Fabrication and Characterization study of Micro Thin Film Electrolyte for the Solid Oxide Fuel Cell (SOFC)

Abstract

In this study, Calcium Doped Ceria (CDC) thin film is prepared by the two steps, in the first step calcium doped ceria (CDC) powder is synthesized by co-precipitation method and in the second step, the slurry of calcium doped ceria (CDC) with ball milling and then thin film is casting with help of Tape casting technique. The fabricated thin films were sintered in the range of temperatures (150-750) ℃, in an air atmosphere. Crystal structure revealed that thin film has a cubic fluorite structure, and its average crystallite size is in the range of (53-42) nm. Raman analysis of the thin film was done in the temperature range of 350-750℃. These results showed that CDC thin films have high oxygen vacancies as sintering temperature rises. Which was depicting the high conductivity of the thin film. These results were also verified by the Conductivity measurements. The increase in FWHM of main peaks of Raman spectra, with an increase in temperature resulting in reduction of the crystallite size. Which was also confirmed by XRD results. FTIR results showed the formation of the Ce-O bonds, OH stretching, etc. Furthermore, FTIR spectra of the thin film at various temperatures indicated that OH stretching decreased as temperature increased, indicating that moisture in the sample reduced. Uv visible analysis was done at two different temperatures, 150 and 750℃. Band gap values decreased with increase in the temperatures. It was 3.22eV at 750oC and 3.3eV at 150℃. The conductivity measurements showed that conductivity of thin film was increasing as sintering temperature rises. which was confirmation of Raman results. Thin-film showed the highest conductivity 0.052 Scm-1 at 750℃, the activation energy and electrical band gap calculated from the Arrhenius plot are 0.25 eV and 0.5 eV for the sample sintered at 750oC, respectively. EIS spectra thin-film sintered at 750℃ and 150℃ showed semicircle, which confirms the ionic behavior of the CDC electrolyte thin film. The ohmic resistance also decreased with an increase in the sintering temperature. These results revealed that the thin film shows high ionic conductivity at intermediate temperatures. Which makes it useful for SOFC application.