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, Bi0.9La0.1FeO3 and Bi0.85La0.15FeO3, a pseudotetragonal P4mm symmetry in Bi0.8La0.2FeO3 and a pseudotetragonal P4/mmm symmetry in Bi0.75La0.25FeO3. 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, Bi0.8La0.2FeO3 and Bi0.75La0.25FeO3. Ferroelectricity with remnant polarization of > 9.8 mu C cm(-2) and piezoelectricity with d(33) coefficient of > 25 pC/N were confirmed in all compositions except for Bi0.75La0.25FeO3.