Lead-free ferroelectric thin films obtained by pulsed laser deposition |
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Authors: | N D Scarisoreanu F Craciun A Chis R Birjega A Moldovan C Galassi M Dinescu |
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Institution: | (1) Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Science, Hefei, 230031, P.R. China;(2) Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Science, Hefei, 230031, P.R. China |
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Abstract: | Na0.5Bi0.5TiO3-BaTiO3 (NBT-BT) thin films grown by pulsed laser deposition have been investigated by X-ray diffraction, scanning electron microscopy,
and dielectric spectroscopy in order to clarify the role of substrate temperature on crystalline structure, grain morphology,
and dielectric properties. We have shown that the structural and dielectric properties of NBT-BT thin films with composition
at morphotropic phase boundary (6% BT) critically depend on the substrate temperature: small variations of this parameter
induce structural changes, shifting the morphotropic phase boundary toward tetragonal or rhombohedral side. Higher deposition
temperature (1000 K) favor the formation of rhombohedral phase, films deposited at 923 K and 973 K have tetragonal symmetry
at room temperature. Grains morphology depends also on the deposition temperature. Atomic force micrographs show grains with
square or rectangular shape in a compact structure for films grown at lower temperatures, while grains with triangular shape
in a porous structure are observed for films grown at 1000 K. Dielectric spectroscopy measurements evidenced the phase transition
between ferroelectric and antiferroelectric phase at 370 K. Films grown at 1000 K shown low electrical resistivity due to
their porous structure. High dielectric constant values (about 800 at room temperature and 2700 at 570 K) have been obtained
for films grown at temperatures up to 973 K. |
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