Raman Scattering Study of Piezoelectric (Na0.5K0.5)NbO3-LiNbO3 Ceramics

概要

論文の詳細を見る
A Raman scattering study of (Na0.5K0.5)NbO3 (NKN)-LiNbO3 (LN) lead-free piezoceramics has been carried out on nominal compositions of ($1-x$)NKN-$x$LN ($0 \le x \le 0.70$). The Raman spectra demonstrated a variety of changes with $x$, mainly classified as lattice translations involving motions of the alkaline cations and internal modes of NbO6 octahedra. At $0.05 \le x \le 0.07$, the broadening of the scattering peaks corresponding to the internal modes of the NbO6 octahedra occurred preferably, which is consistent with the evidence for a morphotropic phase boundary (MPB). Furthermore, an abrupt shift was observed in the peak position of the symmetric stretching mode $v_{1}$ to a higher frequency, resulting from the distortion of O-Nb-O angles caused by incorporating small Li ions into the perovskite units. This is considered to be a prologue for the structural transformation in the NKN-LN solid solution from orthorhombic to tetragonal symmetry. At compositions in which $x$ increases above the MPB, the translational mode of the Li+ cation emerged clearly, and the overall scattering pattern gradually changed to complex patterns caused by the formation of a tungsten-bronze K3Li2Nb5O15 (KLN) secondary phase and an increase in the number of distorted LiNbO3-type crystal units.
2005-09-15