Dielectric Response in (K0.5Na0.5) (Nb 1-xSbx)O3+0.5 mol%MnO2 Ceramics to Weak Sinusoidal Fields of Low and Infra-Low Frequencies

The thermal anomalies exhibited as "shoulders" at infra-low frequencies and maximums at low frequencies related to structural transitions in the polar phase of (K0.5Na0.5) (Nb1-xSbx) O3+0.5 mol%MnO2 are found to shift from T ∼ 185°C to T ∼ 140°C at changing concentration x from 0 to 0.05. The range of temperature ΔT(x) corresponding to the difference between positions of the anomalies on the '(T) curve at frequencies 1000 Hz and 1 Hz changes from 0.5 degrees at x = 0 to 2.5 degrees at x = 0.05, which may point to relaxor properties of the given phase transition being present only at rather high concentrations of Sb