An amorphous-like xα-Fe2O3–(1 − x)ZrO2 solid solution system for low temperature resistive-type oxygen sensing

An amorphous-like solid solution of xα-Fe2O3–(1−x)ZrO2 powders has been prepared using the high-energy ball milling technique, and their physical and structural properties have been systematically characterised using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The oxygen gas sensing properties of the screen-printed thick film gas sensors fabricated from such mechanically alloyed materials have been characterised using an automatic gas sensing measurement system. Experimental results show that the particle size of the powders is drastically milled down to 8 nm after 120 h of high-energy ball milling. The TEM result has also revealed an amorphous-like structure agglomerating the sparing nanocrystalline grains together. The resistive-type sensors demonstrate good oxygen gas sensitivity at a very low operating temperature of 320°C. It is believed that the extraordinary high concentration of oxygen vacancies is the critical factor. This sensing mechanism will be discussed.