Gas sensing characteristics of Au sensing electrode fabricated on YSZ single-crystals

The nano-structured gold sensing electrodes (SEs) were fabricated on (100) and (111) surfaces of single-crystal (sc) yttria-stabilized zirconia (YSZ) plates utilizing colloidal gold solution of 5 nm. After annealing at 1000°C, Au was found to form the large square-like domains (ca. 5×5 ¿m) on (100) surface of YSZ, whereas the triangular-like domains with the size of 2-3 ¿m were observed on YSZ(111). Such a discrepancy in morphology of nano-Au SEs resulted in the different sensing properties of the fabricated sensors as well as their short-term stability. While the sensor based on YSZ(100) treated with Au showed high emf responses to the non-methane hydrocarbons (HCs) at 700°C under the wet condition, the sensor based on YSZ(111) gave highly selective and sensitive responses to NH₃.