THERMOPHYSICAL PROPERTIES OF THE LANTHANIDE OXIDES. I. HEAT CAPACITIES, THERMODYNAMIC PROPERTIES, AND SOME ENERGY LEVELS OF LANTHANUM(III) AND NEODYMIUM(III) OXIDES FROM 5 TO 350°K.<sup>1</sup>

Justice, Bruce H.; Westrum, Edgar F.

doi:10.1021/j100796a031

Cited by 68 publications

(11 citation statements)

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“…49 At high temperatures a phononassisted long-range transport yields the high-temperature VRH. At intermediate temperatures the long-range transport ceases, but the individual hopping distance to the probe site is still too small to carry an effective charge transport.…”

Section: B Electron Transport Mechanismmentioning

confidence: 99%

Relaxation of electronic defects in pure and dopedLa2O3observed

et al. 1996

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Slow recovery processes of the electronic environment following the electron-capture decay of 111 In can reduce the amplitude of the perturbed ␥␥-angular correlation of a nuclear decay. This effect was used to quantitatively extract recovery rates of an electrically stable environment at the probe ion 111 Cd in La 2 O 3 . The recovery rates depend on the availability of electrons at the probe site, which in turn is governed by the concentration of electron sources and the transport mechanisms. Both properties are experimentally analyzed by variations of the temperature and oxygen partial pressure and by doping with two ͑Ba, Mg͒ and four-valent ions ͑Ce, Zr͒. Tunneling processes between defect levels in the band gap are proposed to account for the temperature dependence of the recovery rates. Unexpectedly, an enhanced electron availability is observed at temperatures below 200 K. The electric field gradients of substitutional 111 Cd and those generated by intrinsic defects and dopants are analyzed. A comparison to the probe ion 111m Cd, not affected by electron capture, is presented.

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Section: B Electron Transport Mechanismmentioning

confidence: 99%

Relaxation of electronic defects in pure and dopedLa2O3observed

et al. 1996

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“…Although the Schottky contributions may also be studied spectroscopically, the general unavailability of single crystal samples for absorption spectroscopy or for paramagnetic resonance experiments have tended to favor the calorimetric approach. Our initial measurements [2] on neodymium sesquioxide led to the estimation of levels more than an order of magnitude smaller than those estimated by Penny [3] from crystal-field splittings, but later, other spectroscopy [4] confirmed, in this instance, the calorimetric values.…”

Section: Lanthanide Schottky Lorementioning

confidence: 57%

“…Recognition of the importance of the Schottky thermophysical contribution came with a 1963 series of papers by Justice and Westrum [2] who studied the lanthanide sesquioxides and obtained an unusually rich yield of data concerning the energetics of the trivalent ions in these compounds. Although the Schottky contributions may also be studied spectroscopically, the general unavailability of single crystal samples for absorption spectroscopy or for paramagnetic resonance experiments have tended to favor the calorimetric approach.…”

Section: Lanthanide Schottky Lorementioning

confidence: 99%

Schottky contributions in chemical thermodynamics

Westrum

1985

Journal of Thermal Analysis

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Cryogenic heat-capacity determinations provide a useful tool for the determination of the energetic spectrum of condensed phases and also reveal information on their discrete electronic level structures as well. We have been interested in applying these techniques to actinide elements and have in recent months been working up the techniques to unravel the corresponding data for the lanthanide compounds--where opposite trends in cationic masses and molar volumes provide an opportunity to test theories useful for the resolution of excess heat capacity from lattice contributions.As an important aspect of heat capacities---especially of compounds with d andfelectrons--the Schottky contribution deserves to be much better known--by chemists, by physicists, and by students of thermodynamics. These remarks are designed to further that goal. Schottky's "Orphaned" contributionWerner Schottky first showed in 1922 [1] that a contribution to the energetics--spectroscopic or thermophysical---of a substance could be expected from excited electronic levels. The splitting of the ground-level term by the crystalline electric field also gives rise to the appearance of such a "Schottky anomaly" or "Schottky contribution" either in the heat capacity or in other thermophysical properties. The manifestation of this contribution to the heat capacity is a characteristic bellshaped curve skewed out on the high-temperature side. The temperature of the peak is related to the energetic separation of the levels and the maximum height is determined by the ratio of the degeneracies. Moreover, the total entropy under the curve is also related to the number of levels and the degeneracies involved. When the electronic energy increments are sufficiently small, the Schottky anomaly occurs at so low a temperature that, in comparison to the lattice contribution, the Schottky contribution stands out clearly. When energy levels are sufficiently spread so as to cause the occurrence of the contribution near or above ambient temperature, the maximum is typically so spread out as to be unrecognized unless the heat capacities of isostructural substances with nearly identical atomic masses are used for John Wiley & Sons, Limited, Chichester Akad~miai Kiadr, Budapest

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“…The accuracy in various energy levels can be verified from the measured and calculated Schottky heat capacity. This type of correlation of heat capacity with spectroscopy data is largely studied for compounds like RE2O3 [33][34][35][36][37][38][39][40][41], RE2S3 [42][43][44][45][46][47], RE (OH)3 [48][49][50][51][52] and REPO4 [53][54][55][56][57][58][59][60][61][62][63][64]. …”

Section: Heat Capacity Of Re6uo12(s)(re=la Pr Nd Sm)mentioning

confidence: 99%