Induced instability in local structure and ferroelectric polarization of rare earth modified BZT relaxor ceramics.

Chemically induced instability in local symmetry of rare earth modified barium zirconate titanate relaxor ceramics Ba 1-x Ln 2x/3 Zr 0.3 Ti 0.7 O 3 (Ln = Sc, La, Sm, Nd, Eu and Gd), where x = 0.02–0.10 and its effect on structural, microstructural, interband transition along with ferroelectric switching polarization are studied experimentally. Rare earth substitution induced A-site vacancies and distortion in three dimensional cation-oxygen networks leads to random local strain with short range ordering. In addition, these cations control the formation of grain, grain boundaries and band gap values. Substitution of rare earth ions induced intermediate energy levels in between conduction and valence band and guided the emission spectra towards blue-green region. At room temperature polarization hysteresis loop and normalized capacitance versus electric field loop indicated the existence of relaxation and polarization switching mechanism in these materials. However, at room temperature feeble polarization switching is observed in case of scandium, europium and gadolinium based BZT compositions indicated a weak relaxor phase whereas in lanthanum, samarium, neodymium substituted BZT materials shows a dominating relaxor phases induced by static and dynamic of nano size polar regions separated by non-polar region. [ABSTRACT FROM AUTHOR]