Cerium thermodynamic data

Careful analyses of the thermodynamic data of the praseodymium and terbium oxides led to the construction of their RCL-O2 phase diagrams (Hyde et al., 1966 Hyde and Eyring, 1965). The cerium oxides were studied by means of X-ray powder diffraction (Bevan, 1955) and the CeOx-02 phase diagram was constructed from equilibrium reaction studies at oxygen pressures down to 10-24 atm and temperatures up to 1200 °C (Bevan and Kordis, 1964 Ricken et al., 1984). It is worth to notice that the phase diagrams of Ce0x-02, PrCb-Cb, and Tb0x-02 systems... 

Several review articles and books on the lanthanide higher oxides, which include thermodynamic properties, have been published (Eyring, 1979 Haire and Eyring, 1994 Trovarelli, 2002 Adachi and Imanaka, 1998 Adachi et al., 2005). The systematic thermodynamic data of the cerium, praseodymium, and terbium oxides can be found in Bevan s and Eyring s papers (Hyde et al., 1966 Hyde and Eyring, 1965 Bevan and Kordis, 1964). 

Gingerich et al. (1972) have observed a number of cerium sulphide species containing two cerium atoms per molecule. Smoes et al. (1977) have reported similar results for the eueropium-sulphur system. Table 19 summarizes the thermodynamic data of these sulphide species. 

The known phase relationships, crystallographic and thermodynamic data of the known rare earth binary phase diagrams have been critically evaluated. The intra rare earth binary alloy systems will be reported in order of increasing atomic number with the exception of scandium and yttrium, which will follow lutetium in that order. The first system to be considered is lanthanum-cerium (atomic numbers 57 and 58) followed by lanthanum-praseodymium (atomic numbers 57 and 59), etc. Following... 

High temperature vaporization studies have yielded the thermodynamic data shown in table 27.5 on the cerium oxide system. 

Thermodynamic data calculated for the hydrolytic species of cerium(IV) are listed in Table 8.54. 

Table 8.54 Thermodynamic data for cerium(IV) species at 25 °C and comparison with data available in the literature.

The closest redox-stable analogue of Ce(IV) is thorium(IV), for which a large data base of thermodynamic parameters is available for the carboxylic add complexes (Martell and Smith 1977). Using the ionic radii of Shannon (1976) and recalling that the stability of lanthanide and actinide complexes is derived almost exclusively from electrostatics, we can estimate that a 16% increase in the log of the stability quotients for thorium (since AG oc Z /r oc log should provide a reasonable estimate for the corresponding complexes of cerium(IV) [rce(CN = 8) = 0.97 A, r iCN = 10) = 1.13 A, (l/rce)/(l/ xh) = 116, CN = coordination number]. 

Knowing the excitation spectrum one can compute the thermodynamic properties. In the local-moment regime they exhibit low-temperature T 7 ) Kondo anomalies that are due to the resonance states. For example, the static magnetic susceptibilty x(T), the specific heat, various transport coefficients and also dynamical quantities (photoemission spectra, dynamical structure function for neutron scattering) have been calculated (Bickers et al. 1985, Cox et al. 1986). An excellent model system for comparison with experimental data are the dilute (La, Ce)Bg alloys because of a fourfold degenerate Fg ground state of cerium (Zirngiebl et al. 1984). 

The last chapter (134) in this volume is an extensive review by Colinet and Pasturel of the thermodynamic properties of landianide and actinide metallic systems. In addition to compiling useful theiTnodynamic data, such as enthalpies, entropies, and free eneigies of formation and of mixing, the authors have made an extensive comparative analysis of the thermodynamic behavior of the rare earths and actinides when alloyed with metallic elements. They note that when alloyed with non-transition metals, the enthalpies of formation of uranium alloys are less negative than those of the rare earths while those of thorium and plutonium are about the same as the latter. For transition metal alloys the formation enthalpies of thorium and uranium are more negative than diose of the rare earths and plutonium (the latter two are about the same). The anomalous behaviors of cerium, europium and ytterbium in various compounds and alloys are also discussed along with the effect of valence state changes found in uranium and plutonium alloys. 

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