Structural phase transitions in AgTa{sub 0.5}Nb{sub 0.5}O{sub 3} thin films.
Octahedral tilt transitions in epitaxial AgTa{sub 0.5}Nb{sub 0.5}O{sub 3} (ATN) films grown on (001){sub p} (where p = pseudocubic) oriented SrRuO{sub 3}/LaAlO{sub 3} and LaAlO{sub 3} 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{sub 3} {leftrightarrow} M{sub 2} phase transition has been suppressed by -250 K due to the fact that the correlation length for rotations about c{sub 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(001){sub p}-type reflections. On cooling, pronounced ordering of B-cation displacements occurred at {approx}60 K which is significantly lower compared to bulk ({approx}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{sub p} thereby reducing the effective strength of interactions between the tilting and cation displacements.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); National Science Foundation (NSF); Engineering and Physical Science Research Council U.K.
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 990173
- Report Number(s):
- ANL/MSD/JA-67975; TRN: US201020%%193
- Journal Information:
- J. Appl. Phys., Vol. 107, Issue Jun. 22, 2010
- Country of Publication:
- United States
- Language:
- ENGLISH
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