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Effect of pressure on phase transitions in K 1− x Na x MnF 3 ( x = 0.04)
Author(s) -
Åsbrink S.,
Waśkowska A.,
Krane H. G.,
Gerward L.,
Olsen J. Staun
Publication year - 1999
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/s002188989801098x
Subject(s) - monoclinic crystal system , tetragonal crystal system , octahedron , orthorhombic crystal system , crystallography , phase transition , diamond anvil cell , phase (matter) , chemistry , diffraction , ion , x ray crystallography , synchrotron radiation , synchrotron , crystal structure , materials science , condensed matter physics , optics , physics , organic chemistry
The pressure‐induced phase transition sequence in the title compound, potassium sodium fluoromanganate, has been investigated by single‐crystal X‐ray diffraction using synchrotron radiation and a diamond anvil pressure cell. Na ions at 4% of the K sites shift the ferrodistortive phase transition to the lower pressure of 2.75 (5) GPa compared to 3.12 GPa in the parent compound KMnF 3 . The transition is illustrated by the critical behaviour of the unit‐cell dimensions, the pressure‐dependent evolution of the MnF octahedral rotation and related macroscopic spontaneous strain. As far as precision of the present experiment allows, the observations show that the 4% of Na admixture at the K sites does not substantially change the nature of the transition at . The main effect of pressure is to stabilize the tetragonal phase II. The expected further evolution of the MnF octahedral tiltings, leading to the orthorhombic and monoclinic phases, has not been observed up to 8.33 GPa.