Effects of thickness of CeO 2-added Au electrodes of YSZ-based gas sensors on VOC-sensing properties

Yttria-stabilized zirconia (YSZ)-based gas sensors attached with CeO 2 -added Au sensing electrodes (SEs) were fabricated by using spin-coating method (the number of individual spin-coating (and subsequent drying) cycles ( x ): 5, 10, 15), and their toluene-sensing properties were investigated in this study. The 24 wt% CeO 2 -added SE fabricated with the fewest spin-coating cycles ( x : 5) showed that the island-like agglomerated particles (50 - 100 nm in diameter) were isolated with each other. The increase in the x value increased the size of the agglomerated particles as well as reduced the distance among them. On the other hand, the thickness of the 32 wt % CeO 2 -added Au SEs increased in columnar form with an increase in the x value. Toluene response of the sensors using the 24 wt% CeO 2 -added Au SE decreased with an increase in the SE thickness, while that of the sensors using the 32 wt% CeO 2 -added Au SE increased with an increase in the SE thickness. Electrochemical impedance measurement elucidated the increase in the length of triple phase boundaries with an increase in the SE thickness irrespective of the amount of CeO 2 in the SEs. It is also confirmed that the morphological differences originating from the amount of CeO 2 significantly affect the dependences of the toluene responses of all sensors on the SE thickness.