The effect of A-site cation on ferroelectric properties in Na0.5Bi0.5TiO3-based materials: Correlation between Burns temperature and remanent polarization

The effect of cation radius mismatch on the relaxor to paraelectric state transition temperature of the lead free ferroelectric Na0.5-xRbxBi0.5TiO3 was examined, and the observed trend was different from manganite perovskites. The transition temperatures of these compounds were estimated from the temperature dependent dielectric curves. The nature of the dielectric curve at the transition temperature was broad unlike a normal ferroelectric. The dependency of the transition temperature on the A-site cation radius mismatch was explained through the correlation among polarizations of the polar nanoregions (PNRs). An asymmetric nature in the imaginary part of the impedance spectra was observed for the composition with higher disorder at the A-site, which is attributed to the relaxation time distribution of the PNRs. The decrement in the value of remanent polarization ( P r ) with the increment in A-site substitution was also noticed. A relationship between the transition temperature from the relaxor to paraelectric state and P r of the A-site disorder Na0.5Bi0.5TiO3-based systems was attempted to be established.