Orientation of an oxygen-induced non-axially symmetric electric field gradient at Ta in Nb

Wrede, U.; Schaefer, Th.; Vianden, R.

doi:10.1007/bf01312840

Cited by 10 publications

(4 citation statements)

References 13 publications

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“…At elevated temperatures (between 900 and 1273 K), the value of vQ1 decreases from 320 MHz to 274 MHz. This value is close to the quadrupole frequency associated with Hf impurity trapping an interstitial oxygen (Wrede et al 1986). Hence, the observed frequency of v m at elevated temperatures may be attributed to the formation of oxygen mediated defect complexes at Hf sites.…”

Section: Effect Of Hydrogen On Defect Recover) In Nbhfsupporting

confidence: 70%

Cold-worked and hydrogen chargedNbHf as studied by TDPAC and positron lifetime measurements

et al. 1998

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Time differential perturbed angular correlation (TDPAC) and positron lifetime measurements on cold-worked and hydrogen charged NbHf indicate a strong binding of hydrogen decorated vacancy clusters with Hf impurities. Both TDPAC and positron lifetime results are mutually consistent on this aspect. Transformation of H-vacancy clusters into H-bubbles is indicated by the positron lifetime behaviour at annealing temperatures beyond 900 K. Impurity effects like oxygen pickup and coating of voids cannot be ruled out at elevated temperatures.

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Section: Effect Of Hydrogen On Defect Recover) In Nbhfsupporting

confidence: 70%

Cold-worked and hydrogen chargedNbHf as studied by TDPAC and positron lifetime measurements

et al. 1998

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“…Values of quadruopole frequency and asymmetry parameter for the weak component have been found to be ω Q = 43.8(7) Mrad/s and η = 0.65(3) with δ = 0. This signal arises possibly due to trapping of an oxygen atom in the interstitial site of the Hf lattice [16]. It has been found that up to 773 K, the component fractions do not change appreciably (Tab.…”

Section: Resultsmentioning

confidence: 99%

Oxidation of Hafnium and Diffusion of Hafnium Atoms in Hexagonal Close-Packed Hafnium; Microscopic Investigations by Perturbed Angular Correlations

Dey

2012

Zeitschrift Für Naturforschung A

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Time-differential perturbed angular correlation (TDPAC) studies in hafnium metal (∼ 5% Zr) have been carried out at different temperatures. It is found that hafnium metal on heating at 873 K continuously for two days in air, transforms partially and abruptly to HfO 2 while no component of oxide has been observed for heating up to 773 K and during initial heating at 873 K for 1 day. This result is strikingly different to that expected from the Arrhenius theory. Also, a strong nuclear relaxation effect has been observed at 873 K due to rapid fluctuation of hafnium atoms in hexagonal closepacked (hcp) hafnium. At this temperature, ∼ 45% probe nuclei experience static perturbation due to monoclinic HfO 2 , ∼ 50% experience fluctuating interaction, and ∼ 5% produce static defect configuration of hcp hafnium. With lowering of temperature, defect configurations of hafnium increase at the cost of fluctuating interaction. An almost total fluctuating interaction observed in hcp hafnium at a temperature much lower than its melting point is another interesting phenomenon.

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“…It is intriguing that ω Q = 42.10(3) Mrad/s and η = 0.68(1) has been reported for 0.1% hafnium in the bcc metal niobium with a trapped interstitial oxygen atom on the second nearest neighbour octahedral position using 181 Hf(β − ) 181 Ta TDPAC [22]. Of course, a bcc metal with a hafnium impurity -a well-known getter -should not be compared with an ultrapure hafnium metal (hcp) where the oxygen trapping would have to occur during the 17.8 µs half life of the start level of the γ-γ-cascade in the daughter nucleus 181 Ta.…”

Section: Discussionmentioning

confidence: 99%

Recoil Induced Room Temperature Stable Frenkel Pairs in a-Hafnium Upon Thermal Neutron Capture

Butz

Das²,

Dey

et al. 2013

Zeitschrift Für Naturforschung A

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Ultrapure hafnium metal (110 ppm zirconium) was neutron activated with a thermal neutron flux of 6.6 · 10 12 cm −2 s −1 in order to obtain 181 Hf for subsequent time differential perturbed angular correlation (TDPAC) experiments using the nuclear probe 181 Hf(β − ) 181 Ta. Apart from the expected nuclear quadrupole interaction (NQI) signal for a hexagonal close-packed (hcp) metal, three further discrete NQIs were observed with a few percent fraction each. The TDPAC spectra were recorded for up to 11 half lives with extreme statistical accuracy. The fitted parameters vary slightly within the temperature range between 248 K and 373 K. The signals corresponding to the three additional sites completely disappear after 'annealing' at 453 K for one minute. Based on the symmetry of the additional NQIs and their temperature dependencies, they are tentatively attributed to Frenkel pairs produced by recoil due to the emission of a prompt 5.694 MeV γ-ray following thermal neutron capture and reported by the nuclear probe in three different positions. These Frenkel pairs are stable up to at least 373 K.

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Orientation of an oxygen-induced non-axially symmetric electric field gradient at Ta in Nb

Cited by 10 publications

References 13 publications

Cold-worked and hydrogen chargedNbHf as studied by TDPAC and positron lifetime measurements

Cold-worked and hydrogen chargedNbHf as studied by TDPAC and positron lifetime measurements

Oxidation of Hafnium and Diffusion of Hafnium Atoms in Hexagonal Close-Packed Hafnium; Microscopic Investigations by Perturbed Angular Correlations

Recoil Induced Room Temperature Stable Frenkel Pairs in a-Hafnium Upon Thermal Neutron Capture

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