Open AccessPhonons and relaxations in unfilled tetragonal tungsten-bronzes
Author(s) -
E. Buixaderas,
J. Dec
Publication year - 2021
Publication title -
materials and devices
Language(s) - English
Resource type - Journals
ISSN - 2495-3911
DOI - 10.23647/ca.md20202108
Subject(s) - tetragonal crystal system , phonon , materials science , raman spectroscopy , condensed matter physics , tungsten , anharmonicity , relaxation (psychology) , ferroelectricity , permittivity , dielectric , phase transition , soft modes , terahertz radiation , phase (matter) , optics , optoelectronics , chemistry , physics , psychology , social psychology , organic chemistry , metallurgy
The lead-free unfilled tetragonal tungsten-bronzes SBN and CBN are investigated by Raman, infrared and high-frequency dielectric spectroscopies. The substitution in the different channels affects phonons as well as relaxations. Relaxations in SBN show similar qualitative behaviour on increasing Sr content and relaxor behaviour, but for the extreme relaxor samples all characteristic frequencies are higher with stronger contribution to the permittivity in the GHz-THz range is stronger. The presence of a soft anharmonic central mode in the THz range together with the slowing down of a relaxation from GHz to MHz ranges reveals the coexistence of displacive and order-disorder scenarios for the ferroelectric phase transition in this family.