Ferroelectric phase transitions studies in 0.5Ba(Zr0.2Ti0.8) O3-0.5(Ba0.7Ca0.3)TiO3 ceramics

The ferroelectric phase transitions in 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT 50/50) ceramics,fabricatedbyasolidstatereaction,werestudiedbyusing X-Ray diffraction, Raman spectroscopy, and measuring electric polarization, dielectric permittivity and pyroelectric current. Xraydiffraction(XRD)confirmsthecoexistenceoftetragonal(T) andrhombohedral(R)phasesatroomtemperature.Thetemperature dependence of the Raman modes frequency reveals the existenceoftwophasetransitionscorrespondingtotherhombohedral – tetragonal, and tetragonal - cubic close to 30 and 100 °C, respectively. The temperature dependence of electric polarization,pyroelectriccurrent,anddielectricpermittivityfurther supports theferroelectric (tetragonal) toparaelectric (cubic) phasetransition.Moreover,thedielectricpermittivityrevealsthe diffuseness of the phase transition and is attributed to the compositional fluctuations of different polar micro-regions.

This study has been partially funded by: (i) Portuguese Foundation for Science and Technology (FCT) under the Project PTDC/FIS/098943/2008 and strategic Project PEST-C/FIS/UI0607/ 2011; (ii) European COST Action MP1308-TO-BE; (iii) Project Norte070124-FEDER-000070 Nanomateriais Multifuncionais. The authors J.P.B.S., K.C.S. and K.K. are grateful for financial support through the FCT Grants SFRH/BPD/92896/2013, SFRH/BPD/68489/2010 and SFRH/BPD/87215/2012, respectively. The authors would also like to thank Engineer José Santos for technical support at Thin Films Laboratory.