Effects of oxygen effusion on the high temperature resistivity of bulk La2CuO4+delta

We have studied the oxygen effusion by simultaneous measurements of evolved gas pressure and resistivity as-synthesized La2CuO4+delta from room temper ature to 920 degreesC The result shows that the resistivity of the sample i s closely coupled to the amount of effused oxygen. The resistivity; increas es sharply between 270 degreesC and 400 degreesC. which is attributed to th e decreasing number of holes due to evolved gas. Around 800 degreesC, anoth er oxygen effusion peak was observed corresponding to a resistivity decreas e. This can be attributed to the release of lattice oxygen. Our data sugges t that the surface desorption of oxygen molecules is accompanied by the sim ultaneous loss of doped holes in the CuO2 planes.