Effects of ionic size on oxygen sensing properties of Sr substituted Ho123 ceramic rods utilising hot spot phenomena

Abstract

The I-V characterisation of Ho(Ba 2-xSr x)Cu3O 7-δ (x50, 0.2 and 0?8) ceramic sensor rod with hot spot in flowing oxygen between 0 and 100% pO2 revealed good oxygen response with output current observed to strongly depend on pO2. All the samples showed higher sensitivity to p O2 below 20% with reduced electrical power consumption in Sr substituted rods. The x50.2 rod showed improvement in output current stability, reproducibility and transition of output current response between 20 and 100% pO 2 compared to the x50 rod. Conductivity was found to be proportional to pO 1/62 above 60% for x=0 rod and above 40% for Sr substituted rods, while lower pO 2 conductivity was proportional to pO 1/42 , in agreement with the mass action law indicating difference in oxygen ionisation. The results are also discussed in terms of the possible influence of hot spot temperature on the structure of Ho123 and changes in oxygen activation energy as a result of the difference in ionic sizes between Ba 2+ and Sr 2+. © W. S. Maney & Son Ltd. 2011.