Effect of Cu and Co addition on CO gas-sensing properties of TiO₂ prepared by oxidation of mechanically-synthesized TiN composites

Cu-and Co-added TiO₂ sensing material composites were prepared by oxidizing TiN-Cu and TiN-Co composites that were synthesized using ball milling in an N₂ atmosphere. Structural characterization was performed using X-ray diffraction, field emission scattering electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The pure, Co-and Cuadded TiO₂ sensing materials were prepared by oxidizing the synthesized TiN, TiN-Cu and TiN-Co powders at 600 °C. The additive Cu in the TiO₂ powder was changed to CuO crystals while the additive Co formed the CoTiO₃ phase. Therefore, the CuO phase was segregated and grown regardless of the TiO₂, however the additive Co in the TiO₂ was not cohered. The Coadded TiO₂ had greater responses than that of the Cu-added sample at all operating temperatures and showed the highest response of 5.32 at 1000 ppm CO gas. The higher sensing response of the Co-added TiO₂ resulted in an enhancement of the grain surface and incorporation with catalytic metals by highly dispersed Co.