Аннотация
We performed temperature-dependent Raman scattering studies on
K0.2Na0.8NbO3 ceramics and compared the results with those for NaNbO3.
The wavenumbers associated with NbO6 vibrations suggest the existence of
two phase transitions, as occurs with pure NaNbO3 ceramics. Although the
disorder on the Na/K site does not change either the room temperature
phase of K0.2Na0.8NbO3 or the sequence of phase transitions compared
with NaNbO3, it changes the temperature of the lowest phase transition
and strongly modifies the temperature of the antiferroelectric --> new
phase II phase transition. Additionally, the linewidth analysis shows
that the orientational mechanism is the dominant contribution to
linewidth, although the anharmonic contribution is increased, when
compared with NaNbO3, owing to the random distribution of potassium in
the sodium niobate matrix. Copyright (C) 2004 John Wiley Sons, Ltd.
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