Influence of Pr3+ substitution at Ba-site of Eu(Ba1−xPrx)2Cu3O7−δ ceramic rods with hot-spot on oxygen sensing properties

In this work, we prepared Eu(Ba1−xPrx)2Cu3O7−δ rods by the solid-state reaction method to investigate the influences of changes in structure and the expected decrease in average Cu valence on oxygen sensing properties of self-heating rods with hot-spots. X-ray powder diffraction analysis showed that orthorhombicity of the structure reduces with increasing Pr3+ concentration. After the hot-spot became visible, samples x=0 and x=0.05 showed a sudden drop in current before remaining constant with increasing voltage. This is suggested to be due to steep increase in resistivity caused by the sudden increase in temperature of the hot-spot together with the structural changes that lead to reduction in oxygen content. However, for the x=0.25 and x=0.4 rods the output current shows no sudden drop. Our results also showed that the reduced magnitude of the output current with increasing Pr3+ could be attributed to the reduction in intrinsic hole concentration. The output current for all samples showed strong dependence on pO2. Although the sensitivity of the output current to pO2 between 50% pO2 and 100% pO2 reduces with increasing x, the stability and repeatability of the output current seem to improve. Also, while substitution of Pr3+ reduces the magnitude of the output current, it produces a better response time toward different pO2.