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Brillouin study of phase transitions in KNbW 2 O 9 bronze
Author(s) -
Ma̧czka M.,
Ko J.H.,
Kojima S.,
Majchrowski A.,
Hanuza J.
Publication year - 2003
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1004
Subject(s) - brillouin zone , orthorhombic crystal system , bronze , phase transition , condensed matter physics , phase (matter) , raman spectroscopy , crystal (programming language) , coupling (piping) , brillouin spectroscopy , hexagonal crystal system , brillouin scattering , symmetry (geometry) , crystallography , chemistry , optics , materials science , crystal structure , physics , laser , geometry , composite material , metallurgy , programming language , organic chemistry , computer science , mathematics
High‐resolution Brillouin spectra of KNbW 2 O 9 crystallizing in the hexagonal bronze structure were obtained for the first time in the temperature range 293–723 K. Weak anomalies in sound velocity were observed for the sound waves corresponding to the c 11 elastic constant at 535, 597 and 671 K. Additionally, a strong increase in the intensity of Brillouin lines was observed near 530 K. These anomalies are attributed to phase transitions occurring in the KNbW 2 O 9 crystal between two phases of unknown symmetry (at 535 K), two orthorhombic phases (at 597 K) and between orthorhombic and hexagonal phases (at 671 K). The character of the observed anomalies suggests that the coupling is squared in order parameter and linear in strain. Copyright © 2003 John Wiley & Sons, Ltd.