Abstract: Al2O3 ceramics were pressureless sintered at 1500 ℃, 1550 ℃ and 1600 ℃ with 0.25wt; CaO, 1wt; MgO and 2.75wt; SiO2 as additives.The DC electrical resistivity of Al2O3 ceramics were investigated in the range of 150-400 ℃ and the relative humidity range of 40;-100; respectively.The phase composition and microstructure of Al2O3 samples were characterized by XRD and SEM.The results show that the temperature increases from 150 ℃ to 400 ℃, the DC resistivity of the samples decreases by about 2 to 2.5 orders of magnitude.The relative humidity increases from 40; to 100;, the DC resistivity of the samples decrease by about 3 to 4 orders of magnitude.At the same testing condition, the higher DC resistivity of Al2O3 samples sintered at 1500 ℃ is caused by the microstructure with smaller grain and higher porosity.

Key words: Al2O3 ceramics were pressureless sintered at 1500 ℃, 1550 ℃ and 1600 ℃ with 0.25wt; CaO, 1wt; MgO and 2.75wt; SiO2 as additives.The DC electrical resistivity of Al2O3 ceramics were investigated in the range of 150-400 ℃ and the relative humidity range of 40;-100; respectively.The phase composition and microstructure of Al2O3 samples were characterized by XRD and SEM.The results show that the temperature increases from 150 ℃ to 400 ℃, the DC resistivity of the samples decreases by about 2 to 2.5 orders of magnitude.The relative humidity increases from 40; to 100;, the DC resistivity of the samples decrease by about 3 to 4 orders of magnitude.At the same testing condition, the higher DC resistivity of Al2O3 samples sintered at 1500 ℃ is caused by the microstructure with smaller grain and higher porosity.