scholarly journals Phonons and relaxations in unfilled tetragonal tungsten-bronzes

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
E. Buixaderas ◽  
J. Dec
Keyword(s):  
Phase Transition ◽  
High Frequency ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Lead Free ◽  
Qualitative Behaviour ◽  
Characteristic Frequencies ◽  
Slowing Down ◽  
Central Mode ◽  
Thz Range

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.

scholarly journals A monoclinic-tetragonal ferroelectric phase transition in lead-free (K0.5Na0.5)NbO3-x%LiNbO3 solid solution

2012 ◽  
Vol 111 (10) ◽  
pp. 103503 ◽  
Author(s):  
Wenwei Ge ◽  
Yang Ren ◽  
Jialiang Zhang ◽  
Christopher P. Devreugd ◽  
Jiefang Li ◽  
...  
Keyword(s):  
Phase Transition ◽  
Solid Solution ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Lead Free

Study of ferroelectric phase transition in new lead free Ba(Ca1/3Nb2/3)O3 compound

2017 ◽  
Vol 518 (1) ◽  
pp. 73-84
Author(s):  
M. Pastor ◽  
Patri Tirupathi ◽  
Nawnit Kumar ◽  
Amrish K. Panwar ◽  
M. Chopkar ◽  
...  
Keyword(s):  
Phase Transition ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Lead Free

Critical anomalies in EPR spectra near the ferroelectric phase transition in tris-sarcosine calcium chloride crystals

1985 ◽  
Vol 63 (3) ◽  
pp. 377-386 ◽  
Author(s):  
S. Jerzak ◽  
M. Fujimoto
Keyword(s):  
Phase Transition ◽  
Calcium Chloride ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Soft Mode ◽  
Dielectric Measurements ◽  
Slowing Down ◽  
Transition Mechanism ◽  
Paramagnetic Probes ◽  
Line Widths

A comparative EPR study with various paramagnetic probes of iron-group elements has been carried out on the ferroelectric phase transition in tris-sarcosine calcium chloride (TSCC) crystals. These ions have yielded complementary results, and one probe was found to be insufficient to obtain necessary information about the transition mechanism. While the soft-mode vector is inferred from the VO++ spectra, either Cr+++ or Fe+++ ions are best suited to observe the critical phenomena near the transition temperature (Tc ~ 130 K). A critical broadening above Tc and an asymmetrical splitting below Tc are observed in the Cr+++ and Fe+++ spectra. The Mn++ spectra are unique in that the order–parameter fluctuation appears only slightly in the line widths above Tc, while the critical region below Tc is characterized by the coexistence of para- and ferroelectric phases. The critical slowing-down effect in the EPR line widths is found to be consistent with that observed in dielectric measurements, suggesting that sarcosine dipoles in TSCC crystals are associated with the elementary dipole for spontaneous polarization.

Sign in / Sign up

Export Citation Format

Share Document