Abstract:
The relationship between depolarization temperature $T_d$ and polymorphic phase transition temperature $T_{\mathrm{F-R}}$ in poorly studied relaxor hot-pressed ceramics (K$_{0.5}$Na$_{0.5}$) $\cdot$ NbO$_3$–0.02 Ba$_2$NaNb$_5$O$_{15}$ was studied. Dielectric and optical properties of polarized samples were measured for this purpose. It was found that the temperatures $T_d$ and $T_{\mathrm{F-R}}$ do not match. The obtained results are discussed in terms of the degree of the phase transition diffuseness and the size of the polar regions. It is suggested that the relative position of the depolarization temperature and the temperature of transition of the polarized sample to the relaxor phase $T_{\mathrm{F-R}}$ does not depend on the type of phase boundary (polymorphic or morphotropic), but is related only to the size of the polar regions.
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