique coupled with measurements of the electromotive force (EMF). The focus of the research was to emphasise modifications of the thermodynamic properties connected with the nanocrystalline state. The results obtained are discussed in relation to significant changes in the overall concentration of defects.

Hydriding properties of Ti-substituted non-stoichiometric AB 2 alloys

Stoichiometric Ti 0.1Zr 0.9Mn 0.9V 0.1Fe 0.5Co 0.5 and non-stoichiometry (Ti 0.1Zr 0.9) 1.1Mn 0.9V 0.1Fe 0.5Co 0.5, Ti 0.1Zr 0.9(Mn 0.9V 0.1) 1.1Fe 0.5Co 0.5 and Ti 0.1Zr 0.9Mn 0.9V 0.1Fe 0.55Co 0.55 alloys have been synthesized and the lattice constants and unit cell volume have been obtained by using powder X-ray diffractograms. Pressure-composition (PC) isotherms have been obtained in the temperature and pressure ranges 30–125 °C and 0.1–30 bar using pressure reduction method and the effect of non-stoichiometry on the hydrogen absorption properties have been studied. Maximum hydrogen storage capacity is around 3.4 hydrogen atoms per formula unit at 30 bar and 30 °C in Ti 0.1Zr 0.9Mn 0.9V 0.1Fe 0.5Co 0.5. The relative partial molar enthalpy (Δ H H) and relative partial molar entropy (Δ S H) of the dissolved hydrogen have been calculated from the PC isotherms and their variation with hydrogen concentration has been plotted to identify the existence of different phases. The powder X-ray diffraction patterns of Ti 0.1Zr 0.9Mn 0.9V 0.1Fe 0.5Co 0.5–H x ( x=1.6 and 3.2) have been obtained in order to study the effect of hydrogenation on the crystal structure. The activation energy and diffusion coefficient of dissolved hydrogen in Ti 0.1Zr 0.9Mn 0.9V 0.1Fe 0.5Co 0.5 have been calculated from the kinetics of hydrogen absorption measurements at different temperatures and compared with Ti 0.1Zr 0.9Mn 0.9V 0.1Fe 0.5Ni 0.5. The effect of non-stoichiometry on the kinetics of hydrogen absorption at 50 °C has been studied and discussed.

Experimental vapor pressures and derived thermodynamic properties of aqueous solutions of lithium sulfate from 423 to 573 K

Vapor pressures of four aqueous lithium sulfate solutions (0.279, 0.886, 1.322, and 1.600 mol kg −1) have been measured in the temperature range from 423.15 to 573.15 K with a constant-volume piezometer immersed in a precision liquid thermostat. The static method was used to measure of vapor pressure. The total uncertainty of temperature, pressure, and composition measurements were estimated to be less than 10 mK, 0.2, and 0.014%, respectively. The vapor pressures of pure water were measure to confirm the accuracy of the method for aqueous lithium sulfate solutions taken from the apparatus and procedure of measurements. The results for pure water were compared with high-accuracy P S– T S measurements by other authors and with values calculated from IAPWS formulation. Useful thermodynamic functions (water activities, excess relative partial molar entropy, and relative partial molar enthalpy values of solvent) were derived using measured values of vapor pressure for the solution and pure water. The measured and derived thermodynamic properties for solution were compared with data reported in the literature. Present results are consistent with most of the previous thermodynamic data for the pure water and H 2O + Li 2SO 4 solutions.

Thermodynamic properties of DyNi intermetallic compounds

Electromotive force (EMF) measurements for various DyNi intermetallic compounds in two-phase coexisting states were carried out in the temperature range of 673–773 K in a molten LiCl–KCl–DyCl 3 (0.5 mol%) system. The activities and relative partial molar Gibbs free energies of Dy were obtained from the measured EMFs for various DyNi intermetallic compounds, DyNi 2, DyNi 3, Dy 2Ni 7, and DyNi 5. The relative partial molar entropies and enthalpies of Dy were also calculated from the temperature dependence of the EMFs. The activities and relative partial molar properties of Ni in the compounds were calculated from the activities of Dy by using Gibbs–Duhem equation. Finally, the standard Gibbs free energies of formation for the DyNi intermetallic compounds were estimated.

Gibbs Energy and Entropy of Mixing in the NaNO 2 -KNO 3 System

The activity and activity coefficients of the components of the NaNO2-KNO3 system, determined from the experimental data on the saturated vapor pressure at 798, 823, and 848 K, are used to calculate the relative and excess partial molar Gibbs energies (ΔG i and ΔG i e x c), entropies (ΔS i and ΔS i e x c), and integral relative and excess thermodynamic functions (ΔG, ΔG e x c, ΔS, and ΔS e x c) of the system.

Thermodynamic characterisation of some doped lanthanum chromites used as interconnects in SOFC

The solid-oxide electrolyte galvanic cell method has been employed in order to characterize, from the thermodynamic point of view, some materials based on substituted lanthanum chromites: La 1− x M x CrO 3 (where M=Sr, Ca; x=0.2, 0.3) and La 0.8Sr 0.2Cr 0.95Mg 0.05O 3. The thermodynamic properties represented by the relative partial molar free energies, enthalpies and entropies of oxygen dissolution in the perovskite phase, as well as the partial pressures of oxygen, have been obtained as a function of temperature and substituent nature within the temperature range of 1073–1273 K and in reducing atmosphere (10 −5 Pa). The influence of oxygen stoichiometry change on thermodynamic properties was examined using the data obtained by a coulometric titration technique coupled with EMF measurements. An attempt to verify a previously proposed defect-structure model is also made.

Hydrogen storage studies in Zr 0.9Ho 0.1MnFe 0.5Co 0.5 and Zr 0.9Ho 0.1MnFe 0.5Ni 0.5

The hydrogen storage properties and the thermodynamics of dissolved hydrogen in the C14 hexagonal Laves phase Zr 0.9Ho 0.1MnFe 0.5Co 0.5 and Zr 0.9Ho 0.1MnFe 0.5Ni 0.5 alloys are studied. The partial replacement of Ho in Zr site in ZrMnFe 0.5Co 0.5 and ZrMnFe 0.5Ni 0.5 alloys leads to the expansion of their lattices. The pressure–composition (p–c) isotherms of Zr 0.9Ho 0.1MnFe 0.5Co 0.5 and Zr 0.9Ho 0.1MnFe 0.5Ni 0.5 in the pressure and temperature ranges 0.6⩽ P(bar)⩽20 and 30⩽ T(°C)⩽100 show sloppy plateau ( α+ β) region. The average relative partial molar enthalpy of dissolved hydrogen at the ( α+ β) region in Zr 0.9Ho 0.1MnFe 0.5Co 0.5-H and Zr 0.9Ho 0.1MnFe 0.5Ni 0.5-H are −15.5 kJ ( mol H ) −1 and −14.5 kJ ( mol H ) −1, respectively. Similarly the average relative partial molar entropy of dissolved hydrogen at the two-phase region in Zr 0.9Ho 0.1MnFe 0.5Co 0.5-H and Zr 0.9Ho 0.1MnFe 0.5Ni 0.5-H are −51 J K −1 ( mol H ) −1 and −50 J K −1 ( mol H ) −1, respectively. The presence of α, ( α+ β)- and β-phases as seen in the p–c isotherms, is seen from the powder diffractograms of the alloy hydrides. The kinetics of hydrogen absorption in these alloys are quite fast which is between 15 and 20 min at room temperature.

Oxygen nonstoichiometry of undoped BaTiO 3− δ

Oxygen nonstoichiometry ( δ) of “undoped”, polycrystalline BaTiO 3− δ (but with two different nominal purity) has been measured as a function of oxygen partial pressure in the range of 10 −15≤ P O 2 /atm≤0.1 at elevated temperatures (1073≤ T/K≤1273) by a solid-state coulometric titration technique. Each isotherm varies sine-hyperbolically against log( P O 2 ) with an inflexion point therein (corresponding to the electronic stoichiometric composition or δ=0). The nonstoichiometry variation is attributed to oxygen vacancies compensated mostly by background and/or intrinsic acceptors in the higher P O 2 region and by electrons in the lower P O 2 region. The purity effect on nonstoichiometry is discussed. The intrinsic electronic excitation equilibrium constant is evaluated and compared exhaustively with the reported. The relative partial molar enthalpy and entropy of component oxygen are also evaluated as functions of the nonstoichiometry.

Solubility and kinetic properties of deuterium in single crystal Pd

The pressure–composition (PC) behavior of deuterium in single crystal Pd has been measured over a temperature range extending from room temperature to 393 K. These data allow the determination of (i) relative partial molar enthalpy and entropy, without the contribution of the configuration entropy, for the dilute solid solution phase, (ii) enthalpy and entropy change characterizing the α→α′ phase transformation, and (iii) Gibbs free energy loss associated with the PC thermodynamic hysteresis. Comparison of these quantities with published data for polycrystal Pd and with our own polycrystal Pd measurements show good agreement, indicating grain boundary interfaces and second phase inclusions known to exist in polycrystalline Pd do not influence these thermodynamic properties. The time dependence of deuterium absorption and desorption from the gas phase has been measured in both single and polycrystal Pd as well. The activation energy and diffusion constant of deuterium in the solid solution phase of Pd agree with published values. The time dependence of deuterium absorption and desorption within the miscibility gap are reduced by approximately two orders of magnitude compared to solid solution behavior. The two-phase kinetic data exhibit an Arrhenius behavior with a factor of two increase in the activation energy compared to diffusion. This is attributed to the phase transformation process controlling the deuterium absorption/desorption kinetic behavior when the Pd–D system is within the miscibility gap.

Hydrogen absorption studies in ZrMnFe 0.7Co 0.3

The hydrogen absorption, kinetics of hydrogen absorption and thermodynamics of dissolved hydrogen in C14 Laves phase alloy ZrMnFe 0.7Co 0.3 are studied in the ranges 1≤ P (bar)≤30 and 303≤ T (K)≤473. Substituting Co at Fe site in ZrMnFe leads to the contraction of the lattice and subsequently increases the plateau pressure with a reduction in hydrogen intake capacity. The relative partial molar enthalpy and entropy of dissolved hydrogen in ZrMnFe 0.7Co 0.3–H are found to be in the ranges −(6–11) kJ (mol H) −1 and −(20–42) J K −1 (mol H) −1, respectively. The presence of α, ( α+ β) and β phases as seen in the P-C isotherms, is further confirmed by thermodynamic studies and kinetics of hydrogen absorption.

Hydrogen absorption–desorption characteristics, kinetics of hydrogen absorption and thermodynamics of dissolved hydrogen in Zr 0.1Tb 0.9Fe 1.5Co 1.5

The hydrogen absorption and desorption pressure–composition isotherms of the PuNi 3 type rhombohedral Zr 0.1Tb 0.9Fe 1.5Co 1.5 are investigated by using a Sieverts’ type apparatus based on pressure reduction method in the ranges 75≤ T(°C)≤150 and 0.01≤ P(bar)≤30. The hydrogen solubility properties are compared with those of Zr 0.1Tb 0.9Fe 3 to study the effect of Co substitution at the Fe site. The P–C isotherms show the α→(α+β) transition at an average hydrogen concentration ( y= n H/ n fu) of 0.2 and (α+β)→β transition at an average value of y=2.5. Further, the plateau pressure of Zr 0.1Tb 0.9Fe 1.5Co 1.5–H at any given temperature increases when compared to that of Zr 0.1Tb 0.9Fe 3–H. It is found that hysteresis is quite small in the temperature regions investigated. At a hydrogen concentration of 3.1 hydrogen atoms per formula unit, the host lattice is accompanied by an expansion of about 16% without any change in crystal structure as evidenced by powder X-ray diffraction studies of Zr 0.1Tb 0.9Fe 1.5Co 1.5H 3.1. The thermodynamical parameters viz., the relative partial molar enthalpy (Δ H H) and the relative partial molar entropy (Δ S H) of dissolved hydrogen are found to be in the ranges −(17–23) kJ(mol H) −1 and −(48–66) JK −1(mol H) −1 respectively for absorption and, +(19–23) kJ(mol H) −1 and +(46–72) JK −1(mol H) −1 for desorption. From the dependence of Δ H H on y, the different phases [α, (α+β), β] and phase boundaries [α→(α+β)], [(α+β)→β] of the alloy–hydrogen system are identified. The different phases identified by the thermodynamic studies agree well with those seen in the hydrogen absorption isotherms of the respective alloy. These phases are further confirmed through powder X-ray diffraction studies. The kinetic studies show that the rate of hydrogen absorption is relatively slow when compared with Zr 0.1Tb 0.9Fe 3–H.

Hydrogen solubility properties of Ti0.42Zr0.08Fe0.50 alloy

The hydrogen solubility properties were investigated with the aim of developinghydrides of Ti based alloys for hydrogen storage applications. The hydrogen absorptioncharacteristics and the thermodynamics of the dissolved hydrogen in Ti 0.42Zr 0.08Fe 0.50 were investigated in the ranges 0 ⩽ P⧸bar ⩽ 40 and 323 ⩽ T⧸K ⩽ 473 by pressure reduction method and compared with TiFe and Ti 0.45Fe 0.45B 0.1. The hydrogen intake capacity at any particular temperature and hydrogenequilibrium pressure is larger in the α phase of Ti 0.42Zr 0.08Fe 0.50–H compared to that in TiFe–H and nearly the same in the β phase. The plateau pressurein Ti 0.42Zr 0.08Fe 0.50 –H at any temperature is slightly higher than that inTiFe–H. The absolute values of the relative partial molar enthalpy and entropy of the dissolvedhydrogen in Ti 0.42Zr 0.08Fe 0.50–H are comparable to TiFe–H. The relativepartial molar enthalpy and entropy of hydrogen absorption decreases with the increase ofhydrogen content in the α phase of Ti 0.42Zr 0.08Fe 0.50–H and moreor less remain constant in the α+ β phase.

Nonstoichiometry (δ) and High-Temperature Thermodynamic Properties of (Mg0.22Mn0.07Fe0.71)3−δO4 Ferrite Spinel

Nonstoichiometry of (Mg0.22Mn0.07Fe0.71)3−δO4 ferrite has been measured in the temperature range of 1000×1200°C as a function of oxygen activity (aO2) using a solid state coulometric titration technique. At a given temperature, the nonstoichiometry (δ) was found to vary with the oxygen activity as δ=[V]0 · a2/3O2 −[I]0·a−2/3O2 where [V]0 and [I]0 are constants. This aO2-dependence of δ was explained in terms of Frenkel disorder, i.e., cation vacancy and interstitial. From the temperature dependence of the defect constants ([V]0 and [I]0) and the oxygen activity for the stoichiometric composition (δ=0), thermodynamic quantities such as enthalpies for the defect formation reactions and relative partial molar enthalpy and entropy of oxygen were calculated.