Microstructure-Relaxor Property Relationship
of Pb(Sc_0.5Nb_(1-x)/2Ta_x/2O₃ Thin Films

Abstract

Highly oriented PbSc_0.5Nb_(1-x)/2Ta_x/2O₃ (PSNT; 0 ≤ x ≤ 1) thin films were grown on La_0.5Sr_0.5CoO (LSCO) coated MgO substrate with an in plane epitaxial relationship PSNT [100] ‖ LSCO [100] ‖ MgO [100] by pulsed laser deposition technique. Dielectric studies of PSNT films as a function of temperature and frequency showed relaxor ferroelectric behavior in the full compositional range contrary to bulk samples of same composition. However, these films showed lower dielectric permittivity values, enhanced frequency dispersion, and shift of dielectric maximum temperature (T_m ) to lower temperature compared to the bulk counterpart. Non-linear Vogel-Fulcher relation support the relaxor behavior of PSNT films, although, Vogel-Fulcher fit yielded low activation energy (E << kT) consistent with the glassy-like behavior of relaxor ferroelectric. High resolution transmission electron microscopy (HRTEM) images of PSNT films indicate the presence of small nano-ordered regions, long range ordered regions in crystal lattice plane, and disordered regions. The size of the ordered regions changed with the compositions. Nb-rich films have nanoscale ordered regions of about 5 nm (diameter) whereas Ta-rich films have large ordered regions (>40 nm width). But both kind of films showed disorder microstructure which support the relaxor ferroelectric behavior.

Keywords:

• Relaxor ferroelectrics
• thin films
• nano-ordered regions

Acknowledgments

This work was partially supported by NSF grant NSF-EFRI-RPI-1038272, DoD grant W911MF-11-1-0204, and DoE grant DE-FG02-08ER46526 (Fellowship to Ms Correa).