Characteristics of P-type Semiconducting MgCr₂O₄-TiO₂ Ceramics for Gas Sensing Devices

Abstract

Gas detection characteristics of p-type semiconducting MgCr₂O₄-TiO₂ ceramics are discussed for diluted H₂, NH₃, C₂H₄, and CO gases in air. These ceramics were produced by sintering mixed oxide powders with 1.0 wt% doping of CaO, SnO₂, Nb₂O₅, ZnO, or ZrO₂. Adsorption and desorption of these gases were detected by the change of electrical resistance. It was found that the resistance change followed first-order reversible reaction as induced by the change of the potential barrier height at the grain boundaries of the ceramics. The dissociation constants of the first-order reaction agreed well with those derived from the fitting to the Langmuir isotherm equation. Dopant dependent characteristics are also discussed for respective gases.