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Effect of Deuteration on Phase Transitions in Vanadium Dioxotetrafluoride
The crystals of (ND 4 ) 3 VO 2 F 4 with a high degree of deuteration (~87%) have been grown and a significant (~1.5%) increase in the unit cell volume has been detected. The decrease in the chemical pressure leads to a change in the sequence of phase transitions due to wedging-out of one of the rhom...
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Published in: | Physics of the solid state 2019-02, Vol.61 (2), p.192-200 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | The crystals of (ND
4
)
3
VO
2
F
4
with a high degree of deuteration (~87%) have been grown and a significant (~1.5%) increase in the unit cell volume has been detected. The decrease in the chemical pressure leads to a change in the sequence of phase transitions due to wedging-out of one of the rhombic phases observed in (NH
4
)
3
VO
2
F
4
. The thermal physical studies have been carried out and the entropies, deformations, and pressure coefficients related to structural transformations have been determined. The
T
–
p
phase diagram has been built and the pressure and temperature boundaries of crystal phase stability have been determined. The dielectric studies demonstrate a nonferroelectric nature of the phase transitions in (ND
4
)
3
VO
2
F
4
. The experimental and model entropies are compared. Based on the decrease in the entropy as a result of deuteration, a hypothesis on significant but not limited anharmonism of vibrations of ammonia tetrahedral corresponding to the disordering is proposed. |
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ISSN: | 1063-7834 1090-6460 |
DOI: | 10.1134/S1063783419020082 |