Structural transformation and ferroelectric–paraelectric phase transition in Bi1−xLaxFeO₃(x= 0–0.25) multiferroic ceramics

Bi1-xLaxFeO3 (x ≤ 0-0.25) multiferroic ceramics were prepared to study the compositional driven structural transformation and ferroelectric- paraelectric phase transition. Rietveld-refined crystal structure parameters revealed the existence of a rhombohedral R3c symmetry in BiFeO3, a triclinic P1 symmetry in Bi0.95La0.05FeO3, Bi0.9La 0.1FeO3 and Bi0.85La0.15FeO 3, a pseudotetragonal P4mm symmetry in Bi0.8La 0.2FeO3 and a pseudotetragonal P4/mmm symmetry in Bi 0.75La0.25FeO3. La substitution led to the ferroelectric-paraelectric phase transition accompanying abrupt changes of Raman scattering spectra in Bi0.8La0.2FeO3 and Bi0.75La0.25FeO3, besides the release of weak ferromagnetism in Bi0.85La0.15FeO3, Bi 0.8La0.2FeO3 and Bi0.75La 0.25FeO3. Ferroelectricity with remnant polarization of >9.8 νC cm-2 and piezoelectricity with d33 coefficient of >25 pC/N were confirmed in all compositions except for Bi 0.75La0.25FeO3.