Debye Length and Gas Sensor Mechanism of Undoped and Sm₂O₃-Doped ZnO Ceramics

Abstract

The temperature dependence of Debye length of undoped and Sm₂O₃-doped ZnO ceramic specimens in air and the changes in electrical resistivity caused by admission of propane gas were investigated. The Debye length of the both specimens increased as temperature increased from 100° to 550°C. Especially the Debye length of undoped ZnO specimens was 0.31μm at room-temperature (27°C) and 0.4μm at 550°C. Only specimens, whose neck radii were smaller than the Debye length, showed a decrease in electrical resistivity under the admission of propane gas. This mechanism is explained by the gate action of pinch-off potential at the necks.