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Vibrational Spectra of a K 0.30 Na 0.10 Sr 0.48 Ba 0.32 Nb 0.2 O 0.6 Single Crystal Studied by Raman and Infrared Reflectivity Spectroscopy
Author(s) -
Xia H.R.,
Xia H.R.,
Chen H.C.,
Yu H.,
Wang K.X.,
Zhao B.Y.
Publication year - 1998
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(199811)210:1<47::aid-pssb47>3.0.co;2-w
Subject(s) - raman spectroscopy , potassium niobate , tetragonal crystal system , materials science , infrared spectroscopy , infrared , octahedron , spectroscopy , strontium barium niobate , crystallography , curie temperature , crystal structure , chemistry , condensed matter physics , optics , ferromagnetism , ferroelectricity , optoelectronics , physics , organic chemistry , quantum mechanics , dielectric
Potassium and sodium (K/Na)‐modified strontium barium niobate (SBN) of the idealized formula (K x Na 1— x ) 0.4 (Sr y Ba 1— y ) 0.8 Nb 2 O 6 (KNSBN), with x = 0.75, y = 0.60, a Curie temperature of (200 ± 2) °C, and a laser damage threshold larger than 600 MW/cm 2 at 4 pps, crystallizes with a filled tungsten bronze (TB) type structure in the tetragonal system. The lattice constants are a = (1.2488 ± 0.0001) and c = (0.3955 ± 0.0001) nm at room temperature. There are five formulas per unit cell. The lattice vibrational spectrum of KNSBN, which arises mainly from internal vibrations of the Nb–O octahedra and studied by Raman and infrared reflectivity spectroscopy, typifies a tetragonal TB type structure. The results shown in Figs. 1 to 6 are typical for vibrational spectra. The NbO 6 clusters form the rigid Nb–O octahedra, and the rigidity of the lattice is mainly ascribed to five vibrations, as a non‐degenerate symmetric Nb–O stretching vibration (ν 1 ), a doubly degenerate symmetric O–Nb–O stretching vibration (ν 2 ), a triply degenerate antisymmetric Nb–O stretching vibration (ν 3 ), a triply degenerate antisymmetric O–Nb–O bending vibration (ν 4 ), and a triply degenerate symmetric O–Nb–O bending vibration (ν 5 ). The KNSBN crystals as well as the SBN crystals show good structural quality and mechanical properties, and large linear electro‐optical and pyroelectric coefficients. Besides, the nonlinear optical property of KNSBN is better than that of SBN.