Gas-sensitive resistor properties of the solid solution series Tix(Sn1−ySby)1−xO2 (0<x<1, y=0, 0.01, 0.05)

Abstract

The response to carbon monoxide, methane and water vapour of gas-sensitive resistors fabricated from solid solution compounds Ti x (Sn 1–y Sb y ) 1–x O 2 where 0<x<1 and y=0, 0.01, 0.05 has been studied. For the single phase materials the variation of both conductance and conductance activation energy with composition has been explained using either a surface trap limited conductance model for undoped materials or a Schottky barrier controlled conductance for Sb-doped materials. The effect of dopant density and surface composition on the gas response has been explained using a compensated semiconductor conduction model. The surface states controlling response to water vapour are not the same as those controlling response to the combustible gases. The adsorbed oxygen states responsible for gas sensitivity lie closer to the conduction band edge for TiO 2 than for SnO 2 . The surface oxygen states and surface water states are closer in energy on TiO 2 than on SnO 2 . The resistivity and gas sensitivity of spinodally decomposed materials could be interpreted in terms of the phase diagram which indicated no differences from the behaviour of the single-phase components.