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Lattice thermal expansion behaviour of spinel HgCr 2 Se 4
Author(s) -
Kistaiah P.,
Reddy C. V.,
Murthy K. S.
Publication year - 1986
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889886089872
Subject(s) - thermal expansion , spinel , diffraction , lattice constant , lattice (music) , materials science , thermodynamics , ferromagnetism , powder diffraction , phase (matter) , thermal , analytical chemistry (journal) , condensed matter physics , chemistry , crystallography , metallurgy , optics , physics , organic chemistry , chromatography , acoustics
An accurate value of the lattice parameter of the spinel ferromagnetic semiconductor HgCr 2 Se 4 has been determined at different temperatures, ranging from 298 to 770 K, by X‐ray powder diffraction. The data have been used to evaluate the coefficient of thermal expansion, α, at various temperatures. The temperature dependence of the coefficient of expansion can be represented by the equation α = 10.059 × 10 −6 − 1.862 × 10 −8 T + 3.017 × 10 −11 T 2 , where T is the temperature in K. The diffraction pattern of HgCr 2 Se 4 , obtained at 785(5) K, was completely different from that at room temperature. The high‐temperature phase persisted up to 900 K, and above this the compound decomposed. Furthermore, the new phase was retained when the sample was cooled from 900 K to room temperature. These results suggest an irreversible structural phase transformation in HgCr 2 Se 4 at 785 K. An attempt is made to explain this interesting high‐temperature thermal behaviour of HgCr 2 Se 4 in relation to its structure and other physical properties.