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Structural and Electric Properties of Epitaxial Na0.5Bi0.5TiO3-Based Thin Films

: Magalhaes, Bruno; Engelhardt, Stefan; Molin, Christian; Gebhardt, Sylvia; Nielsch, Kornelius; Hühne, Ruben

Volltext ()

Coatings 11 (2021), 6, Art. 651, 12 S.
ISSN: 2079-6412
Deutsche Forschungsgemeinschaft DFG
HU1726/3; SPP 1599 "Ferroic cooling"
Deutsche Forschungsgemeinschaft DFG
HU1726/8; SPP 1599 "Ferroic cooling"
Deutsche Forschungsgemeinschaft DFG
GE2078/3; SPP 1599 "Ferroic cooling"
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IKTS ()
ferroelectrics; epitaxy; thin films; pulsed laser deposition

Substantial efforts are dedicated worldwide to use lead-free materials for environmentally friendly processes in electrocaloric cooling. Whereas investigations on bulk materials showed that Na0.5Bi0.5TiO3 (NBT)-based compounds might be suitable for such applications, our aim is to clarify the feasibility of epitaxial NBT-based thin films for more detailed investigations on the correlation between the composition, microstructure, and functional properties. Therefore, NBT-based thin films were grown by pulsed laser deposition on different single crystalline substrates using a thin epitaxial La0.5Sr0.5CoO3 layer as the bottom electrode for subsequent electric measurements. Structural characterization revealed an undisturbed epitaxial growth of NBT on lattice-matching substrates with a columnar microstructure, but high roughness and increasing grain size with larger film thickness. Dielectric measurements indicate a shift of the phase transition to lower temperatures compared to bulk samples as well as a reduced permittivity and increased losses at higher temperatures. Whereas polarization loops taken at −100 °C revealed a distinct ferroelectric behavior, room temperature data showed a significant resistive contribution in these measurements. Leakage current studies confirmed a non-negligible conductivity between the electrodes, thus preventing an indirect characterization of the electrocaloric properties of these films.