Raman spectra of (K, Na)(Nb, Ta)O3 single crystal

Abstract

The Raman scattering spectra for lead-free piezoelectric single crystal (K,Na)(Nb,Ta)O 3 (KNNT) were intensively investigated to explore its crystallographic structure. For the [011] C oriented sample, 12 Raman peaks were identified from the room temperature Raman spectrum. The υ 3 , υ 4 and υ 6 modes which should be Raman silent in normal perovskites were observed due to the low symmetry (Pm) of KNNT single crystal. The temperature dependent Raman spectra indicated that the orthorhombictetragonal phase transition happened at about 68 °C, and the Curie temperature (T C) is about 225 °C. The merging of 2 υ 5 modes at T C was ascribed to the vanishing of polarization. The backscattering polarized Raman spectra of KNNT single crystals with different orientations were analyzed. The Raman modes were identified using polarized selection rules based on group theory.

Pressure- and Temperature-Induced Structural Phase Diagram of Lead-Free (K0.5Na0.5)NbO3–0.05LiNbO3 Single Crystals: Raman Scattering and Infrared Study

“…In order to analyze the specific discrepancy of phonon modes with the pressure, we reveal in Figure 2c, d a Lorentzian-shape decomposition for four selected pressures (0, 1.68, 5.01, and 9.48 GPa for KNN-LN Generally, a perfect NbO 6 octahedron has six phonon vibrations: the symmetric stretching mode A 1g (ν 1 ), asymmetric stretching modes E g (ν 2 ) and F 1u (ν 3 ), asymmetric bending mode F 1u (ν 4 ), symmetric bending mode F 2g (ν 5 ), and the inactive mode F 2u (ν 6 ). 44,45 The ν 1 , ν 2 , and ν 5 modes have Raman scattering activity among these vibrations. The whole vibrational configuration can be regarded as the translational mode of basic ions and the rotational mode of the NbO 6 octahedron in the frequency range below 200 cm −1 .…”

NaSr2Nb5O15:Yb3+, Ho3+, Tm3+ transparent glass ceramics: Up‐conversion optical thermometry and energy storage property

“…Moreover, the peak at 424 cm −1 is caused by O–Nb–O bending vibration and Nb–O chain stretching vibration. The peak at 750 cm −1 is ascribed to the stretching vibration of the Nb–O bond 37–43 . Using the Lorentz fitting method, the effective phonon energy of the GC750 sample can be estimated from the following equation: $$$$\begin{equation}{E_{ph}} = \frac{{\mathop \sum \nolimits_i {x_i}{w_i}{A_i}}}{{\mathop \sum \nolimits_i {w_i}{A_i}}}\;\;\end{equation}$$$$where w i is the half‐width, A i is the peak intensity, and x i is the peak position of the Lorentz‐fitted phonon band 44 .…”

“…The higher the value of the stability parameter, the better vibration of the Nb-O bond. [37][38][39][40][41][42][43] Using the Lorentz fitting method, the effective phonon energy of the GC750 sample can be estimated from the following equation:…”

Dynamic Evolution of Polar Regions in KTa0.56Nb0.44O3 near the Para-Ferroelectric Phase Transition

“…The A 1 (1LO) mode at 172 cm −1 can be described as the vibration of the K + cations versus the NbO 6 /TaO 6 octahedral units. 24,25 The A 1 (2TO) mode at 199 cm −1 , which is related to the Fano resonance, 26 is where the niobium ions vibrate against the NbO 6 /TaO 6 octahedral units, as shown in Figure 1d. The B 1 +E(3TO) mode at 278 cm−1 (Figure 1f−g) is the wing- flapping vibration of the four oxygen atoms in the same plane.…”