Microstructure-Relaxor Property Relationship of Pb(Sc0.5Nb(1-x)/2Tax/2O3 Thin Films

Highly oriented PbSc0.5Nb(1-x)/2Tax/2O3 (PSNT; 0 <= x <= 1) thin films were grown on La0.5Sr0.5CoO (LSCO) coated MgO substrate with an in plane epitaxial relationship PSNT [100] parallel to LSCO [100] parallel to 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.