Degradation of the electrical conductivity in stabilised zirconia system

Characterisation of conductivity of the (Ce xY0.2-x)Sc0.6 Zr3.2O8-δ (0 < x < 0.2) system and composition Ce0.04Y0.02Sc0.67Zr3.27O 7.66 as function of time

“…The stability of the conductivity is in agreement with results from Haering et al [9,11]. After 1800 h, shaded area in Fig.…”

“…This is in agreement with Haering et al [9] and Nomura et al [15], who state that compositions with scandia content lower than 11 mol%, present degradation in conductivity in first the 500 h but when scandia content is higher than 11 mol% no degradation is observed in the first 500 h. The total dopant content is higher than 11 mol% for all compositions in the system.…”

“…In addition, the increase of vacancies will create an electrostatic interaction between the oxygen vacancies and the dopant cations. This leads to an ordering of the cations during annealing causing the formation of anions microdomains, therefore causing conductivity degradation [9,11,15,16]. In Fig.7 grain boundaries are well defined and the hill and valley microstructure can be observed.…”

“…Zhang et al [8] state that there are four possible microstructural changes, which are responsible for the decrease in conductivity of doped zirconia electrolytes caused by ageing: (1) precipitation of long range ordered phases; (2) formation and precipitation of tetragonal phase in the cubic grains; (3) segregation of dopant-rich layer near grain boundaries and triple points and (4) trapping of oxygen vacancies ( ) towards dopant cations with time due to the Coulombic force, short range ordering of oxygen vacancies. In point (2) the formation and precipitation occur as a result of "growing" of the metastable tetragonal (t or t') or cubic phase in the ZrO 2 -Y 2 O 3 system and the t'-phase in the ZrO 2 -Sc 2 O 3 system into low-dopant tetragonal and dopant-rich cubic phases [7,9,10]. Phase transformation of the zirconia electrolytes can be caused, not only by the type of dopants and dopant concentrations, but also by ageing.…”

Concentration-dependent ionic conductivity and thermal stability of magnetron-sputtered nanocrystalline scandia-stabilized zirconia

“…The existence of these phases comes from the small difference in the ion radius between the Sc 3+ dopant and the Zr 4+ host cation, and hence a small barrier for redistribution of the dopants. This means that the crystal structure, and hence properties, of the SSZ films are highly sensitive to the synthesis method and the thermal history [5]. An 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 4 enhancement in ionic conductivity was found in sol-gel derived nanocrystalline 8SSZ (8.0 mol% Sc 2 O 3 ) thin films, due to grain size effects [6,7].…”