Abstract
Gd2CoMnO6 and Y2CoMnO6 double perovskite ceramics were obtained from the
polymeric precursors method and investigated by X-ray diffraction, X-ray
photoelectron spectroscopy (XPS), scanning electron microscopy (SEM),
Raman and Fourier Transform Infrared (FTIR) spectroscopies. Our results
show that these samples present similar structural and vibrational
characteristics that are fully compatible with a monoclinic structure
belonging to the P2(1)/n space group, with ordered Co2+ and Mn4+
cations. Infrared-reflectivity spectroscopy was employed to investigate
the polar phonon features and to determine the intrinsic dielectric
response of the materials. In particular, the extrapolated dielectric
constants at the lower frequency infrared limit showed to be independent
on the particle size, and were determined as epsilon'(intr)approximate
to 17.8 and 16.0, for Gd2CoMnO6 and Y2CoMnO6, respectively. Otherwise,
it is shown that for smaller RE radius the FTIR bands become more
evidenced, due to a higher octahedral rotation and lower <Co-O-Mn> angle
into the distorted monoclinic structure.
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