Phase transformations in some rare earth-hydrogen systems

M. H. Mintz; Z. Hadari; M. Bixon

doi:10.1016/0022-5088(74)90025-3

Phase transformations in some rare earth-hydrogen systems

M. H. Mintz, Z. Hadari, M. Bixon

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Abstract

The ranges of stability of Pr, Nd and Sm hydrides were investigated using simultaneous TG-DTA techniques. Measurements were made over a temperature range 25-700 °C, at 700 Torr hydrogen pressure. A new, low-temperature hexagonal phase has been detected in the NdH₂-NdH₃ system. Its structure is similar to the hexagonal, heavier lanthanide hydride phases. However, unlike these structures the NdH_{3 - x} hexagonal phase transforms irreversibly on heating to the f.c.c. structure, which remains metastable at room temperature. The enthalpy changes associated with the hexagonal to f.c.c. transitions in the NdH₂-NdH₃ and SmH₂-SmH₃ systems were estimated to be 1.6 ± 0.3 kcal/mole and 4 ± 0.4 kcal/mole, respectively. No phase transition has been detected in the PrH₂-PrH₃ system.

Original language	English
Pages (from-to)	331-335
Number of pages	5
Journal	Journal of the Less-Common Metals
Volume	37
Issue number	3
DOIs	https://doi.org/10.1016/0022-5088(74)90025-3
State	Published - 1 Jan 1974
Externally published	Yes

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General Engineering

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title = "Phase transformations in some rare earth-hydrogen systems",

abstract = "The ranges of stability of Pr, Nd and Sm hydrides were investigated using simultaneous TG-DTA techniques. Measurements were made over a temperature range 25-700 °C, at 700 Torr hydrogen pressure. A new, low-temperature hexagonal phase has been detected in the NdH2-NdH3 system. Its structure is similar to the hexagonal, heavier lanthanide hydride phases. However, unlike these structures the NdH3 - x hexagonal phase transforms irreversibly on heating to the f.c.c. structure, which remains metastable at room temperature. The enthalpy changes associated with the hexagonal to f.c.c. transitions in the NdH2-NdH3 and SmH2-SmH3 systems were estimated to be 1.6 ± 0.3 kcal/mole and 4 ± 0.4 kcal/mole, respectively. No phase transition has been detected in the PrH2-PrH3 system.",

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T1 - Phase transformations in some rare earth-hydrogen systems

AU - Mintz, M. H.

AU - Hadari, Z.

AU - Bixon, M.

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N2 - The ranges of stability of Pr, Nd and Sm hydrides were investigated using simultaneous TG-DTA techniques. Measurements were made over a temperature range 25-700 °C, at 700 Torr hydrogen pressure. A new, low-temperature hexagonal phase has been detected in the NdH2-NdH3 system. Its structure is similar to the hexagonal, heavier lanthanide hydride phases. However, unlike these structures the NdH3 - x hexagonal phase transforms irreversibly on heating to the f.c.c. structure, which remains metastable at room temperature. The enthalpy changes associated with the hexagonal to f.c.c. transitions in the NdH2-NdH3 and SmH2-SmH3 systems were estimated to be 1.6 ± 0.3 kcal/mole and 4 ± 0.4 kcal/mole, respectively. No phase transition has been detected in the PrH2-PrH3 system.

AB - The ranges of stability of Pr, Nd and Sm hydrides were investigated using simultaneous TG-DTA techniques. Measurements were made over a temperature range 25-700 °C, at 700 Torr hydrogen pressure. A new, low-temperature hexagonal phase has been detected in the NdH2-NdH3 system. Its structure is similar to the hexagonal, heavier lanthanide hydride phases. However, unlike these structures the NdH3 - x hexagonal phase transforms irreversibly on heating to the f.c.c. structure, which remains metastable at room temperature. The enthalpy changes associated with the hexagonal to f.c.c. transitions in the NdH2-NdH3 and SmH2-SmH3 systems were estimated to be 1.6 ± 0.3 kcal/mole and 4 ± 0.4 kcal/mole, respectively. No phase transition has been detected in the PrH2-PrH3 system.

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ER -

Phase transformations in some rare earth-hydrogen systems

Abstract

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