Empirical confirmation of a bredig transition in UO2

Ralph, J. M.; Hyland, G. J.

doi:10.1016/0022-3115(85)90397-6

Cited by 53 publications

(29 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Measured elastic constants [2,3,29] do show a softening above 2400 K in the region where fast-ion behavior is expected in UO 2 , but the variation below this temperature is already very large. There is a high increase in specific heat [31][32][33][34][35][36][37][38][39] at high temperatures in UO 2 . Its behavior complies with the general belief that fluorites in general show a diffuse transition at about 0.8 T m (T m = melting point, T m of UO 2 is 3120 K).…”

Section: Introductionmentioning

confidence: 99%

Atomistic modeling of the vibrational and thermodynamic properties of uranium dioxide, UO2

Goel

Choudhury

Chaplot

2008

Journal of Nuclear Materials

View full text Add to dashboard Cite

Section: Introductionmentioning

confidence: 99%

Atomistic modeling of the vibrational and thermodynamic properties of uranium dioxide, UO2

Goel

Choudhury

Chaplot

2008

Journal of Nuclear Materials

View full text Add to dashboard Cite

“…Calculated specific heat at constant pressure, C P (T) have been compared with available data [36][37][38][39][40] in Fig. 3 for both the systems.…”

Section: Specific Heatmentioning

confidence: 99%

“…Neutron scattering measurements [34] indicate that the anionic sub-lattice in UO 2 becomes heavily disordered in the region of 2300 K. Measured elastic constants [35] do show a softening above 2400 K in the region where fast-ion behavior is expected in UO 2 , but the variation below this temperature is already very large. There is a large increase in specific heat [36][37][38]] at high temperatures in UO 2 . Li 2 O shows a sudden decrease in the value of the C 11 elastic constant at the transition temperature, T c~1 200 K (the melting point T m of Li 2 O is 1705 K [22]), but there seems no drastic change in the specific heat [39,40].…”

Section: Introductionmentioning

confidence: 99%

“…Knowledge of the thermodynamic and transport properties of nuclear materials [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] at high temperatures is of great interest. UO 2 belongs to the class of superionics, wherein fast-ion conduction processes involving rapid diffusion of a significant fraction of the oxygen atoms within an essentially rigid framework of uranium atoms occurs.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Fast ion diffusion, superionic conductivity and phase transitions of the nuclear materials UO₂ and Li₂O

Goel

Choudhury

Chaplot

2007

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

Lattice dynamics and molecular dynamics studies of the oxides UO 2 and Li 2 O in their normal as well as superionic phase are reported. Lattice dynamics calculations have been carried out using a shell model in the quasiharmonic approximation. The calculated elastic constants, phonon frequencies and specific heat are in good agreement with reported experimental data, which help validate the interatomic potentials required for undertaking molecular dynamics simulations. The calculated free energies reveal high pressure fluorite to cottunite phase transitions at 70 GPa for UO 2 and anti-fluorite to anti-cotunnite phase transformation at 25 GPa for Li2O, in agreement with reported experiments. Molecular dynamics studies shed important insights into the mechanisms of diffusion and superionic behavior at high temperatures. The calculated superionic transition temperature of Li 2O is 1000 K, while that of UO2 is 2300 K.

show abstract

“…Data for the temperature dependence of the enthalpy of UO 2 , obtained using drop calorimetry methods, showed a clear peak in the specific heat at %2610 K [87]. However, the structural origin of this feature was questioned by some groups, who proposed an alternative explanation in terms of electronic disorder (small polarons of the type 2U 4 þ $ U 5 þ þ U 3 þ ), because the band gap of UO 2 ($2 eV) was much smaller than the formation energy for anion Frenkel defects ($5 eV) [88,89].…”

Section: Oxide Fluoritesmentioning

confidence: 99%

Superionic Materials: Structural Aspects

Hull

2009

Solid State Electrochemistry I

View full text Add to dashboard Cite

Superionic conductors are solids which show high levels of ionic conductivity, which often approach values more typical of ionic liquids. This behavior is associated with the presence of extensive dynamic disorder within the crystalline lattice, and the nature of the defects has long proved a challenge to both experimental and computational approaches. This chapter provides a short introduction to the major techniques used to probe the structure-property relationships within superionic conductors, highlighting the roles of X-ray diffraction, neutron diffraction, EXAFS, NMR, and molecular dynamics methods. The relative advantages and limitations of each method are briefly described, followed by a discussion of the major families of highly conducting compounds and an assessment of the current state of knowledge concerning their structural properties. OverviewThe high levels of ionic conductivity associated with superionic conductors, which often approach values more typical of ionic liquids, are associated with the presence of extensive dynamic disorder within the crystalline lattice. As a consequence, a full understanding of the interplay between the structural and conducting properties of these important materials requires a detailed characterization of both the long-range arrangement of the ions within the crystal lattice and the short-range ion-ion correlations within the defects. The presence of significant levels of disorder, which can be both intrinsic (thermally induced) and extrinsic (due to chemical doping) in origin, presents a challenge to the conventional experimental methods used to provide structural information. In the case of superionic conductors, no one technique can provide a complete picture, and it is often necessary to employ several complementary approaches, of which X-ray diffraction (XRD), neutron diffraction, Solid State Electrochemistry I: Fundamentals, Materials and their Applications. Edited by Vladislav V. Kharton

show abstract

Empirical confirmation of a bredig transition in UO2

Cited by 53 publications

References 9 publications

Atomistic modeling of the vibrational and thermodynamic properties of uranium dioxide, UO2

Atomistic modeling of the vibrational and thermodynamic properties of uranium dioxide, UO2

Fast ion diffusion, superionic conductivity and phase transitions of the nuclear materials UO₂ and Li₂O

Superionic Materials: Structural Aspects

Contact Info

Product

Resources

About

Empirical confirmation of a bredig transition in UO2

Cited by 53 publications

References 9 publications

Atomistic modeling of the vibrational and thermodynamic properties of uranium dioxide, UO2

Atomistic modeling of the vibrational and thermodynamic properties of uranium dioxide, UO2

Fast ion diffusion, superionic conductivity and phase transitions of the nuclear materials UO2 and Li2O

Superionic Materials: Structural Aspects

Contact Info

Product

Resources

About

Fast ion diffusion, superionic conductivity and phase transitions of the nuclear materials UO₂ and Li₂O