Ba
x
Sr1
-
x
TiO3 (BST, x = 0.5) thin films were prepared on Pt/TiO2/SiO2/Si substrates using a diol-based sol−gel method. Two different solvents were employed, ethylene glycol and propylene glycol
(1,2-propanediol). The influence of the solvent on the sol structure, microstructure development, and
dielectric properties of BST thin films is analyzed and discussed. It is observed that films prepared with
ethylene glycol show higher values of the dielectric permittivity (∼40% higher) and lower values of
dielectric losses when compared with films prepared from propylene glycol precursors. The dielectric
permittivitty is 459 and 302 at 1 kHz for films prepared with ethylene glycol and 1,2-propanediol,
respectively, and annealed at 800 °C. IR studies revealed that the stabilization of a titanium precursor
with propylene glycol is incomplete. During the phase-formation process, a higher content of a second
phase is formed for the propylene glycol-delivered films. However, microstructure analyses revealed
smaller grain size and surface roughness and higher density for films prepared with ethylene glycol.
These differences are attributed to the relative high boiling point and latent heat of vaporization and to
the linear molecular structure of ethylene glycol. Ethylene glycol as a solvent allows for the preparation
of BST thin films with improved dielectric properties.
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