Abstract: LaF₃ and La_1-xPb_xF_3-x (x=0.05～0.15) solid solution materials were prepared and their AC conductivities were measured at frequency of 10kHz Presence of an appropriate amount of PbF₂ made the conductivity increase, and the conductivity of La_0.95 Pb_0.05 F_2.95 was about one order of magnitude higher than that of pure LaF₃. Four solid galvanic cells made of La_0.95 Pb_0.05 F_2.95 as electrolyte were investigated as potentiometric oxygen sensor. The sensor cell of BiF₃(Bi)/La_0.95 Pb_0.05 F_2.95/Pt showed shorter response than the others. The 90% response of the cell took as short as 80s, while oxygen partial pressure changed from 0.21×10⁵Pa to 1.0×10⁵Pa at 150℃.The electrochemical reaction on the sensing electrode was referred to as "two electron reaction".

Key words: lanthanum trifluoride, solid state electrolyte, oxygen sensor, conductivity