Der Dampfdruck des Protactinium(V)-chlorids

Weigel, F.; Hoffmann, G. W.; Meer, N. Ter

doi:10.1524/ract.1969.11.34.210

Cited by 6 publications

(2 citation statements)

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“…However, the cubic bixbyite phase is thermodynamically stable at standard temperature and pressure conditions and also under typical scandate cathode operating conditions of high temperature (T~1200 K) and low pressure (P~10 -10 Torr). 29,32 Therefore, our conditions of interest rule out all Sc 2 O 3 polymorphs except the cubic bixbyite phase. Fig.…”

Section: A Dft Methods and Sc 2 O 3 Structurementioning

confidence: 99%

Intrinsic defects and conduction characteristics of Sc2O3in thermionic cathode systems

2012

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Recent experimental observations indicate that bulk Sc 2 O 3 (~200 nm thick), an insulator at room temperature and pressure, must act as a good electronic conductor during thermionic cathode operation, leading to the observed high emitted current densities and overall superior emission properties over conventional thermionic emitters which do not contain Sc 2 O 3 . Here, we employ ab initio methods using both semilocal and hybrid functionals to calculate the intrinsic defect energetics of Sc and O vacancies and interstitials and their effects on the electronic properties of Sc 2 O 3 in an effort to explain the good conduction of Sc 2 O 3 observed in experiment. The defect energetics were used in an equilibrium defect model to calculate the concentrations of defects and their compensating electron and hole concentrations at equilibrium. Overall, our results indicate that the conductivity of Sc 2 O 3 solely due to the presence of intrinsic defects in the cathode operating environment is unlikely to be high enough to maintain the magnitude of emitted current densities obtained from experiment, and that presence of impurities are necessary to raise the conductivity of Sc 2 O 3 to a high enough value to explain the current densities observed in experiment. The necessary minimum impurity concentration to impart sufficient electronic conduction is very small (approximately 7.5x10 -3 ppm) and is probably present in all experiments.

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Section: A Dft Methods and Sc 2 O 3 Structurementioning

confidence: 99%

Intrinsic defects and conduction characteristics of Sc2O3in thermionic cathode systems

2012

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“…4.12 Preparation of some chlorides and oxychlorides of Pa(IV) and Pa(V) (Muxart and Guillaumont, 1974;Pal'shin et al, 1968a). preparation of radiochemically pure 231 Pa and 234 Pa (Malm and Fried, 1950;Merinis et al, 1966;Brown, 1971). The vapor pressures of PaCl 5 and PaBr 5 have been measured by Weigel et al (1969Weigel et al ( , 1974 in the temperature range 490-635 K; the boiling points, extrapolated to 760 torr, were 420 and 428 C, respectively. The thermal stability studies of Brown and co-workers (1976b) show that PaI 4 is stable up to a temperature of 330 C, and that PaI 5 is stable to 200-300 C.…”

Section: Compoundmentioning

confidence: 99%