Microwave sintering of plasma-sprayed yttria stabilized zirconia electrolyte coating

In this work, microwave (MW) was used to sinter atmospheric plasma-sprayed 8 mol% yttria stabilized zirconia (YSZ) electrolytes coatings. Three types of coatings were studied: pure YSZ coating, 5 wt% BaTiO₃ filled YSZ coating and 10 wt% BaTiO₃ filled YSZ coating. Microstructures and ionic conductivities of as-sprayed and MW-sintered coatings were characterized. The results indicated that that the pure YSZ coating can hardly be sintered by the MW sintering and it can only be heated up to 900 °C. For two composite coatings, BaTiO₃ particles distributed in the composite coating act as a good MW susceptor and thereby, a good heat source for sintering YSZ matrix. After a MW sintering at 1450 °C for about 30 min, an obvious structural modification was noticed: the lamellar and columnar crystal features of as-sprayed plasma-sprayed YSZ coatings were modified to equiax crystal in the sintered coatings. Ionic conductivity of sintered 5 wt% BaTiO₃ filled YSZ composite coatings were elevated to about twice of as-sprayed coating. A further increase of BaTiO₃ content to 10 wt% in the composite coating enhanced the sintering efficiency, however, the ionic conductivity of composite coatings was decreased.