A new type of solid-electrolyte gas sensor for chlorine in an O-2-cont
aining atmosphere has been fabricated by combining an MgO-stabilized z
irconia tube with an auxiliary phase containing metal chloride. The se
nsor gives fairly good sensing characteristics to 1-100 ppm Cl-2 at 55
0-650 degrees C, with the e.m.f. response changing linearly with a cha
nge in the logarithm of the Cl-2 concentration. With a multicomponent
auxiliary phase of BaCl2-KCl-MgO, the times for 90% response and 90% r
ecovery on switching between 4 and 40 ppm Cl-2 at 550 degrees C are 6
s and 2 min, respectively. The e.m.f. response to Cl-2 is hardly influ
enced by coexistent CO2, while it shifts significantly in the presence
of water vapour.