Mechanism of humidity sensing of Ti-doped MgCr2O4 ceramics

Abstract The mechanism of humidity sensing of Ti-doped MgCr 2 O 4 ceramics has been investigated using a combination of various techniques,such as cyclic voltammetry, electron spin resonance spectroscopy (ESR), microcalorimetry and point of zero zeta potential measurements, to illustrate the importance of the distribution of acidic and basic sites on the surface. Powder X-ray diffraction patterns prior to the measurements confirm the singlephase behavior of MgCr 2 O 4 as well as the expansion of the spinel lattice with the incorporation of Ti. The evidence obtained from electrochemical and ESR experiments indicates the crucial role of the Cr 3+ /Cr 2+ redox change on the surface as the main reason for humidity sensing.