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Schneider, Jürgen ; Paulus, Daniel ; Kita, Jaroslaw ; Moos, Ralf:
Rapid Posttreatment of Powder Aerosol Deposited Functional Ceramics Using LED Radiation.
2025
Veranstaltung: International Symposium on Green Processing for Advanced Ceramics - IGPAC 2025
, 5.10.-9.10.2025
, Ise-Shima/Mie, Japan.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung
,
Poster
)
Abstract
The powder aerosol deposition method (PAD or ADM) is an innovative ceramic coating technique that enables the deposition of dense ceramic films at room temperature, directly from powder without the need for binders or high-temperature sintering. During the deposition process, powder particles are accelerated at high velocities toward the substrate, where they fragment upon impact and form a nanocrystalline film. This mechanism was first described by Akedo and explains the nanocrystalline microstructure of the films. However, the resulting films often exhibit internal stresses and lattice distortions, which can compromise their functional performance, especially their electrical conductivity. The ability to tune the electrical conductivity of functional materials is of great interest for applications in energy storage and energy harvesting. This study explores the potential of thermal post-treatment using high-power light-emitting diodes (LEDs) to restore the functional properties of thermoelectric CuFeO₂ and solid electrolyte Li₇La₃Zr₂O₁₂ (LLZO) thin films fabricated via powder aerosol deposition (PAD). Previous investigations by Nazarenus have demonstrated the considerable advantage of this technique for enhancing PAD film performance. In the present work, a modified experimental setup was employed, enabling controlled exposure of the samples to LED radiation over defined time intervals. The system allows remote adjustment of LED power and operating duration, thereby facilitating precise control of the energy input into the PAD films. Prior to sample deposition, screen- printed substrates were prepared. The custom-designed substrates with screen-printed interdigital electrode (IDE) and thermocouple structures were used to enable in situ measurements of temperature and electrical resistance during post-treatment. In addition to utilizing commercially available LLZO, ceramic CuFeO2 powder was synthesized via a solid- state reaction. Both materials were deposited onto the custom-fabricated substrates using the powder aerosol deposition method. For CuFeO2 and Li7La3Zr2O12, substrates featuring IDE structures were employed, as well as substrates combining IDE structures with integrated thermocouples. The former type was used primarily for electrical characterization of samples. Four-wire substrates were additionally used for electrical characterization of CuFeO2 samples. A schematic representation of the experimental setup for annealing and characterizing PAD films on IDE and combined IDE and thermocouple structures can be seen. The use of these custom-built sensors with IDE structure and a Type S thermocouple according to Steiner enabled high-resolution monitoring of temperature evolution at the interface between PAD films and substrates during LED exposure. Time dependent temperature variations, as well as changes induced by different LED operating powers, were accurately captured. This allowed for the precise determination of heating rates and temperatures associated with his novel annealing approach. Through comparing the initial electrical resistance with the electrical resistance after annealing at room temperature, the remanent change in electrical conductivity was calculated.
These investigations allowed for establishing a correlation between the maximum temperature achieved during thermal post-treatment and the resulting changes in the electrical conductivity of the films.
To investigate the impact of film thickness on the electrical conductivity at room temperature post treatment, CuFeO₂ and Li₇La₃Zr₂O₁₂ films of different thicknesses were subjected to LED annealing using defined, incrementally increased radiation power levels. After each annealing step, the electrical conductivity of the films was measured at room temperature to monitor changes in their functional performance. Following the final annealing protocol, the PAD films were examined using a scanning electron microscope to verify the accuracy of thickness measurements and to assess any potential damage caused by the annealing process. A cross section of a fractured CuFeO2-PAD film and a LLZO-PAD film can be seen.
In addition, optical absorption measurements were conducted on CuFeO₂-PAD films deposited on glass substrates. Using transmission and reflection data from UV-vis-NIR spectroscopy, the films' absorption characteristics in the relevant wavelength range of the high-power LED were evaluated. This provided further insight into the interaction of optical radiation with the nanocrystalline film structure and its potential contribution to thermal effects during irradiation.
Finally, a direct comparison between LED-based and furnace-based annealing was performed. CuFeO₂ films on four-wire substrates and temperature sensors were subjected to identical maximum temperatures in both systems. The electrical conductivity was determined after each post-treatment step, and the corresponding temperature was recorded at the film–substrate interface to enable direct evaluation of the effects of the heating method. Reference samples were thermally annealed in a laboratory furnace at the temperatures measured in the radiation experiments. This approach enables a comparative analysis of conventional thermal post-treatment in a furnace with the novel approach utilizing high-power LEDs.
In this work emphasis is placed on characterizing the temperature evolution of the films during LED irradiation and evaluating the feasibility of this approach as an alternative to conventional furnace-based annealing. Furthermore, the relative contributions of optical and thermal energy to the observed post-treatment effects are systematically examined.
In a nutshell, using the powder aerosol deposition method, ceramic films can be manufactured at room temperature. With a very small and focused energy input, the functional properties of the films can be improved, so that they resemble the properties of their conventionally prepared ceramic counterparts. Therefore, we see the combination of powder aerosol deposition and LED annealing as step towards real green processing for advanced ceramics.
Weitere Angaben
| Publikationsform: | Veranstaltungsbeitrag (Poster) |
|---|---|
| Begutachteter Beitrag: | Ja |
| Institutionen der Universität: | Fakultäten > Fakultät für Ingenieurwissenschaften Fakultäten > Fakultät für Ingenieurwissenschaften > Lehrstuhl Funktionsmaterialien > Lehrstuhl Funktionsmaterialien - Univ.-Prof. Dr.-Ing. Ralf Moos Profilfelder > Advanced Fields > Neue Materialien Forschungseinrichtungen > Zentrale wissenschaftliche Einrichtungen > Bayreuther Materialzentrum - BayMAT |
| Titel an der UBT entstanden: | Ja |
| Themengebiete aus DDC: | 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften |
| Eingestellt am: | 13 Okt 2025 06:58 |
| Letzte Änderung: | 13 Okt 2025 06:58 |
| URI: | https://eref.uni-bayreuth.de/id/eprint/94871 |