Temperature-dependent lattice dynamics and electronic transitions in0.93Pb(Zn1/3Nb2/3)

Abstract

The lattice dynamics and electronic transitions of 0.93Pb(Zn 1/3 Nb 2/3)O 3-0.07PbTiO 3 (PZN-7%PT) single crystal have been investigated by means of temperature dependence polarized Raman scattering and ellipsometric spectra. The rhombohedral-tetragonal and tetragonal-cubic transformations as well as intermediate temperature are extracted based on the locations, intensity, and linewidths of Raman modes in different geometries. Moreover, the redshift behavior of the electronic transition at about 3.7 eV as a function of temperature follows the Bose-Einstein law. Interestingly, the dramatically different optical responses of PZN-7%PT below 3.7 eV during the phase transitions can be observed experimentally and explained by the first-principles calculations, which reveal the potential application of no-contact optical methods in judging the phase transformations and symmetries of ferroelectric crystals.

Exploring optoelectronic properties and mechanisms of layered ferroelectric K4Nb6O17 nanocrystalline films and nanolaminas

“…8a indicates the direct electron transition of optical band gap, which is approximately 2.95 eV. As a well-known problem of calculations based on DFT, the calculated optical band gaps are underestimated by about 20–30%, as compared to the experimental values 40 . So it is understandable that the value is smaller than that derived by the experimental results (3.6 eV for KN-NL).…”

“…Raman scattering is sensitive to the change in the coordination of local symmetry, which gives information about the molecular vibrations and distortions of the crystal lattice 33, 40, 43 . IR reflectance spectroscopy is an attractive and powerful tool for optical characterization of semiconductor materials 44, 45 .…”

“…Thus, the optoelectronic properties of its films become a key research issue need to be solved urgently, such as its ferroelectricity, infrared and ellipsometric spectra. Note that spectroscopic ellipsometry (SE) is a powerful and nondestructive tool that allows us to simultaneously obtain the thickness and optical parameters of a multilayer system without the Kramers-Krönig transformation (KKT) 33, 40, 41 .…”

Structural Transformations in Ferroelectrics Discovered by Raman Spectroscopy

“…Figure 1 shows the polarized Raman spectra of 0.62PT-0.38BMT single crystal at representative temperature of 80 K. It can be found that the Raman spectra is consistent with previous reports of the tetragonal crystal structure. Comparing to the theoretical calculations and experimental results, three main regions with different kinds of vibration in the lattice can be distinguished: (1) Low frequency below 150 cm In order to understand the relationship between negative thermal expansion (NTE) and lattice dynamic behavior for the 0.62PT-0.38BMT crystal, Figure 2 presents the polarized Raman spectra in different temperature point from 80 to 850 K. It can be found that the peak position and intensity of the polarized Raman phonon modes have a decreasing trend with increasing temperature, while the broadening of the Raman modes is observed, which is consist with the other ferroelectrics [17]. It should be pointed that around the temperature range of 600-700 K, the lowest phonon modes occurs (marked by the dashed rectangles).…”

Lattice Dynamics, Dielectric Constants, and Phase Diagram of Bismuth Layered Ferroelectric Bi3Ti1−xWxNbO9+δ Ceramics

“…According to previous investigation, these dopants should satisfy two major circumstances: 15 firstly, their valence states should be higher than that of Ti 4+ ions; secondly, they should be in concert with the original B-site Ti 4+ ions in radii. 20 FIR reflectance spectra of the BTWN100x ceramics were measured by Bruker Vertex 80V Fourier transform infrared spectrometer (Bruker Co., Billerica, MA) equipped with a 6-lm-thick mylar beam splitter, a DTGS detector, and a Hg lamp source. The W 6+ cations decrease oxygen vacancies and make the polar ions more movable, which effectively improve ferroelectric fatigue.…”