Physical and Microstructural Properties of NiO‐ and Ni‐YSZ Composite Thin Films Fabricated by Pulsed‐Laser Deposition at T≤700°C

Abstract

The physical and microstructural properties of NiO‐ and Ni‐YSZ composite thin films deposited by pulsed‐laser deposition have been investigated for nanoporous anode electrodes of SOFC applications. An NiO‐YSZ thin film which was deposited at room temperature and postannealed at 700°C exhibited a fine porous structure, but electrical conduction was not detected when reduced. On the other hand, 700°C‐deposited NiO‐YSZ films showed appropriate crystallinity and exhibited electrical conductivity after reduction; however, massive Ni agglomeration occurred and porous structures were not obtained as intended. It was shown that as the Ni content and the reduction temperature increase, the coarsening becomes much more severe.

Suppression of Ni agglomeration in PLD fabricated Ni-YSZ composite for surface modification of SOFC anode

“…In some cases, desirable microstructures, such as a nano-porous structure and an interpenetrating nano-composite structure, 19,22 as well as promising electrochemical performances, such as lower overpotentials and electrode resistances, [20][21][22] were reported. However, in many cases, even more massive metal phase agglomeration was observed after the reduction or thermal treatments of the thin film composites regardless of the deposition methods, 1,13,[15][16][17][18] which leads to the loss of the connectivity and the poor high temperature stability of electrodes.…”

“…[1][2][3][4][5][6][7][8] However, for realizing miniaturized SOFCs for portable applications, it is necessary to lower operating temperature from a conventional operation range (≥800 • C) without performance compromise to cut down the burden in thermal insulation in an integrated power pack. 1,2,4,5 To lower the operating temperature of SOFCs, employing thin film electrolytes for reducing the ohmic resistance has been studied intensively. 2,[4][5][6][7][8][9] Nevertheless, due to the current constriction, 10,11 nano-structured electrodes should be employed as well for taking advantage of the electrolyte thickness reduction.…”

“…2,[4][5][6][7][8][9] Nevertheless, due to the current constriction, 10,11 nano-structured electrodes should be employed as well for taking advantage of the electrolyte thickness reduction. 1,2,10,11 The current constriction indicates that if the particle size of the electrode is much bigger in dimension * Corresponding author. Tel.…”

“…1,10 To obtain nano-structured electrodes for thin electrolytes, most of thin film base SOFCs use single phase noble metal electrodes such as porous Pt fabricated by sputtering, 4,6,8,10,12 but the metal coarsening at operating temperatures eventually leads to serious problems such as the reduction of the triple phase boundary length and thus degradation of the cell performance. 10,12 Therefore, ceramic-metal composites (cermets) fabricated by thin film deposition methods 1,[13][14][15][16][17][18][19][20][21][22] were investigated actively to prevent the metal coarsening since the ceramic network in the nano-composite is expected to retain the excessive metal grain growth 6,23 as in conventional SOFCs. In some cases, desirable microstructures, such as a nano-porous structure and an interpenetrating nano-composite structure, 19,22 as well as promising electrochemical performances, such as lower overpotentials and electrode resistances, [20][21][22] were reported.…”

Yttria and ceria doped zirconia thin films grown by pulsed laser deposition

“…The YSZ is a standard electrolyte for SOFCs, which are potential candidates for next generation portable and mobile power sources [3][4][5][6][7][8][9][10] . Standard YSZ electrolytes operate at high temperatures (800-1000 °C) due to their ionic conductivity properties which become efficient enough only at this temperature range.…”