Characterization of NO_x sensor using doped In₂O₃

To develop a highly sensitive gas sensor monitoring NO_x, various kinds of n-type semiconductors made of In₂O₃ were prepared, and the relations between doped elements and gas sensitivities or response times were studied. Consequently, it was found that the samples doped with less than 1 at.% alkali-earth metal components have high sensitivities and responsiveness. The gas-absorbing phenomena were investigated using highly sensitive thermal analysis. From the result, it was indicated that alkali-earth component-doped In₂O₃ materials have higher adsorption ability of NO_x than pure In₂O₃ has.