Low-temperature performance of yttria-stabilized zirconia prepared by atomic layer deposition

Ionic properties of ultrathin yttria-stabilized zirconia thin films fabricated by atomic layer deposition with water, oxygen, and ozone

“…Another interesting property of ALD YSZ electrolytes is proton conduction [9][10][11]. Proton incorporation and diffusion in YSZ were first reported by Wagner [12].…”

“…Proton incorporation and diffusion in YSZ were first reported by Wagner [12]. The proton incorporation mechanism of YSZ suggested the incorporation of water into the oxide ion vacancies as hydroxyl ions (OH − ) [9][10][11]. The oxide ion vacancies (V O ·· ) are created to maintain overall charge neutrality as the 4+ host cations (Zr 4+ ) are replaced by the 3+ dopant cations (Y 3+ ) in YSZ.…”

“…The oxide ion vacancies (V O ·· ) are created to maintain overall charge neutrality as the 4+ host cations (Zr 4+ ) are replaced by the 3+ dopant cations (Y 3+ ) in YSZ. Recent studies have revealed enhanced proton transport in nano-granular YSZ [9][10][11][13][14][15][16][17][18]; this is due to the high population of vacancies on the grain surface for compensation of space charge potentials in the vicinity of grain boundary regions [19]. Hence, water or hydroxyl groups preferentially adsorb or chemisorb onto the grain surface, which lead to high concentration of protons in nano-granular YSZ compared to micro-granular materials [13][14][15]17,18].…”

“…Hence, water or hydroxyl groups preferentially adsorb or chemisorb onto the grain surface, which lead to high concentration of protons in nano-granular YSZ compared to micro-granular materials [13][14][15]17,18]. In this respect, it is reasonable that a substantial amount of protons are incorporated into ALD YSZ films comprised of nanoscale grains [9][10][11]. Incorporation of protons is significant at low temperatures as water or OH − is thermodynamically stable under 100-150°C while OH − groups decompose and completely diffuse out as water vapor above 350°C; therefore, the ionic conductivity at 50°C is close to that at 350°C where oxide ion conduction is dominant.…”

“…Incorporation of protons is significant at low temperatures as water or OH − is thermodynamically stable under 100-150°C while OH − groups decompose and completely diffuse out as water vapor above 350°C; therefore, the ionic conductivity at 50°C is close to that at 350°C where oxide ion conduction is dominant. We successfully ran micro-SOFCs with 100 nm-thick ALD YSZ displaying an open circuit voltage close to 1 V below 100°C [11].…”