Study of reoxidation in heavily La-doped barium titanate ceramics

The ceramic samples of (1-x)BaTiO3+1/2xLa2O3+(2+x)mol%TiO2 (0.003≤x≤0.15) were prepared by sintering in reducing atmosphere of H2, subsequently reoxidized in air. The effect of heavily La dopant on the resistivity and microstructure of the reoxidized samples were investigated by means of scanning electron microscopy and electric properties testing. The results show that the critical concentration of La-doped samples increased obviously compared with the samples sintered in air. The grain size decreased with the increase of La-donor content. The positive temperature coefficient resistivity effect of the sample increased when a change reoxidizing temperature range of 600 deg. C ∼1200 deg. C. The maximum of ρmax/ρmin ratio was ∼700 at the reoxidizing temperature of 1100 deg. C when x=0.8mol%.