Thermodynamic properties of uranium compounds. Part 3.—Low-temperature heat capacity and entropy of UP and U<sub>3</sub>P<sub>4</sub>

The heat capacities of triuranium tetraarsenide (U3As4) and triuranium tetraantimonide (U3Sb4) , measured by adiabatic calorimetry over the temperature range 5-950 K, show sharp)t-shaped transitions at 196.1 and 147.5 K, respectively. The maxima are related to the appearance of permanent magnetic moments below 198 and 148 K. Excess cooperative entropies associated with ferromagnetic ordering are tentatively estimated as 6.7 for U3As 4 and 6.8 cal K ~ mole-t for U3Sb 4. These are larger than the two literature values reported for U3P 4 (1.5 and 3.1 cal K-j mole-J). The fact that these entropy of transition values are much smaller than would be expected from ASt = R In (2J + 1) for the 3H 4 ground term (J = 4) and that the observed heat capacities at high temperatures are much larger than would be expected from lattice plus dilational contributions are evidence of crystal field effects. The total electronic entropies to 950K are estimated as 11.05 and 12.95 cal K ~mole-~ for U~As4 and 1.13Sb4, respectively. Thermal functions for both U3As 4 and U3Sb 4 are integrated from the experimental data up to 950 K.

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“…The excess entropy for U3P4, which has been calculated from heat-capacity values given in Refs. [14] and [15], is plotted as well.…”

Section: Discussionmentioning

confidence: 99%

“…to be metallic [l]. Low-temperature heat-capacity data for U3P4 [14,15] have been reported in two works, which disagree by a factor of two on the entropy of transition (as,).…”

Section: Introductionmentioning

confidence: 99%

Actinoid pnictides—I

Alles

Falk

Westrum

et al. 1977

Journal of Inorganic and Nuclear Chemistry

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“…UCl-, N, : De Novion and Costa [61,62] [64] and [50]. U3As4, U3Sb, : Both compounds have been considered in the recent careful study of Alles et al [65] from 5 to 950 K and their specific heat curves are very close except for the Curie anomalies.…”

Section: Pseudo -Binary Compoundsmentioning

confidence: 99%

“…than for U3P4. The former data were thought better defined in [65] than in [50] because [65] worked down to 5 K but the recent low tempe-…”

Section: Pseudo -Binary Compoundsmentioning

confidence: 99%

The specific heat of actinide compounds : are those measurements useful ?

Blaise

1979

J. Phys. Colloques

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The experimental difficulties and the problem of the separation of heat capacity data in its different components are briefly recalled. Then a review is given of the specific heat measurements made on the principal binary and ternary actinide compounds. In each case, the results are used to discuss the electronic structure models. Attention is drawn on the interest of studying the critical phenomena in the actinide compounds. Some examples and suggestions are issued from the systems above mentioned

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“…U P orders antiferromagnetically a t about 125 K with a type 1 magnetic structure and the ordered moment changes abruptly a t 23 K with no change of the magnetic structure [4 to 61. In addition to the change of the ordered moment, a drop in NMR frequency [7], a sharp peak in the specific heat versus temperature curve [8], a change of the thermal expansion coefficient from positive to negative [91, and a steep increase in the electrical resistivity also occur a t near 23 K [lo]. UAs orders antiferromagnetically a t 127 K with type 1 structure.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Susceptibility of UP and UAs

Troć

Lam

1974

Physica Status Solidi (b)

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The magnetic susceptibility of UP and UAs have been measured as a function of temperature from 4.2 to 1000 K and the results are compared with published results in the literature. From the temperature dependence of the magnetic susceptibility, the most likely 5f3 electronic configuration of the uranium ion in these two compounds are deduced using a nonperturbative (full J-mixing) crystal-field theory. E s wurde der Temperaturverlauf der magnetischen Suszeptibilitiit von UP und UAs im Bereich von 4,2 bis 1000 K gemessen. Die erhaltenen Resultate werden mit den Ergebnissen anderer Autoren verglichen. Die Analyse der Temperaturabhgngigkeit der magnetischen Suszeptibilitgt mit Kristallfeld-Theorie ohne Storung (volle J-Mischung) fiihrt zu der SchluBfolgerung, da13 die Elektronenkonfiguration des Uranions in diesen beiden Verbindungen 5f3 ist.

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Thermodynamic properties of uranium compounds. Part 3.—Low-temperature heat capacity and entropy of UP and U₃P₄

Cited by 69 publications

References 1 publication

Actinoid pnictides—I

Actinoid pnictides—I

The specific heat of actinide compounds : are those measurements useful ?

Magnetic Susceptibility of UP and UAs

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Thermodynamic properties of uranium compounds. Part 3.—Low-temperature heat capacity and entropy of UP and U3P4

Cited by 69 publications

References 1 publication

Actinoid pnictides—I

Actinoid pnictides—I

The specific heat of actinide compounds : are those measurements useful ?

Magnetic Susceptibility of UP and UAs

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Thermodynamic properties of uranium compounds. Part 3.—Low-temperature heat capacity and entropy of UP and U₃P₄