Structural studies of Ni{sub 2+x}Mn{sub 1-x}Ga by powder x-ray diffraction and total energy calculations
- UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore, 452017 Madhya Pradesh (India)
- School of Materials Science and Technology, Banaras Hindu University, Varanasi, 221005 Uttar Pradesh (India)
- Raja Ramanna Centre for Advanced Technology, Indore, 452013 Madhya Pradesh (India)
- LCMP, S. N. Bose National Centre for Basic Sciences, Kolkata, 700098 West Bengal (India)
The crystal structure of Ni{sub 2+x}Mn{sub 1-x}Ga has been studied as a function of composition (x) by powder x-ray diffraction. For Ni{sub 2.24}Mn{sub 0.75}Ga, where one-fourth of the Mn atoms are replaced by Ni, the experimentally determined lattice constants are in good agreement with theoretical equilibrium lattice constants calculated by minimization of total energy using full potential linearized augmented plane-wave method. For 0.15{<=}x{<=}0.35, a nonmodulated tetragonal martensitic phase is obtained at room temperature, whose lattice constant c increases and a decreases linearly with increasing x following Vegard's law. A 7M modulated monoclinic phase is obtained for x=0.2 due to annealing. The small width of the hysteresis of the martensitic transition shows its thermoelastic nature that is the characteristic of a shape memory alloy. Phase coexistence is observed for 0.1{<=}x{<=}0.15 at room temperature, confirming the first-order nature of the martensitic transition.
- OSTI ID:
- 20957760
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 75, Issue 10; Other Information: DOI: 10.1103/PhysRevB.75.104107; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ANNEALING
FERROMAGNETIC MATERIALS
GALLIUM ALLOYS
LATTICE PARAMETERS
MANGANESE ALLOYS
MARTENSITE
MONOCLINIC LATTICES
NICKEL ALLOYS
PHASE TRANSFORMATIONS
POWDERS
SHAPE MEMORY EFFECT
STOICHIOMETRY
TEMPERATURE RANGE 0273-0400 K
THERMOELASTICITY
VEGARD LAW
WAVE PROPAGATION
X-RAY DIFFRACTION