Akademik Veri Yönetim Sistemi
JOURNAL OF APPLIED PHYSICS, cilt.107, sa.12, 2010 (SCI-Expanded)
Octahedral tilt transitions in epitaxial AgTa0.5Nb0.5O3 (ATN) films grown on (001)(p) (where p =pseudocubic) oriented SrRuO3/LaAlO3 and LaAlO3 substrates were characterized by electron diffraction and high resolution x-ray diffraction. It was found that the ATN films exhibited octahedral rotations characteristic of the Pbcm space group, similar to those seen in bulk materials; however, the temperature of the M-3 <-> M-2 phase transition has been suppressed by similar to 250 K due to the fact that the correlation length for rotations about c(p) was significantly reduced. The average off-center B-cation displacements, which signify the degree of long-range order for these local cation positions, were negligibly small compared to bulk materials, as inferred from the near-zero intensity of the 1/4(00l)(p)-type reflections. On cooling, pronounced ordering of B-cation displacements occurred at approximate to 60 K which is significantly lower compared to bulk (approximate to 310 K). The onset of this ordering coincides with a broad maximum in relative permittivity as a function of temperature. It is believed that point and planar defects in thin ATN films disrupt the complex sequence of in-phase and antiphase rotations around c(p) thereby reducing the effective strength of interactions between the tilting and cation displacements. (C) 2010 American Institute of Physics. [doi:10.1063/1.3447753]