Enhanced grain-boundary conduction in polycrystalline Ce0.8Gd0.2O1.9 by zinc oxide doping: Scavenging of resistive impurities

Sinterability, reducibility, and electrical conductivity of fast oxide-ion conductors La1.8R0.2MoWO9 (R=Pr, Nd, Gd and Y)

“…Decreased densification at higher sintering temperatures may be attributed to oversintering, which leads to rapid grain growth and large pore formation. Our previous studies [28][29][30] revealed that the influence of porosity on the performance of ceramic electrolyte is considerably limited when the relative density exceeds 94%. Furthermore, molybdenum volatilizes at a high sintering temperature.…”

Improving SiO 2 impurity tolerance of Ce 0.8 Sm 0.2 O 1.9 : Synergy of CaO and ZnO in scavenging grain-boundary resistive phases

“…In our previous reports [21,22], with the addition of ZnO, strongly aggregated secondary phases mainly consisting of Si (~35 at%), Ca (~5 at%) and the trivalent rareÀearth element (~55 at %) could be found both on the surface and in the bulk of dopedceria ceramic electrolytes after high temperature (e.g., 1600 C) thermal etching; this phenomenon was proven to be associated with the enhanced GB conductivity. In the present study, the observed secondary phases contain higher Ca concentrations (>20 at%) and lower Sm concentrations (<40 at%) (Fig.…”

“…Table 1 shows the values of sintering temperature, relative density, and average grain size of the sintered samples. Given the sintering-aid effect of ZnO [21,22], the relative density of the ZnOadded samples sintered at 1400 C is comparable with that of the SDC series samples sintered at 1600 C. The grain sizes of the SDCxSi series samples (4.61e6.23 mm) are apparently smaller than SDC (10.04 mm) under the same sintering conditions (1600 C), which indicate that SiO 2 addition may inhibit SDC grain growth during sintering. On the other hand, the similarity in average grain size between pristine SDC (10.04 mm) and SDC0.2Siþ2Ca (9.80 mm)…”

“…Previously, we reported that the addition of 1 mol% ZnO can effectively increase the grain boundary conductivities of doped ceria electrolytes, especially for those silica-contaminated cases [21,22]. Meanwhile, the analysis by field emission transmission electron microscopy (FETEM) equipped with EDS revealed that the siliceous and ZnO phases were separately aggregated at the triple grain junction areas in ZnO-added specimens (as shown in Fig.…”

“…The GB resistivity showed high correlation with SiO 2 concentration. The FETEM-EDS analysis revealed that the scavenging process occurs via a novel mechanism in which ZnO phase and the resistive siliceous phases are separately and strongly aggregated in non-wetting configurations [21,22]. (Fig.…”