Effect of annealing on the permittivity of ceramic films prepared by the Aerosol Deposition Method

Titelangaben

Schubert, Michael ; Exner, Jörg ; Stöcker, Thomas ; Moos, Ralf:
Effect of annealing on the permittivity of ceramic films prepared by the Aerosol Deposition Method.
2015
Veranstaltung: PACRIM 11, The 11th Pacific Rim Conference of Ceramic Societies , 30.08.-04.09.2015 , Jeju, Korea.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung , Poster )

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Abstract

The Aerosol deposition Method (ADM) is a novel ceramic coating method, which allows manufacturing dense ceramic films at room temperature directly from powders without any high temperature sintering steps and without expensive vacuum processes. Due to its deposition mechanism based on collision and densification of fine ceramic powder particles on a substrate it is also called “Room Temperature Impact Consolidation” (RTIC).

Ceramic particles are accelerated up to several hundred m/s and ejected on a target. There, they build dense ceramic layers by fraction of the particles into fragments with typical crystallite sizes of about 20 nm. Such small crystallite sizes affect the functional properties, for example the permittivity of the deposited layers. To investigate the influence of the AD process on the relative permittivity, several films with different materials (Al2O3, TiO2, SrTiO3 and PZT) have been deposited covering a wide permittivity spectrum.

For this investigation, the materials were sprayed on an interdigital electrode structure. The capacitances of the resulting layer were measured by impedance spectroscopy. With the help of a numerical model that considers the field distributions, the permittivities were calculated. As the results were lower than the reported bulk material data, a post-deposition annealing process was added. The annealing temperatures were stepwise increased from 100 °C up to 800 °C in 100 °C steps with measurements at room temperature between the steps. After annealing, all materials (except SrTiO3) showed a permittivity as expected for bulk materials. SrTiO3, however started with a by far low permittivity, which astonishingly decreased even more after annealing. So, in case of SrTiO3 more research is necessary (e.g. measurements in plate capacitor setup combined with XRD) to explain this uncommon result and to clarify the processes taking place in the AD film.