A Study on Sc₂O₃‐Stabilized Zirconia Obtained by MOCVD as a Potential Electrolyte for Solid Oxide Fuel Cells

Abstract

Dense, crack-free thin films (<5 mu m) of the nanostructured scandia-zirconia system (Sc2O3:ZrO2) stabilized in the cubic-fluorite phase (c-ZrO2) are deposited through conventional low-pressure metal-organic(LP-MO) CVD by using beta-diketonate metal complexes as precursors [(Zr(tmhd)4 and Sc(tmhd)3, with tmhd?=?2,2,6,6-tetramethyl-3,5-heptanedionate]. The compositional (energy dispersive X-ray spectroscopy EDX), structural (X-ray diffraction XRD) and morphological (field emission gunenvironmental scanning electron microscopy FEG-ESEM) analyses, confirmed the growth of dense partially and fully stabilized ZrO2, a suitable electrolyte for solid oxide fuel cells (SOFC). Results of impedance spectroscopy, which investigates the electrical conductivity of coating, deposited as thin as possible to guarantee the uniform covering of a porous substrate, are reported. Results of thin films of yttria-zirconia system (Y2O3:ZrO2), deposited with the same method, are also reported for comparison

State-of-the-Art Thin Film Electrolytes for Solid Oxide Fuel Cells

“…However, 8ScSZ thin films were not fully stabilized in the cubic structure, which have a minor tetragonal phase according to the XRD patterns. The cross-sectional scanning electron microscopy (SEM) micrographs of the 8ScSZ thin films confirmed crack-free, thick, and dense coatings adherent to Al 2 O 3 and NiO/YSZ porous substrates [101]. The electrical properties of 8ScSZ thin films on Al 2 O 3 substrates were investigated and the results showed activation energy of 1.09 eV for oxygen ion diffusion and ionic conductivity of 0.002 S cm À1 at 600 C. The ionic conductivity of 8ScSZ at 600 C is twice that of 13 mol% yttria-stabilized zirconia (13YSZ) prepared in the same manner [101], which is consistent with the ionic conductivity enhancement observed for ScSZ compared to YSZ with the different synthesis routes [79].…”

“…Thus, we will discuss the studies reported in the literature for <10 μm thick ScSZ films. These thin film electrolytes have been grown by chemical vapor deposition [101], wet powder spraying [102], electrostatic spray deposition [103], sol-gel deposition [104], dip coating [105], drop-coating [106], pulsed laser deposition [107], and molecular beam epitaxy [58] techniques. The results of these studies will be summarized in this section including theoretical simulation studies on SCSZ.…”

“…The results of these studies will be summarized in this section including theoretical simulation studies on SCSZ. The ScSZ thin film electrolytes with 8 mol% Sc 2 O 3 (8ScSZ) have been grown by metal organic chemical vapor deposition (MOCVD) on Si(100), Al 2 O 3 , and NiO/YSZ cermet substrates to study their ionic transport properties [101]. The thickness of the electrolyte was kept at 1 and 3.5-4 μm for Al 2 O 3 and NiO/YSZ cermet substrates, respectively, to align with the different porosities of the electrodes.…”

Chemical Vapour Deposition of Scandia-Stabilised Zirconia Layers on Tubular Substrates at Low Temperatures

“…In work [ 32 ], ScSZ and Al 2 O 3 -doped ScSZ layers were synthesised by the MOCVD method in the presence of plasma. Interesting results were obtained in the work [ 43 ], where ScZ layers were deposited on porous substrates using this technique.…”