Open AccessRAMAN-SPECTROSCOPIC STUDY OF FERROELASTIC PHASE TRANSITION IN LANTHANUM PENTAPHOSPHATES
Author(s) -
T Chen,
Hong Gy
Publication year - 1986
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.35.1521
Subject(s) - lanthanum , materials science , raman spectroscopy , soft modes , phase transition , monoclinic crystal system , coupling (piping) , phase (matter) , condensed matter physics , nuclear magnetic resonance , analytical chemistry (journal) , crystallography , optics , crystal structure , chemistry , composite material , optoelectronics , physics , inorganic chemistry , organic chemistry , chromatography , dielectric , ferroelectricity
The soft optic mode spectra of monoclinic I lanthanum pentaphosphates LnP5O14(Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb) are measured in the range of 20-300℃. The Ag-B2g and Ag-Ag soft modes in different LnP5O14 all soften to 20 cm-1 at ferroelastic transition temperature Tc. Another Bg-B3g soft mode softens to 38cm-1 at Tc. The coupling of Ag-B2gsoft mode with e5, plays an essential role in the phase trasition and the temperature dependence of soft-mode intensity can be described by means of the bilinear mode-coupling model. The increment of Tc from La to Tb in this system is owing to the lanthanum contraction.