학술논문
Thermal expansion behaviour and phase stability of AFeAs (A = Ca, Sr and Eu) using powder diffraction technique.
Document Type
Article
Author
Source
Subject
*THERMAL expansion
*PHASE equilibrium
*X-ray powder diffraction
*LATTICE constants
*EUROPIUM
*IRON
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Language
ISSN
0304-4289
Abstract
The thermal expansibilities and phase stabilities of AFe As (A = Ca, Sr and Eu) have been investigated by powder diffraction techniques in the temperature range 5-600 K. We found the anisotropic thermal expansivities with temperature for all the compounds. The lattice parameter in the tetragonal phase ( A ) of CaFe As contracts with increasing temperature, whereas C expands. The rate of contraction in A is lower than the rate of expansion in C . Other compounds show normal thermal expansion behaviour along both a- and c-axes. In-plane expansion (i.e., along the a-axis) is found to be the smallest for EuFe As and the highest for BaFe As . However, the rate of change of thermal expansivities along out-of-plane (i.e., along the c-axis) is higher as we go from Ba, Sr, Eu and Ca, respectively. Above 600 K, we notice the appearance /disappearance of certain reflections which suggest that tetragonal phase is not stable above this temperature for these compounds. [ABSTRACT FROM AUTHOR]